Published references
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These publications have a reference to ProboStat™ or other NORECS products
All 1-25 26-50 51-75 76-100 101-125 126-150 151-175 176-200 201-225 226-250 251-275 276-300 301-325 326-350 351-375 376-400 401-425 426-450 451-475 476-500 501-525 526-550 551-575 576-600 601-625 626-650 651-675 676-MOX-Based Resistive Gas Sensors with Different Types of Sensitive Materials (Powders, Pellets, Films), Used in Environmental Chemistry
ID=716| Author |
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| Source |
Chemosensors
Volume: 11,
Issue: 2,
Pages: 95 Time of Publication: 2023 |
| Abstract | The identification of an unknown gaseous species or the composition of a gaseous mixture can be performed using various experimental techniques such as: mass spectrometry, chromatography, nuclear magnetic resonance (NMR), infrared (IR), X-Rays, or by combining these analytical techniques (in automated analyzers). Unfortunately, these techniques use highly expensive equipment and require the use of qualified personnel. Using gas sensors is a viable and inexpensive alternative. The most commonly used sensors in the field are resistive type chemosensors (chemiresistors), due to their simple detection mechanism and low manufacturing costs. The detection principle of these sensors is based on the catalytic reaction between the sensitive material of the sensor and the target gas. This reaction occurs with the release or consumption of electrons, influencing the overall electrical resistance of the sensor. This review describes various MOX-based chemiresistors, which contain different types of sensitive substrates, such as powders, pellets or films, as well as a clear tendency towards sensor miniaturization and the constant improvement of the fabrication techniques towards greener and more cost-effective synthesis routes over time. The goal of this research was to obtain sensors with high 3S parameters (sensitivity, selectivity, and stability), that can be mass-produced and implemented on a wide scale. |
| Keywords | resistive gas sensors; chemiresistors; sensitivity; selectivity; stability; eco-friendly; low-cost; miniaturized; micro-sensors; mass-produced |
| Remark |
https://doi.org/10.3390/chemosensors11020095 Link |
Two Types of Negative Thermal Expansion Observed in PbCr1–xTixO3
ID=715| Authors |
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| Source |
Chem. Mater.
Time of Publication: 2023
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| Abstract | Two negative thermal expansions (NTEs) with different mechanisms were observed in solid solutions of perovskite-type oxides PbCrO3 and PbTiO3. PbCr1–xTixO3 was found to adopt a cubic structure the same as that of PbCrO3 for x ≤ 0.6 and a PbTiO3-type tetragonal structure for x ≥ 0.7. The NTE observed at x ≤ 0.6 was accompanied by a cubic-to-cubic phase transition originating from the rearrangement of Pb2+/Pb4+ in a complex local structure called a charge glass. The volume shrinkage of −2.5% observed in PbCrO3 is sufficiently large despite the absence of intermetallic charge transfer, which is the origin of pressure-induced cubic-to-cubic phase transition and 9.8% volume collapse. The NTE in the tetragonal phase was caused by the ferroelectric-to-paraelectric phase transition, the same as in PbTiO3. We succeeded in significantly lowering the working temperature of PbTiO3 as an NTE material by Cr substitution while retaining a large volume shrinkage of 0.6%. |
| Remark |
https://doi.org/10.1021/acs.chemmater.2c02896 Link |
General characterization and potential use of Moroccan lizardite clay in ceramics: Technological and dielectric studies
ID=714| Authors |
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| Source |
Open Ceramics
Volume: 13,
Pages: 100332 Time of Publication: 2023 |
| Abstract | This work focuses on the characterization of lizardite and studying the technological and dielectric features of ceramics based on this geomaterial by experimental measurements. Note that, the physical evaluation (dielectric properties) of magnesian clay has never been studied. Natural lizardite was extracted from the Beni Boussera massif (Rif, Morocco), and was characterized in terms of chemical, physical, mineralogical and thermal aspects. A purification process was carried out to identify the mineral phases present in this material. The results showed that the studied material is mainly composed of silica (47.16 wt%) and magnesia (31.21 wt%), it is also richer in clay minerals such as lizardite and chlorite. The ceramic specimens were prepared by the uniaxial pressing method, followed by sintering to different temperatures (i.e., 900, 1000, 1100, and 1200 °C). The influence of the sintering temperature on porosity, density, shrinkage, water absorption, mechanical and microstructural properties of ceramics was evaluated, as well as chemical resistance and dielectric properties were studied. The evaluation of the optimized ceramic materials shows that good dielectric properties are obtained when sintered at a temperature of 1100 °C with a dielectric constant of 1.33, a dielectric loss of around 0.08, and a conductivity of 4.86 E−8 S/cm, at high frequency. Furthermore, the obtained ceramic specimen has a porosity of 17%, a density of 2.02 g/cm3, a water absorption of 9.86%, and a mechanical strength of 19.3 MPa. As a consequence, the results obtained have provided ceramics based on a natural resource with favorable technological and mechanical properties, and very interesting dielectric properties. |
| Remark |
https://doi.org/10.1016/j.oceram.2023.100332 Link |
Effect of Steam to Carbon Dioxide Ratio on the Performance of a Solid Oxide Cell for H2O/CO2 Co-Electrolysis
ID=713| Authors |
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| Source |
Nanomaterials
Volume: 13,
Issue: 2,
Pages: 299 Time of Publication: 2023 |
| Abstract | The mixture of H2 and CO, the so-called syngas, is the value-added product of H2O and CO2 co-electrolysis and the feedstock for the production of value-added chemicals (mainly through Fischer-Tropsch). The H2/CO ratio determines the process in which syngas will be utilized and the type of chemicals it will produce. In the present work, we investigate the effect of H2O/CO2 (steam/carbon dioxide, S/C) ratio of 0.5, 1 and 2 in the feed, on the electrochemical performance of an 8YSZ electrolyte-supported solid oxide cell and the H2/CO ratio in the outlet, under co-electrolysis at 900 °C. The B-site iron doped lanthanum strontium chromite La0.75Sr0.25Cr0.9Fe0.1O3-δ (LSCF) is used as fuel electrode material while as oxygen electrode the state-of-the art LSM perovskite is employed. LSCF is a mixed ionic-electronic conductor (MIEC) operating both under a reducing and oxidizing atmosphere. The cell is electrochemically characterized under co-electrolysis conditions both in the presence and absence of hydrogen in the feed of the steam and carbon dioxide mixtures. The results indicate that under the same concentration of hydrogen and different S/C ratios, the same electrochemical performance with a maximum current density of approximately 400 mA cm−2 is observed. However, increasing p(H2) in the feed results in higher OCV, smaller iV slope and Rp values. Furthermore, the maximum current density obtained from the cell does not seem to be affected by whether H2 is present or absent from the fuel electrode feed but has a significant effect on the H2/CO ratio in the analyzed outlet stream. Moreover, the H2/CO ratio seems to be identical under polarization at different current density values. Remarkably, the performance of the LSCF perovskite fuel electrode is not compromised by the exposure to oxidizing conditions, showcasing that this class of electrocatalysts retains their reactivity in oxidizing, reducing, and humid environments. |
| Keywords | Co-electrolysis; perovskite oxide; doping; lanthanum chromite; LSCF; solid oxide; SOEC; syngas; steam to carbon dioxide ratio |
| Remark |
https://doi.org/10.3390/nano13020299 Link |
Centrosymmetric Tetragonal Tungsten Bronzes A4Bi2Nb10O30 (A = Na, K, Rb) with a Bi 6s Lone Pair
ID=712| Authors |
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| Source |
Chem. Mater.
Volume: 35,
Issue: 1,
Pages: 17–26 Time of Publication: 2023 |
| Abstract | A first-principles study of the tetragonal tungsten bronze (TTB) K4Bi2Nb10O30 has suggested that the Bi 6s lone pair causes in-plane polarization (within the a–b plane), corresponding to the one found in Pb5Nb10O30 (PN), in contrast to the out-of-plane polarization (along c) found in most TTBs. Replacing PN with KBN potentially opens for a lead-free analogue to morphotropic phase boundaries known in TTBs based on PN. Here, we report on the synthesis and properties of A4Bi2Nb10O30 (ABN, A = Na, K, Rb) with the objective to determine the structure and electrical properties, paying particular attention to the role of the Bi 6s lone pair. The ABN materials were synthesized via conventional solid-state synthesis in a two-step process. Convergent-beam electron diffraction demonstrated a centrosymmetric tetragonal space group for the two compounds KBN and RBN, and ferroelectric polarization–electric field measurements confirmed the lack of hysteretic behavior in line with the observed centrosymmetric symmetry. Non-ambient powder X-ray diffraction demonstrated the signature of a phase transition for KBN and RBN, as several weak satellite reflections vanished during heating and reappeared upon cooling. Dielectric spectroscopy supported the observation of an anomaly due to the presence of a weak maximum in the electrical permittivity at temperatures corresponding to the disappearance of the satellite reflections. Possible explanations for the absence of polarization in ABN TTBs are discussed with particular attention to the suppression of the 6s2 lone pair effect of Bi and the size of A-site cations in the TTB crystal structure. |
| Remark |
https://doi.org/10.1021/acs.chemmater.2c01944 Link |
The Role of Strain in Proton Conduction in Multi-Oriented BaZr0.9Y0.1O3−δ Thin Film
ID=711| Authors |
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| Source |
ACS Appl. Mater. Interfaces
Volume: 14,
Issue: 50,
Pages: 55915–55924 Time of Publication: 2022 |
| Abstract | Within the emerging field of proton-conducting fuel cells, BaZr0.9Y0.1O3−δ (BZY10) is an attractive material due to its high conductivity and stability. The fundamentals of conduction in sintered pellets and thin films heterostructures have been explored in several studies; however, the role of crystallographic orientation, grains, and grain boundaries is poorly understood for proton conduction. This article reports proton conduction in a self-assembled multi-oriented BZY10 thin film grown on top of a (110) NdGaO3 substrate. The multiple orientations are composed of different lattices, which provide a platform to study the lattice-dependent conductivity through different orientations in the vicinity of grain boundary between them and the substrate. The crystalline stacking of each orientation is confirmed by X-ray diffraction analysis and scanning transmission electron microscopy. The transport measurements are carried out under different gas atmospheres. The highest conductivity of 3.08 × 10–3 S cm–1 at 400 °C is found under a wet H2 environment together with an increased lattice parameter of 4.208 Å, while under O2 and Ar environments, the film shows lower conductivity and lattice parameter. Our findings not only demonstrate the role of crystal lattice for conduction properties but also illustrate the importance of self-assembled strategies to achieve high proton conduction in BZY10 thin films. |
| Keywords | BaZrO3 thin film; BaZr0.9Y0.1O3−δ strained structure; proton conduction; crystallographic orientation |
| Remark |
https://doi.org/10.1021/acsami.2c12657 Link |
Low temperature ammonia synthesis by surface protonics over metal supported catalysts
ID=710| Author |
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| Source |
Faraday Discussions
Time of Publication: 2023
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| Abstract | Low-temperature ammonia synthesis by applying an electric field to a solid heterogeneous catalyst was investigated to realize an on-demand, on-site catalytic process for converting distributed renewable energy into ammonia. By applying an electric field to the catalyst, even at low temperatures, the reaction proceeds efficiently by an "associative mechanism" in which proton-conducting species on the support surface promote the formation of N2Had intermediates through surface protonics. Kinetics, isotope exchange, infrared spectroscopy, X-ray spectroscopy, and AC impedance analysis were performed to clarify the effect of metal and catalyst support structure on the reaction, and an evaluation method for the surface protonics of the support was established to analyze the reaction mechanism, and further analysis using computational chemistry was also conducted. The elementary step determining catalytic activity changed from N2 dissociation to N2H formation, and this difference resulted in high activity for ammonia synthesis at low temperatures even when using base metal catalysts such as Fe and Ni. |
| Remark |
DOI: 10.1039/x0xx00000x Link |
Experimental application of a laser-based manufacturingprocess to develop a free customizable, scalablethermoelectric generator demonstrated on a hot shaft
ID=709| Authors |
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| Source |
Engineering Reports
Time of Publication: 2022
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| Abstract | Geometry, design, and processing in addition to the thermoelectric materialproperties have a significant influence on the economic efficiency and perfor-manceofthermoelectricgenerators(TEGs).WhileconventionalBULKTEGsareelaborate to manufacture and allow only limited variations in geometry, printedTEGs are often restricted in their application and processing temperature due totheuseoforganicmaterials.Inthiswork,aproof-of-conceptforfabricatingmod-ular, customizable, and temperature-stable TEGs is demonstrated by applyingan alternative laser process. For this purpose, low temperature cofired ceram-ics substrates were coated over a large area, freely structured and cut withoutmasks by a laser and sintered to a solid structure in a single optimized thermalpost-processing.Ascalabledesignwithcomplexgeometryandlargecoolingsur-face for application on a hot shaft was realized to prove feasibility. Investigationson sintering characteristics up to a peak temperature of 1173K, thermoelec-tric material properties and temperature distribution were carried out for aCa3Co4O9/Ag-based prototype and evaluated using profilometer, XRD, and IRmeasurements. For a combined post-processing, an optimal sintering profilecould be determined at 1073K peak temperature with a 20min holding time.Temperaturegradientsofupto100Kcouldbeachievedalongathermocouple.Asingle TEG module consisting of 12 thermocouples achieved a maximum powerof0.224μWandopen-circuitvoltageof134.41mVatanaveragehot-sidetemper-ature of 413.6 K and temperature difference of 106.7 K. Three of these modulescombined into a common TEG with a total of 36 thermocouples reached a maxi-mumpowerof0.58Kandopen-circuitvoltageof319.28mVwithalesseraveragehot-side temperature of 387.8 K and temperature difference of 83.4 K. |
| Remark |
https://doi.org/10.1002/eng2.12590 Link |
A New Electroactive and Stable Electrode Based on Praseodymium Molybdate for Symmetrical SOFCs
ID=708| Authors |
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| Source |
Russian Journal of Electrochemistry
Volume: 58,
Pages: 989–997 Time of Publication: 2022 |
| Abstract | The electrochemical activity of a new electrode material based on Pr5Mo3O16 + δ (РМž) within the composition of a symmetrical solid oxide fuel cell (S-SOFC) of the electrolyte-supported design is studied. The model S-SOFC of the РМž/Ce0.9Gd0.1O1.95(GDC)/Zr0.84Y0.16O1.92(YSZ)/GDC/PMO composition demonstrated the maximum power density of 28 mW/cm2 at 900°С. To improve the power characteristics of S-SOFC, the porous buffer GDC layer is modified by the method of Pr6O11 infiltration. It is found that the addition of electroactive Pr6O11 into the GDC buffer layer provides the three-fold increase in the fuel-cell power density with the maximum of 90 mW/cm2 at 900°С. The 10 h life-time test of the model S-SOFC with the РМž/GDC + Pr6O11/YSZ/GDC + Pr6O11/PMO composition carried out at a load of 0.7 V reveals the absence of any considerable degradation in fuel cell power characteristics. The results obtained suggest that the new electrode material based on PMO holds promise for the development of S-SOFC. |
| Remark | Link |
Surface protonic conductivity in chemisorbed water in porous nanoscopic CeO2
ID=707| Authors |
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| Source |
Applied Surface Science
Volume: 611,
Issue: A,
Pages: 155590 Time of Publication: 2023 |
| Abstract | CeO2 surfaces play decisive roles in heterogeneous catalysis of important processes. Here, we investigate adsorption and dissociation of water and migration of protons on internal surfaces of nanoscopic porous CeO2. Sorption and thermogravimetry confirm literature suggestions that the surface is hydrogenated to Ce3+ ions and protons H+. The following chemisorption is dissociative, yet weak, and physisorption sets in only at the very highest relative humidities, reflecting hydrophobic behaviour. We link sample conductivities to surface protonic conductances via a brick layer model and show that behaviours at high, intermediate, and low temperatures with, respectively, positive, close to zero, and negative apparent activation energies and pH2O1/2, pH2O1, and pH2O3/2 dependences, can be attributed to different models of migration all within the chemisorbed layer, without contribution from physisorbed water. While CeO2 may special in this respect due to the effect of the hydrogenated surface, we believe the extended models of transport in the chemisorbed layer may apply also to other oxides. Unsaturated chemisorption may play an important role for CeO2 as catalyst in that the surface is left available for reactant molecules, still with availability of dissociated and mobile protons in the chemisorbed layer and electronic defects by Ce3+ in the surface. |
| Keywords | Ceria; CeO2; Porous; Hydrogenation; Water adsorption; Chemisorption; Conductivity; Protonic; Surface; Brick layer model |
| Remark |
https://doi.org/10.1016/j.apsusc.2022.155590 Link |
Ni-doped A-site excess SrTiO3 thin films modified with Au nanoparticles by a thermodynamically-driven restructuring for plasmonic activity
ID=706| Authors |
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| Source |
Catalysis Today
Time of Publication: 2023
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| Abstract | Plasmonically active nanoparticles offer a promising pathway to extend the absorption range of photocatalysts. While not necessarily catalytically active themselves, these particles allow the absorption of lower energy photons in wide band gap photocatalysts. Here, we present A-site excess SrTiO3 thin films, doped with Ni, where through a subsequent exsolution process we created well-socketed Ni nanoparticles in the surface of SrTiO3. These were galvanically replaced by Au, resulting in well-socketed Au nanoparticles with variable size on the surface, depending on the galvanic replacement time. Photoelectrochemical measurements and electron energy loss spectroscopy revealed the improved photoresponse of the thin films by plasmonic activity of the nanoparticles. The energy of the plasmon peak suggests that the main improvement results from the injection of hot charge carriers. Our study opens new avenues for the design and synthesis of the next generation of photocatalytic materials. |
| Remark |
In press, https://doi.org/10.1016/j.cattod.2022.11.011 Link |
Structural, Optical, and Sensing Properties of Nb-Doped ITO Thin Films Deposited by the Sol–Gel Method
ID=705| Authors |
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| Source |
Gels
Volume: 8,
Issue: 11,
Pages: 717 Time of Publication: 2022 |
| Abstract | The aim of the present study was the development of Nb-doped ITO thin films for carbon monoxide (CO) sensing applications. The detection of CO is imperious because of its high toxicity, with long-term exposure having a negative impact on human health. Using a feasible sol–gel method, the doped ITO thin films were prepared at room temperature and deposited onto various substrates (Si, SiO2/glass, and glass). The structural, morphological, and optical characterization was performed by the following techniques: X-ray diffractometry (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV/Vis/NIR spectroscopic ellipsometry (SE). The analysis revealed a crystalline structure and a low surface roughness of the doped ITO-based thin films. XTEM analysis (cross-sectional transmission electron microscopy)showed that the film has crystallites of the order of 5–10 nm and relatively large pores (around 3–5 nm in diameter). A transmittance value of 80% in the visible region and an optical band-gap energy of around 3.7 eV were found for dip-coated ITO/Nb films on SiO2/glass and glass supports. The EDX measurements proved the presence of Nb in the ITO film in a molar ratio of 3.7%, close to the intended one (4%). Gas testing measurements were carried out on the ITO undoped and doped thin films deposited on glass substrate. The presence of Nb in the ITO matrix increases the electrical signal and the sensitivity to CO detection, leading to the highest response for 2000 ppm CO concentration at working temperature of 300 ◦C. |
| Remark |
https://doi.org/10.3390/gels8110717 Link |
Ultrafast Crystallization and Sintering of Li1.5Al0.5Ge1.5(PO4)3 Glass and Its Impact on Ion Conduction
ID=704| Authors |
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| Source |
ACS Appl. Energy Mater.
Volume: 5,
Issue: 11,
Pages: 14466–14475 Time of Publication: 2022 |
| Abstract | Li1.5Al0.5Ge1.5(PO4)3 (LAGP) is among the most promising solid electrolytes for the next generation’s all-solid-state lithium batteries. However, preparing LAGP electrolytes is time- and energy-intensive. In this work, LAGP glassy powders were sintered and crystallized in 180 s by ultrafast high-temperature sintering (UHS) under conditions attractive for continuous industrial processes (i.e., ambient pressure and atmosphere). The fast heating rates characteristic of UHS significantly delay crystallization, potentially decoupling crystallization and sintering. Furthermore, electrochemical impedance spectroscopy (EIS) characterizations reveal that LAGP sintered and crystallized by UHS has an ionic conductivity of 1.15 × 10–4 S/cm, slightly lower than conventionally annealed samples (1.75 × 10–4 S/cm). The lower conductivity can be attributed to poorer intergrain contact. To overcome this issue, additives such as B2O3 and Li3BO3 are used, resulting in ∼2 and ∼5 times higher grain boundary conductivity for LAGP+1 wt % B2O3 and LAGP+1 wt % Li3BO3, respectively, compared to LAGP. Overall, this work provides insights into unraveling the impact of UHS sintering on the LAGP Li+ conduction mechanism. |
| Remark |
https://doi.org/10.1021/acsaem.2c03009 Link |
Development and characterization of highly stable electrode inks for low-temperature ceramic fuel cells
ID=703| Authors |
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| Source |
Journal of Power Sources
Volume: 552,
Pages: 232263 Time of Publication: 2022 |
| Abstract | Inkjet printing is a potential contactless and mask-free additive manufacturing approach for solid oxide fuel cells. Here, a highly stable cathode ink using La0.6Sr0.4Co0.2Fe0.8O3 was developed and characterized with particle size analysis, viscosity, surface tension, density, and thermal analysis. Both fresh and 6-months stored inks showed excellent jetability behavior with a Z number of 2.77 and 3.45, respectively. The ink was successfully inkjet-printed on a (LiNaK)2CO3-Gd:CeO2 porous electrolyte substrate to fabricate a symmetric cell. The electrochemical impedance spectroscopy measurements showed that at 550 °C the inkjet printing lowered the ohmic resistance to one-third (from 1.05 Ω cm2 to 0.37 Ω cm2) and the mass diffusion resistance by 4.25 times (from 6.09 Ω cm2 to 1.43 Ω cm2) as compared to drop-casted cell by creating a hierarchical porous structure and increasing reaction sites. Successful inkjet printing of the functional electrode material opens up a new avenue for the fabrication of the low-temperature ceramic fuel cells. |
| Keywords | Inkjet printing; Ceramics; Electrode; Solid oxide fuel cell; Stability |
| Remark |
https://doi.org/10.1016/j.jpowsour.2022.232263 Link |
Native point defects and polaron transport in zirconium pyrovanadate
ID=702| Authors |
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| Source |
Solid State Ionics
Volume: 386,
Pages: 116033 Time of Publication: 2022 |
| Abstract | Density functional theory calculations and electrochemical impedance spectroscopy have been combined to derive a defect model for ZrV2O7 to rationalize its electrical conductivity behavior. ZrV2O7 shows slight vanadium over-stoichiometry, yielding the predominant defect pair: V5+ on Zr sites (VZr•) charge-compensated by electron polarons as V4+ on V sites (VV′). Small polaron hopping is the dominating conduction mechanism with a calculated polaron self-trapping energy of −0.22 eV. The polarons can, however, be strongly bound as V4+ substituted on Zr sites (VZr×), with a calculated binding energy of −0.97 eV with respect to free polarons. The temperature dependency of the electrical conductivity exhibits a crossover between two regimes at 550 °C, and the apparent activation energy increases with increasing temperature from 0.3 to 0.86 eV. According to the defect model, which includes the concentration ratio of free and bound polarons, free polaron hopping predominates the electrical conductivity at lower temperatures while the thermally activated transition from bound to free polarons predominates at higher temperatures. |
| Keywords | Point defects; Free polarons; Bound polarons; Zirconium pyrovanadate |
| Remark |
https://doi.org/10.1016/j.ssi.2022.116033 Link |
Surface kinetics and bulk transport in La2Ni0.5Cu0.5O4+δ membranes from conductivity relaxation
ID=701| Authors |
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| Source |
Journal of European Ceramic Society
Volume: 43,
Issue: 2,
Pages: 462-467 Time of Publication: 2023 |
| Abstract | This work reports conductivity relaxation measurements on both uncoated (1.2 mm thick) and coated (2.0 mm thick) La2Ni0.5Cu0.5O4+δ membranes in the temperature range between 550 and 850 °C and oxygen partial pressures from 0.01 to 1.0 atm. The results show that surface kinetics has a significant effect on the relaxation profiles, especially at low temperatures and should not be neglected when extracting transport parameters. Oxygen chemical diffusion and surface exchange coefficients have been determined by transient conductivity with surface modification. Higher activation energy of surface exchange compared to bulk diffusion is observed for La2Ni0.5Cu0.5O4+δ, similar to that for La2NiO4+δ. Based on the oxygen partial pressure dependence of the surface exchange coefficient, it has been revealed that oxygen dissociative adsorption rate-limits the surface exchange. |
| Keywords | Conductivity relaxation; Surface modification; Surface exchange mechanisms; Oxygen diffusion; La2Ni0.5Cu0.5O4+δ; La2NiO4+δ |
| Remark |
https://doi.org/10.1016/j.jeurceramsoc.2022.10.046 Link |
Sintering and electrical properties of proton conducting BSZCY151020
ID=700| Author |
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| Source |
Time of Publication: 2022
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| Remark |
Master Thesis Link |
Electrospun Ca3Co4−xO9+δ nanofibers and nanoribbons: Microstructure and thermoelectric properties
ID=699| Authors |
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| Source |
J Am Ceram Soc.
Volume: 106,
Pages: 1170–1181 Time of Publication: 2023 |
| Abstract | Oxide-based ceramics offer promising thermoelectric (TE) materials for recy- cling high-temperature waste heat, generated extensively from industrial sources. To further improve the functional performance of TE materials, their power factor should be increased. This can be achieved by nanostructuring and texturing the oxide-based ceramics creating multiple interphases and nanopores, which simultaneously increase the electrical conductivity and the Seebeck coef- ficient. The aim of this work is to achieve this goal by compacting electrospun nanofibers of calcium cobaltite Ca3 Co 4−xO 9+δ, known to be a promising p-type TE material with good functional properties and thermal stability up to 1200 K in air. For this purpose, polycrystalline Ca3 Co 4−xO 9+δ nanofibers and nanorib- bons were fabricated by sol–gel electrospinning and calcination at intermediate temperatures to obtain small primary particle sizes. Bulk ceramics were formed by sintering pressed compacts of calcined nanofibers during TE measurements. The bulk nanofiber sample pre-calcined at 973 K exhibited an improved Seebeck coefficient of 176.5 S cm−1 and a power factor of 2.47 μW cm−1 K−2 similar to an electrospun nanofiber-derived ceramic compacted by spark plasma sintering. |
| Remark |
DOI: 10.1111/jace.18842 Link |
Effects of Ni-NCAL and Ni–Ag electrodes on the cell performances of low-temperature solid oxide fuel cells with Sm0.2Ce0·8O2-δ electrolyte at various temperatures
ID=698| Authors |
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| Source |
International Journal of Hydrogen Energy
Volume: 47,
Issue: 94,
Pages: 40067-40082 Time of Publication: 2022 |
| Abstract | Three low-temperature solid oxide fuel cells are built using Sm0.2Ce0·8O2-δ (SDC) as the electrolyte. Cell A is symmetrical and features Ni–LiNi0.8Co0·15Al0·05O2 (Ni–NCAL) electrodes, Cell B comprises a Ni–NCAL anode and a Ni–Ag cathode, and Cell C is fabricated using a Ni–NCAL cathode and a Ni–Ag anode. The ohmic resistance and polarization resistance (Rp) of Cells B and C are significantly higher than those of Cell A. The reduction of NCAL at the anodes of Cells A and B yields LiOH and Li2CO3 phases, and the Ni particles generated on the surfaces of the NCAL particles improve the catalytic activity of the cells. Li2CO3–LiOH melts at temperatures >450 °C and penetrates the porous SDC electrolyte layer, causing its densification and abnormal grain growth and increasing its ionic conductivity to >0.2 S/cm at low temperatures. The high open-circuit voltages (OCVs) (0.970–1.113 V) of the cells during electrochemical measurements are ascribed to the Li2CO3–LiOH phase which serves as an electron-blocking layer for the SDC electrolytes. As the reduction of NCAL approaches completion, the anode comprises only Ni phase, which hinders the charge transfer process. The triple-phase-boundary (TPB) area at cathode of Cell B is significantly lower than that of Cell A; therefore, the catalytic activity of Cell B for the oxygen reduction reaction is lower than that of Cell A. Consequently, the maximum power density (MPD) of Cell B is less than half of that of Cell A. The large Rp value of Cell C is ascribed to its low TPB area at Ni–Ag anode which has no reaction with H2 during operation. No visible sintering of the SDC electrolyte layer is observed for Cell C; therefore, its ionic conductivity is considerably smaller than those of the electrolyte layers of Cells A and B. The OCVs of Cell C (0.281–0.495 V) are significantly lower than the typical OCVs of ceria-based SOFCs. This is attributed to the porous SDC electrolyte layer of Cell C. The large Rp values and the low OCVs contribute to the low MPDs of Cell C at various temperatures. |
| Keywords | Solid oxide fuel cell; NCAL electrode; Polarization; Cell performance |
| Remark |
https://doi.org/10.1016/j.ijhydene.2022.09.148 Link |
Tuning the Thermoelectric Performance of CaMnO3-Based Ceramics by Controlled Exsolution and Microstructuring
ID=697| Authors |
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| Source |
CS Appl. Energy Mater.
Volume: 5,
Issue: 10,
Pages: 12396–12407 Time of Publication: 2022 |
| Abstract | The thermoelectric properties of CaMnO3−δ/CaMn2O4 composites were tuned via microstructuring and compositional adjustment. Single-phase rock-salt-structured CaO–MnO materials with Ca:Mn ratios larger than unity were produced in reducing atmosphere and subsequently densified by spark plasma sintering in vacuum. Annealing in air at 1340 °C between 1 and 24 h activated redox-driven exsolution and resulted in a variation in microstructure and CaMnO3−δ materials with 10 and 15 vol % CaMn2O4, respectively. The nature of the CaMnO3−δ/CaMn2O4 grain boundary was analyzed by transmission electron microscopy on short- and long-term annealed samples, and a sharp interface with no secondary phase formation was indicated in both cases. This was further complemented by density functional theory (DFT) calculations, which confirmed that the CaMnO3−δ indeed is a line compound. DFT calculations predict segregation of oxygen vacancies from the bulk of CaMnO3−δ to the interface between CaMnO3−δ and CaMn2O4, resulting in an enhanced electronic conductivity of the CaMnO3−δ phase. Samples with 15 vol % CaMn2O4 annealed for 24 h reached the highest electrical conductivity of 73 S·cm–1 at 900 °C. The lowest thermal conductivity was obtained for composites with 10 vol % CaMn2O4 annealed for 8 h, reaching 0.56 W·m–1K–1 at 700 °C. However, the highest thermoelectric figure-of-merit, zT, was obtained for samples with 15 vol % CaMn2O4 reaching 0.11 at temperatures between 800 and 900 °C, due to the enhanced power factor above 700 °C. This work represents an approach to boost the thermoelectric performance of CaMnO3−δ based composites. |
| Remark |
https://doi.org/10.1021/acsaem.2c02012 Link |
Magnetron sputtered LSC-GDC composite cathode interlayer for intermediate-temperature solid oxide fuel cells
ID=696| Authors |
|
| Source |
International Journal of Hydrogen Energy
Volume: 47,
Issue: 89,
Pages: 37967-37977 Time of Publication: 2022 |
| Abstract | The paper investigates the influence of the La0.6Sr0.4CoO3-δ-Gd0.1Ce0.9O1.95 (LSC-GDC) composite cathode interlayer on the operation of solid oxide fuel cells (SOFCs). Thin composite layers with the different GDC content are obtained by the reactive magnetron sputtering. The impact of the high-temperature annealing on the LSC-GDC phase composition is studied by the X-ray diffraction instrument using additionally a synchrotron radiation. The NiO-YSZ anodes with the YSZ electrolyte thin film and GDC barrier layer are used for the SOFC fabrication. The current-voltage curves and impedance spectra of SOFCs are obtained in the temperature range of 700–800°С. It is shown that not annealed composite layers with ∼50 vol% GDC content possess the most efficient electrochemical activity. The maximum power density of the SOFC with the LSC-GDC interlayer is 1322, 1041 and 796 mW/cm2 at 800, 750 and 700 °C, respectively, which is 20–35% higher than that of the cell without cathode interlayer. |
| Remark |
https://doi.org/10.1016/j.ijhydene.2022.08.281 Link |
Dealing with degradation in solid oxide electrochemical cells: novel materials and spectroscopic probes
ID=695| Authors |
|
| Source |
Universidad de Zaragoza, PhD thesis
Time of Publication: 2022
|
| Remark | Link |
Nanostructured La0.75Sr0.25Cr0.5Mn0.5O3–Ce0.8Sm0.2O2 Heterointerfaces as All-Ceramic Functional Layers for Solid Oxide Fuel Cell Applications
ID=694| Authors |
|
| Source |
ACS Appl. Mater. Interfaces
Volume: 14,
Issue: 37,
Pages: 42178–42187 Time of Publication: 2022 |
| Abstract | The use of nanostructured interfaces and advanced functional materials opens up a new playground in the field of solid oxide fuel cells. In this work, we present two all-ceramic thin-film heterostructures based on samarium-doped ceria and lanthanum strontium chromite manganite as promising functional layers for electrode application. The films were fabricated by pulsed laser deposition as bilayers or self-assembled intermixed nanocomposites. The microstructural characterization confirmed the formation of dense, well-differentiated, phases and highlighted the presence of strong cation intermixing in the case of the nanocomposite. The electrochemical properties─solid/gas reactivity and in-plane conductivity─are strongly improved for both heterostructures with respect to the single-phase constituents under anodic conditions (up to fivefold decrease of area-specific resistance and 3 orders of magnitude increase of in-plane conductivity with respect to reference single-phase materials). A remarkable electrochemical activity was also observed for the nanocomposite under an oxidizing atmosphere, with no significant decrease in performance after 400 h of thermal aging. This work shows how the implementation of nanostructuring strategies not only can be used to tune the properties of functional films but also results in a synergistic enhancement of the electrochemical performance, surpassing the parent materials and opening the field for the fabrication of high-performance nanostructured functional layers for application in solid oxide fuel cells and symmetric systems. |
| Keywords | thin films, hydrogen oxidation reaction, symmetric functional layers, solid oxide cells, nanocomposites |
| Remark |
https://doi.org/10.1021/acsami.2c14044 Link |
Correlations between structure, microstructure and ionic conductivity in (Gd,Sm)-doped ceria†
ID=693| Authors |
|
| Source |
Physical Chemistry Chemical Physics
Volume: 24,
Issue: Cristina Artini, Massimo Viviani, Sabrina Presto, Sara Massardo, Maria Maddalena Carnasciali, Lara Gigli and Marcella Pani ,
Pages: 23622-23633 Time of Publication: 2022 |
| Remark |
https://doi.org/10.1039/D2CP03255D Link |
High-temperature electrical conductivity and electrochemical activity in oxygen redox reaction of La-doped Sr2FeCo0.5Mo0.5O6-δ
ID=692| Authors |
|
| Source |
Journal of Solid State Electrochemistry volume
Volume: 26,
Pages: 2771–2779 Time of Publication: 2022 |
| Abstract | High-temperature electrical conductivity and electrochemical activity in the oxygen redox reaction of Sr2FeCo0.5Mo0.5O6-δ (SFCM) and Sr1.6La0.4FeCo0.5Mo0.5O6-δ (LSFCM) at variable oxygen partial pressure have been studied. We have found that the partial replacement of Sr2+ by La3+ results in a substantial decrease in the total electrical conductivity due to a decrease in the hole charge carrier concentration. Detailed analysis of the high- and low-frequency parts of the impedance spectra at pO2 = 0.1–1 atm and 873–1173 K has revealed different rate-limiting steps in the oxygen redox reaction for SFCM and LSFCM resulted from different oxygen vacancy concentrations in these materials. For SFCM, the oxygen redox reaction is limited by the processes of adsorption and dissociation of oxygen molecules, while for LSFCM by the charge transfer occurring at the triple phase boundary. |
| Remark | Link |
Effects of LiNi0.8Co0.15Al0.05O2 electrodes on the conduction mechanism of Sm0.2Ce0.8O2−δ electrolyte and performance of low-temperature solid oxide fuel cells
ID=691| Authors |
|
| Source |
Journal of Power Sources
Volume: 546,
Pages: 231995 Time of Publication: 2022 |
| Abstract | In this study, three low-temperature solid oxide fuel cells are constructed using Ce0.8Sm0.2O2−δ (SDC) as the electrolyte and Ni–LiNi0.8Co0.15Al0.05O2 (Ni–NCAL) and Ni–Ag as the electrodes. Cell A with symmetrical Ni–NCAL electrodes exhibits the best electrochemical performance. During operation, the Ni–NCAL anode is reduced by H2 atmosphere to form LiOH and Li2CO3. The Li2CO3–LiOH melt produced at >450 °C permeates the SDC electrolyte layer, causing its densification and grain growth in addition to the Li+-ion doping of SDC grains. The maximum electrical conductivity of the Li+-ion-doped SDC at 550 °C is at least one order of magnitude smaller than that of the SDC–Li2CO3–LiOH composite electrolyte (0.331 S cm−1). The ohmic and polarization resistances of Cell A at 550 °C are 0.168 and 0.256 Ω cm2, respectively, and its open-circuit voltage is 1.065 V, indicating the presence of dense SDC electrolyte and electron-blocking layers. The maximum power density of the cell at 550 °C is 535.2 mW·cm−2, which is primarily due to the high catalytic activity for the hydrogen oxidation and oxygen reduction reactions at the electrodes and large electrical conductivity of the SDC–Li2CO3–LiOH composite electrolyte at low temperatures. |
| Remark |
https://doi.org/10.1016/j.jpowsour.2022.231995 Link |
Efficiencies of cobalt- and copper-based coatings applied by different deposition processes for applications in intermediate-temperature solid oxide fuel cells
ID=690| Authors |
|
| Source |
International Journal of Hydrogen Energy
Volume: 47,
Issue: 76,
Pages: 32628-32640 Time of Publication: 2022 |
| Abstract | Solid Oxide Fuel Cells (SOFCs) are electrochemical conversion devices that produce electricity directly by oxidising a fuel. The interconnects between the individual cells need to be coated to limit Cr(VI) evaporation from the steel and to preserve electrical conductivity. Physical Vapour Deposition (PVD)-coated samples with Ce/Co, Ce/Cu, and Ce/MnCu, and Thermal Spray (TS)-coated Mn/Co, Cu and Mn/Cu and AISI 441 steel samples were exposed at 650 °C for up to 1000 h. The PVD Ce/Co and Ce/Cu coatings, as well as the TS Mn/Co coating, exhibited the formation of a thin protective Cr2O3 scales underneath the coating. These samples also exhibited the lowest area-specific resistance (ASR) values. The remainder of the samples exhibited much higher mass gains and higher ASR values. Cr(VI) evaporation measurements showed that all the coatings behaved approximately the same despite the PVD coatings being only about one-tenth of the thickness of the TS coatings. |
| Remark |
https://doi.org/10.1016/j.ijhydene.2022.07.168 Link |
Synthesis of a Novel Nanoparticle BaCoO2.6 through Sol-Gel Method and Elucidation of Its Structure and Electrical Properties
ID=689| Authors |
|
| Source |
Journal of Nanomaterials
Time of Publication: 2022
|
| Abstract | The physical properties of cobalt oxide with varied oxidation states, and coordination numbers, in the transition series, have numerous applications. The present study explores the physical properties of BaCoO2.6 nanoparticles synthesized through the sol-gel method. The X-ray diffraction figure exhibits a 25 nm crystallite size hexagonal phase. The observational data shows the reduction in the real part of impedance (), dielectric constant (), dielectric loss (), and a raise in ac conductivity of mixed type of conduction with an elevation in frequency analyzed through impedance spectroscopy. The conductivity due to grain and grain boundaries is shown foremost in the complex impedance analysis. The plot of (Seebeck coefficient) in the low-temperature range indicates p-type behavior and the metal-insulator transition in the as-synthesized sample. The sample characteristics suggest applications in optical and switching devices. The Seebeck coefficient is the generation of potential difference when subjected to temperature difference. Thermoelectric materials are associated with the concept of high electrical conductivity like crystals and low thermal conductivity to that of glass. Nanothermoelectric materials can decrease further the thermal conductivity through phonon scattering. Electrical characterization suggests the presence of both NTCR and PTCR behavior in the sample, and hence, it explores the application in thermistor/resistance temperature detector’s (RTD) and low dielectric constant and loss to electro-optical and higher conversion efficiency to storage devices. Additionally, impedance spectroscopy helps in the study of electrochemical systems and solid-state devices wherein the transition of metal-insulator is an add-on to the research. |
| Remark |
https://doi.org/10.1155/2022/3877879 Link |
Conduction mechanism of donor and acceptor doped sodium niobate-based ceramics
ID=688| Authors |
|
| Source |
Ceramics International
Volume: 48,
Issue: 21,
Pages: 32073-32080 Time of Publication: 2022 |
| Abstract | Recently, NaNbO3 (NN) has become a hot topic of current research due to its antiferroelectric energy storage properties, which demand that the ceramics withstand large applied electric fields. The breakdown strength is dependent on conduction properties, but there is limited research on the conduction mechanisms of NN. Here we report that A-site donor-doping of Bi3+ (BixNa1-3xNbO3) and B-site acceptor-doping of Mg2+ (NaNb1-2/5yMgyO3) in NN lead to dramatic changes in the magnitude of the bulk conductivity (σb) and the conduction mechanism of NN ceramics. Undoped NN exhibits mixed conduction behavior with an oxide ion transport number (tion) of ∼0.44, and σb of ∼10−6 S/cm at 600 °C. A low level of Bi3+ doping (x = 0.06) suppresses the NN mixed conduction mechanism to electron conduction (tion ∼ 0), and the bulk conductivity increases significantly, σb > 10−4 S/cm at 600 °C. On the other hand, Mg2+ doping (y = 0.06) samples mainly change the σb, with the mixed ion/hole conduction (tion ∼ 0.43) and σb > 10−4 S/cm at 700 °C. The results show that the conductivity of NN increases and exhibits different conduction mechanisms with the doping of Bi3+ and Mg2+. Aliovalent doping is not beneficial to improving the insulation properties. Thus, this work provides theoretical guidance for the study of energy storage characteristics and the suppression of leakage behavior of high-temperature dielectric capacitors. |
| Keywords | NaNbO3; Conduction mechanisms; Chemical doping; Defect |
| Remark |
https://doi.org/10.1016/j.ceramint.2022.07.146 Link |
Effect of high pressure-high temperature treatment on the microstructure and dielectric properties of cobalt doped СaСu3Тi4ž12
ID=687| Authors |
|
| Source |
Journal of Physics and Chemistry of Solids
Volume: 169,
Pages: Journal of Physics and Chemistry of Solids Time of Publication: 2022 |
| Abstract | The results of studying the effect of high pressures and high temperatures (8 GPa, 1273 K) used in the process of thermobaric treatment of CaCu3-xCoxTi4O12 ceramics (x = 0; 0.4; 0.6), initially prepared by solid-phase synthesis, on the structure and electrical characteristics are presented. The dielectric parameters were evaluated in a temperature interval (293–1000) K in a frequency range 1 Hz–32 MHz. It was established that the value of dielectric permittivity ε of samples upon thermobaric treatment is an order of magnitude higher than ε of samples prepared by solid-phase synthesis. The main reasons for the high values of dielectric permittivity are both the intragrain effects related, among other things, to hopping mechanism of polaron motion, and the polarization effects provided by the presence microstructure inhomogeneities. The latter are nonconducting boundaries of conducting grains and, in some examined materials, microscopic-scale surfaces of inhomogeneities, which appeared due to deformation during thermobaric treatment. At high temperatures, oxygen vacancies make the main contribution to the observed values of dielectric permittivity. |
| Keywords | Oxide ceramics; Synthesis; High pressure-high temperature; Microstructure; Dielectric properties |
| Remark |
https://doi.org/10.1016/j.jpcs.2022.110870 Link |
Characterization of Y and Mn co-substituted BaZrO3 ceramics: Material properties as a function of the substituent concentration
ID=686| Authors |
|
| Source |
Solid State Ionics
Volume: 382,
Pages: Mariya E. Ivanova Time of Publication: 2022 |
| Abstract | Innovations in materials science are the key element for solving technological challenges. Various energy and environmental applications require designing materials with tailored compositions, microstructures and specific target-oriented performance. Y and Mn co-substituted BaZrO3, e.g. BaZr0.85Y0.15Mn0.05O3-δ, has previously attracted attention as a membrane material for H2 separation from gas mixtures due to its mixed proton-electron conductivity leading to appreciable levels of H2-flux at elevated temperatures and its good thermo-chemical stability under reducing environments. In the present work, we developed ceramic materials within the BaZr0.8Y0.2-xMnxO3-δ series, where x = 0.02–0.15. The study of their functional properties in dependence of the Y-to-Mn ratio disclosed that thermal expansion and hydration decrease by increasing the Mn content as well as the total electrical conductivity. In addition to that, XPS analysis and near edge X-ray absorption fine structure spectra (NEXAFS) in the vicinity of O K-edge and Mn L2,3-edges indicated that the Mn atoms oxidation state in the surface and in the bulk range from Mn2+ to Mn4+ depending on the ambient conditions that can be encountered in MPEC electrodes, which it is suggested to be related with a hydration mechanism mediated by Mn oxidation and subsequent proton attachment to oxygen neighbors, similar to LSM. |
| Remark |
https://doi.org/10.1016/j.ssi.2022.115959 Link |
Effect of Mn doping on the structural, spectral, electrical, ferromagnetic and piezoelectric properties of 0.7BFO-0.3BTO lead-free ceramics
ID=685| Authors |
|
| Source |
Journal of Alloys and Compaunds
Volume: 917,
Pages: 165303 Time of Publication: 2022 |
| Abstract | Lead-free 0.7BiFeO3-0.3BaTi1−xMnxO3 ceramics, where x ranges from 1% -- 10%, were prepared by conventional solid state reaction method. Effect of addition of MnO2 on the structural, spectral, electrical, magnetic and piezoelectric properties of 0.7BiFeO3-0.3BaTiO3 material were studied systematically. The previous studies have emphasized on the doping in BiFeO3 rather than doping in BaTiO3 in BiFeO3-BaTiO3 system. Our work focuses on the influence of Mn doping in BaTiO3 in the BiFeO3-BaTiO3 system. All the ceramics were calcined at the optimum temperature of 800 °C to minimize the impurity phases to a great extent. The synthesized ceramics have a co-existence of R and T phases with a space group of R3c and P4mm respectively with a small amount of Bi25FeO40 impurity. The sample for x = 0.01 has R as the host phase rather than T phase, but as the concentration of Mn increases to 0.10, the R phase and T phase start forming a more stable solid solution. Additionally, the doping effect of Mn on grain and grain boundary was studied at 300 °C and illustrated by their equivalent circuits with the help of ZView 2 software. The grain resistance decreased significantly for the sample with x = 0.10. Hence, the addition of MnO2 significantly enhanced the electrical and piezoelectric properties of the 0.7BiFeO3-0.3BaTiO3 material. The improved electrical properties at high temperature and low frequencies εr =1.8 × 109, σ = 4.1 × 10−3 S cm−1 and piezoelectric property d33 = 128 pC/N was obtained for x = 0.10. |
| Remark |
https://doi.org/10.1016/j.jallcom.2022.165303 Link |
From quaternary to senary high entropy antimonide nanoparticles by a facile and scalable thermal treatment method
ID=684| Authors |
|
| Source |
Materials Research Bulletin
Volume: 153,
Pages: 111873 Time of Publication: 2022 |
| Abstract | Transition metal antimonides form a class of intermetallic compounds, which has drawn considerable attention due to their potential applications in various fields. However, the formation of nanostructures containing multiple transition metal elements has been a challenge. Here, a new class of multicomponent antimonide nanoparticles with chemical composition ranging from quaternary to senary were synthesized via a simple, reproducible, and scalable thermal treatment method. This method allows uniform elemental distributions in a single nanoparticle, demonstrating the ability to obtain medium- and high-entropy antimonide nanostructures. The mechanism of formation was proposed and the characteristics of obtained nanoparticles were investigated by X-ray diffraction, field emission scanning electron microscopy, and high-resolution transmission electron microscopy. Under the achieved optimal synthesis conditions, the formation of a single-phase with a hexagonal structure (P63/mmc) was observed for the quaternary and quinary samples, whereas in the case of the senary samples, a trace of minor impurity can be observed. |
| Keywords | Intermetallic compounds; Nanostructures; Electron microscopy; X-ray diffraction; Crystal structure |
| Remark |
https://doi.org/10.1016/j.materresbull.2022.111873 Link |
Performance of membranes based on novel Ce0.8Sm0.2O2-δ /Ag cermet and molten carbonates for CO2 and O2 separation
ID=683| Authors |
|
| Source |
Chemical Engineering Science
Volume: 255,
Pages: 117673 Time of Publication: 2022 |
| Abstract | This work proposes a cermet infiltrated with a mixture of Li2CO3/Na2CO3/K2CO3 as a dense membrane to selectively separate CO2 and O2 at high temperatures. The cermet consisted of a mixture of the Ce0.8Sm0.2O2-δ (SDC) ceramic and silver as the metallic phase. This type of membrane is a novel design of the ceramic/carbonates type and represents an improvement of state-of-art designs by avoiding microstructural changes in the metallic phase and improving chemical inertness and wettability with the carbonate phase. First, an SDC nanostructured powder was chemically synthesized by direct combustion of urea: lanthanide nitrates-based deep eutectic solvent; then, SDC and silver powders were mixed in a 50:50 vol% ratio by using high energy ball milling. The mixture was uniaxially pressed and sintered to form a support. This cermet exhibited excellent wettability properties against the ternary molten carbonate phase; therefore, it readily allowed infiltration of the molten salts to form a dense membrane. Hence, the cermet showed excellent electronic conductivity as well as corrosion resistance in contact with carbonates for 200 h of continuous immersion. The cermet-carbonate membrane showed permselectivity by separating CO2 and O2 at high temperatures. It reaches simultaneous permeation values of 0.49 and 0.26 ml·min−1·cm−2, for CO2 and O2, respectively, at 850 °C. Finally, continuous permeation tests at 825 °C for 85 h proved the excellent chemical stability of the cermet-carbonate membrane. Any chemical reactivity was not observed between the cermet and the carbonates. |
| Keywords | Cermet; Molten carbonate membrane; CO2 separation; O2 separation |
| Remark |
https://doi.org/10.1016/j.ces.2022.117673 Link |
La1-xSrxMO3 (M = Co, Mn, Cr) interconnects in a 4-leg all-oxide thermoelectric generator at high temperatures
ID=682| Authors |
|
| Source |
Journal of Physics and Chemistry of Solids
Volume: 167,
Pages: 110739 Time of Publication: 2022 |
| Abstract | We herein report tests at high temperatures of a 4-leg oxide thermoelectric generator consisting of two pairs of p-type Ni0.98Li0.02O (Li–NiO) and n-type Zn0.98Al0.02O (Al–ZnO), assembled with various conducting perovskite oxides as interconnects. Using a custom-built testing system, we evaluated performance and stability at a hot side (furnace) temperature of up to 1000 °C under temperature differences up to ΔT = 600 °C in air. With a La0.6Sr0.4CoO3 (LSC) interconnect, a maximum power output of 18 mW was achieved with TH = 940 and TC = 340 °C (ΔT = 600 °C). Power maxima with La0.8Sr0.2MnO3 (LSM) and La0.8Sr0.2CrO3 (LSCr) as interconnects were lower, 6 mW and 2 mW, respectively, under similar conditions, attributed to their lower thermal and electrical conductivities. This demonstrates the requirements and potential of oxide interconnects for stable use of all-oxide thermoelectric generators at high temperatures in ambient air. |
| Keywords | Thermoelectric generator; Oxide; Interconnect; NiO; ZnO; La0.6Sr0.4CoO3 (LSC) |
| Remark |
https://doi.org/10.1016/j.jpcs.2022.110739 Link |
The effect of alkaline earth metal substitution on thermoelectric properties of A0.98La0.02MnO3-δ (A = Ca, Ba)
ID=681| Authors |
|
| Source |
Processing and Application of Ceramics
Volume: 16,
Issue: 1,
Pages: 78–82 Time of Publication: 2022 |
| Abstract | The thermoelectric properties of ceramics with composition A0.98La0.02MnO3-δ are anticipated to vary with the basicity and atomic portion of the alkaline earth metal, A. In the present investigation ceramic powder precursors with composition A0.98La0.02MnO3-δ (A = Ca, Ba) were synthesized by the solid-state method and sintered in air at 1400 °C. Seebeck coefficient, electrical and thermal conductivities were characterized for both materials from 100 to 900 °C in air. The highest zT of 0.10 at 900 °C was reached for Ca0.98La0.02MnO3-δ. The high zT is attributed to the enhanced electronic conductivity (∼90 S/cm at 900 °C) due to La doping. zT for Ba0.98La0.02MnO3-δ reached its highest value (0.02) at 800 °C corresponding to a low electronic conductivity (∼2 S/cm), while the thermal conductivity was significantly reduced compared to Ca0.98La0.02MnO3-δ reaching ∼1 W/(m·K) combined with a high Seebeck coefficient, −290 μV/K. The present data represent a valuable basis for further development of these materials with respect to applications in thermoelectric devices. |
| Remark |
https://doi.org/10.2298/PAC2201078S Link |
Boundary Investigation of High-Temperature Co-Electrolysis Towards Direct CO2 Electrolysis
ID=680| Authors |
|
| Source |
Journal of The Electrochemical Society
Volume: 169,
Pages: 034531 Time of Publication: 2022 |
| Abstract | In the temperature range of high temperature co-electrolysis of both steam and carbon dioxide, the reverse water-gas shift reaction (RWGS) takes place. Prior studies were conducted with a narrow gas composition range to investigate the role of RWGS during co-electrolysis. The results for steam electrolysis, CO 2 electrolysis, and co-electrolysis caused different conclusions regarding the role of electrochemical CO2 and H 2 O conversion compared to RWGS during co-electrolysis. This work aims to resolve the role of CO2 conversion as part of RWGS in co-electrolysis. The boundary is characterized by AC and DC measurements over a broad gas composition range from CO 2 electrolysis towards co-electrolysis with nearly 50%eq H 2 O. Especially, the electrochemical CO2 reduction and CO2 conversion in the RWGS are compared to clarify their role during co-electrolysis. The results revealed that gas composition determined the predominant reaction (H 2 O or CO2 reduction). The cell performance of co-electrolysis in the boundary region up to 5% eq H2 O was similar to the performance of CO2 electrolysis. Up to 30%eq H 2 O, the performance increases with H 2 O concentration. Here, both CO2 and H 2 O electrolysis occur. Above 30% eq H 2 O, steam electrolysis and the RWGS reaction both dominate the co-electrolysis process. |
| Remark | Link |
Site occupancy, luminescence and dielectric properties of β-Ca3(PO4)2-type Ca8ZnLn(PO4)7 host materials
ID=679| Authors |
|
| Source |
Journal of Alloys and Compounds
Volume: 908,
Pages: 164521 Time of Publication: 2022 |
| Abstract | Phosphates of Ca8ZnLn(PO4)7 (Ln3+ = La – Nd, Sm – Lu) with β-Ca3(PO4)2-type structure were prepared by high-temperature solid-state technique on air. All compounds of Ca8ZnLn(PO4)7 are centrosymmetric and have Rc space group, which has been proved by several methods such as second-harmonic generation, dielectric spectroscopy, and Rietveld analysis. The influence of Ln3+ on the structure, luminescent properties and temperature of phase transitions, which corresponds with “tetrad” effect, has been investigated. The bandgap width and location of 4f Ln3+ and Ln2+ levels relatively to the energy bands were determined using the data of luminescent spectroscopy. |
| Remark |
https://doi.org/10.1016/j.jallcom.2022.164521 Link |
Tuning of the microstructural and electrical properties of undoped BaTiO3 by spark plasma sintering
ID=678| Authors |
|
| Source |
Open Ceramics
Volume: 9,
Pages: 100244 Time of Publication: 2022 |
| Abstract | The distribution of oxygen vacancies in BaTiO3 specimens can greatly affect material electrical properties. Spark plasma sintering followed by annealing in controlled pO2 atmospheres offers the potential to control the oxygen vacancy distribution. Impedance spectroscopy has been used to study the electrical characteristics of undoped BaTiO3 specimens prepared at 1200 °C under a pressing pressure of 5 MPa and 50 MPa using spark plasma sintering (SPS). For both samples, at temperatures greater than 750 °C, the total conductivity is determined by the bulk conductivity (σb), while at temperatures between 550 °C–750 °C the total conductivity is determined by the grain boundary conductivity (σgb). Below 550 °C, the total conductivity is determined by the BaTiO3–Pt interface conductivity (σel). The bulk, grain boundary and electrode interface resistances and activation energies are lower for samples sintered and pressed at 50 MPa, compared to specimens sintered and pressed at 5 MPa. Plots of grain boundary conductivity (σgb) vs. oxygen partial pressure (pO2) (log(σgb) vs. log(pO2)), over the temperature range 517 °C–683 °C, have slopes of approximately 4.0 indicating that doubly charged oxygen vacancies () are located at the grain boundaries. The grain boundary region and BaTiO3–Pt interface conductivities are highly sensitive to the oxygen partial pressure. Therefore, SPS sintered BaTiO3 specimens that have been subjected to controlled annealing could be used to tailor BaTiO3 dielectric properties, as well as have potential applications in high temperature O2 sensing. Furthermore, analysis of a.c. conductivity using the Jonscher model reveals that the governing charge transport mechanism is via quantum mechanical tunneling (QMT), which operates at temperatures when grain boundaries control the total conductivity. The mechanism switches to the correlated barrier hopping (CBH) model at temperatures when the bulk controls the total conductivity. |
| Remark |
https://doi.org/10.1016/j.oceram.2022.100244 Link |
Mesophase Transitions in [(C2H5)4N][FeBrCl3] and [(CH3)4N][FeBrCl3] Ferroic Plastic Crystals
ID=677| Authors |
|
| Source |
Chem. Mater.
Volume: 34,
Issue: 6,
Pages: 2585–2598 Time of Publication: 2022 |
| Abstract | Plastic crystals are supramolecular materials that possess a unique high entropy mesophase at elevated temperatures, where a long-range structural symmetry coexists with a local molecular orientational disorder. The transition to mesophase can involve a large entropy change useful for thermal energy storage and influences the temperature range of ferroelectric and piezoelectric properties, important for sensor applications. Synchrotron X-ray diffraction and pair distribution function analysis were used to study the structure, while calorimetry, dielectric, leakage current measurements, and density functional theory were used to investigate the influence of the organic cation on the structure and properties of tetraethylammonium bromotrichloroferrate(III) [(C2H5)4N][FeBrCl3] and tetramethylammonium bromotrichloroferrate [(CH3)4N][FeBrCl3]. The [(C2H5)4N][FeBrCl3] mesophase transition had an entropy change of 151.5 J·K–1·kg–1, while [(CH3)4N][FeBrCl3] had only 49 J·K–1·kg–1. This was explained by the [(C2H5)4N][FeBrCl3] mesophase having less long-range structural symmetry and more local orientational disorder, of both the cations and anions, compared to [(CH3)4N][FeBrCl3]. Both materials exhibited at least two conductive mechanisms below the transition, vacancy-mediated ionic and electronic conduction. The introduction of anion orientational freedom, as opposed to cation orientational freedom, at the mesophase transition was most influential for the electrical properties. Introduction ARTICLE SECTIONS |
| Remark |
https://doi.org/10.1021/acs.chemmater.1c03778 Link |
Contact angle screening and asymmetric dual-phase CO2 separation membranes
ID=676| Authors |
|
| Source |
Journal of Membrane Science
Volume: 652,
Pages: 120447 Time of Publication: 2022 |
| Abstract | Dual-phase CO2 separation membrane consisting of molten carbonates confined in a solid matrix can separate CO2 at high temperatures. The contact angle of molten carbonates to different oxides that can potentially serve as membrane supports was screened between 450 and 650 °C. These oxides have different electrical transport properties, including oxide ion, mixed, and electronic conducting. The contact angles vary between 80° and 10° for different materials. Asymmetric membranes were fabricated using wettable oxide ion conductors BTM and CGO (Bi0.8Tm0.2O1.5 and Ce0.8Gd0.2O2-δ) infiltrated with molten carbonates supported by the most "non-wetting" oxide BPR (Bi0.8Pr0.2O1.5) selected in the contact angle screening. The membranes show CO2 flux in the range of 0.035–0.35 ml/min cm2 at temperatures from 500 to 650 °C. Compared to a symmetric membrane with similar total membrane thickness, the asymmetric architecture significantly reduces the effective membrane thickness and increases CO2 flux. After the CO2 flux measurements, the membrane was examined with SEM and EDS mapping, showing that the molten carbonates were mainly confined within the top membrane and sealing area without penetrating the support layer. |
| Remark |
https://doi.org/10.1016/j.memsci.2022.120447 Link |
NaMn0.2Fe0.2Co0.2Ni0.2Ti0.2O2 high-entropy layered oxide – experimental and theoretical evidence of high electrochemical performance in sodium batteries
ID=675| Authors |
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| Source |
Energy Storage Materials
Volume: 47,
Pages: 500-514 Time of Publication: 2022 |
| Abstract | Li-ion batteries, widely used in portable electronics, electric vehicles, and energy storage systems, are an integral element of our daily life. However, the limitation of lithium sources, which leads to high prices, prompts the search for alternatives. Recently there has been noticed a rapid interest in Na-ion batteries technology. Especially, suitable cathode structures are investigated to accumulate larger sodium ions. In this paper, the high entropy layered oxide NaMn0.2Fe0.2Co0.2Ni0.2Ti0.2O2 is presented which achieves superior electrochemical properties with a stable capacity of ca. 180 mAh g−1. The understanding of its high performance is based on a complex study of the multiphase intercalation mechanism. The combination of advanced structural analysis by XAS, in situ XRD, TEM, and computational DFT modelling gives a new concept on the nature of O3-P3 structure reorganization. The presented experimental and theoretical evidence indicates that the P3 phase of layered oxides is energetically favourable for a lower sodium content for specific transition metal-oxide pair distance. Fundamental understanding of the nature of phase transformation is crucial for tailoring structural composition, where the desirable O3-P3 reorganization will occur, resulting in achieving high-performance cathodes. |
| Remark |
https://doi.org/10.1016/j.ensm.2022.02.038 Link |
Investigation of magnetic properties and converse magnetoelectric effect in the composite of doped barium hexaferrite with potassium niobate, 0.5BaFe10Sc2O19-0.5KNbO3 and 0.5BaFe10In2O19-0.5KNbO3
ID=674| Authors |
|
| Source |
Physica B: Condenced Matte
Volume: 663,
Pages: 413736 Time of Publication: 2022 |
| Abstract | This study investigates the magnetic and electric properties of the 0.5BaFe10Sc2O19-0.5KNbO3 (0.5BFSc2O-0.5KNO) and 0.5BaFe10In2O19-0.5KNbO3 (0.5BFIn2O-0.5KNO) composite samples. Refined X-ray diffraction (XRD) studies substantiate the presence of both ferrimagnetic (BFSc2O and BFIn2O) and ferroelectric KNbO3 phase with the ratio (0.5:0.5) in both the compounds without any impure phase. By electric poling the samples with an electric field of 2.5 kV/cm, magnetization shows a different behaviour (decreasing in Sc and increasing in doped composite), can be attributed to the electric field induced changes of spin states due to stress induced at the interface of ferrimagnetic (FM)/ferroelectric (FE) regions. Strong converse magnetoelectric coupling (CME) was observed in both the compounds, with a large electric field modulation in magnetism (80%) in the 0.5BFInO-0.5KNO composite. Dielectric studies reveal the presence of ferroelectric (FE-Tc) transition around the magnetic Curie temperature (FM-Tc) of respective composites, further indicates the presence of converse magnetoelectric coupling in both systems. |
| Remark |
https://doi.org/10.1016/j.physb.2022.413736 Link |
Tailored and Improved Protonic Conductivity through Ba(ZxCe10−x)0.08Y0.2O3−δ Ceramics Perovskites Type Oxides for Electrochemical Devices
ID=673| Authors |
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| Source |
ChemElectroChem
Time of Publication: 2022
|
| Abstract | Acceptor-doped barium zirconate cerate electrolytes constitute prospective materials for highly efficient and environmentally friendly electrochemical devices. This manuscript employs a systematic approach to further optimize ionic conductivity in Ba(ZrxCe10−x)0.08Y0.2O3−δ, (1≤x≤9) oxides for moderate temperature electrolysis. We found two new composition variants by fixing a cerium/zirconium ratio of 5/4 at the perovskite B-site with incremental zirconium, an observation that contrasts many reports suggesting a linear decrease in conductivity with increasing zirconium. As a result, the composition BaZr0.44Ce0.36Y0.2O3−δ demonstrates a superior ionic conductivity (10.1 mS cm−1 at 500 °C) to stability trade-off whereas, BaZr0.16Ce0.64Y0.2O3−δ exhibits the highest conductivity (11.5 mS cm−1 at 500 °C) among the studied pellets. The high protonic conductivity is associated with a high degree of hydration, as confirmed by thermo-gravimetric analysis. In addition, both compositions as electrolytes allow successful hydrogen production in a steam electrolyzer prototype. Electrolysis voltage as low as 1.3 V is attainable at current densities of 600 and 500 mA/cm2 respectively at 600 °C, achieving 82 % current efficiencies with the later electrolyte. |
| Keywords | https://chemistry-europe.onlinelibrary.wiley.com/doi/full/10.1002/celc.202101663 |
| Remark |
https://doi.org/10.1002/celc.202101663 Link |
On the mechanism of Mn(II)-doping in Scandia stabilized zirconia electrolytes
ID=672| Authors |
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| Source |
Acta Materialia
Volume: 227,
Pages: 117695 Time of Publication: 2022 |
| Abstract | Cubic Scandia-stabilized zirconia (ScSZ) is an attractive electrolyte material for solid oxide cells due to its significant ionic conductivity, provided that the phase transition to its rhombohedral polymorph upon cooling is suppressed. The latter is achieved with addition of a secondary co-dopant, albeit it may be at the detriment of its ionic conductivity Here, we thoroughly investigate how MnO2 (0.5–10 mol%) as a co-dopant impacts on the sinterability, thermal expansion, crystal structure and ionic conductivity of ZrO2 doped with 10 mol% Scandia (10ScSZ), and we provide new insight on the chemistry of dissolved manganese in the fluorite lattice. Reactive sintering of 2 mol% MnO2 mixed with 10ScSZ enables to produce dense electrolyte with significant reduction of the peak sintering temperature and stabilisation of the cubic structure down to room temperature. Combined density functional theory and X-ray photoelectron spectroscopy analyses reveal that manganese predominantly enters the structure as Mn2+ during reactive sintering, with a prevalence of higher valence states at the surface and grain boundaries. The highest oxide ion conductivity is achieved for 2 mol% doped 10ScSZ (120 mScm−1 at 800 °C) and it decreases with increasing Mn concentration. For all compositions, the bulk conductivity remains independent of pO2 – corroborating a limited electronic conductivity contribution from Mn-doping. The grain boundary conductivity is found to decrease with sintering time and pO2, which is attributed to the chemistry and concentration of segregated manganese at the surface and grain boundaries, yielding depletion of oxygen vacancies in the space charge layer. |
| Keywords | Electrical conductivity; SOFC; Reactive sintering; ScSZ; Stability |
| Remark |
https://doi.org/10.1016/j.actamat.2022.117695 Link |
Detailed characterization of oxide-ion and proton transport numbers in Sr–Ti layered perovskites using an improved electromotive force method
ID=670| Authors |
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| Source |
Journal of Materials Research
Time of Publication: 2022
|
| Abstract | Numerous Sr–Ti-based layered perovskite-structured compounds exhibit protonic conductivity. In a previous study, we found that a new Sr2Ti0.95Al0.05O4−δ (STA05) layered perovskite also shows evidence of protonic conductivity. However, Sr–Ti-based layered perovskites are also potential oxide-ion conductors. Detailed transport numbers for both protons and oxide-ions in Sr–Ti-based layered perovskites remain unclear. To solve this problem, we here propose an improved approach based on electromotive force (emf) measurements to account for the contributions of thermal emf and polarization to the total conductivity. In the first step of this study, the conditions for investigating actual emfs were evaluated using measurements of yttria-stabilized zirconia as a typical oxide-ion conductor. The optimized emf technique was subsequently used to evaluate the transport numbers of STA05, which was found to exhibit no oxide-ion transport. Thus, STA05 is concluded to be a mixed proton and electron conductor.. |
| Remark | Link |
Impedance spectroscopy study of Au electrodes on Gd-doped CeO2 (GDC) – Molten Li2CO3+Na2CO3 (LNC) composite electrolytes
ID=669| Authors |
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| Source |
Journal of Power Sources
Volume: 522,
Pages: 230986 Time of Publication: 2022 |
| Abstract | We herein report an impedance spectroscopy study of Au electrodes on Gd-doped CeO2 (GDC) – molten Li2CO3+Na2CO3 (LNC) composite electrolytes in O2 and O2+CO2 atmospheres. Complementary measurements of Au on GDC alone are provided for supporting insight. We find that the adsorption of CO2 on GDC in O2+CO2 atmospheres effectively blocks oxygen adsorption and severely slows oxygen reduction kinetics. The conductivity of the composite is dominated by the GDC phase in the solid-solid temperature region, while the LNC phase dominates above its melting point, and no further enhancement e.g. by interfacial effects are found. The incorporation of LNC melt into GDC results in a significant reduction in the polarisation resistance of Au electrodes in O2 atmospheres, as the melt mediates the reaction by a peroxide mechanism. In O2+CO2 atmospheres, however, the polarisation resistance of Au electrodes on GDC-LNC membranes is significantly higher, higher even than that on GDC. This we assign again to the blocking adsorption of CO2 (or carbonate) on the surfaces of ceria and the sluggish transport and reactions now mediated by carbonate-carried oxide species (CO42−) instead of peroxide species. |
| Keywords | Molten carbonate fuel cells; MCFC; CeO2; Gd-doped; GDC; GDC-Molten carbonate composite electrolyte; Oxygen electrode; Mechanism |
| Remark | Link |
Lanthanum strontium cobaltite as interconnect in oxide thermoelectric generators
ID=668| Authors |
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| Source |
Solid State Sciences
Volume: 124,
Pages: 106801 Time of Publication: 2022 |
| Abstract | Issues related to use of metallic interconnects in oxide thermoelectric generators (TEGs) need to be addressed to secure performance and durability. Metal interconnects suffer from high cost of noble metals or chemical instability and contact resistance of non-noble metals, arising from oxidation, evaporation, and delamination in the oxidising conditions of ambient air at high operating temperatures. This work introduces the use of a stable and highly conducting ceramic oxide, in our case p-type lanthanum strontium cobaltite (La0.6Sr0.4CoO3, LSC) as interconnect. We verified the thermochemical stability of LSC in contact with p-type Ni0.98Li0.02O (Li–NiO) and n-type Zn0.98Al0.02O (Al–ZnO) and examined the electrical characteristics. An area specific contact resistance (ASRc) of ∼1800 Ω cm2 for a direct p-n junction was reduced to ∼400 mΩ cm2 for a p-LSC-n junction at a temperature of 300 °C, validating the concept. The use of a screen-printed LSC/Al–ZnO composite as a thin interconnect layer was found to decrease the contact resistance of the junction further to ∼260 mΩ cm2 at 300 °C, attributed to increased effective area of the LSC/Al–ZnO p-n junction. |
| Keywords | Thermoelectric generator; All-oxide; Thermoelectric materials; Oxides; Interconnect; Oxide; p-n-junction; Ohmic; LaCoO3; Sr-substituted; La0.6Sr0.4CoO3 |
| Remark | Link |
Oxide Ion and Proton Conductivity in a Family of Highly Oxygen-Deficient Perovskite Derivatives
ID=667| Authors |
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| Source |
J. Am. Chem. Soc.
Volume: 144,
Issue: 1,
Pages: 615–624 Time of Publication: 2022 |
| Abstract | Functional oxides showing high ionic conductivity have many important technological applications. We report oxide ion and proton conductivity in a family of perovskite-related compounds of the general formula A3OhTd2O7.5, where Oh is an octahedrally coordinated metal ion and Td is a tetrahedrally coordinated metal ion. The high tetrahedral content in these ABO2.5 compositions relative to that in the perovskite ABO3 or brownmillerite A2B2O5 structures leads to tetrahedra with only three of their four vertices connected in the polyhedral framework, imparting a potential low-energy mechanism for O2– migration. The low- and high-temperature average and local structures of Ba3YGa2O7 (P2/c, a = 7.94820(5) Å, b = 5.96986(4) Å, c = 18.4641(1) Å, and β = 91.2927(5) ° at 22 °C) were determined by Rietveld and neutron pair distribution function (PDF) analysis, and a phase transition to a high-temperature P1121/a structure (a = 12.0602(1) Å, b = 9.8282(2) Å, c = 8.04982(6) Å, and γ = 107.844(3)° at 1000 °C) involving the migration of O2– ions was identified. Ionic conductivities of Ba3YGa2O7.5 and compositions substituted to introduce additional oxide vacancies and interstitials are reported. Most phases show proton conductivity at lower temperatures and oxide ion conductivity at high temperatures, with Ba3YGa2O7.5 retaining proton conductivity at high temperatures. Ba2.9La0.1YGa2O7.55 and Ba3YGa1.9Ti0.1O7.55 appear to be dominant oxide ion conductors, with conductivities an order of magnitude higher than that of the parent compound. |
| Remark |
https://doi.org/10.1021/jacs.1c11966 Link |
Advanced metal oxide infiltrated electrodes for boosting the performance of solid oxide cells
ID=666| Authors |
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| Source |
J. Mater. Chem. A
Time of Publication: 2021
|
| Abstract | An efficient way for boosting the performance of solid oxide electrodes is the infiltration of metallic nanoparticles into both electrodes. In this work we will focus on improving the performance of standard lanthanum strontium manganite oxygen electrodes, by the addition of different metal oxide nanoparticles. First studies will be performed using cerium oxide nanoparticles, as this is the classic oxide already proposed in the literature. Other novel metal oxides such as praseodymium or manganese oxide will be explored, as studies in the literature for these two metal oxides are very scarce. The effect of metal oxide infiltration into LSM/YSZ oxygen electrodes will be studied in both symmetrical cells and complete microtubular cells using conventional fuel electrodes (NiO-YSZ) and electrolytes (YSZ). The obtained current densities in both fuel cell and electrolysis modes are significantly enhanced in comparison with other results in the literature for microtubular configuration. |
| Remark |
DOI: 10.1039/D1TA07902F Link |
Reaction Sintering of Ca3Co4O9 with BiCuSeO Nanosheets for High-Temperature Thermoelectric Composites
ID=665| Authors |
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| Source |
Journal of Electronic Materials volume
Volume: 51,
Pages: 532–542 Time of Publication: 2022 |
| Abstract | Ceramic composites composed of oxide materials have been synthesized by reaction sintering of Ca3Co4O9 with BiCuSeO nanosheets. In situ x-ray diffraction and thermogravimetric analyses of the compound powders were conducted to understand the phase transformations during heating up to 1173 K. Further thermogravimetric analyses investigated the thermal stability of the composites and the completion of reaction sintering. The microstructure of the formed phases after reaction sintering and the composition of the composites were investigated for varying mixtures. Depending on the amount of BiCuSeO used, the phases present and their composition differed, having a significant impact on the thermoelectric properties. The increase of the electrical conductivity at a simultaneously high Seebeck coefficient resulted in a large power factor of 5.4 μW cm−1 K−2, more than twice that of pristine Ca3Co4O9. |
| Remark | Link |
High-performance anode-supported solid oxide fuel cells with co-fired Sm0.2Ce0.8O2-δ/La0.8Sr0.2Ga0.8Mg0.2O3−δ/Sm0.2Ce0.8O2-δ sandwiched electrolyte
ID=664| Authors |
|
| Source |
International Journal of Hydrogen Energy
Volume: 47,
Issue: 8,
Pages: 5429-5438 Time of Publication: 2022 |
| Abstract | In this study, intermediate-temperature solid oxide fuel cells (IT-SOFCs) with a nine-layer structure are constructed via a simple method based on the cost-effective tape casting-screen printing-co-firing process with the structure composed of a NiO-based four-layer anode, a Sm0.2Ce0·8O2-δ(SDC)/La0·8Sr0.2Ga0.8Mg0·2O3−δ (LSGM)/SDC tri-layer electrolyte, and an La0·6Sr0·4Co0·2Fe0·8O3-δ (LSCF)-based bi-layer cathode. The resultant SDC (4.14 μm)/LSGM (1.47 μm)/SDC (4.14 μm) tri-layer electrolyte exhibits good continuity and a highly dense structure. The Ro and Rp values of the single cell are observed to be 0.15 and 0.08 Ω cm2 at 800 °C, respectively, and the MPD of the cell is 1.08 Wcm-2. The high MPD of the cell appears to be associate with the significantly lower area-specific resistance and the reasonably high OCV. Compared to those with a similar electrolyte thickness reported in prior studies, the nine-layer anode-supported IT-SOFC with a tri-layer electrolyte developed by the study demonstrates superior cell properties. |
| Remark | Link |
Synthesis, structure and ionic conductivity of nanocrystalline Ce1−xLaxO2−δ as an electrolyte for intermediate temperature solid oxide fuel cells
ID=663| Authors |
|
| Source |
Journal of Alloys and Compounds
Volume: 896,
Pages: 163012 Time of Publication: 2022 |
| Abstract | La-doped CeO2 nanoparticles of composition Ce1−xLaxO2−δ (0 ≤ x ≤ 0.1) have been studied here as prospective electrolytes for intermediate temperature solid oxide fuel cells (IT-SOFCs). They were synthesized by auto-combustion method and the powder samples were calcined at 700 °C to get ultrafine nanocrystalline particles. They were characterized by XRD, Raman, FTIR, XPS, DRS, FESEM/EDX, particle size analyzer and ac-impedance techniques. Ionic conductivity was measured from 350 − 750 °C. The Ce0.90La0.1O2−δ (0.1 LDC) and Ce0.95La0.05O2−δ (0.05 LDC) showed a maximum conductivity of 8.89 × 10−3 and 8.32 × 10−3 S cm−1 at 700 °C, respectively. The σt of 0.1 LDC = 1.01 × 10−2 S cm−1 at 750 °C. The activation energy of 0.1 LDC and 0.05 LDC was found to be 0.70 eV and 0.87 eV, respectively. These values are higher than those reported for La-doped CeO2 in literature. The SOFC performance with 0.05 LDC as electrolyte showed open circuit voltage of 0.81 V and maximum power density of 41 mW cm−2 at 650 °C using hydrogen as fuel. |
| Remark | Link |
Unlocking bulk and surface oxygen transport properties of mixed oxide-ion and electron conducting membranes with combined oxygen permeation cell and oxygen probe method
ID=662| Authors |
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| Source |
Journal of Membrane Science Volume: 644, Pages: 120082 Time of Publication: 2022 |
| Abstract | Surface exchange kinetics and bulk diffusion of oxygen are of paramount importance to the activity of oxygen electrocatalysis and performance of electrochemical devices such as fuel cell, metal-air batteries, and oxygen separation membranes. Conventional approaches to obtaining these transport properties are often limited to single property under a specific non-operation related condition. Here we use a combined oxygen permeation cell and oxygen probe methodology to simultaneously attain rates of oxygen surface exchange and bulk conductivity/chemical diffusivity of three representative mixed oxide-ion and electron conductors, namely SrCo0.9Ta0.1O3-δ (SCT), La0.6Sr0.4CoO3-δ (LSC) and La0.6Sr0.4FeO3-δ (LSF), operated under a steady-state oxygen flux. The results explicitly show that SCT exhibit the highest oxide-ion conductivity/chemical diffusivity, fastest rates of surface oxygen exchange kinetics, thus promising to be the best oxygen electrocatalyst. We have also mapped out the distribution of oxygen chemical potential gradient across the membranes and applied B-transport number concept to illustrate the rate-limiting steps in the overall oxygen permeation process. |
| Remark | Link |
Improved thermoelectric properties in ceramic composites based on Ca3Co4O9 and Na2Ca2Nb4O13
ID=661| Authors |
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| Source |
Open Ceramics
Volume: 8,
Pages: 100198 Time of Publication: 2021 |
| Abstract | The oxide materials Ca3Co4O9 and Na2Ca2Nb4O13 were combined in a new ceramic composite with promising synergistic thermoelectric properties. Both compounds show a plate-like crystal shape and similar aspect ratios but the matrix material Ca3Co4O9 with lateral sizes of less than 500 nm is about two orders of magnitude smaller. Uniaxial pressing of the mixed compound powders was used to produce porous ceramics after conventional sintering. Reactions between both compounds and their compositions were thoroughly investigated. In comparison to pure Ca3Co4O9, mixing with low amounts of Na2Ca2Nb4O13 proved to be beneficial for the overall thermoelectric properties. A maximum figure-of-merit of zT = 0.32 at 1073 K and therefore an improvement of about 19% was achieved by the ceramic composites. |
| Remark |
https://doi.org/10.1016/j.oceram.2021.100198 Link |
Glass-ceramic composites as insulation material for thermoelectric oxide multilayer generators
ID=660| Authors |
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| Source |
Time of Publication: 2021
|
| Abstract | Thermoelectric generators can be used as energy harvesters for sensor applications. Adapting the ceramic multilayer technology, their production can be highly automated. In such multilayer thermoelectric generators, the electrical insulation material, which separates the thermoelectric legs, is crucial for the performance of the device. The insulation material should be adapted to the thermoelectric regarding its averaged coefficient of thermal expansion α and its sintering temperature while maintaining a high resistivity. In this study, starting from theoretical calculations, a glass-ceramic composite material adapted for multilayer generators from calcium manganate and calcium cobaltite is developed. The material is optimized towards an α of 11 × 10−6 K−1 (20–500°C), a sintering temperature of 900°C, and a high resistivity up to 800°C. Calculated and measured α are in good agreement. The chosen glass-ceramic composite with 45 vol.% quartz has a resistivity of 1 × 107 Ωcm and an open porosity of <3%. Sintered multilayer samples from tape-cast thermoelectric oxides and screen-printed insulation show only small reaction layers. It can be concluded that glass-ceramic composites are a well-suited material class for insulation layers as their physical properties can be tuned by varying glass composition or dispersion phases. |
| Remark |
https://doi.org/10.1111/jace.18235 Link |
Electrical properties of yttria-stabilised hafnia ceramics
ID=659| Authors |
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| Source |
Phys. Chem. Chem. Phys.
Volume: 23,
Pages: 25951 Time of Publication: 2021 |
| Abstract | Cubic, yttria-stabilised hafnia, YSH, ceramics of general formula, YxHf1xO2x/2: x = 0.15, 0.30 and 0.45 were sintered at 1650–1750 1C and characterised by impedance spectroscopy. All three compositions are primarily oxide ion conductors with a small amount of p-type conductivity that depends on atmospheric conditions and appears to increase with x. The electronic conductivity is attributed to hole location on under-bonded oxide ions and the absorption of oxygen molecules by oxygen vacancies, both of which occur on substitution of Hf4+ by Y3+. Composition x = 0.15 has the highest total conductivity and shows curvature in the Arrhenius plot at high temperatures, similar to that of the most conductive yttria-stabilised zirconia. |
| Remark | Link |
Electrochemical Performance of SrWO4 Electrolyte for SOFC
ID=658| Authors |
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| Source |
The International Journal of Integrated Engineering
Volume: 13,
Issue: 1,
Pages: 74-80 Time of Publication: 2021 |
| Abstract | cheelite structured SrWO4 material was synthesized by the solid-state sintering method and studied with respect to phase stability and ionic conductivity under condition of technological relevance for SOFC applications. The resulting compound was crystallized in the single phase of tetragonal scheelite structure with the space group of I41/a. Room temperature X-ray diffraction and subsequent Rietveld analysis confirms its symmetry, space group and structural parameters. Analysis by SEM illustrated a highly dense structure. SrWO4 sample shows lower conductivity compared to the raditional BCZY perovskite structured materials. SrWO4 sample exhibited an ionic conductivity of 1.93 × 10−6 S cm-¹ at 1000°C in dry Ar condition. Since this scheelite type compound demonstrated significant conductivity and a dense microstructure, it could serve in SOFC as a mixed ion-conducting electrolyte. |
| Remark | Link |
Electrical properties and charge compensation mechanisms of Cr-doped rutile, TiO2
ID=657| Authors |
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| Source |
Phys. Chem. Chem. Phys.
Volume: 23,
Pages: 22133-22146 Time of Publication: 2021 |
| Remark | Link |
Protonic Transport Properties of Perovskite Heterostructures A Thin Film Study
ID=656| Author |
|
| Source |
Time of Publication: 2021
|
| Remark |
Master Thesis Materials Science for Energy and Nanotechnology Link |
Expanded Chemistry and Proton Conductivity in Vanadium-Substituted Variants of γ-Ba4Nb2O9
ID=655| Authors |
|
| Source |
Chem. Mater.
Volume: 33,
Issue: 18,
Pages: 7475–7483 Time of Publication: 2021 |
| Abstract | We have substantially expanded the chemical phase space of the hitherto unique γ-Ba4Nb2O9 type structure by designing and synthesizing stoichiometric ordered analogues γ-Ba4V1/3Ta5/3O9 and γ-Ba4V1/3Nb5/3O9 and exploring the solid-solution series γ-Ba4VxTa2–xO9 and γ-Ba4VxNb2–xO9. Undoped Ba4Ta2O9 forms a 6H-perovskite type phase, but with sufficient V doping the γ-type phase is thermodynamically preferred and possibly more stable than γ-Ba4Nb2O9, forming at a 200 °C lower synthesis temperature. This is explained by the fact that Nb5+ ions in γ-Ba4Nb2O9 simultaneously occupy 4-, 5-, and 6-coordinate sites in the oxide sublattice, which is less stable than allowing smaller V5+ to occupy the former two and larger Ta5+ to occupy the latter. The x = 1/3 phase γ-Ba4V1/3Ta5/3O9 shows greatly improved ionic conduction compared to the x = 0 phase 6H-Ba4Ta2O9. We characterized the structures of the new phases using a combination of X-ray and neutron powder diffraction. All compositions hydrate rapidly and extensively (up to 1/3 H2O per formula unit) in ambient conditions, like the parent γ-Ba4Nb2O9 phase. At lower temperatures, the ionic conduction is predominately protonic, while at higher temperatures it is likely other charge carriers make increasing contributions. |
| Remark |
https://doi.org/10.1021/acs.chemmater.1c02340 Link |
Electrical transport in a molten-solid V2O5–ZrV2O7 composite
ID=654| Authors |
|
| Source |
J. Mater. Chem. A
Volume: 9,
Pages: 18537-18545 Time of Publication: 2021 |
| Abstract | Molten-solid composite oxides are candidates as oxygen transport membranes (OTMs) at intermediate temperatures (500–700 °C). Effects of the constituent phases and interphases on surface reactions and transport processes in these composites are elusive. Here we contribute fundamental insight to such materials systems, applying electrochemical impedance spectroscopy (EIS) and electromotive force (emf) measurements to investigate the electrical conductivity characteristics of a 30 mol% V2O5–ZrV2O7 composite with a eutectic melting point at ∼670 °C. When V2O5 melts and increases the V2O5 volume percolation, the electrical conductivity increases by a factor of 10 and the activation energy increases from 0.21 to ∼0.7 eV. The oxygen red-ox reaction at the surface changes from being rate limited by charge transfer processes to mass transfer processes as a consequence of fast oxygen exchange in molten V2O5 as compared to the all-solid composite. These effects coincide with the ionic transport number rising from essentially zero to ∼0.4, reflecting a significant increase in the relative oxide ion conductivity. Oxygen permeation across a 30 mol% V2O5–ZrV2O7 membrane was estimated to be in the same order as for several dual-phase membranes, but one magnitude lower than for single-phase mixed conducting membranes at intermediate temperatures. |
| Remark |
DOI: 10.1039/D1TA03750A Link |
Evaluation of Materials for Use in Open-Cycle Magnetohydrodynamic Power Generation
ID=653| Author |
|
| Source |
Time of Publication: 2021
|
| Remark |
Michael S. Bowen for the degree of Master of Science in Mechanical Engineering Link |
Anode-supported solid oxide fuel cells with multilayer LSC/CGO/LSC cathode
ID=652| Authors |
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| Source |
Fuel Cells
Volume: 21,
Issue: 4,
Pages: 408-412 Time of Publication: 2021 |
| Abstract | The multilayer La0.6Sr0.4CoO3/Ce0.9Gd0.1O2/La0.6Sr0.4CoO3 (LSC/CGO/LSC) thin film cathode of the solid oxide fuel cell (SOFC) with the different thickness of the LSC and CGO layers are obtained by magnetron sputtering. Cathodes are deposited onto the NiO/8YSZ anode-supported 8YSZ/CGO bilayer electrolyte. The influence of the deposited multilayer cathode on the SOFC performance is investigated in the temperature range between 800 and 600°C. It is shown that the thin-film multilayer cathode allows increasing the SOFC efficiency, and the obtained optimum thickness of the LSC and CGO layers provides the maximum power density for SOFCs. The maximum power density of 2430, 1170, and 290 mW cm–2 is obtained respectively at 800, 700, and 600°C for the SOFCs with the LSC/CGO/LSC layer 50/50/50 nm thick. The polarization resistance measured at 800 and 750°C on the symmetric SOFC with the CGO electrolyte and LSC/CGO/LSC cathode is 0.17 and 0.3 Ω cm2, respectively. |
| Remark | Link |
Performance and Processes of Pure CO2 Electrolysis in Solid Oxide Cells
ID=651| Authors |
|
| Source |
ECS Transactions
Volume: 103,
Issue: 1,
Pages: 501 Time of Publication: 2021 |
| Abstract | Pure carbon dioxide (CO2) electrolysis presents a sustainable method for the production of carbon monoxide (CO). CO is an important feedstock for producing base chemicals for the chemical industry. High-temperature CO2 electrolysis in solid oxide electrolysis cells (SOECs) make it possible to recycle climate-damaging CO2 and utilize renewable energy sources for the conversion to CO. We thoroughly investigated the direct CO2 electrolysis electrochemically with respect to the process parameters temperature, fuel utilization, load, flow rates, and CO2:CO feed gas ratio. With faradaic efficiencies of about 100% and high current densities of up to 1.5 Abold dotcm,-2 the results show the high potential of pure CO2 electrolysis. |
| Remark | Link |
Metal Supported Proton Conducting Ceramic Cell with Thin Film Electrolyte for Electrolysis Application
ID=650| Authors |
|
| Source |
ECS Transactions
Volume: 103,
Issue: 1,
Pages: 693 Time of Publication: 2021 |
| Abstract | Manufacturing of metal supported proton conducting ceramic cells is investigated in the present study. A low temperature fabrication route was chosen to avoid metal corrosion during the fabrication process, in which pulsed laser deposition (PLD) was employed to apply the thin-film BaZr0.7Ce0.2Y0.1O3-δ electrolyte layer. The surface condition of the support layer is a critical aspect to produce a dense and gas-tight electrolyte layer by PLD. In order to decrease the average size of the 10-30 µm large pores in metal substrate down to the nano-scale, different powders with different particles size were successfully fabricated and integrated into a pore-size graded structure to form a homogeneous porous surface whose size distribution meets the requirements for making a dense PLD coating layer. An electrolyte layer with the intended phase is achieved with a thickness of around 1 µm. Initial electrochemical investigation with a Pt oxygen electrode showed a total resistance of 4.92 Ω cm2 at 600°C at OCV. |
| Remark | Link |
Boundaries of High-Temperature Co-Electrolysis Towards Direct CO2-Electrolysis
ID=649| Authors |
|
| Source |
ECS Transactions
Volume: 103,
Issue: 1,
Pages: 493 Time of Publication: 2021 |
| Abstract | In this work, the transition boundary of high-temperature co-electrolysis towards pure CO2-electrolysis was investigated. AC and DC measurements with H2O concentrations from 0.0%eq to 39.7%eq led to the identification of the underlying electrochemical processes. Comparison of CO2 conversion in the (R)WGS reaction with electrochemical CO2 reduction by means of area specific resistance (ASR) showed that gas composition determines the dominant reduction reaction (H2O or CO2 reduction). The cell performance of CO2-electrolysis was found to be comparable to co-electrolysis in the boundary region up to around 4.7 %eq H2O. The threshold for the perception of CO2-electrolysis during co-electrolysis has been established to be around 31.7 %eq H2O. The hypothesis that pre-domination of CO2-electrolysis increases with decreasing H2O concentrations below this boundary limit was underlined by measurement results. |
| Remark | Link |
The Electrochemical Society, find out more The Electrochemical Society, find out more Metal Supported Proton Conducting Ceramic Cell with Thin Film Electrolyte for Electrolysis Application
ID=647| Authors |
|
| Source |
ECS Transactions
Volume: 103,
Pages: 693 Time of Publication: 2021 |
| Abstract | Manufacturing of metal supported proton conducting ceramic cells is investigated in the present study. A low temperature fabrication route was chosen to avoid metal corrosion during the fabrication process, in which pulsed laser deposition (PLD) was employed to apply the thin-film BaZr0.7Ce0.2Y0.1O3-δ electrolyte layer. The surface condition of the support layer is a critical aspect to produce a dense and gas-tight electrolyte layer by PLD. In order to decrease the average size of the 10-30 µm large pores in metal substrate down to the nano-scale, different powders with different particles size were successfully fabricated and integrated into a pore-size graded structure to form a homogeneous porous surface whose size distribution meets the requirements for making a dense PLD coating layer. An electrolyte layer with the intended phase is achieved with a thickness of around 1 µm. Initial electrochemical investigation with a Pt oxygen electrode showed a total resistance of 4.92 Ω cm2 at 600°C at OCV. |
| Remark | Link |
Syngas production with CO2 utilization through the oxidative reforming of methane in a new cermet-carbonate packed-bed membrane reactor
ID=646| Authors |
|
| Source |
Journal of Membrane Science
Volume: 637,
Pages: 119607 Time of Publication: 2021 |
| Cermet; Gas Separation; Membrane reactor; Oxidative reforming of methane | |
| Remark |
https://doi.org/10.1016/j.memsci.2021.119607 Link |
Structural and Electrochemical Properties of Scandia Alumina Stabilized Zirconia Thin Films
ID=645| Authors |
|
| Source |
Coatings
Volume: 11,
Issue: 7,
Pages: 800 Time of Publication: 2021 |
| Abstract | This work presents a systematic investigation of scandia alumina stabilized zirconia (ScAlSZ, composition: ZrO2:Sc2O3:Al2O3 93:6:1 wt.%) thin films (~2 μm). Thin films were formed by the e-beam evaporation method on 450 °C substrates. The influence of Al concentration on thin film microstructure, structure, and electrochemical properties was characterized by EDS, XRD, Raman, and EIS methods. It was found that the aluminum concentration in the deposited thin films decreased with an increase in the deposition rate. The concentration of Al changed from 15.9 to 3.8 at.% when the deposition rates were 0.2 and 1.6 nm/s, respectively. The crystallinity of the thin films depended strongly on the concentration of Al, resulting in an amorphous phase when Al concentration was 22.2 at.% and a crystalline phase when Al concentration was lower. ScAlSZ thin films containing 15.9 at.% of Al had monoclinic and tetragonal phases, while thin films with 1.6 and 3.8 at.% of Al had a mixture of cubic, tetragonal, and monoclinic phases. The phase transition was observed during the thermal annealing process. Cubic and rhombohedral phases formed in addition to monoclinic and tetragonal phases appeared after annealing ScAlSZ thin films containing 15.9 and 22.2 at.% of aluminum. The highest total ionic conductivity (σbulk = 2.89 Sm−1 at 800 °C) was achieved for ScAlSZ thin films containing 3.8 at.% of Al. However, thin films containing a higher concentration of aluminum had more than 10 times lower total conductivity and demonstrated changes in activation energy at high temperatures (>560 °C). Activation energies changed from ~1.10 to ~1.85 eV. |
| Keywords | electron beam deposition; scandia alumina stabilized zirconia (ScAlSZ); solid oxide fuel cells (SOFC); ionic conductivity |
| Remark |
https://doi.org/10.3390/coatings11070800 Link |
Anomalous grain boundary conduction in BiScO3-BaTiO3 high temperature dielectrics
ID=644| Authors |
|
| Source |
Acta Materialia
Volume: 216,
Pages: 117136 Time of Publication: 2021 |
| Remark |
https://doi.org/10.1016/j.actamat.2021.117136 Link |
Preparation of NdBaCo2O5+δ–Ce0.9Gd0.1O1.95 composite cathode by in situ sol-mixing method and its high-temperature electrochemical properties
ID=643| Authors |
|
| Source |
Journal of Alloys and Compounds
Volume: 885,
Pages: 160901 Time of Publication: 2021 |
| Abstract | NdBaCo2O5+δ-xCe0.9Gd0.1O1.95 (NBCO-xCGO, x = 0 ~ 8 wt%) composite materials are prepared by novel sol-mixing method and evaluated as cathodes for intermediate-temperature solid oxide fuel cells. The chemical compatibility, thermal expansion behavior and electrochemical performance of NBCO-xCGO composite cathodes are studied. There is no chemical reaction between NBCO and CGO after sintering at 1100 °C for 12 h. Introducing CGO leads to the decrease of both thermal expansion coefficient and conductivity. Among all the composites, NBCO-5CGO shows the lowest polarization resistance of 0.034 Ω cm2 at 700 °C. The anode-supported single-cell with NBCO-5CGO cathode exhibits a maximum power density of 1.0 W cm−2 at 700 °C. The electrochemical impedance spectrum measurement combining with the distribution of relaxation times analysis proves that the addition of CGO nanoparticles significantly improves the surface oxygen dissociation process, and the charge transfer process is identified to be the reaction limiting step to control the oxygen reduction kinetics on NBCO-5CGO composite cathode. |
| Keywords | Intermediate-temperature solid oxide fuel cell; Composite cathode; Distribution of relaxation times analysis; Oxygen reduction kinetics |
| Remark |
https://doi.org/10.1016/j.jallcom.2021.160901 Link |
Valence state of europium and samarium in Ln2Hf2O7 (Ln = Eu, Sm) based oxygen ion conductors
ID=642| Authors |
|
| Source |
Ceramics International
Volume: 47,
Issue: 19,
Pages: 26898-26906 Time of Publication: 2021 |
| Remark | Link |
Impedance spectroscopy studies of the chlorophosphate glasses
ID=641| Authors |
|
| Source |
Materials Today: Proceedings
Time of Publication: 2021
|
| Remark |
https://doi.org/10.1016/j.matpr.2021.06.041 Link |
Optical properties and frequency-dependent conductivity of K2O-BaO-TiO2-P2O5 glasses
ID=640| Authors |
|
| Source |
Materials Today: Proceedings
Time of Publication: 2021
|
| Abstract | The glass compositions (20-x)K2O-xBaO–30TiO2–50P2O5 with (0�¯≤�¯x�¯≤�¯20�¯mol%) were elaborated using the conventional quenching method. Their related glass-ceramics were developed by controlled crystallization under heat treatments. UV–visible absorption was employed to study the optical properties of the glasses. This technique showed the reduction of Ti4+ to Ti3+ ion content with the substitution of K2O by BaO, and it was found that the BaO addition reduces the structural disorder in the studied glasses. The electrical properties of the glass-ceramics were carried out by impedance spectroscopy in the frequency range from 10�¯Hz to 1�¯MHz under various temperatures from room temperature to 550�¯K. The obtained results showed that the electrical conductivity follows Jonscher’s universal power law and the electrical motion process in the glass-ceramics is provided by the hopping mechanism. |
| Remark | Link |
Synthesis and Triple Conductive Properties of Ba and Fe Co-Doped Sr2TiO4 Based Layered Perovskite: (BaxSr2-x) (Ti0.9Fe0.1)O4-δ (X= 0.05, 0.10)
ID=639| Authors |
|
| Source |
Key Engineering Materials
Volume: 888,
Pages: 37-42 Time of Publication: 2021 |
| Abstract | This study investigated the effects of Ba substitution on protonic conductive properties in the Fe doped Sr2TiO4 layered perovskite. We synthesized sintered samples of (BaxSr2-x)(Ti0.90Fe0.10)O4-δ (x= 0.05, 0.10) (BSTF05, BSTF10). The result of X-ray diffraction suggests that solid solute limitation of Ba is between x= 0.05 and 0.10. BSTF05 at 600 °C shows proton and oxide-ion conductivities as well as elecronic conductivity. It means that BSTF05 is a triple conductor at 600 °C under oxidation atmosphere. The proton conductivities in BSTF05 are lower than that in Ba un-doped Sr2(Ti0.9Fe0.1)O4-δ evaluated in our previous work, suggesting that the effect of the Ba substitution on proton defect generation is small. The redox reaction of Fe ions is more important for creation of proton defects in the layered perovskites. |
| Remark |
https://doi.org/10.4028/www.scientific.net/KEM.888.37 Link |
Electrochemical, Thermal, and Structural Features of BaF2–SnF2 Fluoride-Ion Electrolytes
ID=638| Authors |
|
| Source |
J. Phys. Chem. C
Volume: 125,
Issue: 23,
Pages: 12568–12577 Time of Publication: 2021 |
| Abstract | Fluoride-ion-conducting compounds are key materials for solid electrolytes in all-solid-state fluoride shuttle batteries (FSBs) and widely regarded as promising rechargeable batteries. However, their ionic conductivities are still insufficient to allow room-temperature operation. Particularly, the transportation of F ions through solid-state ionic devices is yet to be fully understood. We studied the electrochemical, thermal, and structural features of BaF2–SnF2 solid electrolytes by means of AC impedance, differential scanning calorimetry, X-ray diffraction, and neutron diffraction experiments. The substitution of Ba by Sn atoms increased the electrical conductivity of BaF2–SnF2 to 107–109 times that of BaF2; particularly, (BaF2)0.47(SnF2)0.53 exhibited the highest electrical conductivity (σ = 4.1 × 10–3 S/cm at room temperature) with the lowest activation energy (Ea = 17.9 kJ/mol). Structural analysis revealed that (BaF2)0.47(SnF2)0.53 consists of a tetragonal structure (T-phase) and residual amounts of the cubic structure (C-phase). The T-phase could be refined on the basis of a [−SnSnMMSnSn−]-layered structure (M = BaxSn1–x) with three nonequivalent fluorine sites: F1, F2, and F3. The anisotropic displacement of F3 was more pronounced toward F1; thus, the “–F1–F3–F1–” zigzag network between the M and Sn layers plays a key role in two-dimensional fast F-ion diffusion. |
| Remark |
https://doi.org/10.1021/acs.jpcc.1c03326 Link |
Effect of ball-milling on the phase formation and enhanced thermoelectric properties in zinc antimonides
ID=637| Authors |
|
| Source |
Materials Science and Engineering: B
Volume: 271,
Pages: 115274 Time of Publication: 2021 |
| Abstract | We report the phase formation mechanism and the enhanced thermoelectric properties of zinc antimonide (ZnSb) thermoelectric material. The phase pure ZnSb thermoelectric material is achieved using high-energy ball milling of Zn and Sb in a shorter span of time. The ZnSb phase formation is explained by the kinetic energy transferred to the powders during milling for the solid-state reaction between Zn and Sb to form the desired ZnSb phase. The repeatability in transport properties up to three thermal cycles corroborates the thermal stability of the processed samples. The thermoelectric figure of merit obtained at 600 K is ~ 0.76 for the processed phase pure ZnSb sample, the highest value in binary ZnSb reported so far. Our results address the ZnSb phase evolution in a shorter milling time and the enhanced thermoelectric properties of the ZnSb materials. The observations will help to scale up the processing of high-performance ZnSb thermoelectric materials. |
| Keywords | Zinc antimonide; Thermoelectric materials; Ball milling; Phase formation kinetics; X-ray diffraction; Figure of merit |
| Remark |
https://doi.org/10.1016/j.mseb.2021.115274 Link |
Enhanced activity of catalysts on substrates with surface protonic current in an electrical field – a review
ID=636| Authors |
|
| Source |
Chem. Commun.
Volume: 57,
Pages: 5737 Time of Publication: 2021 |
| Abstract | It has over the last few years been reported that the application of a DC electric field and resulting current over a bed of certain catalyst-support systems enhances catalytic activity for several reactions involving hydrogen-containing reactants, and the effect has been attributed to surface protonic conductivity on the porous ceramic support (typically ZrO2, CeO2, SrZrO3). Models for the nature of the interaction between the protonic current, the catalyst particle (typically Ru, Ni, Co, Fe), and adsorbed reactants such as NH3 and CH4 have developed as experimental evidence has emerged. Here, we summarize the electrical enhancement and how it enhances yield and lowers reaction temperatures of industrially important chemical processes. We also review the nature of the relevant catalysts, support materials, as well as essentials and recent progress in surface protonics. It is easily suspected that the effect is merely an increase in local vs. nominal set temperature due to the ohmic heating of the electrical field and current. We address this and add data from recent studies of ours that indicate that the heating effect is minor, and that the novel catalytic effect of a surface protonic current must have additional causes. |
| Remark | Link |
In situ cofactor regeneration enables selective CO2 reduction in a stable and efficient enzymatic photoelectrochemical cell
ID=635| Authors |
|
| Source |
Applied Catalysis B: Environmental Volume: 296, Pages: 120349 Time of Publication: 2021 |
| Abstract | Mimicking natural photosynthesis by direct photoelectrochemical (PEC) reduction of CO2 to chemicals and fuels requires complex cell assemblies with limitations in selectivity, efficiency, cost, and stability. Here, we present a breakthrough cathode utilizing an oxygen tolerant formate dehydrogenase enzyme derived from clostridium carboxidivorans and coupled to a novel and efficient in situ nicotinamide adenine dinucleotide (NAD+/NADH) regeneration mechanism through interfacial electrochemistry on g-C3N4 films. We demonstrate stable (20 h) aerobic PEC CO2-to-formate reduction at close to 100 % faradaic efficiency and unit selectivity in a bio-hybrid PEC cell of minimal engineering with optimized Ta3N5 nanotube photoanode powered by simulated sunlight with a solar to fuel efficiency of 0.063 %, approaching that of natural photosynthesis. |
| Remark |
https://doi.org/10.1016/j.apcatb.2021.120349 Link |
A high-entropy manganite in an ordered nanocomposite for long-term application in solid oxide cells
ID=634| Authors |
|
| Source |
Nature Communications
Volume: 12
Time of Publication: 2021
|
| Abstract | The implementation of nano-engineered composite oxides opens up the way towards the development of a novel class of functional materials with enhanced electrochemical properties. Here we report on the realization of vertically aligned nanocomposites of lanthanum strontium manganite and doped ceria with straight applicability as functional layers in high-temperature energy conversion devices. By a detailed analysis using complementary state-of-the-art techniques, which include atom-probe tomography combined with oxygen isotopic exchange, we assess the local structural and electrochemical functionalities and we allow direct observation of local fast oxygen diffusion pathways. The resulting ordered mesostructure, which is characterized by a coherent, dense array of vertical interfaces, shows high electrochemically activity and suppressed dopant segregation. The latter is ascribed to spontaneous cationic intermixing enabling lattice stabilization, according to density functional theory calculations. This work highlights the relevance of local disorder and long-range arrangements for functional oxides nano-engineering and introduces an advanced method for the local analysis of mass transport phenomena. |
| Remark | Link |
3D Printing the Next Generation of Enhanced Solid Oxide Fuel and Electrolysis Cells
ID=633| Authors |
|
| Source |
Electronic Supplementary Material (ESI) for Journal of Materials Chemistry A.
Time of Publication: 2020
|
| Remark | Link |
Microstructure and electrochemical behavior of layered cathodes for molten carbonate fuel cell
ID=632| Authors |
|
| Source |
Journal of Power Sources
Volume: 500,
Pages: 229949 Time of Publication: 2021 |
| Abstract | In the present paper, we demonstrate how modifications of the microstructure and the chemical composition can influence the electrochemical behavior of cathodes for molten carbonate fuel cells (MCFCs). Based on our experience, we designed new MCFC cathode microstructures combining layers made of porous silver, nickel oxide or nickel foam to overcome common issues with the internal resistance of the cell. The microstructures of the standard NiO cathode and manufactured cathodes were extensively investigated using scanning electron microscopy (SEM) and porosity measurements. The electrochemical behavior and overall cell performance were examined by means of electrochemical impedance spectroscopy and single-cell tests in operation conditions. The results show that a porous silver layer tape cast onto standard NiO cathode and nickel foam used as a support layer for tape cast NiO porous layer substantially decrease resistance components representing charge transfer and mass transport phenomena, respectively. Therefore, it is beneficial to combine them into a three-layer cathode since it facilitates separation of predominant physio-chemical processes of gas and ions transport in respective layers ensuring high efficiency. The superiority of the three-layer cathode has been proven by low impedance and high power density as compared to standard NiO cathode. |
| Remark | Link |
Influence of Doping on the Transport Properties of Y1−xLnxMnO3+δ (Ln: Pr, Nd)
ID=631| Author |
|
| Source |
Crystals
Volume: 11,
Pages: 510 Time of Publication: 2021 |
| Abstract | It has been documented that the total electrical conductivity of the hexagonal rare-earth manganites Y0.95Pr0.05MnO3+δ and Y0.95Nd0.05MnO3+δ, as well as the undoped YMnO3+δ, is largely dependent on the oxygen excess δ, which increases considerably at temperatures below ca. 300 ◦C in air or O2. Improvement for samples maintaining the same P63cm crystal structure can exceed 3 orders of magnitude below 200 ◦C and is related to the amount of the intercalated oxygen. At the same time, doping with Nd3+ or Pr3+ affects the ability of the materials to incorporate O2, and therefore indirectly influences the conductivity as well. At high temperatures (700–1000 ◦C) and in different atmospheres of Ar, air, and O2, all materials are nearly oxygen-stoichiometric, showing very similar total conduction with the activation energy values of 0.8–0.9 eV. At low temperatures in Ar (δ ≈ 0), the mean ionic radius of Y1−xLnx appears to influence the electrical conductivity, with the highest values observed for the parent YMnO3. For Y0.95Pr0.05MnO3+δ oxide, showing the largest oxygen content changes, the recorded dependence of the Seebeck coefficient on the temperature in different atmospheres exhibits complex behavior, reflecting oxygen content variations, and change of the dominant charge carriers at elevated temperatures in Ar (from electronic holes to electrons). Supplementary cathodic polarization resistance studies of the Y0.95Pr0.05MnO3+δ electrode document different behavior at higher and lower temperatures in air, corresponding to the total conduction characteristics. |
| Remark | Link |
Preparation and characterization of (La,Ca,Sr)(Fe,Co)O3-d cathodes for solid oxide fuel cells
ID=630| Author |
|
| Source |
Time of Publication: 2021
|
| Remark |
Master Thesis Link |
Fabrication of a Silicide Thermoelectric Module Employing Fractional Factorial Design Principles
ID=629| Authors |
|
| Source |
Journal of Electronic Materials volume
Volume: 50,
Pages: 4041–4049 Time of Publication: 2021 |
| Abstract | Thermoelectric modules can be used in waste heat harvesting, sensing, and cooling applications. Here, we report on the fabrication and performance of a four-leg module based on abundant silicide materials. While previously optimized Mg2Si0.3Sn0.675Bi0.025 is used as the n-type leg, we employ a fractional factorial design based on the Taguchi methods mapping out a four-dimensional parameter space among Mnx-εMoεSi1.75−δGeδ higher manganese silicide compositions for the p-type material. The module is assembled using a scalable fabrication process, using a Cu metallization layer and a Pb-based soldering paste. The maximum power output density of 53 μW cm–2 is achieved at a hot-side temperature of 250 °C and a temperature difference of 100 °C. This low thermoelectric output is related to the high contact resistance between the thermoelectric materials and the metallic contacts, underlining the importance of improved metallization schemes for thermoelectric module assembly. |
| Remark | Link |
Ceramic composites based on Ca3Co4−xO9+δ and La2NiO4+δ with enhanced thermoelectric properties
ID=628| Authors |
|
| Source |
Open Ceramics
Volume: 6,
Pages: 100103 Time of Publication: 2021 |
| Abstract | Ceramic composites were produced by combining the oxide materials Ca3Co4−xO9+δ and La2NiO4+δ. Both compounds were characterized by a plate-like crystal shape, but crystal sizes differed by around two orders of magnitude. The composite materials could be successfully prepared by using uniaxial pressing of powder mixtures and pressureless sintering to a porous ceramic. Possible reactions between both materials during sintering were analyzed. The ceramic composites with low amounts of La2NiO4+δ showed enhanced thermoelectric properties, caused by an increasing power factor and simultaneously decreasing thermal conductivity. For the evaluation of the thermoelectric properties, two different types of Ioffe plots were utilized. The maximum figure-of-merit zT at 1073 K was 0.27 for the pure Ca3Co4−xO9+δ as well as for the sample containing 5 wt% La2NiO4+δ. However, the average in the temperature range of 373 K to 1073 K could be increased by 20% for the composite material. |
| Keywords | Calcium cobalt oxide; Composite; Ceramic; Lanthanum nickelate; Reaction sintering; Thermoelectric; Power factor; Figure-of-merit |
| Remark | Link |
Amorphous ZnO modified anatase TiO2 thin films templated by tripropylamine and their electrical properties
ID=627| Authors |
|
| Source |
Thin Solid Films
Volume: 729,
Pages: 138697 Time of Publication: 2021 |
| Abstract | In the present study we report on a low cost synthesis of amorphous ZnO modified anatase TiO2 (40 and 20 mol% ZnO) thin films deposited via sol-gel spin coating technique on glass substrate. The effects of the composition on the structural, morphological and surface chemistry properties were discussed and correlated with the electrical behavior. Thus, by X-ray diffraction and Raman spectroscopy only TiO2 indexed in the anatase crystalline structure was identified without any ZnO characteristic crystalline phase. The surface chemistry assessed by X-ray Photoelectron spectroscopy highlighted the presence of Ti4+ in TiO2 as well as the presence of Zn2+ coordinated in the amorphous ZnO proved by the Auger ZnLMM transition shifted toward lower binding energies. The films are continuous, homogeneous with grain size below 20 nm and exhibit an intergranular porosity, as it was displayed by Scanning Electron Microscopy. The sensor signal towards CO exposure is strongly related to the amount of the ZnO amorphous phase formation. Thus, we found that a higher content of the ZnO amorphous phase leads to a lower sensitivity. The electrical and sensing measurements were performed in the temperature range (room temperature 400 °C), over the range of CO concentrations (0-2000 ppm). The sensor containing 20 mol.% amorphous ZnO exhibits a good sensitivity at ~300 °C for a low CO concentration . |
| Keywords | Amorphous zinc oxide; Titanium dioxide; Mixed oxides; Sol-gel spin coating technique; Electrical conductivity; Carbon monoxide detection |
| Remark | Link |
The Effect of Thin Functional Electrode Layers on Characteristics of Intermediate Temperature Solid Oxide Fuel Cell
ID=626| Authors |
|
| Source |
Russian Journal of Electrochemistry
Volume: 57,
Pages: 97–103 Time of Publication: 2021 |
| Abstract | The thin-film multilayer structure of the membrane-electrode assembly in a solid oxide fuel cell which involves a NiO/ZrO2:Y2O3 anode functional layer and a La0.6Sr0.4CoO3 cathode functional layer and also a bilayer ZrO2:Y2O3/Ce0.9Gd0.1O1.95 electrolyte is formed by magnetron sputtering onto a supporting NiO/ZrO2:Y2O3 anode. The effect of the functional electrode layers involved in the structure of a solid oxide fuel cell on its efficiency is studied. The volt–ampere characteristics of multilayer fuel cells are studied in the temperature range of 800–600°C. It is shown that the inclusion of a thin (600 nm thick) cathode functional layer into the structure of the membrane–electrode assembly enhances the fuel cell efficiency by reducing the polarization losses on electrodes. The maximum power density of the fuel cell with the cathode functional layer is 2290 and 500 mW/cm2 at 800 and 600°С, respectively. The simultaneous presence of anode and cathode functional layers is found to be unwelcome because gives rise to diffusion limitations on the anode. |
| Remark | Link |
Impedance spectroscopy of manganese-doped mixed alkali phosphate glasses
ID=625| Authors |
|
| Source |
Materials Today: Proceedings
Time of Publication: 2021
|
| Abstract | Glassy-compositions in the system 49.95[xNa2O-(1-x)K2O]-0.1MnO2-49.95P2O5 (with x = 0–1 mol%) were elaborated using melt quenching method. The amorphous state of the samples is ensured by the XRD diffraction technique. The electrical properties including dc conductivity, ac conductivity, and electrical modulus were investigated over a large frequency domain at various temperatures. The evolution of the electric conductivity shows a non-linear variation with the composition. It is found that the activation energy is more sensitive to the substitution of the alkali elements and presents a minimum in the intermediate composition (x = 0.5). The non-linearity behavior of the composition dependence of the electrical parameters is a fingerprint of the mixed alkali effect in the glasses under study. The frequency-dependent of the conductivity follows Jonscher’s power law and the correlated barrier hopping mechanism (CBH) was appropriate for the conduction process inside the glasses. In order to avoid the polarization effect due to the electrodes, the electrical modulus formalism is applied to the impedance data. The results obtained show that conduction relaxation is a non-Debye type. |
| Keywords | Phosphate; Glasses; Mixed alkali effect; Electrical conductivity; Relaxation |
| Remark |
https://doi.org/10.1016/j.matpr.2021.03.467 Link |
Metal-Support Interaction and Electrochemical Promotion of Nano- Structured Catalysts for the Reverse Water Gas Shift Reaction
ID=624| Author |
|
| Source |
Time of Publication: 2021
|
| Abstract | ii Abstract The continued release of fossil-fuel derived carbon dioxide (CO2) emissions into our atmosphere led humanity into a climate and ecological crisis. Converting CO2 into valuable chemicals and fuels will replace and diminish the need for fossil fuel-derived products. Through the use of a catalyst, CO2 can be transformed into a commodity chemical by the reverse water gas shift (RWGS) reaction, where CO2 reacts with renewable hydrogen (H2) to form carbon monoxide (CO). CO then acts as the source molecule in the Fischer-Tropsch (FT) synthesis to form a range of hydrocarbons to manufacture chemicals and fuels. While the FT synthesis is a mature process, the conversion of CO2 into CO has yet to be made commercially available due to the constraints associated with high reaction temperature and catalytic stability. Noble metal ruthenium (Ru) has been widely used for the RWGS reaction due to its high catalytic activity, however, several constraints hinder its practical use, associated with its high cost and its susceptibility to deactivation. The doping or bimetallic use of non-noble metals iron (Fe) and cobalt (Co) is an attractive option to lower material cost and tailor the selectivity of the CO2 conversion towards the RWGS reaction without compromising catalytic activity. Furthermore, employing nanostructured catalysts as nanoparticles is a viable solution to further lower the amount of metal used and utilize the highly active surface area of the catalyst. Dispersing nanoparticles on ionically conductive supports/solid electrolytes which contain species like O2-, H+, Na+, and K+, provide an approach to further enhance the reaction. This phenomenon is referred to as metal-support interaction (MSI), allowing for the ions to back spillover from the support and onto the catalyst surface. An in-situ approach referred to as Non-Faradaic Modification of catalytic activity (NEMCA), also known as electrochemical promotion of catalysis (EPOC) is used to in- situ control the movement of ionic species from the solid electrolyte to and away from the catalyst. Both the MSI and EPOC phenomena have been shown to be functionally equivalent, meaning the ionic species act to alter the work function of the catalyst by forming an effective neutral double layer on the surface, which in turn alters the binding energy of the reactant and intermediate species to promote the reaction. The main objective of this work is to develop a catalyst that is highly active and selective to the RWGS reaction at low temperatures (< 400 °C) by employing the MSI and EPOC iii phenomena to enhance the catalytic conversion. The electrochemical enhancement effect will lower energy requirements and allow the RWGS reaction to take place at moderate temperatures. Catalysts composed of Ru, Fe and Co were synthesized through the polyol synthesis technique and deposited on mixed-ionically conductive and ionically conductive supports to evaluate their performance towards the RWGS reaction and the MSI effect. The nano-structured catalysts are deposited as free-standing nanoparticles on solid electrolytes to in-situ promote the catalytic rate through the EPOC phenomenon. Furthermore, Density Functional Theory (DFT) calculations were performed to correlate theory with experiment and elucidate the role polarization has on the binding energy of reactant and intermediate species. The high dispersion of RuFe nanoparticles on ion-containing supports like samarium- doped ceria (SDC) and yttria-stabilized zirconia (YSZ) led to an increase in the RWGS activity due to the MSI effect. A direct correlation between experimental and DFT modeling was established signifying that polarization affected the binding energy of the CO molecule on the surface of Ru regardless of the type of ionic species in the solid electrolyte. The electrochemical enhancement towards the RWGS reaction has been achieved with iron-oxide (FeOx) nanowires on YSZ. The in-situ application of O2- ions from YSZ maintained the most active state of Fe3O4 and FeO towards the RWGS reaction and allowed for persistent-promoted state that lasted long after potential application. Finally, the deposition of FeOx nanowires on Co3O4 resulted in the highest CO2 conversion towards the RWGS reaction due to the metal-oxide interaction between both metals, signifying a self-sustained electro-promoted state. |
| Remark |
Thesis submitted to the University of Ottawa in partial Fulfillment of the requirements for the Degree of Doctor of Philosophy Link |
Versatile four-leg thermoelectric module test setup adapted to a commercial sample holder system for high temperatures and controlled atmospheres
ID=623| Authors |
|
| Source |
Review of Scientific Instruments
Volume: 92,
Pages: 043902 Time of Publication: 2021 |
| Abstract | A high temperature thermoelectric test setup for the NORECS ProboStat™ sample holder cell has been designed, constructed, and tested. It holds four thermoelectric legs of up to 5 × 5 mm2 area each and flexible height, allows various interconnects to be tested, and utilizes the spring-load system of the ProboStat for fixation and contact. A custom stainless steel support tube flushed with water provides the cold sink, enabling large temperature gradients. Thermocouples and electrodes as well as the gas supply and outer tube use standard ProboStat base unit feedthroughs and dimensions. The setup allows for testing in controlled atmospheres with the hot side temperature of up to around 1000 °C and a temperature gradient of up to 600 °C. We demonstrate the test setup on a four-leg Li–NiO/Al–ZnO module with gold interconnects. The comparison between the predicted performance based on individual material parameters and the experimentally obtained module performance underlines the necessity for testing materials in combination, including interconnects. The four-leg setup allows versatile match-screening, performance evaluation, and long-term stability studies of thermoelectric materials in combination with hot and cold side interconnects under realistic operational conditions. |
| Remark | Link |
Crystal structure, dielectric and optical properties of β-Ca3(PO4)2-type phosphates Ca9-xZnxLa(PO4)7:Ho3+
ID=622| Authors |
|
| Source |
Journal of Luminescence
Volume: 236,
Pages: 118083 Time of Publication: 2021 |
| Abstract | A series of new phosphates Ca9-xZnxLa(PO4)7:Ho3+ with the β-Ca3(PO4)2-type structure was synthesized by the solid state route. An intense near infra-red (NIR) emission according to intraconfigural 4f-4f transitions of Ho3+ ions 5I7 – 5I8 (~2 μm) and 5I6 – 5I8 (~1.156 μm) was observed. The obtained phases were studied by a combination of methods including synchrotron powder X-ray diffraction, dielectric spectroscopy, second harmonic generation, differential scanning calorimetry, luminescence spectroscopy. The structure of Ca8ZnLa(PO4)7 was refined by the Rietveld method in centrosymmetric space group Rc. The Ca2+ → Zn2+ substitution in the M5 site leads to a transformation from polar R3c space group (x = 0 – 0.5) to centrosymmetric Rc space group (x = 0.6–1) and to the increased integral intensity of luminescence with maxima at x = 1. It was concluded that the crystal site engineering in the Ho3+-containing β-Ca3(PO4)2-type hosts offers a promising way to obtain new NIR phosphors for use in the creation of biocompatible bone tissue fillers. |
| Remark | Link |
Fused filament fabrication for anode supported SOFC development: Towards advanced, scalable and cost-competitive energetic systems
ID=621| Authors |
|
| Source |
International Journal of Hydrogen Energy
Volume: 46,
Issue: 51,
Pages: 26174-26184 Time of Publication: 2021 |
| Remark | Link |
Thermal Conductivity and Thermoelectric Power of Compounds in the Cu–Ge–As–Se System
ID=620| Authors |
|
| Source |
Technical Physics volume
Volume: 66,
Pages: 41–45 Time of Publication: 2021 |
| Abstract | The influence of temperature (in the interval of 300–400 K) and concentrations on the electrical conductivity, thermal conductivity, and thermoelectric power of copper chalcogenide-based crystals with the general formula (GeSe)1 – x(CuAsSe2)x has been considered. Heat transfer mechanisms have been determined. It has been found that the temperature dependence of thermal conductivity is nonmonotonic with a singularity at 358 K. Thermoelectric figure of merit ZT has been calculated. |
| Remark | Link |
Modeling the process of capacitive deionization of solutions at supposing complex structure of the pores of the electrodes
ID=619| Authors |
|
| Source |
Journal of Mathematical Chemistry volume
Volume: 59,
Pages: 1054–1067 Time of Publication: 2021 |
| Abstract | An electrochemical cell was created and experimentally tested and the process of intense capacitive deionization (CDI) of aqueous solutions in a cyclic mode was studied. The paper presents a developed mathematical model for CDI process on electrodes with complex structure of pore space. This allows to describe the process and obtain results that are in good agreement with the experimental ones. Model parameters are easily determined at one stage of the deionization process. |
| Remark | Link |
Mixed ionic-electronic transport in the high-entropy (Co,Cu,Mg,Ni,Zn)1-xLixO oxides
ID=618| Authors |
|
| Source |
Acta Materialia
Volume: 208,
Pages: 116735 Time of Publication: 2021 |
| Abstract | A series of the high-entropy (Co,Cu,Mg,Ni,Zn)1-xLixO oxides with a lithium substitution level of x = 0, 0.05, 0.10, 0.15, 0.20, 0.25, and 0.30 is evaluated in terms of the crystal structure, morphology and transport properties, with thorough studies aimed at elucidation of the nature of different contributions to the total electrical conductivity. It is found that cubic Fm-3m structure is preserved in the whole investigated series, with (Co,Cu,Mg,Ni,Zn)0.8Li0.2O composition showing a high internal strain, supporting to some degree one of the so-called core effects, anticipated for the high-entropy materials. For samples with Li content x > 0.20 the strain is relaxed by formation of the oxygen vacancies. As unambiguously evidenced by DC polarization experiments and measured impedance spectroscopy data with ionically-blocking Au and reversible Li electrodes used, the previously reported in the literature transition to the lithium superionic conductivity in the Li-rich compounds, up to σi ≈ 1–10⋅10−3 Scm−1, is more complex, with emergence of the electronic conduction as well, reaching similar magnitude for (Co,Cu,Mg,Ni,Zn)0.7Li0.3O. The observed behavior upon increase of lithium concentration (x) can be explained by a qualitative change of the nature of the electronic and ionic defects present in (Co,Cu,Mg,Ni,Zn)1-xLixO series, with initial oxidation of 3d metals (mainly Co), followed by possible formation of the interstitial lithium, and final emergence of the oxygen vacancies. Furthermore, the recorded electrochemical properties of (Co,Cu,Mg,Ni,Zn)0.7Li0.3O lithium cell electrode, suggesting presence of intercalation-like behavior at the initial stages of lithiation, confirm the proposed mixed ionic-electronic conductivity. |
| Keywords | High-entropy oxides; Crystalline oxides; Lattice defects; Mixed conductor; Li-ion battery |
| Remark |
https://doi.org/10.1016/j.actamat.2021.116735 Link |
The performance of intermediate temperature solid oxide fuel cells with sputter deposited La1-xSrxCoO3 interlayer
ID=617| Authors |
|
| Source |
Journal of Electroceramics
Volume: 45,
Pages: 156–163 Time of Publication: 2020 |
| Abstract | The paper studies the performance of the intermediate temperature solid oxide fuel cells with the sputter deposited La1-xSrxCoO3 (LSC) interlayer between the cathode and electrolyte. The sputter deposition of the LSC thin films is carried out in argon gas and in a mixture of argon and oxygen gases and then are annealed at 600, 800 and 1000 °C in air for 2 h. The structure and composition of the sputter deposited LSC films are investigated by the X-ray diffraction analysis, scanning and transmission electron microscopies, and energy-dispersive X-ray spectroscopy. The polarization resistance of the sputter deposited LSC films (600 nm thick) on the symmetric cells is 0.13, 0.45 and 2.48 Ohm·cm2 measured at 800, 700 and 600 °C, respectively. Measurements are performed by electrochemical impedance spectroscopy. The maximum power density of the anode-supported solid oxide fuel cells with the yttria-stabilized zirconia/gadolinia-doped ceria bilayer electrolyte, LSC interlayer, and LSC cathode is 2.27, 1.58 and 0.68 W/cm2 measured at 800, 700 and 600 °C, respectively. These values of the power density are respectively 1.4, 1.6 and 2.3 times higher than that of the reference cell without the LSC interlayer. |
| Remark | Link |
Near-Broken-Gap Alignment between FeWO4 and Fe2WO6 for Ohmic Direct p–n Junction Thermoelectrics
ID=616| Authors |
|
| Source |
ACS Appl. Mater. Interfaces
Volume: 13,
Issue: 6,
Pages: 7416–7422 Time of Publication: 2021 |
| Abstract | We report a near-broken-gap alignment between p-type FeWO4 and n-type Fe2WO6, a model pair for the realization of Ohmic direct junction thermoelectrics. Both undoped materials have a large Seebeck coefficient and high electrical conductivity at elevated temperatures, due to inherent electronic defects. A band-alignment diagram is proposed based on X-ray photoelectron and ultraviolet–visible light reflectance spectroscopy. Experimentally acquired nonrectifying I–V characteristics and the constructed band-alignment diagram support the proposed formation of a near-broken-gap junction. We have additionally performed computational modeling based on density functional theory (DFT) on bulk models of the individual compounds to rationalize the experimental band-alignment diagram and to provide deeper insight into the relevant band characteristics. The DFT calculations confirm an Fe-3d character of the involved band edges, which we suggest is a decisive feature for the unusual band overlap. |
| Keywords | thermoelectric oxides, broken-gap junction, Ohmic contact, band alignment, p-n junction, computational first-principles modeling |
| Remark |
https://doi.org/10.1021/acsami.0c19341 Link |
Effect of the Ba/K ratio on structural, dielectric and energy storage properties of BaO–K2O–TiO2–P2O5 glass-ceramics
ID=615| Authors |
|
| Source |
Physics and Chemistry of Glasses - European Journal of Glass Science and Technology Part B
Volume: 61,
Issue: 6,
Pages: 213-221 Time of Publication: 2020 |
| Abstract | xBaO–(20–x)K2O–30TiO2–50P2O5 with (0≤x≤20 mol%) glasses were successfully elaborated by the melt quenching while their related glass-ceramics were developed by controlled crystallisation. Density and molar volume measurements, differential thermal analysis and Raman spectroscopy were carried out to examine the glassy structure, the results revealed that the addition of BaO increases the reticulation and reinforces the glass network by the creation of strengthened linkages. X-ray diffraction has identified the formation of MTi2(PO4)3 with M=(K, Ba0.5) in all the glass-ceramics (GC) and the precipitation of a secondary BaTiP2O8 phase when x increase beyond 10 mol%. The dielectric properties of the glass-ceramics were studied by impedance spectroscopy, it showed that the addition of BaO induces an enhancement of both thermal and frequency stability of the dielectric parameters (εr and tan δ). The glass-ceramic with 5 mol% of BaO GC-(x=5) presents the highest dielectric constant and the lowest dielectric loss. The P-E hysteresis loops were recorded at room temperature and the energy storage parameters of the glass-ceramics were determined. These parameters were significantly improved by the increase of the BaO content and the optimum parameters were obtained for GC-(x=5). The dielectric and energy storage parameters were discussed according to the structure data. |
| Remark |
DOI: https://doi.org/10.13036/17533562.61.6.015 Link |
Modification of Ruddlesden-Popper-type Nd2-xNi0.75Cu0.2M0.05O4±δ by the Nd-site cationic deficiency and doping with Sc, Ga or In: Crystal structure, oxygen content, transport properties and oxygen permeability
ID=614| Authors |
|
| Source |
Journal of Solid State Chemistry
Volume: 296,
Pages: 121982 Time of Publication: 2021 |
| Abstract | Nd2-xNi0.75Cu0.2M0.05O4±δ (x = 0 and 0.1; M = Sc, Ga, and In) Ruddlesden-Popper-type oxides are obtained by a sol-gel route and characterized concerning phase composition and crystal structure. It is found that the largest In3+ cannot be effectively introduced into the structure, while Nd stoichiometric and cation-deficient Nd2-xNi0.75Cu0.2Sc0.05O4±δ and Nd2-xNi0.75Cu0.2Ga0.05O4±δ (x = 0; 0.1) can be obtained as single-phase materials. Systematic characterization of the crystal structure at high temperatures, oxygen content, as well as transport properties reveals that while the Nd-site deficiency has rather negligible influence on the structure, it causes a substantial decrease of the oxygen content, which at high temperatures leads to a change of the dominant type of defects from the oxygen interstitials to the vacancies for Nd1.9Ni0.75Cu0.2Sc0.05O4±δ and Nd1.9Ni0.75Cu0.2Ga0.05O4±δ. The Nd-site deficiency also causes a decrease of the total conductivity. Importantly, all the examined materials exhibit full chemical stability in CO2 atmosphere, which together with moderate thermal expansion makes them good candidates for the oxygen transport membranes, which can be used e.g. in the air separation technologies. The selected Sc- and Ga-doped compounds evaluated as ceramic membranes show relatively high oxygen fluxes, with the highest value of 0.78 mL cm-2 min-1 at ca. 880 °C registered for 0.9 mm thick, dense Nd1.9Ni0.75Cu0.2Ga0.05O4±δ membrane. |
| Keywords | Ruddlesden-Popper oxides; Nonstoichiometric compounds; Crystal structure; Transport properties; Oxygen permeation membranes |
| Remark | Link |
A heavily subtituted manganite in an ordered nanocomposite for long-term energy applications
ID=613| Authors |
|
| Source |
Research Square
Time of Publication: 2021
|
| Abstract | The implementation of nano-engineered composite oxides opens up the way towards the development of a novel class of superior energy materials. Vertically aligned nanocomposites are characterized by a coherent, dense array of vertical interfaces, which allows for the extension of local effects to the whole volume of the material. Here, we use such a unique architecture to fabricate highly electrochemically active nanocomposites of lanthanum strontium manganite and doped ceria with unprecedented stability and straight applicability as functional layers in solid state energy devices. Direct evidence of synergistic local effects for enhancing the electrochemical performance, stemming from the highly ordered phase alternation, is given here for the first time using atom-probe tomography combined with oxygen isotopic exchange. Interface-induced cationic substitution, enabling lattice stabilization, is presented as the origin of the observed long-term stability. These findings reveal a novel route for materials nano-engineering based on the coexistence between local disorder and long-range arrangement. |
| Keywords | Nano-engineered composite oxides; Energy materials; Nanocomposites |
| Remark |
DOI: https://doi.org/10.21203/rs.3.rs-134793/v1 Link |
Improved environmental stability of thermoelectric ceramics based on intergrowths of Ca3Co4O9–Na0.75CoO2
ID=612| Authors |
|
| Source |
Ceramics International
Volume: 47,
Issue: 8,
Pages: 11687-11693 Time of Publication: 2021 |
| Abstract | Ceramics based on calcium and sodium cobaltates are promising high-temperature thermoelectric oxide materials with complementary advantages. Ca3Co4O9 is stable at high temperatures, whereas Na0.75CoO2 can be easily processed as a textured ceramic with excellent thermoelectric properties. Na0.75CoO2, however, lacks long-term stability and degrades in even a relatively mild humid environment. In this work, we present a novel approach to the synthesis of complex composite materials based on intergrowths of sodium and calcium cobaltates that have excellent thermoelectric performance and improved stability. We synthesized samples with the mixed composition (3-x)Ca3Co4O9–4x(Na0.75CoO2) in an over-pressured oxygen atmosphere. Samples with the mixed Ca–Na composition developed textured microstructures composed of intergrowths of both end-members, as revealed by transmission electron microscopy. We also examined the thermoelectric performance of the investigated materials after exposure to high humidity and found that the composition with x = 0.8 (Ca:Na = 2.75) has long-term stability. |
| Keywords | Composite materials; Microstructure; Transmission electron microscopy; Thermoelectric |
| Remark | Link |
Time-Enhanced Performance of Oxide Thermoelectric Modules Based on a Hybrid p–n Junction
ID=611| Authors |
|
| Source |
ACS Omega
Volume: 6,
Issue: 1,
Pages: 197–205 Time of Publication: 2020 |
| Abstract | The present challenge with all-oxide thermoelectric modules is their poor durability at high temperatures caused by the instability of the metal-oxide interfaces at the hot side. This work explains a new module concept based on a hybrid p–n junction, fabricated in one step by spark plasma co-sintering of Ca3Co4–xO9+δ (CCO, p-type) and CaMnO3−δ/CaMn2O4 (CMO, n-type). Different module (unicouple) designs were studied to obtain a thorough understanding of the role of the in situ formed hybrid p–n junction of Ca3CoMnO6 (CCMO, p-type) and Co-oxide rich phases (p-type) at the p–n junction (>700 °C) in the module performance. A time-enhanced performance of the modules attributed to this p–n junction formation was observed due to the unique electrical properties of the hybrid p–n junction being sufficiently conductive at high temperatures (>700 °C) and nonconductive at moderate and low temperatures. The alteration of module design resulted in a variation of the power density from 12.4 (3.1) to 28.9 mW/cm2 (7.2 mW) at ΔT ∼ 650 °C after 2 days of isothermal hold (900 °C hot side). This new concept provides a facile method for the fabrication of easily processable, cheap, and high-performance high-temperature modules. |
| Remark | Link |
Comparative investigation on the functional properties of alkaline earth metal (Ca, Ba, Sr) doped Nd2NiO4+δ oxygen electrode material for SOFC applications
ID=610| Authors |
|
| Source |
Journal of Alloys and Compounds
Volume: 860,
Pages: 158490 Time of Publication: 2021 |
| Abstract | Functional properties of Nd2NiO4+δ based materials doped with different alkaline earth metal ions for SOFC applications is studied extensively and compared in this article. Phase pure powders of Nd2NiO4 +δ and Nd1.7A0.3NiO4+δ (A=Ca, Sr and Ba) were synthesized by solid state route at 1250 °C from the constituent precursor oxides and carbonates. Good compatibility of these cathode materials with GDC electrolyte is confirmed through XRD analysis of the composite powder heat treated at 1250 °C. Electrical conductivity of undoped Nd2NiO4+δ is found to attain a maximum at ~470 °C and then decreases noticeably with increase in temperature. The decrease in conductivity at higher temperatures is not significant for alkaline earth metal ion doped systems. In the lower temperature range, electrical conductivity decreases with alkaline earth metal ion doping and this decrement is more as the size of the dopant cation increases with an exception for Sr doped samples. However, at the operating temperature of the fuel cell (say 800 °C) electrical conductivity of Ca and Sr doped Nd2NiO4+δ are higher than the undoped material. Polarization resistance of the cathode materials are evaluated from the measured impedance spectra of symmetric cells and activation energy for oxygen reduction reaction is calculated from the Arrhenius plot of polarization resistance. Activation energy decreases with alkaline earth metal ion doping and this decrease is more in case of Ca doping followed by Sr and Ba doping. Electrolyte supported button cells fabricated under identical processing conditions were tested at 800 °C; highest power density of 188 mW cm−2 is obtained for the cell having Ca doped Nd2NiO4+δ as oxygen electrode. |
| Keywords | SOFC; Air electrode; Nd2NiO4; Area specific resistance; I-V characteristics |
| Remark |
https://doi.org/10.1016/j.jallcom.2020.158490 Link |
Synthesis and processing of SOFC components for the fabrication and characterization of anode supported cells
ID=609| Authors |
|
| Source |
Boletín de la Sociedad Española de Cerámica y Vidrio
Time of Publication: 2020
|
| Abstract | In this article, it is intended to evaluate the performances of previously synthesized different nanometric compounds as SOFC components under real conditions. For this purpose, anodic supports SOFCs have been manufactured in different configurations. The compounds NiO-(Y2O3)0.08(ZrO2)0.92 (NiO–YSZ), (Y2O3)0.08(ZrO2)0.92 (YSZ), Sm0.2Ce0.8O1.9 (SDC), La0.6Sr0.4FeO3 (LSF) and LaNi0.6Fe0.4O3 (LNF) were used as anode support, electrolyte, barrier, cathode and contact layer, respectively. To obtain the cells, the anode supports were produced by uniaxial pressing and the remaining layers were added using the airbrush technique, assembling them by different sintering processes. The cells developed have been electrochemically tested in a temperature range between 750 and 865 °C. Additionally, degradation tests have been carried out under constant current. Moreover, to characterize the microstructure of the cells, a scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectroscopy (EDX) analyzer has been used. The results obtained show that the incorporation of cathode and contact layers increases the power densities and decreases the total resistances of the cells with respect to the cell without cathode, especially with the addition of the LNF contact layer. Despite the improvement obtained, more tests have to be carried out in order to optimize the performance of SOFC devices in degradation tests. |
| Keywords | Solid oxide fuel cells; Processing; Composite; Degradations; Electrochemical impedance spectra |
| Remark |
Available online 22 December 2020 Link |
Increasing the thermal expansion of proton conducting Y-doped BaZrO3 by Sr and Ce substitution
ID=608| Authors |
|
| Source |
Solid State Ionics
Volume: 359,
Pages: 115534 Time of Publication: 2021 |
| Abstract | Proton conducting oxide electrolytes find potential application in proton ceramic fuel cells and electrolyzers operating at intermediate temperatures, e.g. 400–600 °C. However, state-of-the-art proton conducting ceramics based on Y-doped BaZrO3 (BZY) have lower thermal expansion coefficient (TEC) than most commonly applied or conceived supporting electrode structures, making the assembly vulnerable to degradation due to cracks or spallation. We have increased the TEC of 20 mol% Y-doped BZY (BZY20) by partially substituting Ba and Zr with Sr and Ce, respectively, to levels which still maintain the cubic structure and sufficiently minor n-type conduction; (Ba0.85Sr0.15)(Zr0.7Ce0.1Y0.2)O2.9 (BSZCY151020). High temperature XRD shows that this material has a cubic structure (space group ) in the temperature range of 25–1150 °C and a linear TEC of ~10 × 10−6 K−1, as compared to the ~8 × 10−6 K−1 for BZY. It exhibited a DC conductivity of ~5 mS cm−1 at 600 °C in wet H2. This electrolyte with increased TEC may find application in proton ceramic electrochemical cells in general and metal supported ones in particular. |
| Keywords | Barium zirconate; BZY; Thermal expansion coefficient; TEC; Conductivity; Proton; Proton ceramic electrochemical cells; Metal-supported |
| Remark |
https://doi.org/10.1016/j.ssi.2020.115534 Link |
Properties of Barium Cerate Thin Films Formed Using E-Beam Deposition
ID=607| Authors |
|
| Source |
Crystals
Volume: 10,
Pages: 1152 Time of Publication: 2020 |
| Abstract | This article focuses on the properties of the BaCeO3 thin films formed by electron-beam vapor deposition and investigates the formation of barium cerates on supports with different thermal expansion coefficients (Stainless Steel, Invar, Glass Sealing, and Inconel substrates) and the influence of the technological parameters on the properties of the formed thin films with an emphasis on the stability of the films. Morphology and phase composition and mechanical and electrical properties were investigated. It was found that the main factors influencing the phase composition and morphology of the films are the temperature of the support and the deposition rate. However, the mechanical properties of the films are mostly influenced by strains introduced to thin films by using different supports. Two interesting features of the electrical properties of the studied strained films were noticed: the film with the highest in-plane tensile strain showed the lowest activation energy of total conductivity, whereas the film with the lowest strain showed the highest value of total conductivity. |
| Remark | Link |
Reversible fuel electrode supported solid oxide cells fabricated by aqueous multilayered tape casting
ID=606| Authors |
|
| Source |
J. Phys. Energy
Volume: 3,
Issue: 2,
Pages: 024002 Time of Publication: 2021 |
| Abstract | Fuel electrode supported solid oxide cells (SOCs) have been developed on an industrial scale using the aqueous tape-casting technique. The NiO–yttria-stabilized zirconia Y2O3–ZrO2 (YSZ) fuel electrode and YSZ electrolyte have been manufactured by multilayer co-laminated tape casting. Details of the tape-casting slurry formulations are described and discussed. Two types of cells were fabricated with different microstructures of the NiO–YSZ support discussed. Good electrochemical performance and stability in SOFC mode at 750 °C and 0.7 V for both button cells reaching around >0.75 W cm−2 and with no measurable degradation after >700 h were observed. The selected cell was scaled up to large-area cells (36 cm2 of the active area) and electrochemically tested at 750 °C in a single repetition unit (SRU) in SOFC (Solid Oxide Fuel Cell), SOEC (Solid Oxide Electrolysis Cell) and co-SOEC (Solid Oxide co-Electrolysis Cell) mode, and in a short-stack of two SRUs in SOFC mode. A current up to 17 A was obtained at 1.4 V (0.7 V cell−1) with the short-stack configuration in SOFC mode, corresponding to ∼0.5 A cm−2 and 24 W. The performances of the aqueous-based SOC cells can be considered highly remarkable, thus supporting the success in scaling the fabrication of SOC stacks using more environmentally friendly processes than conventional ones. |
| Remark | Link |
Towards efficient oxygen separation from air: Influence of the mean rare-earth radius on thermodynamics and kinetics of reactivity with oxygen in hexagonal Y1-xRxMnO3+δ
ID=605| Authors |
|
| Source |
Acta Materialia
Volume: 205,
Pages: 116544 Time of Publication: 2021 |
| Abstract | It is documented that the mean radius of rare-earth cations occupying Y1-xRx sublattice in Y1-xRxMnO3+δ hexagonal oxides plays a decisive role in terms of thermodynamics and kinetics of reactivity of the materials with oxygen, and consequently, influences strongly the oxygen storage performance in thermal swing processes conducted in oxygen and air. Y1-xRxMnO3+δ samples with designed being close to the critical one, at the border of stability between hexagonal- and perovskite-type phases, can reversibly incorporate/release significant amounts of oxygen in pure O2 or air atmospheres, at the moderate temperatures on the order of 200–300¯°C. Characteristic temperatures of oxidation and reduction are dependent on , therefore, it is possible to adjust conditions of the temperature swing operation by the chemical doping in Y1-xRxMnO3+δ with larger rare-earth elements. Crucial from a practical point of view, an increase of the oxidation temperature in such compounds greatly enhances the speed of the oxidation process (20¯°C increase can reduce half-time of oxidation twice), which is found to be the limiting factor concerning the performance. Based on the comprehensive studies of the physicochemical properties of Y1-xRxMnO3+δ, the optimized Y0.95Pr0.05MnO3+δ composition is proposed, doped only with a small amount of more expensive praseodymium. The material exhibits excellent oxygen storage-related properties and is able for the effective production of oxygen in air by the thermal swing process, utilizing medium-/low-temperature industrial waste heat. |
| Remark | Link |
Tuning the RWGS Reaction via EPOC and In Situ Electro-oxidation of Cobalt Nanoparticles
ID=604| Authors |
|
| Source |
ACS Catal.
Volume: 10,
Issue: 24,
Pages: 14916–14927 Time of Publication: 2020 |
| Abstract | The electrochemical promotion of catalytic activity by non-noble transition metals is rarely reported in the literature. Here, Co nanoparticles were utilized for the electrochemical activation of CO2 hydrogenation under atmospheric pressure conditions. A range of transient kinetic experiments in conjunction with X-ray photoelectron spectroscopy and imaging techniques were employed to correlate the observed catalytic activity with the electronic and morphological characteristics of the cobalt catalyst surface. Our results show that migrating ions from the solid electrolyte to the catalyst surface has a dual effect, which has an impact on the observed catalytic behavior. First, they lead to an electrochemically formed double layer on the catalyst surface, which effectively modifies the catalyst work function and consequently alters the observed catalytic rate. Second, they have a profound effect on the oxidation state of cobalt and therefore on the structure of the cobalt oxide particles formed. The presence of Co oxide phases upon anodic polarization shows up to a 5-fold increase in the catalytic rate of the reverse water gas shift (RWGS) reaction. The enhancement of the catalytic activity observed in this work, with a relatively inexpensive cobalt oxide film, is comparable to that obtained with noble metal catalysts in classical EPOC studies. The present study also demonstrates that the formation of different oxide phases can be controlled accurately by electrochemical means and used to tune the catalytic activity and selectivity of cobalt. The reported results could guide the design and operation of more selective and active catalytic processes for the RWGS reaction. |
| Keywords | electrochemical promotion, cobalt oxide, CO2 hydrogenation, XPS, RWGS |
| Remark | Link |
From insulator to oxide-ion conductor by a synergistic effect from defect chemistry and microstructure: acceptor-doped Bi-excess sodium bismuth titanate Na0.5Bi0.51TiO3.015
ID=603| Authors |
|
| Source |
Journal of Materials Chemistry A
Issue: 47
Time of Publication: 2020
|
| Abstract | The influence of Ti-site acceptor-doping (Mg2+, Zn2+, Sc3+, Ga3+ and Al3+) on the electrical conductivity and conduction mechanism of a nominally Bi-excess sodium bismuth titanate perovskite, Na0.5Bi0.51TiO3.015 (NB0.51T), is reported. Low levels of acceptor-type dopants can introduce appreciable levels of oxide-ion conductivity into NB0.51T, i.e., 0.5% Mg-doping for Ti4+ can enhance the bulk conductivity of NB0.51T by more than 3 orders of magnitude with the oxide-ion transport number going from <0.1 for NB0.51T to >0.9 at 600 °C. The intriguing electrical behaviour in acceptor-doped NB0.51T dielectrics is a synergistic effect based on the defect chemistry and ceramic microstructure in these materials. NB0.51T ceramics with extremely low levels of doping show an inhomogeneous microstructure with randomly distributed large grains embedded in a small grained matrix. This can be considered as a two-phase composite with large grains as a conductive phase and small grains as an insulating phase based on an empirical conductivity – grain size relationship. Variation in the fraction of the conductive, large grained phase with increasing doping levels agrees with the oxide-ion transport number. This electrical two-phase model is supported by finite element modelling. This study reveals the significance of ceramic microstructure on the electrical conduction behaviour of these materials and can provide a guideline for selecting suitable doping strategies to meet the electrical property requirements of NBT-based ceramics for different applications. |
| Remark | Link |
Thermally stable, low resistance Mg2Si0.4Sn0.6/Cu thermoelectric contacts using SS 304 interlayer by one step sintering
ID=602| Authors |
|
| Source |
Materials Research Bulletin
Volume: 136,
Pages: 111147 Time of Publication: 2021 |
| Abstract | Device fabrication using Mg2Si1-xSnx thermoelectric (TE) material for 600–800 K application requires stable and low resistance electrical contacts between TE legs and the electrodes. In this study, n-type Mg2Si0.38Sn0.6Bi0.02 was hot-pressed with Cu electrodes in a single step, resulting in Cu3Mg2Si and Cu4MgSn phases at the interface. Although the specific contact resistance (rc) across the interface was 4.4 ± 0.9 μΩ.cm2, the electrical resistivity of the TE leg increased by approximately 60 % due to Cu diffusion through the interface. Incorporating the SS304 interlayer to prevent Cu diffusion increased rc to 6.1 ± 2 μΩ.cm2. Upon annealing at 723 K for 3–15 days, rc remained at <10 μΩ.cm2 with an approximately 15 % decrease in the power factor. However, without SS304, rc increased to 41.5 ± 18 μΩ.cm2, with 65 % reduction in the power factor. Thus, this work demonstrates the fabrication of thermally stable Cu/Mg2Si0.4Sn0.6 joints by using the SS304 interlayer in a single-step process. |
| Remark | Link |
NiO–ZnO based junction interface as high-temperature contact materials
ID=601| Author |
|
| Source |
Ceramics International
Volume: 47,
Issue: 6,
Pages: 8053-8059 Time of Publication: 2021 |
| Abstract | Contact materials play a crucial role in an electronic device operating at moderate and elevated temperatures where chemical and thermal stability is of great importance. Oxide materials and their interfaces are potential candidates as high-temperature contact materials due to their high chemical and thermal stabilities. In this work, polycrystalline oxides of Ni0.98Li0.02O and Zn0.98Al0.02O were used to make junction interfaces, where the solid-state synthesis method was used to obtain the individual oxide materials. After assembly of the junction interfaces, properties such as electrical, chemical, and thermal stabilities of the interfaces were investigated. The electrical properties were assessed through current-voltage (I–V) and electrochemical impedance spectroscopy (EIS) measurements, where the interface revealed a transition from electrically rectifying to slightly ohmic contact within a temperature range from 500–1000 °C. After annealing the junction interfaces at these elevated temperatures, no secondary phase was observed at the junction interface, i.e., the interfaces remain chemically stable. Moreover, the effect of isothermal annealing on the I–V characteristics curve of the junction showed an increased reverse current output over long annealing time, attributed mainly to the increased effective contact area at the junction interface and cation inter-diffusion processes. Furthermore, an investigation of the cation inter-diffusion mechanism revealed mainly lattice diffusion of Zn2+ into Ni0.98Li0.02O, while Ni2+ diffusion into Zn0.98Al0.02O exhibited both lattice and grain-boundary diffusion mechanisms. |
| Keywords | Interfaces; Thermal stability; Electrical properties; Diffusion |
| Remark | Link |
Processing Ceramic Proton Conductor Membranes for Use in Steam Electrolysis
ID=600| Authors |
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| Source |
Membranes
Volume: 10,
Issue: 11,
Pages: 339 Time of Publication: 2020 |
| Abstract | Steam electrolysis constitutes a prospective technology for industrial-scale hydrogen production. The use of ceramic proton-conducting electrolytes is a beneficial option for lowering the operating temperature. However, a significant challenge with this type of electrolyte has been upscaling robust planar type devices. The fabrication of such multi-layered devices, usually via a tape casting process, requires careful control of individual layers’ shrinkages to prevent warping and cracks during sintering. The present work highlights the successful processing of 50 × 50 mm2 planar electrode-supported barium cerium yttrium zirconate BaZr0.44Ce0.36Y0.2O2.9 (BZCY(54)8/92) half cells via a sequential tape casting approach. The sintering parameters of the half-cells were analyzed and adjusted to obtain defect-free half-cells with diminished warping. Suitably dense and gas-tight electrolyte layers are obtained after co-sintering at 1350 °C for 5 h. We then assembled an electrolysis cell using Ba0.5La0.5CoO3−δ as the steam electrode, screen printed on the electrolyte layer, and fired at 800 °C. A typical Ba0.5La0.5CoO3−δ|BaZr0.44Ce0.36Y0.2O3−δ(15 μm)|NiO-SrZr0.5Ce0.4Y0.1O3−δ cell at 600 °C with 80% steam in the anode compartment reached reproducible terminal voltages of 1.4 V @ 500 mA·cm−2, achieving ~84% Faradaic efficiency. Besides electrochemical characterization, the morphology and microstructure of the layered half-cells were analyzed by a combination of high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and energy-dispersive X-ray spectroscopy. Our results also provide a feasible approach for realizing the low-cost fabrication of large-sized protonic ceramic conducting electrolysis cells (PCECs). |
| Remark | Link |
Cation-driven electrical conductivity in Ta-doped orthorhombic zirconia ceramics
ID=599| Authors |
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| Source |
Ceramics International
Volume: 47,
Issue: 5,
Pages: 7248-7252 Time of Publication: 2021 |
| Abstract | This paper is devoted to the study of the electrical conductivity of tantalum-doped zirconia ceramics prepared by spark plasma sintering. In this study, the temperature dependence of conductivity in as-prepared specimens and in those previously annealed in air is determined and compared. A semi-empirical model, which is based on the oxidation states of the cations, has been developed and successfully assessed. According to this, the conductivity is basically controlled by the diffusion of tetravalent zirconium cations in both cases, although the concentration of these species varies drastically with the amount of induced oxygen vacancies. This is a quite unexpected fact, since conductivity is normally controlled by anionic diffusion in zirconia ceramics. This option is forbidden here due to the presence of substitutional pentavalent cations. Therefore, conductivity values are much lower than those reported in trivalent or divalent substitutional cation doped zirconia ceramics. |
| Remark | Link |
Direct Solid Oxide Electrolysis of Carbon Dioxide:Analysis of Performance and Processes
ID=598| Authors |
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| Source |
Processes
Volume: 8,
Pages: 1390 Time of Publication: 2020 |
| Abstract | Chemical industries rely heavily on fossil resources for the production of carbon-basedchemicals. A possible transformation towards sustainability is the usage of carbon dioxide as asource of carbon. Carbon dioxide is activated for follow-up reactions by its conversion to carbonmonoxide. This can be accomplished by electrochemical reduction in solid oxide cells. In thiswork, we investigate the process performance of the direct high-temperature CO2electrolysis bycurrent-voltage characteristics (iV) and Electrochemical Impedance Spectroscopy (EIS) experiments.Variations of the operation parameters temperature, load, fuel utilization, feed gas ratio and flowrate show the versatility of the procedure with maintaining high current densities of 0.75 up to1.5 A·cm−2, therefore resulting in high conversion rates. The potential of the high-temperature carbondioxide electrolysis as a suitable enabler for the activation of CO2as a chemical feedstock is thereforeappointed and shown. |
| Remark | Link |
Structural, optical, and dielectric properties of Bi2O3-K2O-TiO2-P2O5 glasses and related glass-ceramics
ID=597| Authors |
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| Source |
Phase Transitions
Volume: 93,
Issue: 10-11
Time of Publication: 2020
|
| Abstract | The glasses in the Bi2O3-K2O-TiO2-P2O5 system were elaborated by the conventional quenching method. Their structure was studied by Raman spectroscopy, and additional information is determined from density measurements and thermal analysis. The optical absorption of the glasses is investigated and it is found that the optical gap and the Urbach energy decrease and increase, respectively, with increasing Bi2O3 content. The crystallization of the glasses was performed under controlled heat treatments to develop glass-ceramics. Their dielectric constants are carried out by impedance spectroscopy. The variations of the permittivity (µr) and the dielectric loss (tanδ) versus frequency and temperature are determined. It is evidenced that the introduction of Bi2O3 in the glasses diminished the dispersion at low frequencies. The presence of bismuth oxide in the materials is also beneficial since it allowed the formation of glass-ceramics with high dielectric constant and low dielectric loss. |
| Remark | Link |
Strategies to Mitigate the Degradation of Stainless-SteelInterconnects Used in Solid Oxide Fuel Cells
ID=596| Author |
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| Source |
Time of Publication: 2020
|
| Abstract | Interconnects are a vital part of solid oxide fuel cells (SOFC), where they electricallyconnect individual cells to form a fuel cell stack. They are a main contributor to theoverall stack cost and the limited life-time of fuel cells, and, therefore, improvementscarried out on the interconnect level could further the commercialization of SOFCs.The limited life-time of the interconnect is related to the material used today, ferriticstainless steels (FSS). FSS interconnects are more cost-effective than previously usedceramics, but they degrade under the conditions prevalent in an SOFC: high temperaturesbetween 600°C and 850°C, and a p(O2) gradient. Certain corrosion phenomena thatoccur, such as Cr evaporation and continuous oxide scale growth, negatively impact cellperformance due to cathode poisoning and increased electrical resistance, respectively.These phenomena have been found to be effectively mitigated by coatings, such as the(Co,Mn)3O4(MCO) coating, or reactive element coatings, such as Ce.The present thesis examines these coatings with regard to three aspects: (i) doesthe semi-conducting spinel coating affect the electrical resistance of the interconnectnegatively, or is its conductivity negligible in comparison to the continuously growingCr2O3scale below it; (ii) does the coating self-heal if it is cracked even at intermediatetemperatures, i.e. 650°C and 750°C, or do the cracks persist and increase Cr evaporation;and (iii) is the long-term stability of the state-of-the-art Ce/Co coating (10 nm Ce/640 nmCo) still effective after 35 000 h, or not. The second aspect is not only important tounderstand corrosion behavior, but it would also allow for large-scale roll-to-roll PVDcoating, which is significantly more cost-effective than batch coating.Another corrosion phenomenon that is elucidated within the scope of this work is thedual atmosphere effect. This effect leads to increased corrosion on the air-facing side ofthe interconnect if the FSS is exposed to a dual atmosphere, i.e. air on one side andhydrogen on the other side, compared to if the FSS is exposed to an air-only atmosphere.A new theory as to why the dual atmosphere effect occurs is proposed, and it is indirectlyverified by means of excluding all other possibilities. Factors that influence the dualatmosphere effect are discussed, and it is shown how the dual atmosphere effect could, inpart, be mitigated. |
| Keywords | Solid Oxide Fuel Cell; Corrosion; Interconnect; Cr Evaporation; Area SpecificResistance; Deformation; Long-term; Dual Atmosphere; Hydrogen |
| Remark |
THESIS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY Link |
Processing and properties of translucent bismuth sodium titanate ceramics
ID=595| Authors |
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| Source |
Journal of the European Ceramic Society
Volume: 41,
Issue: 2,
Pages: 1221-1229 Time of Publication: 2021 |
| Abstract | Lead-free bismuth sodium titanate piezoceramics were processed by a solid-state route with a novel precursor approach. By carefully controlling the processing parameters and sintering atmospheres, translucent ceramics with pore-free, homogeneous microstructures with exceptionally low dielectric loss at elevated temperatures. The pore-free microstructure can influence the operating life of a dielectric device positively, since pores and other microstructural defects are usually responsible for material failures within devices. Synchrotron and surface X-ray diffraction experiments revealed a clear dependence of the crystal structure on sintering parameters and defect chemistry. Microstructural analysis showed a dependency of a secondary phase on the sintering atmosphere. The grain size could be adjusted using a shortened grinding process instead of using the common methods like increasing calcining or sintering temperature. |
| Remark | Link |
Mitigation of grain boundary resistance inLa2/3-xLi3xTiO3perovskite as an electrolyte forsolid-state Li-ion batteries
ID=594| Authors |
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| Source |
J Mater Sci Energy materials
Pages: 2435–2450 Time of Publication: 2021 |
| Abstract | In this work, we report that modification of the chemical composition of grainboundaries of La2/3-xLi3xTiO3double perovskite, one of the most promising Li-ion conducting solid electrolytes, can be a convenient and versatile way ofcontrolling the space charge potential, leading to a mitigated electrical resistanceof the grain boundaries. Two groups of additives are investigated: lithium-enriching agents (Li3BO3, LiF) and 3dmetal ions (Co2?,Cu2?), both expected toreduce the Schottky barrier. It is observed that Li-containing additives workeffectively at a higher sintering temperature of 1250°C. Regarding copper, itshows a much stronger positive impact at lower temperature, 1150°C, while theaddition of cobalt is always detrimental. Despite overall complex behavior, it isdocumented that the decreased space charge potential plays a more importantrole in the improvement of lithium conduction than the thickness of the grainboundaries. Among the proposed additives, modification of La2/3-xLi3xTiO3by2 mol.% Cu2?results in the space charge potential reduction by 32 mV inrelation to the reference sample, and the grain boundary specific conductivityincrease by 80%, as measured at 30°C. Introduced additive allows to obtain asimilar effect on the conductivity as elevating the sintering temperature, whichcan facilitate manufacturing procedure. |
| Remark | Link |
Crystal structures and proton transport properties of Sr2(Ti1-xMx)O4-δ (M = Fe, Al)
ID=593| Authors |
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| Source |
Solid State Sciences
Volume: 108,
Pages: 106407 Time of Publication: 2020 |
| Abstract | This study focuses on the effects of acceptor dopants in proton-conductive Sr2TiO4-based layered perovskites. We synthesized Sr2Ti0.9Fe0.1O4-δ (STF10) and Sr2Ti0.95Al0.05O4-δ (STA05) and evaluated the influence of ion substitution on their crystal structures, electrical conductivities, and proton transport properties. Our obtained results suggest that a redox reaction is the more favorable mechanism for the introduction of proton defects to Fe-doped samples compared with water vapor absorption, while the reverse is true for Al-doped samples. STF10 was found to exhibit a larger electrical conductivity at low temperatures than STA05. In addition, STF10 presented a proton transport number of 0.5 at 600 °C, while the corresponding value for STA05 was 0.5–0.6 at 450–600 °C. The higher proton transport number of STA05 at 450–550 °C compared to that of STF10 indicates that the Al-dopant suppressed the electronic conductivity owing to its constant valency. We therefore considered that characterization of the changes in material properties related to ion substitution can serve as a guide for material selection when developing proton-conducting solid oxide fuel cell technologies. |
| Remark | Link |
Dynamics of Hydroxyl Anions Promotes Lithium Ion Conduction in Antiperovskite Li2OHCl
ID=592| Authors |
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| Source |
Chem. Mater.
Volume: 32,
Issue: 19,
Pages: 8481–8491 Time of Publication: 2020 |
| Abstract | Li2OHCl is an exemplar of the antiperovskite family of ionic conductors, for which high ionic conductivities have been reported, but in which the atomic-level mechanism of ion migration is unclear. The stable phase is both crystallographically defective and disordered, having ∼1/3 of the Li sites vacant, while the presence of the OH– anion introduces the possibility of rotational disorder that may be coupled to cation migration. Here, complementary experimental and computational methods are applied to understand the relationship between the crystal chemistry and ionic conductivity in Li2OHCl, which undergoes an orthorhombic to cubic phase transition near 311 K (≈38 °C) and coincides with the more than a factor of 10 change in ionic conductivity (from 1.2 × 10–5mS/cm at 37 °C to 1.4 × 10–3 mS/cm at 39 °C). X-ray and neutron experiments conducted over the temperature range 20–200 °C, including diffraction, quasi-elastic neutron scattering (QENS), the maximum entropy method (MEM) analysis, and ab initio molecular dynamics (AIMD) simulations, together show conclusively that the high lithium ion conductivity of cubic Li2OHCl is correlated to “paddlewheel” rotation of the dynamic OH– anion. The present results suggest that in antiperovskites and derivative structures a high cation vacancy concentration combined with the presence of disordered molecular anions can lead to high cation mobility. |
| Remark | Link |
Conduction properties of acceptor-doped BaTiO3–Bi(Zn1/2Ti1/2)O3-based ceramics
ID=591| Authors |
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| Source |
Journal of Materials Science
Volume: 55,
Pages: 16290–16299 Time of Publication: 2020 |
| Abstract | A series of acceptor-doped ceramics based on the solid solution, (1-x)BaTiO3–xBi(Zn1/2Ti1/2)O3 (BT-BZT), where x = 0.1, 0.2, 0.3, 0.4, were prepared via solid-state synthesis to investigate the effect of doping and BZT content on conduction properties. Impedance spectroscopy measurements showed an increase in conductivity through acceptor doping with Mg on the Ti-site (Mg′′Ti). Ceramics of the composition, 0.80BaTiO3–0.20Bi(Zn1/2Ti1/2)O3 with 3 mol% Mg′′Ti, showed the highest conductivity in this study at 1.28 mScm−1 (~ 600 °C), an order of magnitude improvement over the stoichiometric composition. Variable pO2 impedance measurements revealed p-type conductivity in the grain while EMF measurements showed that above ~ 550 °C, ions are the dominant charge carriers (transference number, ti = 0.91 at 735 °C). Similarly, all 3 mol% Mg-doped compositions above x = 0.1 were primarily ionic conductors with transference numbers above ti = 0.79 (735 °C). X-ray diffraction data showed a pseudocubic primary phase for all samples with evidence of additional impurity phases accompanying samples with 3 mol% Mg′′Ti or greater. |
| Remark | Link |
Stabilized Charge, Spin, and Orbital Ordering by the 6s2 Lone Pair in Bi0.5Pb0.5MnO3
ID=590| Authors |
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| Source |
Inorg. Chem.
Volume: 59,
Issue: 18,
Pages: 13390–13397 Time of Publication: 2020 |
| Abstract | Bi and Pb ions with charge degree of freedom depending on 6s2 and 6s0 electronic configurations were combined with the Mn ion in a perovskite oxide. Comprehensive theoretical and experimental investigations revealed the Bi3+0.5Pb2+0.5Mn3+0.5Mn4+0.5O3 charge ordered state with CE-type spin and dz2 orbital orderings as observed in La0.5Ca0.5MnO3, Nd0.5Sr0.5MnO3, and Bi0.5Sr0.5MnO3. The charge and orbital orderings were preserved above 500 K owing to the stereochemical activity of Bi3+ and Pb2+ ions which stabilized the structural distortion. |
| Remark | Link |
Ionic conductivity in LixTaOy thin films grown by atomic layer deposition
ID=589| Authors |
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| Source |
Electrochimica Acta
Volume: 361,
Pages: 137019 Time of Publication: 2020 |
| Abstract | The material system Li-Ta-O is a promising candidate for thin-film solid-state electrolytes in Li-ion batteries. In the present study, we have varied the Li content x in LixTaOy thin films grown by atomic layer deposition (ALD) with the aim of improving the Li-ion conductivity. The amorphous films were grown at 225 °C on insulating sapphire and on conductive Ti substrates using tantalum ethoxide (Ta(OEt)5), lithium tert-butoxide (LiOtBu) and water as reactants. The film composition was determined by time-of-flight elastic recoil detection analysis (TOF-ERDA), displaying an almost linear relationship between the pulsed and deposited Li content. The ionic conductivities were determined by in-plane and cross-plane AC measurements, exhibiting an Arrhenius-type behaviour and comparatively weak thickness-dependence. Increasing Li content x from 0.32 to 0.98 increases the film conductivity by two orders of magnitude while higher Li content x = 1.73 results in decreased conductivity. A room-temperature conductivity σRT of ~10−8 S cm−1 is obtained for a 169 nm thick Li0.98TaOy film. The evolution of conductivity and activation energy suggests a competing effect between the concentration and the mobility of mobile Li ions when more Li are incorporated. The compositional dependence of Li transport mechanism is discussed. |
| Keywords | Atomic layer deposition; LixTaOy thin films; Solid-state electrolytes; TOF-ERDA; Ionic conductivity |
| Remark | Link |
Examination of Dielectric Properties of BaTiO3-SrTiO3 Based Systems
ID=588| Author |
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| Source |
Time of Publication: 2020
|
| Abstract | This thesis examines the dielectric properties of two systems based on the perovskite materials barium titanate and strontium titanate. A solid solution was created starting with these base materials and then adding varying amounts of bismuth-zinc titanateand sodium niobate. These compositions were calcined and sintered at temperatures determined to be the most phase-pure by x-ray diffraction. Sintered pellets were then tested using equipment to measure their capacitance as a function of temperature and their strain as a function of applied electric field. From these results and the x-ray diffraction data the lattice parameter and dielectric constant was calculated. The system with sodium niobate had the highest capacitance and dielectric constant overall. The composition with the highest capacitance, greater than 4nf at room temperature at all tested frequencies, and dielectric constant, greater than 4000 at all tested frequencies, was 68.6 mol% barium titanate, 29.4 mol% strontium titanate, and 2 mol% sodium niobate. |
| Remark |
A THESIS, Baccalaureate of Science in Electrical and Computer Engineering Link |
Structural and Electrochemical Properties of Tysonite Ce0.95A0.05F2.95 (A = Mg, Ca, Sr, and Ba): Fast-Fluoride-Ion-Conducting Solid Electrolytes
ID=587| Authors |
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| Source |
J. Phys. Chem. C
Volume: 124,
Issue: 34,
Pages: 18452–18461 Time of Publication: 2020 |
| Abstract | All-solid-state fluoride shuttle batteries (FSBs) present endless possibilities for next-generation rechargeable batteries. However, no standard choice for solid electrolytes and electrodes in FSBs has been established to date. Additionally, details of how F ions travel through the working device are yet to be fully understood. Here, we studied the electrochemical properties of tysonite Ce0.95A0.05F2.95 (A = Ca, Sr, and Ba) and Ce0.95Mg0.05F2.95 (actually, a composite of CeF3 and MgF2) solid electrolytes, and their crystal structures using neutron diffraction data. In particular, Ce0.95Ca0.05F2.95 exhibited the highest electrical conductivity and the shortest bond between F ions. Furthermore, F-vacancies introduced by the substitution of Ca2+ for Ce3+ were accommodated only at the F1 site. The bond valence sum (BVS) analysis results indicated that there was a significant difference in the BVS values of F ions: BVS(F1) = −0.92 on [F1] layers, and BVS(F2) = −1.13 and BVS(F3) = −1.07 on [M (=Ce0.95Ca0.05), F2, F3] layers, which were stacked alternately along the c-axis of the trigonal cell. The BVS(F2) value was relatively lower than the BVS(F1) and BVS(F3) ones, indicating that F2 is tightly bonded to M compared to that of F1 or F3. The findings suggested that F1–F1 and F1–F3 sublattices play a key role in the high mobility of the conducting F ions. |
| Remark | Link |
Synthesis, structure, magnetic behavior and dielectric relaxation of the LaxSr2-xFeхTi1-хO4 (х = 0.5, 0.7) oxide ceramic
ID=586| Authors |
|
| Source |
Journal of Solid State Chemistry
Volume: 292,
Pages: 121687 Time of Publication: 2020 |
| Abstract | This study is devoted to the investigation of the high dielectric constant causes in complex oxides with a structure of the K2NiF4 type. А new thermobaric treated ceramics on the basis conjugate LaxSr2-xFeхTi1-хO4 (х = 0.5, 0.7) solid solutions was synthesized and the study their structure, microstructure, magnetic and dielectric properties was performed. It is shown that antiferromagnetic interactions coexist with ferromagnetic, which become dominant towards to low temperatures; the appearance of two types of magnetic interactions may be related to the presence of magnetic ions of different valences. Different values of the dielectric constants ε are observed in wide region of frequencies 10–107 Hz. In obtained at ambient pressure LaxSr2-xFeхTi1-хO4 (х = 0.5, 0.7) ceramics the highest permittivity ε value is only 30–50 in the frequency range from 1 kHz to 1 MHz. After the samples treatment at 1273 K and P = 4 GPa during 5 min ε increases to 5–102–103 at 293 š and independent of frequency in the range (102–106) Hz. At the temperature increase the permittivity as well increases and the ε value becomes ~106 at, approximately, f = 100 Hz and T = 750 K. An obvious change of samples microstructure and polyhedra structure anisotropy in LaxSr2-xFeхTi1-хO4 (х = 0.5, 0.7) was observed after the thermobaric treatment. Described in this article performed dielectric properties investigations indicate that possible reasons of the high-permittivity origin are specifics of layered structure, microstructure and charge polarization associated with it, Maxwell-Wagner polarization at the grain boundaries and inhomogeneities and small polaron hopping conduction mechanism. |
| Keywords | Complex oxides; Synthesis; Ceramics; High pressure; Magnetization; Dielectric properties |
| Remark |
https://doi.org/10.1016/j.jssc.2020.121687 Link |
Structural and Electrochemical Properties of Tysonite Ce0.95A0.05F2.95 (A = Mg, Ca, Sr, and Ba): Fast-Fluoride-Ion-Conducting Solid Electrolytes
ID=585| Authors |
|
| Source |
J. Phys. Chem. C
Volume: 124,
Issue: 34,
Pages: 18452–18461 Time of Publication: 2020 |
| Abstract | All-solid-state fluoride shuttle batteries (FSBs) present endless possibilities for next-generation rechargeable batteries. However, no standard choice for solid electrolytes and electrodes in FSBs has been established to date. Additionally, details of how F ions travel through the working device are yet to be fully understood. Here, we studied the electrochemical properties of tysonite Ce0.95A0.05F2.95 (A = Ca, Sr, and Ba) and Ce0.95Mg0.05F2.95 (actually, a composite of CeF3 and MgF2) solid electrolytes, and their crystal structures using neutron diffraction data. In particular, Ce0.95Ca0.05F2.95 exhibited the highest electrical conductivity and the shortest bond between F ions. Furthermore, F-vacancies introduced by the substitution of Ca2+ for Ce3+ were accommodated only at the F1 site. The bond valence sum (BVS) analysis results indicated that there was a significant difference in the BVS values of F ions: BVS(F1) = −0.92 on [F1] layers, and BVS(F2) = −1.13 and BVS(F3) = −1.07 on [M (=Ce0.95Ca0.05), F2, F3] layers, which were stacked alternately along the c-axis of the trigonal cell. The BVS(F2) value was relatively lower than the BVS(F1) and BVS(F3) ones, indicating that F2 is tightly bonded to M compared to that of F1 or F3. The findings suggested that F1–F1 and F1–F3 sublattices play a key role in the high mobility of the conducting F ions. |
| Remark | Link |
Structural characterization and electrical/electrochemical studies of Nd1-xBaxCo1-y(Fe, Ti)y O3-δ (0 ≤ x ≤ 0.3, y = 0, 0.2) materials as cathode for SOFCs application
ID=584| Authors |
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| Source |
Journal of Solid State Chemistry
Volume: 292,
Pages: 121682 Time of Publication: 2020 |
| Abstract | Perovskite oxide powders of Nd1-xBaxCo1-y (Fe, Ti)y O3-δ (0 ≤ x ≤ 0.3, y = 0, 0.2) were synthesized by combustion technique and investigated as cathode materials for SOFCs application. The Rietveld refinement of the XRD data confirms the formation of single phase orthorhombic perovskite structure of Pbnm space group within the compositions (0 ≤ x ≤ 0.1, y = 0, 0.2). The microstructural studies revealed the grains generated are irregular in shape and non uniform in size in the micrometer range. The X-ray photoelectron spectroscopy (XPS) analysis confirms the presence of mixed valence states of Co3+/Co4+, Fe3+/Fe4+, Ti4+/Ti3+ and O-Lattice/O-Chemisorbed/O-physisorbed species. The measured average CTE values are varies from 18–25 × 10−6 K−1 in the temperature range 200–900 °C for all the synthesized samples. The electrical conductivity values are found to be 252 Scm−1, 308 Scm−1, 157 Scm−1 at 700 °C for the compositions Nd0.9Ba0·1CoO3-δ (NBC 0.1), Nd0.9Ba0·1Co0·8Fe0·2O3-δ (NBCFO), Nd0.9Ba0·1Co0·8Ti0·2O3-δ (NBCTO), respectively. XRD analysis reveals no chemical reactivity for the compositions NBCFO, NBCTO with 20 mol% gadolinium doped ceria oxide (Ce0.8Gd0.2O2−δ) electrolyte material after firing at 1200 °C for 8 h. The area specific resistances (ASR) were calculated for the symmetrical cells and are found to be 0.67 Ω cm2, 1.07 Ω cm2 at 850 °C for the NBCFO, NBCTO compositions, respectively. Among the compositions evaluated Nd0.9Ba0·1Co0·8Fe0·2O3-δ showed highest total electrical conductivity ~308 Scm−1 and lowest ASR value ~0.67 Ωcm2 compared to all other compositions. Hence the result suggests the synthesized Nd0.9Ba0·1Co0·8Fe0·2O3-δ composition could be a promising cathode material for SOFCs application. |
| Remark | Link |
Effect of the Complexing Agent in the Pechini Method on the Structural and Electrical Properties of an Ionic Conductor of Formula La1−xSrxAlO3−δ (x = 0, 0.05, 0.1, 0.15)
ID=583| Authors |
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| Source |
Advances in Renewable Hydrogen and Other Sustainable Energy Carriers
Pages: 387-393 Time of Publication: 2020 |
| Abstract | The Ion conductors are used as electrolytes in high temperature Solid Oxide Fuel Cells SOFCs. The preparation route has an important role on their structural and electrical properties. In this study, we used a modified Pechini method to prepare an ionic conductor based on lanthanum aluminate doped with strontium La1−xSrxAlO3−δ (x = 0.0.05, 0.1, 0.15). The effect of two complexing agents on structural and electrical properties was studied, we used Ethylene Diamine Tetra Acetic EDTA, and tartaric acid TA as complexing agents. The perovskite phases were obtained at 900 °C and characterized by different techniques; SEM images show that grain size is in the nanometer range, XRD analysis shows that the compounds prepared by use of the two complexing agents crystallize in a perovskite structure with an orthorhombic system and an R3m space group, the doped phases prepared by EDTA have a secondary phase LaSrAl3O7 which is absent in the compounds prepared by tartaric acid. The determination of the ionic conductivity by electrochemical impedance spectroscopy shows clearly the effect of the complexing agent. Indeed we have found that the value of the ionic conductivity is higher for the phases produced by the Pichini method in the presence of tartaric acid as complexing agent. |
| Remark | Link |
High Cu content LaNi1-xCuxO3-δ perovskites as candidate air electrode materials for Reversible Solid Oxide Cells
ID=582| Authors |
|
| Source |
International Journal of Hydrogen Energy
Volume: 45,
Issue: 53,
Pages: 29449-29464 Time of Publication: 2020 |
| Abstract | High Cu content perovskite-type LaNi1-xCuxO3-δ oxides are evaluated as alternative air electrode materials for Solid Oxide Cells. Auto-combustion synthesis allowed to obtain fine oxide powders up to a Cu content of x = 0.75 under ambient pressure. Investigations of the crystal structure, oxygen deficiency, chemical and thermal stability, as well as transport properties reveal satisfactory characteristics, with high total electrical conductivity and high concentration of oxygen vacancies at elevated temperatures. LaNi1-xCuxO3-δ-based electrode layers show low polarization resistance values in La0.8Sr0.2Ga0.8Mg0.2O3-δ-based symmetrical cells. The lowest values for Cu-rich compositions at 800 °C are 0.056 Ω cm−2 for LaNi 0.5Cu0.5O3-δ and 0.054 Ω cm−2 for LaNi0.25Cu0.75O3-δ with La0.2Ce0.8O3-δ buffer layer. For the reversible cell with LaNi0.5Cu0.5O3-δ air electrode, approx. 870 mW cm−2 power density output at 900 °C is obtained when fueled with wet H2, as well as over 3 A cm−2 current density at 2 V in the electrolysis mode. |
| Remark | Link |
Electrical properties of gadolinia-doped ceria for electrodes for magnetohydrodynamic energy systems
ID=581| Authors |
|
| Source |
SN Applied Sciences
Volume: 2
Time of Publication: 2020
|
| Abstract | High temperature conducting ceramics are of current interest for use as electrode materials for magnetohydrodynamic (MHD) power generation systems for their high conductivity values and their excellent stability under extreme conditions including operating temperatures above 2000 °C. Ceria doped with Gd (GDC) has been extensively studied for intermediate temperature applications and shows promise as an efficient electrode material. A summary of the current understanding of the electrical properties of GDC is provided with an emphasis on the higher temperature limits. Experiments to further validate the conclusions drawn in the literature review confirm that with electrical conductivities near 10 S/m at 1100 °C make GDC a good candidate electrode material for an MHD power generator. |
| Remark | Link |
Domain wall conductivity as the origin of enhanced domain wall dynamics in polycrystalline BiFeO3
ID=580| Authors |
|
| Source |
Journal of Applied Physics
Volume: 128,
Pages: 064104 Time of Publication: 2020 |
| Abstract | Despite their primary importance in modern nanoelectronics, conductive domain walls (DWs) can also have a marking effect on the macroscopic response of polycrystalline ferroelectrics. In particular, a large nonlinear piezoelectric response at sub-Hz driving-field frequencies has been previously observed in BiFeO3, which was linked to the conductive nature of the DWs but whose exact origin has never been explained. In this study, by carefully designing the local conductivity in BiFeO3 using chemical doping, we found that the low-frequency piezoelectric nonlinearity is only observed in the sample with a large fraction of conductive DWs. Supported by nonlinear Maxwell–Wagner modeling, we propose that this large response originates from DW displacements inside a specific set of grains or grain clusters in which the internal electric fields are enhanced due to M-W effects. We thus show that these effects likely arise due to the pronounced local anisotropy in the electrical conductivity, varying from grain to grain, whose origin lies in the conductive DWs themselves. The results demonstrate the possibility of controlling the global nonlinear properties of polycrystalline ferroelectrics by engineering local properties. |
| Remark | Link |
Thermal, optical and electrical properties of MnO2-doped mixed sodium potassium phosphate glasses
ID=579| Authors |
|
| Source |
Journal of Thermal Analysis and Calorimetry
Time of Publication: 2020
|
| Abstract | Glasses in the system (1 − x)(0.5NaPO3–0.5KPO3)–xMnO2, with 0 ≤ x ≤ 50 mol%, have been prepared using a melt-quench route. The glasses exhibit a yellow to dark color with the increase in manganese content owing to the presence of Mn2+ and Mn3+ ions in the network. The amorphous state of the glasses is evidenced by the X-ray diffraction. In order to get an insight into the physical and structural aspects of these vitreous materials, we have determined some of their parameters such as density, molar volume and glass transition temperature. From differential thermal analysis scan on heating, we evaluated the glass transition temperature (Tg) of each glass, which corresponds to the phase transition temperature from solid to viscous liquid. The density (ρ) as a structural index is found to increase while the corresponding molar volume decreases with MnO2 content. The structural approach of the studied glasses is evaluated by infrared (IR) and electron paramagnetic resonance (EPR) spectroscopies. IR technique allowed us to identify the coexisting bond vibration modes in the glass network, and it has shown that many structural phosphates units coexist, mainly pyrophosphate and metaphosphate structural groups. EPR experiments have shown the presence of Mn2+ centers in the glasses. The UV–Visible absorption is utilized to estimate the values of the optical band gap (Eg) and Urbach energy (ΔE). The optical band gap energy is determined from both the absorption spectrum fitting (ASF) and Tauc’s methods. These optical parameters are composition dependence. The dc conductivity of the glasses is determined in the temperature range from 303 to 473 K. It decreases with increasing manganese content. It is thermally activated and followed an Arrhenius behavior. The crystallization of glasses is realized by submitting them to heat treatments, and the crystallized phases are identified by XRD analysis. The crystallization kinetic was studied under non-isothermal conditions. The activation energy (Ec) and the Avrami parameter (n) were determined. |
| Remark | Link |
In-situ Ni exsolution from NiTiO3 as potential anode for solid oxide fuel cells
ID=578| Authors |
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| Source |
International Journal of Hydrogen Energy Volume: 45, Issue: 43 Time of Publication: 2020 |
| Abstract | Sample NiTiO3 (NTO) is prepared by the molten salts synthesis route as a potential anode material for solid oxide fuel cell (SOFC) applications. An additional sample impregnated with 5 mol%Ni (N-NTO) is also presented. Structural characterization reveal a pure NiTiO3 phase upon calcination at 850 °C and 1000 °C. Redox characterization by temperature programmed reduction tests indicate the transition from NiTiO3 to Ni/TiO2 at ca. 700 °C. Ni nanoparticles (ca. 26 nm) are exsolved in-situ from the structure after a reducing treatment at 850 °C. Catalytic activity tests for partial oxidation of methane performed in a fixed bed reactor reveal excellent values of activity and selectivity due to the highly dispersed Ni nanoparticles in the support surface. Time-on-stream behavior during 100 h operation in reaction conditions for sample N-NTO yield a stable CH4 conversion. Electrolyte supported symmetrical cells are prepared with both materials achieving excellent polarization resistance of 0.023 Ω cm2 in 7%H2/N2 atmosphere at 750 °C with sample N-NTO. The maximum power density achieved is of 273 mW cm−2 at 800 °C with a commercial Pt ink used as a reference cathode, indicating further improvement of the system can be achieved and positioning the N-NTO material as a promising SOFC anode material. |
| Remark | Link |
Support effects on catalysis of low temperature methane steam reforming
ID=577| Authors |
|
| Source |
RSC Adv.
Volume: 10,
Pages: 26418-26424 Time of Publication: 2020 |
| Abstract | Low temperature (<500 K) methane steam reforming in an electric field was investigated over various catalysts. To elucidate the factors governing catalytic activity, activity tests and various characterization methods were conducted over various oxides including CeO2, Nb2O5, and Ta2O5 as supports. Activities of Pd catalysts loaded on these oxides showed the order of CeO2 > Nb2O5 > Ta2O5. Surface proton conductivity has a key role for the activation of methane in an electric field. Proton hopping ability on the oxide surface was estimated using electrochemical impedance measurements. Proton transport ability on the oxide surface at 473 K was in the order of CeO2 > Nb2O5 > Ta2O5. The OH group amounts on the oxide surface were evaluated by measuring pyridine adsorption with and without H2O pretreatment. Results indicate that the surface OH group concentrations on the oxide surface were in the order of CeO2 > Nb2O5 > Ta2O5. These results demonstrate that the surface concentrations of OH groups are related to the proton hopping ability on the oxide surface. The concentrations reflect the catalytic activity of low-temperature methane steam reforming in the electric field. |
| Remark | Link |
Defects and polaronic electron transport in Fe2WO6
ID=576| Authors |
|
| Source |
Physical Chemistry Chemical Physics
Issue: 27
Time of Publication: 2020
|
| Abstract | We report the synthesis of phase pure Fe2WO6 and its structural characterization by high quality synchrotron X-ray powder diffraction, followed by studies of electric and thermoelectric properties as a function of temperature (200–950 °C) and pO2 (1–10−3 bar). The results are shown to be in accordance with a defect chemical model comprising formation of oxygen vacancies and charge compensating electrons at high temperatures. The standard enthalpy and entropy of formation of an oxygen vacancy and two electrons in Fe2WO6 are found to be 113(5) kJ mol−1 and 41(5) J mol−1 K−1, respectively. Electrons residing as Fe2+ in the Fe3+ host structure act as charge carriers in a small polaron conducting manner. A freezing-in of oxygen vacancies below approximately 650 °C results in a region of constant charge carrier concentration, corresponding to an iron site fraction of XFe2+ ≅ 0.03. By decoupling of mobility from conductivity, we find a polaron hopping activation energy of 0.34(1) eV and a charge mobility pre-exponential u0 = 400(50) cm2 kV−1 s−1. We report thermal conductivity for the first time for Fe2WO6. The relatively high conductivity, large negative Seebeck coefficient and low thermal conductivity make Fe2WO6 an interesting candidate as an n-type thermoelectric in air, for which we report a maximum zT of 0.027 at 900 °C. |
| Remark | Link |
Tailoring the electrical conductivity and hardening in BiFeO3 ceramics
ID=575| Authors |
|
| Source |
Volume: 40,
Issue: 15,
Pages: 5483-5493 Time of Publication: 2020 |
| Abstract | In this report, the influence of cobalt doping and annealing atmosphere on the electrical conductivity and polarization switching of BiFeO3 (BFO) ceramics was studied. Electrical conductivity as well as hardening behavior has been found to increase with introduction of acceptor sites. BFO ceramics doped with Co exhibit p-type conductivity, dominated by Fe4+ defects, which can be successfully reduced during high-temperature annealing in N2. However, indications of local reduction were found, presumably on domain walls and grain boundaries. A mechanism of hardening is proposed, which assumes two types of pinning centers: i) and related and ii) and related, most probably bound into complexes, which are shown to play the key role in the hardening behavior and hysteresis loop pinching and biasing. The results of this study could further promote designing local and bulk conductivity and hardening properties of BFO-based materials. |
| Keywords | Ceramics; Ferroelectric; Point defects; Conductivity; Hardening |
| Remark | Link |
Disagreements between space charge models and grain boundary impedance data in yttrium-substituted barium zirconate
ID=574| Authors |
|
| Source |
Solid State Ionics
Volume: 353,
Pages: 115369 Time of Publication: 2020 |
| Abstract | Although the space charge model is commonly used to explain the high grain boundary resistance in proton conducting yttrium-substituted BaZrO3, it fails in its simplest forms with factors 10–40 to fit experimental data with respect to the characteristic frequency of the grain boundary impedance. We suggest modifications to the model, somewhat improving its fit. Including trapping effects of protons near yttrium substituents reduces the error only by factors less than 1.6. Increasing the width of the grain boundary core reduces the error with factors of 1.5–3. Discretizing the space charge layer, such that protons can only reside on specific, discrete sites, reduces the error with another factor of around 2. Considering reduced proton mobility in the GB by reducing its effective area may give a reduction in the fitting error of a factor of 2. Varying the dielectric constant in the GB does not affect the error considerably. Neither each single modification, nor their combined effect, can, however, account for the majority of the discrepancy between the space charge model and experimental data. |
| Remark | Link |
Insights into Crystal Structure and Diffusion of Biphasic Na2Zn2TeO6
ID=573| Authors |
|
| Source |
ACS Appl. Mater. Interfaces
Volume: 12,
Issue: 25,
Pages: 27821-28924 Time of Publication: 2020 |
| Abstract | The layered oxide Na2Zn2TeO6 is a fast Na+ ion conductor and a suitable candidate for application as a solid-state electrolyte. We present a detailed study on how synthesis temperature and Na-content affect the crystal structure and thus the Na+ ion conductivity of Na2Zn2TeO6. Furthermore, we report for the first time an O′3-type phase for Na2Zn2TeO6. At a synthesis temperature of 900 °C, we obtain a pure P2-type phase, providing peak performance in Na+ ion conductivity. Synthesis temperatures lower than 900 °C produce a series of mixed P2 and O′3-type phases. The O′3 structure can only be obtained as a pure phase by substituting Li on the Zn-sites to increase the Na-content. Thorough analysis of synchrotron data combined with computational modeling indicates that Li enters the Zn sites and, consequently, the amount of Na in the structure increases to balance the charge according to the formula Na2+xZn2–xLixTeO6 (x = 0.2–0.5). Impedance spectroscopy and computational modeling confirm that reducing the amount of the O′3-type phase enhances the Na+ ion mobility. |
| Remark | Link |
Ferroelectric Phase Transitions in Sr9Tm(VO4)7 upon Substitution of Calcium and Lead for Strontium
ID=572| Authors |
|
| Source |
Physics of the Solid State
Volume: 62,
Pages: 856–859 Time of Publication: 2020 |
| Abstract | In Sr9 – xMxTm(VO4)7 system, solid solutions with M = Ca (0 ≤ x ≤ 2) and M = Pb (0 ≤ x ≤ 1) have been prepared by solid-phase synthesis at 1373 K. At room temperature, the single-phase samples are isostructural to the Ca3(VO4)2 ferroelectric (space group R3c, Z = 6). The materials have been characterized by methods of the X-ray phase analysis (XPA), the second harmonic generation (SHG), and the dielectric spectroscopy. The intensity of the change in the SHG signal is changed within the range of 30–50 units with respect to a quartz standard in the dependence on cation–substitute and its concentration. A reversible ferroelectric phase transition is observed in the temperature range 850–960 K. The transition is accompanied by a sharp maximum in the curve of the dependence of the dielectric permittivity on temperature. The absence of the SHG signal at temperatures higher than the transition temperature indicates the centrosymmetricity of the paraelectric phase. |
| Remark | Link |
Electrochemical promotion of Ru nanoparticles deposited on a proton conductor electrolyte during CO2 hydrogenation
ID=571| Authors |
|
| Source |
Applied Catalysis B: Environmental
Volume: 276,
Pages: 119148 Time of Publication: 2020 |
| Abstract | Recycling CO2 into a carbon-neutral source is a beneficial approach in reducing non-renewable energy sources. Herein, the electrochemical promotion of catalysis (EPOC) has been exploited to enhance the catalytic activity of Ru nanoparticles (0.7−1¯nm) deposited on the proton conductor yttria-doped barium zirconate (BZY), as free-standing nanoparticles and supported on Co3O4 semiconductor, for CO2 hydrogenation. Under 250−450¯°C and atmospheric pressure, both methanation and reverse water-gas shift (RWGS) reaction take place simultaneously over the Ru nanoparticles with a superior selectivity to CO. Under anodic polarization, free-standing Ru nanoparticles displayed an increase in CH4 and a decrease in CO production, while the opposite effect was observed under cathodic polarization. Ru supported on Co3O4 displayed a superior catalytic activity mostly due to enhanced metal–support interactions. The electronic effects induced by the pairing of Co3O4 and BZY resulted in a new approach to EPOC applications that brings it closer to industrial application. |
| Remark | Link |
Ceramic-based thermoelectric generator processed via spray-coating and laser structuring
ID=570| Authors |
|
| Source |
Open Ceramics
Volume: 1,
Pages: 100002 Time of Publication: 2020 |
| Abstract | Processing technology to improve the manufacturing of thermoelectric generators (TEGs) is a growing field of research. In this paper, an adaptable and scalable process comprising spray-coating and laser structuring for fast and easy TEG manufacturing is presented. The developed process combines additive and subtractive processing technology towards an adaptable ceramic-based TEG, which is applicable at high temperatures and shows a high optimization potential. As a prototype, a TEG based on Ca3Co4O9 (CCO) and Ag on a ceramic substrate was prepared. Microstructural and thermoelectric characterization is shown, reaching up to 1.65 μW cm−2 at 673 K and a ΔT of 100 K. The high controllability of the developed process also enables adaptation for different kinds of thermoelectric materials. |
| Remark | Link |
Negative Thermal Expansion in Lead-Free La-Substituted Bi0.5Na0.5VO3
ID=569| Authors |
|
| Source |
Chem. Mater.
Volume: 32,
Issue: 11,
Pages: 4832–4837 Time of Publication: 2020 |
| Abstract | Negative thermal expansion (NTE) materials, which shrink upon heating, are required in modern technologies. In this study, new lead-free NTE compounds were obtained by substitution of La in PbTiO3 (PT)-type compounds, Bi0.5Na0.5VO3. Decreasing the stereochemical activity by substitution of La for Bi3+ and electron doping by substitution of La for Na+ were found to destabilize the tetragonal phase and cause a temperature-induced transition to a small cubic phase accompanied by NTE. The temperature hysteresis was suppressed because the phase transition was second order-like. |
| Remark | Link |
Studying the Effects of Siloxanes on Solid Oxide Fuel Cell Performance
ID=568| Authors |
|
| Source |
Time of Publication: 2020
|
| Abstract | Solid oxide fuel cells (SOFCs) are a promising technology for converting landfill gas into electricity, simultaneously providing a renewable source of energy. However, the contaminants present in landfill gas pose an obstacle to using it for energy generation. The research objective was to examine the effect siloxanes in landfill gas have on the performance of Ni-YSZ/Hionic™/LSM SOFCs, particularly through silica deposition on the Ni-YSZ anode. This was accomplished with voltammetric experiments using the ProboStat™ and anode surface analysis using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). To establish whether siloxanes can be detrimental to SOFC operation, hydrogen spiked with varying concentrations of decamethylcyclopentasiloxane (D5), a representative siloxane, was used as a fuel gas. Compared to operation under pure H2, which reliably gives a steady state output, the cell showed a 10% loss in voltage after 3 hours each at 1 ppmv D5 and 5 ppmv D5. Another cell operated on H2 gas containing 10 ppmv D5 experienced a 13% loss in voltage output after 6 hours, and SEM/EDS analysis showed the presence of silica deposits on the cell anodes. This was viewed as water generated via electrochemical reaction hydrolyzing siloxanes to silica and poisoning the SOFC anode. However, when humidified methane, a better landfill gas analogue, was spiked with D5, the cell’s voltage output was stable, and silica was not detected on the anode; instead D5 was deposited as silica on surfaces inside the ProboStat™. Thus, the necessity of humidifying the hydrocarbon fuel also provided a protection against anode poisoning by siloxanes. Nevertheless, experiments with humidified Mahoning Landfill gas failed to reach the expected voltage and current output. It was not clear from SEM/EDS analysis what contaminants were responsible for the decreased cell performance; more surface-sensitive techniques are recommended for further studies. |
| Remark |
Master of Science in Chemistry, Youngstown State University, Department of Chemistry. Link |
High ionic conductivity dysprosium and tantalum Co-doped bismuth oxide electrolyte for low-temperature SOFCs
ID=567| Authors |
|
| Source |
Ionics
Volume: 26,
Pages: 4579–4586 Time of Publication: 2020 |
| Abstract | A novel double dysprosium- and tantalum-doped bismuth oxide electrolyte synthesized by solid-state reaction for low-temperature solid oxide fuel cells (LT-SOFCs) is here reported. The phase structures at room temperature were defined by X-ray powder diffraction (XRD). A stable δ-Bi2O3 phase was obtained by co-doping Bi2O3 with Dy2O3 and Ta2O5 in specific contents. The effect of the co-dopant total content (5–15 mol%) on the ionic conductivity was measured as a function of temperature (300 to 700 °C). Results revealed that the (Dy2O3)13(Ta2O5)2(Bi2O3)85 system showed the highest ionic conductivity as 0.08 S cm−1 at 500 °C, which is three times higher than the binary system reported in the literature (E2O3)20(Bi2O3)80 (20ESB) and in the same range as the ternary system with the highest conductivity reported so far (Dy2O3)8(W2O3)4(Bi2O3)88 (8D4WSB). The lowest activation energy for our system was 0.20 eV at temperatures higher than 550 °C. |
| Remark | Link |
Ruddlesden-Popper-type Nd2-xNi1-yCuyO4±δ layered oxides as candidate materials for MIEC-type ceramic membranes
ID=566| Authors |
|
| Source |
Journal of the European Ceramic Society
Volume: 40,
Issue: 12,
Pages: 4056-4066 Time of Publication: 2020 |
| Abstract | Series of Nd2-xNi1-yCuyO4±δ Ruddlesden-Popper-type oxides is obtained by auto-combustion synthesis method and systematically characterized concerning phase composition, formation of solid state solution, crystal structure, oxygen content, as well as regarding transport properties and oxygen permeability when applied as mixed conducting ceramic membranes. The A-site deficiency x is discussed in terms of structural stability and its effect on the oxygen content, with ongoing modification of total electrical conductivity observed. In selected Nd2-xNi0.75Cu0.25O4±δ oxides the dominating oxygen defects at high temperatures can be changed from oxygen interstitials to vacancies by the induced A-site deficiency, which affects bulk- and surface-related transport coefficients, as it is observed in electrical conductivity relaxation studies. The optimized Nd1.9Ni0.75Cu0.25O4±δ sinters having increased ionic conductivity, as well as fine, well-sintered microstructure allow to achieve one of the higher reported oxygen fluxes for CO2-stable Ruddlesden-Popper-based ceramic membranes (e.g. 0.49¯mL¯cm−2¯min−1 at ca. 880¯°C for 1.05¯mm thickness). |
| Keywords | Ruddlesden-Popper oxides, Nonstoichiometric compounds, Crystal structure, Transport properties, Oxygen permeation membranes |
| Remark |
https://doi.org/10.1016/j.jeurceramsoc.2020.04.054 Link |
Artificial photosynthesisAdvanced nanomaterials and use of biocatalystsfor novel photoelectrochemical cells
ID=565| Author |
|
| Source |
Time of Publication: 2020
|
| Remark |
Thesis submitted for the degree of Philosophiae Doctor, University of Oslo Link |
Oxide Ion and Proton Conductivity in Highly Oxygen-Deficient Cubic Perovskite SrSc0.3Zn0.2Ga0.5O2.4
ID=564| Authors |
|
| Source |
Chem. Mater.
Volume: 32,
Issue: 10,
Pages: 4347–4357 Time of Publication: 2020 |
| Abstract | A series of Zn-substituted compounds, Sr2Sc1–xZnxGaO5–0.5x, based on the brownmillerite-type oxide ion conductor Sr2ScGaO5 have been synthesized, and a single-phase region has been identified at 0.4 ≤ x < 0.6. The structure and dynamics of Sr2Sc0.6Zn0.4GaO4.8 were investigated by X-ray and neutron diffraction, neutron total scattering and pair distribution function (PDF) analysis, impedance spectroscopy, and neutron spectroscopy. The material was found to be a highly disordered cubic perovskite with a remarkable level of oxygen deficiency across a large temperature range. These structural properties lead to an increase of oxide ion conductivity of about two orders of magnitude relative to the parent Sr2ScGaO5. The presence of proton conductivity and some water uptake was suggested by the impedance data and corroborated by thermogravimetric analysis (TGA), solid state nuclear magnetic resonance (NMR), variable temperature X-ray diffraction, and neutron spectroscopy. Both proton and oxide ion conductivity produced a measurable quasi-elastic neutron scattering (QENS) signal, and the onset of each dynamic process could be observed by monitoring the temperature dependence of the elastic and inelastic scattering intensities measured in fixed window scans. Neutron total scattering and PDF studies revealed a local structure that is markedly different from the perovskite average structure, and we propose that Sr2Sc0.6Zn0.4GaO4.8 contains a rare one-coordinate or terminal oxygen site. |
| Remark | Link |
High-performing electrolyte-supported symmetrical solid oxide electrolysis cells operating under steam electrolysis and co-electrolysis modes
ID=563| Authors |
|
| Source |
International Journal of Hydrogen Energy
Volume: 45,
Issue: 28,
Pages: 14208-14217 Time of Publication: 2020 |
| Abstract | Symmetrical solid oxide cells (s-SOC) present several advantages compared to typical configuration, as a reduction of sintering steps or a better thermomechanical compatibility between the electrodes and the electrolyte. Different mixed ionic-electronic conductors (MIEC) have been reported as suitable candidates for symmetrical configuration, allowing operations under steam electrolysis (SOEC) or co-electrolysis (co-SOEC) without the use of reducing safe gas (typically employed in SoA nickel based cells). In the present study, Sr2Fe1.5Mo0.5O6−δ (SFM) electrodes are deposited on both sides of YbScSZ tapes previously coated with a Ce1-xGdxO1.9 (GDC) barrier layer grown by PLD. Electrode sintering temperature is optimized and fixed at 1200 °C by means of electrochemical impedance spectroscopy (EIS) measurements in symmetrical atmosphere. The cell is then characterized at 900 °C in SOEC and co-SOEC modes without the use of any safe gas obtaining high current densities of 1.4 and 1.1 A cm−2 at 1.3 V respectively. Short-term reversibility is finally proven by switching the gas atmosphere between the cathode and anode sides while keeping the electrolysis conditions. Similar performances are obtained in both configurations. |
| Keywords | Solid oxide electrolyser, SOEC, Co-electrolysis, Symmetrical, Energy storage, Safe gas |
| Remark |
https://doi.org/10.1016/j.ijhydene.2020.03.144 Link |
Defect Chemistry of Sodium Bismuth Titanate and itsSolid Solutions
ID=562| Author |
|
| Source |
Time of Publication: 2019
|
| Remark |
Dissertation Link |
Mixed-conducting ceramic-carbonate dual-phase membranes: Gas permeation and counter-permeation
ID=561| Authors |
|
| Source |
Journal of Membrane Science
Volume: 605,
Pages: 118093 Time of Publication: 2020 |
| Abstract | CO2 and O2 permeable ceramic-carbonate dual-phase membranes can be used in membrane reactors for applications such as selective oxidation of hydrocarbons. Two ceramic-carbonate dual-phase membranes consisting of mixed electronic-ionic conducting perovskite-type ceramics of Pr0.6Sr0.4Co0.2Fe0.8 and SrFe0.9Ta0.1O3-δ are studied for CO2 and O2 permeation and counter-permeation. The geometric factors for the carbonate phase and ceramic phase, obtained from the data of helium permeation and electrical conductivity, are used to calculate the effective carbonate and oxygen ionic conductivity in the carbonate and ceramic phase. Without counter-permeation, O2 permeation through the dual-phase membrane is controlled by oxygen ionic conduction in the ceramic phase and CO2 permeation is determined by the total conductance including effective carbonate and oxygen ionic conductivities in both phases. When the dual-phase membrane is exposed to CO2 on one side and O2 on the other side, counter-permeation of CO2 and O2 occurs in the opposite directions across the membrane. With CO2 counter-permeation, the oxygen ionic flux is higher than that without counter-permeation due to an increase in the driving force for oxygen transport. CO2 permeation consumes oxygen ions transporting through the membrane, resulting in a lower O2 permeation flux compared with the O2-only permeation case. However, O2 counter-permeation has negligible effect on CO2 permeation flux for the dual-phase membranes. |
| Remark |
https://doi.org/10.1016/j.memsci.2020.118093 Link |
Reaction mechanism of low-temperature catalysis by surface protonics in an electric field
ID=560| Author |
|
| Source |
Faraday Discuss.
Time of Publication: 2020
|
| Abstract | The process combining heterogeneous catalysts and DC electric field can achieve high catalytic activities, even under mild conditions (<500 K) with less electrical energy consumption. Hydrogen production by steam reforming of methane, aromatics and alcohol, dehydrogenation of methylcyclohexane, dry reforming of methane, and ammonia synthesis are known to proceed at low temperatures in an electric field. In-situ/operando analyses have been conducted using IR, Raman, XAFS, electrochemical impedance spectroscopy, and isotopic kinetic analyses to elucidate the reaction mechanism for these reactions at low temperatures. Results show that surface proton hopping by a DC electric field, called surface protonics, is important for these reactions at low temperatures because of higher surface adsorbate concentrations at lower temperatures. |
| Remark |
Accepted Manuscript, https://doi.org/10.1039/C9FD00129H Link |
Peculiar Properties of Electrochemically OxidizedSmBaCo2−xMnxO5+δ(x=0; 0.5 and 1) A-SiteOrdered Perovskites
ID=559| Authors |
|
| Source |
Crystals
Volume: 10,
Pages: 205 Time of Publication: 2020 |
| Abstract | Fully-stoichiometric SmBaCo2-xMnxO6oxides (x=0, 0.5, 1) were obtained through theelectrochemical oxidation method performed in 1 M KOH solution from starting materials having closeto equilibrium oxygen content. Cycling voltammetry scans allow us to recognize the voltage range(0.3–0.55 V vs. Hg/HgO electrode) for which electrochemical oxidation occurs with high efficiency.In a similarly performed galvanostatic experiment, the value of the stabilized voltage recorded duringthe oxidation increased with higher Mn content, which seems to relate to the electronic structure ofthe compounds. Results of the iodometric titration and thermogravimetric analysis prove that theproposed technique allows for an increase in the oxygen content in SmBaCo2-xMnxO5+δmaterialsto values close to 6 (δ≈1). While the expected significant enhancement of the total conductivitywas observed for the oxidized samples, surprisingly, their crystal structure only underwent slightmodification. This can be interpreted as due to the unique nature of the oxygen intercalation process at room temperature. |
| Remark |
doi:10.3390/cryst10030205 Link |
Dielectric properties of new oxide phases Ln0.65Sr1.35Co0.5Ti0.5O4 (Ln = La, Nd, Pr) with the K2NiF4 - type structure
ID=558| Authors |
|
| Source |
Ceramics International
Volume: 46,
Issue: 10, Part A,
Pages: 15305-15313 Time of Publication: 2020 |
| Abstract | New complex oxides of the composition Ln0.65Sr1.35Co0.5Ti0.5O4 (Ln = La, Nd, Pr) with the K2NiF4 – type structure were synthesized using the citrate-nitrate method. Their crystal chemical characteristics and dielectric properties are researched. Different values of frequency-independent dielectric constants are observed in a wide frequency range of 103–107 Hz in ceramics prepared at a temperature of 1300 °C. The highest permittivity ε is about 102 (at ambient temperature) in the frequency range from 1 kHz to 1 MHz for La0.65Sr1.35Co0.5Ti0.5O4 and Pr0.65Sr1.35Co0.5Ti0.5O4 samples. Co3+ and rare earth elements (La, Nd, Pr) co-doping Sr2TiO4 solid solution distorts the coordination polyhedra (Co,Ti)O6 and SrO9, which leads to an Re ε increase by several times. The surface microstructure of ceramics was investigated. The samples relative density correlates with the dielectric constant value. A sample of the Nd0.65Sr1.35Co0.5Ti0.5O4 composition has a lower relative density and, accordingly, a lower Re ε value. The results of dielectric properties researches show that the structure anisotropy and the samples morphology have a significant effect on the value of the dielectric constant. |
| Keywords | Sol–gel processes Grain size Perovskites Dielectric properties |
| Remark |
https://doi.org/10.1016/j.ceramint.2020.03.071 Link |
Activation of C−H Bond of Propane by Strong Basic Sites Generated by Bulk Proton Conduction on V‐Modified Hydroxyapatites for the Formation of Propene
ID=557| Authors |
|
| Source |
ChemCatChem
Volume: 12,
Issue: 9,
Pages: 2506-2521 Time of Publication: 2020 |
| Abstract | Insights into the catalytic transformation of propane to propene on V‐apatite catalysts are provided based on structure‐reactivity relationships. Substitution of phosphates by vanadates in the hydroxyapatite structure leads to the formation of Ca10(PO4)6‐x(VO4)x(OH)2‐yOy V‐oxy‐hydroxy‐apatite solid solutions (x=0→6). Bulk vanadium incorporation promotes (i) calcium rich terminations (XPS, CO adsorption), (ii) proton deficiency inside the OH− channels (1H NMR) giving rise to O2− native species, (iii) the thermally‐activated formation of additional O2− species along the OH− channels resulting in H‐bonding interaction (in situ DRIFT) and (iv) the proton conduction process that eventually results in the surface exposure of O2− species (in situ impedance spectroscopy). The exposure of Ca2+−O2− surface acid‐base pairs allows the dissociation of hydrogen, emphasizing the strong basicity of the related O2− species. Whereas an increasing vanadium content is beneficial to propene selectivity, it scarcely impacts propane conversion. The reaction proceeds mainly upon oxidative dehydrogenation, even if the minor dehydrogenation route is also observed. Surface O2− generated thanks to proton mobility are involved in the C−H bond activation, as shown by the synergistic effect between the oxidative dehydrogenation of propane reaction and the bulk proton conduction measured under operando conditions. This puts emphasis on the key role of strong basic sites for propane activation. |
| Remark |
https://doi.org/10.1002/cctc.201902181 Link |
First observation of surface protonics on SrZrO3 perovskite under a H2 atmosphere
ID=556| Authors |
|
| Source |
Chem. Commun.
Volume: 56,
Pages: 2699-2702 Time of Publication: 2020 |
| Abstract | This is the first direct observation that surface proton hopping occurs on SrZrO3 perovskite even under a H2 (i.e. dry) atmosphere. Understanding proton conduction mechanisms on ceramic surfaces under a H2 atmosphere is necessary to investigate the role of proton hopping on the surface of heterogeneous catalysts in an electric field. In this work, surface protonics was investigated using electrochemical impedance spectroscopy (EIS). To extract the surface proton conduction, two pellets of different relative densities were prepared: a porous sample (R.D. = 60%) and a dense sample (R.D. = 90%). Comparison of conductivities with and without H2 revealed that only the porous sample showed a decrease in the apparent activation energy of conductivity by supplying H2. H/D isotope exchange tests revealed that the surface proton is the dominant conductive species over the porous sample with H2 supply. Such identification of a dominant conductive carrier facilitates consideration of the role of surface protonics in chemical reactions. |
| Remark | Link |
Mixed-conducting ceramic-carbonate membranes exhibiting high CO2/O2 permeation flux and stability at high temperatures
ID=555| Authors |
|
| Source |
Journal of Advanced Ceramics
Volume: 9,
Issue: 1,
Pages: 94-106 Time of Publication: 2020 |
| Abstract | This investigation demonstrates the feasibility to fabricate high quality ceramic–carbonate membranes based on mixed-conducting ceramics. Specifically, it is reported the simultaneous CO2/O2permeation and stability properties of membranes constituted by a combination of ceramic and carbonate phases, wherein the microstructure of the ceramic part is composed, in turn, of a mixture of fluorite and perovskite phases. These ceramics showed ionic and electronic conduction, and at the operation temperature, the carbonate phase of the membranes is in liquid state, which allows the transport of CO32– and O2– species via different mechanisms. To fabricate the membranes, the ceramic powders were uniaxially pressed in a disk shape. Then, an incipient sintering treatment was carried out in such a way that a highly porous ceramic was obtained. Afterwards, the piece is densified by the infiltration of molten carbonate. Characterization of the membranes was accomplished by SEM, XRD, and gas permeation techniques among others. Thermal and chemical stability under an atmosphere rich in CO2 was evaluated. CO2/O2 permeation and long-term stability measurements were conducted between 850 and 940 °C. The best permeation–separation performance of membranes of about 1 mm thickness, showed a maximum permeance flux of about 4.46×10 -7 mol?m -2 ?s -1 ?Pa -1 for CO 2 and 2.18×10 -7 mol?m -2 ?s -1 ?Pa -1 for O 2 at 940 ?. Membranes exhibited separation factor values of 150–991 and 49–511 for CO2/N2and O2/N2 respectively in the studied temperature range. Despite long-term stability test showed certain microstructural changes in the membranes, no significant detriment on the permeation properties was observed along 100 h of continuous operation. |
| Keywords | CO2 separation; O2 separation; ceramic–carbonate membrane; selectivity |
| Remark | Link |
Indium doping in SrCeO3 proton-conducting perovskites
ID=554| Authors |
|
| Source |
Journal of Solid State Chemistry
Volume: 248,
Pages: 121210 Time of Publication: 2020 |
| Abstract | In this work we present results of studies of In3+ doping in strontium cerate, comprising structural aspects, and oxygen as well as proton conductivity. Crystal structure analysis of single-phase SrCe1-xInxO3-a (x = 0.1, 0.2 and 0.3) materials in 25–900 °C temperature range indicates presence of strong orthorhombic distortion of the perovskite-type structure, similar as for the undoped SrCeO3. Limited sinterability of the obtained powders was mitigated by addition of 1 wt% of NiO, which allowed to manufacture dense sinters at 1400 °C. Electrochemical impedance spectroscopy measurements done in dry synthetic air show decrease of the ionic (oxygen) conductivity with the increase of In content, as well as associated increase of the activation energy. This indicates that formed oxygen vacancies are trapped in the structure. Overall, electrical conductivity for SrCe1-xInxO3-a in H2O- and D2O-containing atmospheres decreases with In content, but respective H+ and D+ transference numbers are larger for samples with higher indium doping. At 500 °C the highest proton and deuterium conductivity was recorded for SrCe0.9In0.1O3-a, reaching up to 0.70·10−4 S cm−1 and 0.26·10−4 S cm−1, respectively. Derived diffusion and surface exchange coefficients are 10−7-10−6 cm2 s−1 and 10−6-10−5 cm s−1, respectively in 500–700 °C temperature range. |
| Keywords | Strontium cerate, In doping, Crystal structure, Hydration, Transport properties, Proton conductivity |
| Remark |
https://doi.org/10.1016/j.jssc.2020.121210 |
A detailed kinetic model for the reduction of oxygen on LSCF-GDC composite cathodes
ID=553| Authors |
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| Source |
Electrochimica Acta
Time of Publication: 2020
|
| Abstract | A kinetic investigation of the Oxygen Reduction Reaction (ORR) is performed on LSCF-GDC composite cathodes (La0.4Sr0.6Co0.2Fe0.8O3-δ/Ce0.9Gd0.1O2-δ 50/50) spanning a wide range of operating conditions. EIS tests are carried out on symmetric cells between 700 °C and 560 °C at OCV, with O2/N2 mixtures at varying O2 molar fraction (5–21%). A dynamic, one-dimensional, physic model of the LSCF-GDC electrode is applied to rationalize the experimental results. The model simulates the spectra by solving mass and charge conservation equations, including terms for gas diffusion in the porous electrode and solid state transport in both the LSCF and the GDC lattice. A thermodynamically consistent, detailed kinetic scheme is applied to describe the ORR mechanism, which takes into account elementary steps of adsorption and desorption, first and second electronation at the gas/electrode interface, interfacial and lattice ion transfer. A full set of rate parameters (pre-exponential factors and activation energies) is derived by fitting to inhouse-measured impedance data, and validated against a well-established literature dataset. The sensitivity analysis supports the prevailing role of the TPB route over the 2 PB route, and highlights that the transfer of a single-charged oxygen adatom from the LSCF surface to the GDC lattice governs the ORR. The model clarifies the origin of distortions in measured impedance arcs, and captures the effect of O2 pressure on the observed electrochemical activity. |
| Remark |
https://doi.org/10.1016/j.electacta.2020.135620 Link |
High performance and toxicity assessment of Ta3N5 nanotubes for photoelectrochemical water splitting
ID=552| Authors |
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| Source |
Catalysis Today
Time of Publication: 2019
|
| Abstract | In this work, Co-based cocatalysts are electrodeposited on mesoporous Ta3N5 nanotubes. The electrodeposition time is varied and the optimized photoelectrode reaches a photocurrent density of 6.3 mA/cm2 at 1.23 V vs. SHE, under simulated solar illumination of 1 Sun, in 1 M NaOH. The best performing electrode, apart from the high photocurrent density, shows improved stability under intense photoelectrochemical water splitting conditions. The dual function of the cocatalyst to improve not only the photoelectrochemical performance, but also the stability, is highlighted. Moreover, we adopted a simple protocol to assess the toxicity of Co and Ta contained nanostructured materials (representing used photoelectrodes) employing the human cell line HeLa S3 as target cells. |
| Remark |
https://doi.org/10.1016/j.cattod.2019.12.031 Link |
A CO2-Tolerant Perovskite Oxide with High Oxide Ion and Electronic Conductivity
ID=551| Authors |
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| Source |
Adv. Mater.
Time of Publication: 2019
|
| Abstract | Mixed ionic–electronic conductors (MIECs) that display high oxide ion con-ductivity (σo) and electronic conductivity (σe) constitute an important family of electrocatalysts for a variety of applications including fuel cells and oxygen sepa-ration membranes. Often MIECs exhibit sufficient σe but inadequate σo. It has been a long-standing challenge to develop MIECs with both high σo and stability under device operation conditions. For example, the well-known perovskite oxide Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) exhibits exceptional σo and electrocatalytic activity. The reactivity of BSCF with CO2, however, limits its use in practical applications. Here, the perovskite oxide Bi0.15Sr0.85Co0.8Fe0.2O3−δ (BiSCF) is shown to exhibit not only exceptional bulk transport properties, with a σo among the highest for known MIECs, but also high CO2 tolerance. When used as an oxygen separation membrane, BiSCF displays high oxygen permeability comparable to that of BSCF and much higher stability under CO2. The combination of high oxide transport properties and CO2 tolerance in a single-phase MIEC gives BiSCF a significant advantage over existing MIECs for practical applications. |
| Remark |
DOI: 10.1002/adma.201905200 Link |
Coexistence of three types of sodium motion in double molybdate Na9Sc(MoO4)6: 23Na and 45Sc NMR data and ab initio calculations
ID=550| Authors |
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| Source |
Phys. Chem. Chem. Phys.
Volume: 22,
Pages: 144-154 Time of Publication: 2020 |
| Abstract | The rechargeable Na-ion batteries attract much attention as an alternative to the widely used but expensive Li-ion batteries. The search for materials with high sodium diffusion is important for the development of solid state electrolytes. We present the results of experimental and ab initio studies of the Na-ion diffusion mechanism in Na9Sc(MoO4)6. The ion conductivity reaches the value of 3.6 × 10−2 S cm−1 at T ∼ 850 K. The 23Na and 45Sc NMR data reveal the coexistence of three different types of Na-ion motion in the temperature range from 300 to 750 K. They are activated at different temperatures and are characterized by substantially different dynamics parameters. These features are confirmed by ab initio calculations of activation barriers for sodium diffusion along various paths. |
| Remark | Link |
Long-term (4 year) degradation behavior of coated stainless steel 441 used for solid oxide fuel cell interconnect applications
ID=549| Authors |
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| Source |
Journal of Power Sources
Time of Publication: 2019
|
| Abstract | The present work aims to investigate the long-term stability of Ce/Co coated AISI 441 used as an interconnect material in solid oxide fuel cells (SOFC). Being a commercially available alloy the use of AISI 441 would greatly reduce the cost of SOFCs in comparison to tailor-made interconnect materials such as Crofer 22 APU. To analyze the long-term stability Ce/Co coated AISI 441 is exposed in air at 800 °C for up to 38 000 h. Mass gain values are recorded continuously. After 7 000, 23 000, and 35 000 h area specific resistance (ASR) measurements are performed, and cross-sections are prepared and analyzed using scanning electron microscopy (SEM) and energy dispersive x-ray (EDX) spectroscopy. Cr-evaporation measurements are conducted on samples exposed for up to 38 000 h. |
| Keywords | SOFC, Interconnect, Corrosion, Ce/Co coating, AISI 441, Long-term |
| Remark |
https://doi.org/10.1016/j.jpowsour.2019.227480 Link |
Identification of barium-site substitution of BiFeO3–Bi0.5K0.5TiO3 multiferroic ceramics: X-ray absorption near edge spectroscopy
ID=548| Authors |
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| Source |
Radiation Physics and Chemistry
Volume: 170
Time of Publication: 2020
|
| Abstract | In this work, the effects of barium substitution on the local structure, dielectric and magnetic properties of the polycrystalline ceramics 0.6BiFeO3–0.4(Bi0.5K0.5)TiO3 (0.6BFO–0.4BKT) system was investigated. A solid-state reaction technique was used to synthesize the materials with barium (Ba) doping of 1, 3, 5, 7, and 10 mol%. XRD analysis reveals the coexistence between tetragonal and rhombohedral phases of single-phase perovskite in pure 0.6BFO–0.4BKT and the rhombohedral reach phase was found with increasing Ba content. XANES simulations indicate that the majority of Ba atoms occupy A-site in BKT lattice of Ba-doped 0.6BFO-0.4BKT, the oxidation state of Fe, Ti, and Ba ions are +3, +4 and+2, respectively. At 5 mol% of Ba doping content, the dielectric measurement shows the morphotropic phase boundary (MPB) and the maximum value of ferromagnetic characteristic were observed, indicating an optimum composition, properties and production conditions. |
| Keywords | X-ray absorption near edge spectroscopy; Barium-doped; Multiferroic ceramics; XANES simulations |
| Remark |
https://doi.org/10.1016/j.radphyschem.2019.108621 Link |
Tuning of Mg content to enhance the thermoelectric properties in binary Mg2+δ Si (δ = 0, 0.1, 0.15, 0.2)
ID=547| Authors |
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| Source |
Materials Research Express
Volume: 6
Time of Publication: 2019
|
| Abstract | We report the enhanced thermoelectric properties of binary Mg2Si by tuning the Mg content. Polycrystalline Mg2+δ Si (where δ is the excess Mg content in the starting composition of the samples and δ = 0, 0.1, 0.15, 0.2) samples were processed by solid-state synthesis route using ball milling followed by rapid spark plasma sintering in order to minimize the Mg loss during processing. Microstructural and x-ray diffraction analysis revealed that, Mg content (δ) of 0.1–0.15 is required to get the binary Mg2Si phase without any elemental Mg/Si phase. Hall effect measurement and Fourier Transform Infrared Spectroscopy analysis show that, the excess Mg content helps to enhance the carrier concentration and charge carrier effective mass due to the occupancy of Mg at the interstitial site in Mg2Si structure. The influence of Mg content on thermoelectric properties, viz., electrical resistivity, Seebeck coefficient and thermal conductivity is investigated from 300 K to 780 K. A marked enhancement in thermoelectric power factor (~1.6 mW m−2K−2) is obtained for Mg2.15Si sample at 780 K. The occupancy of excess Mg at interstitial sites reduces the lattice thermal conductivity by lowering lattice symmetry. A maximum figure of merit (ZT) ~ 0.39 ± 0.03 at 780 K has been achieved in Mg2.15Si sample, the highest among that reported in n-type binary Mg2Si system. This suggests that excess Mg content in the starting composition of Mg2+δ Si helps in stabilizing the phase as well as improves the thermoelectric properties of the Mg2Si. |
| Remark |
https://doi.org/10.1088/2053-1591/ab58fb Link |
Exploring the Role of Manganese on Structural, Transport, and Electrochemical Properties of NASICON-Na3Fe2–yMny(PO4)3–Cathode Materials for Na-Ion Batteries
ID=546| Authors |
|
| Source |
ACS Applied Materials & Interfaces
Volume: 11,
Issue: 46
Time of Publication: 2019
|
| Abstract | Given the extensive efforts focused on protecting the environment, eco-friendly cathode materials are a prerequisite for the development of Na-ion battery technology. Such materials should contain abundant and inexpensive elements. In the paper, we present NASICON-Na3Fe2–yMny(PO4)3 (y = 0, 0.1, 0.2, 0.3, and 0.4) cathode materials, which meet these requirements. Na3Fe2–yMny(PO4)3 compounds were prepared via a solid-state reaction at 600 °C, which allowed to obtain powders with submicron particles. The presence of manganese in the iron sub-lattice inhibits phase transitions, which occurs at ∼95 and ∼145 °C in Na3Fe2(PO4)3, changing the monoclinic structure to rhombohedral and affecting the structural and transport properties. The chemical stability of Na3Fe2–yMny(PO4)3 was thus higher than that of Na3Fe2(PO4)3, and it also exhibited enhanced structural, transport, and electrochemical properties. The observed correlation between the chemical composition and electrochemical properties proved the ability to precisely tune the crystal structure of NASICONs, allowing cathode materials with more desirable properties to be designed. |
| Keywords | Na-ion batteries, XRD, crystal structure |
| Remark |
https://doi.org/10.1021/acsami.9b10184 Link |
Intriguing electrochemistry in low-temperature single layer ceramic fuel cells based on CuFe2O4
ID=545| Authors |
|
| Source |
International Journal of Hydrogen Energy
Time of Publication: 2019
|
| Abstract | A composite of CuFe2O4 and Gd-Sm co-doped CeO2 is studied for a single layer ceramic fuel cell application. In order to optimize the cell performance, the effects of sintering temperatures (600 °C, 700 °C, 800 °C, 900 °C and 1000 °C) were investigated for the fabrication of the cells. It was found that the cells sintered at 700 °C outperformed other cells with a maximum peak power density of 344 mW/cm2 at 550 °C. The electrochemical impedance spectroscopy analysis on the best cell revealed significant ohmic losses (0.399 Ω cm2) and polarization losses (0.174 Ω cm2) in the cell. The HR-TEM and SEM gave microstructural information of the cell. The HT-XRD spectra showed the crystal structures in different sintering temperatures. The cell performance was stable and the composite material did not degrade during an 8 h stability test under open-circuit condition. This study opens up new avenues for the exploration of this nanocomposite material for the low temperature single component ceramic fuel cell research. |
| Keywords | Catalysis; Ceramic; Composite; Fuel cell; Single component |
| Remark |
https://doi.org/10.1016/j.ijhydene.2019.09.175 Link |
Mn-rich SmBaCo0.5Mn1.5O5+δ double perovskite cathode material for SOFCs
ID=544| Authors |
|
| Source |
International Journal of Hydrogen Energy
Volume: 44,
Issue: 50
Time of Publication: 2019
|
| Abstract | SmBaCo0.5Mn1.5O5+δ oxide with Sm-Ba cation-ordered perovskite-type structure is synthesized and examined in relation to whole RBaCo0.5Mn1.5O5+δ series (R: selected rare earth elements). Presence of Sm and 3:1 ratio of Mn to Co allows to balance physicochemical properties of the composition, with moderate thermal expansion coefficient value of 18.70(1)·10−6 K−1 in 300–900 °C range, high concentration of disordered oxygen vacancies in 600–900 °C range (δ = 0.16 at 900 °C), and good transport properties with electrical conductivity reaching 33 S cm−1 at 900 °C in air. Consequently, the compound enables to manufacture catalytically-active cathode, with good electrochemical performance measured for the electrolyte-supported laboratory-scale solid oxide fuel cell with Ni-Gd1.9Ce0.1O2-δ|La0.4Ce0.6O2-δ|La0.8Sr0.2Ga0.8Mg0.2O3-δ|SmBaCo0.5Mn1.5O5+δ configuration, for which 1060 mW cm−2 power density is observed at 900 °C. Furthermore, the tested symmetrical SmBaCo0.5Mn1.5O5+δ|La0.8Sr0.2Ga0.8Mg0.2O3-δ|SmBaCo0.5Mn1.5O5+δ cell delivers 377 mW cm−2 power density at 850 °C, which is a promising result. |
| Keywords | Mn-rich layered perovskites; Physicochemical properties; Cathode materials; SOFC; Symmetrical SOFC |
| Remark |
https://doi.org/10.1016/j.ijhydene.2019.08.254 Link |
Simultaneous CO2 and O2 separation coupled to oxy-dry reforming of CH4 by means of a ceramic-carbonate membrane reactor for in situ syngas production
ID=543| Authors |
|
| Source |
Chemical Engineering Science
Volume: 210
Time of Publication: 2019
|
| Abstract | It is reported the use of a ceramic-carbonate membrane exhibiting CO2 and O2 permeation, coupled with the oxy-carbon dioxide reforming of methane to produce syngas in a membrane reactor arrangement. The studied membrane is made of a porous fluorite/perovskite mixed conducting ceramic infiltrated with molten carbonates. The CO2 and O2 gas mixture used to perform the oxy-dry reforming process is the membrane’s permeate, which reacts with CH4 supplied in the sweep gas with the assistance of a catalyst. The reactor converts from 74 to 99% of CH4 under the studied separation and reaction conditions. The total rate of syngas production reaches 6.25 mL∙min−1∙cm−2 at 875 °C and a H2/CO ratio ranging from 2.1 to 1.3 between 800 and 875 °C. A long-term test shows a stable performance for 300 h. This work suggests the feasibility of this capture-conversion concept for the valorization of CO2 by the efficient production of syngas. |
| Keywords | Inorganic membrane; Gas permeation; Ceramic-carbonate membrane; Oxy-CO2 reforming of methane; Syngas production |
| Remark |
https://doi.org/10.1016/j.ces.2019.115250 Link |
Factors Limiting the Apparent Hydrogen Flux in Asymmetric Tubular Cercer Membranes Based on La27W3.5Mo1.5O55.5 and La0.87Sr0.13CrO3
ID=542| Authors |
|
| Source |
Membranes
Volume: 9
Time of Publication: 2019
|
| Abstract | Asymmetric tubular ceramic–ceramic (cercer) membranes based on La27W3.5Mo1.5O55.5-La0.87Sr0.13CrO3 were fabricated by a two-step firing method making use of water-based extrusion and dip-coating. The performance of the membranes was characterized by measuring the hydrogen permeation flux and water splitting with dry and wet sweep gases, respectively. To explore the limiting factors for hydrogen and oxygen transport in the asymmetric membrane architecture, the effect of different gas flows and switching the feed and sweep sides of the membrane on the apparent hydrogen permeability was investigated. A dusty gas model was used to simulate the gas gradient inside the porous support, which was combined with Wagner diffusion calculations of the dense membrane layer to assess the overall transport across the asymmetric membrane. In addition, the stability of the membrane was investigated by means of flux measurements over a period of 400 h. |
| Keywords | hydrogen permeation; water splitting; surface kinetics; asymmetric tubular membrane; lanthanum tungstate; lanthanum chromite |
| Remark |
doi:10.3390/membranes9100126 Link |
Thermoelectric properties of A-site deficient La-doped SrTiO3 at 100–900 °C under reducing conditions
ID=541| Authors |
|
| Source |
Journal of the European Ceramic Society
Volume: 40,
Issue: 2,
Pages: 401-407 Time of Publication: 2020 |
| Abstract | Lanthanum doped strontium titanate is a potential n-type thermoelectric material at moderate and high temperatures. (La0.12Sr0.88)0.95TiO3 ceramics were prepared by two different routes, conventional sintering at 1500 °C and spark plasma sintering at temperatures between 925 and 1200 °C. Samples with grain size between 40 nm and 1.4 μm were prepared and characterized with respect to their thermoelectric transport properties at temperatures between 100 and 900 °C under reducing conditions (H2/H2O-buffer mixtures). The thermal conductivity was significantly reduced with decreasing grain size reaching a value of 1.3 W m−1. K−1 at 600 °C for grain size of 40 nm and porosity of 19%. Electrical conductivity increased with increasing grain size showing a maximum of 500 S cm−1 at 200 °C for a grain size of 1.4 μm. The highest figure-of-merit (zT) was measured for samples with 1.4 μm average grain size reaching 0.2 at 500 °C. |
| Remark |
https://doi.org/10.1016/j.jeurceramsoc.2019.09.024 Link |
Ceria-Based Dual-Phase Membranes for High-Temperature Carbon Dioxide Separation: Effect of Iron Doping and Pore Generation with MgO Template
ID=540| Authors |
|
| Source |
Membranes
Volume: 9,
Issue: 9,
Pages: 108 Time of Publication: 2019 |
| Abstract | Dual-phase membranes for high-temperature carbon dioxide separation have emerged as promising technology to mitigate anthropogenic greenhouse gases emissions, especially as a pre- and post-combustion separation technique in coal burning power plants. To implement these membranes industrially, the carbon dioxide permeability must be improved. In this study, Ce0.8Sm0.2O2−δ (SDC) and Ce0.8Sm0.19Fe0.01O2−δ (FSDC) ceramic powders were used to form the skeleton in dual-phase membranes. The use of MgO as an environmentally friendly pore generator allows control over the membrane porosity and microstructure in order to compare the effect of the membrane’s ceramic phase. The ceramic powders and the resulting membranes were characterized using ICP-OES, HSM, gravimetric analysis, SEM/EDX, and XRD, and the carbon dioxide flux density was quantified using a high-temperature membrane permeation setup. The carbon dioxide permeability slightly increases with the addition of iron in the FSDC membranes compared to the SDC membranes mainly due to the reported scavenging effect of iron with the siliceous impurities, with an additional potential contribution of an increased crystallite size due to viscous flow sintering. The increased permeability of the FSDC system and the proper microstructure control by MgO can be further extended to optimize carbon dioxide permeability in this membrane system. |
| Keywords | samarium doped ceria; SDC; FSDC; CO2 separation membranes; scavenging effect of iron; permeability |
| Remark |
https://doi.org/10.3390/membranes9090108 Link |
Microstructural and compositional optimization of La0.5Ba0.5CoO3−δ — BaZr1−zYzO3−δ (z=0,0.05 and 0.1) nanocomposite cathodes for protonic ceramic fuel cells
ID=539| Authors |
|
| Source |
J. Phys.: Energy
Volume: 2
Time of Publication: 2019
|
| Abstract | Cathodes are one of the key components of protonic ceramic fuel cells (PCFCs) requiring further development to enhance the performance of PCFCs. This encompasses the optimization of material compositions and microstructures, as well as a further understanding of the electrode processes. Here, a compositional optimization of a La0.5Ba0.5CoO3−δ —BaZrO3-based nano-composite cathode prepared by exsolution of a single-phase material was performed by substituting 5 and 10 mol% Y at the B-site in the BaZrO3 phase. Electrodes with different microstructures were prepared by two different deposition methods, spray coating and screen printing, and by varying the firing temperature from 600°C to 1100 °C. Further, composite electrodes were prepared by directly coating and firing the single-phase materials on the dense electrolyte to prepare symmetric cells. A good adhesion of the cathode to the electrolyte was observed in all cases. In general, a more homogeneous microstructure was observed for the cathodes prepared by screen printing. The single step method encompassing exsolution of the single phase and firing of the symmetric cells yielded significant improvement in the cathode performance compared to the other routes. The best electrochemical performance was observed for La0.5Ba0.5CoO3−δ —BaZr0.9Y0.1O2.95 cathode with an area specific resistance of 4.02 Ω cm2 at 400 °C and 0.21 Ω cm2 at 600 °C in 3% moist synthetic air. These results are among the best reported for cathodes of PCFCs as will be discussed. |
| Keywords | protonic ceramic fuel cells, cathode, exsolution, composites |
| Remark |
https://doi.org/10.1088/2515-7655/ab396c Link |
Conductivity studies on the substituted stannate pyrochlore system Gd2Sn2-x-yMxAyO7 (M= Ti and A = Ru; x = 0.5, 1.0 and 1.5; y = 0.2)
ID=538| Authors |
|
| Source |
Solid State Sciences
Volume: 96
Time of Publication: 2019
|
| Abstract | Studies on the Gd2Sn2-x-yMxAyO7 system (M = Ti and A = Ru; x = 0.5, 1.0 and 1.5; y = 0.2) were carried out and the conductivity of the compounds was analyzed in air. All the substituted compounds form ordered pyrochlore structure. Enhanced conductivity properties were observed for the substituted compounds as compared to the Gd2Sn2O7 system. The more polarizable Ti–O and Ru–O bond and the smaller radius of Ti4+ and Ru4+ as compared to Sn4+ has a combined effect on the increased conductivity properties of the compounds. It is interesting to note that a striking enhancement of the total conductivity is observed for Gd2TiSn0.8Ru0.2O7 (~10−3 S/cm at 1000 °C) as compared to Gd2TiSnO7 (10−6 S/cm at 1000 °C). An optimized number of mobile charge carriers and activation energy for the oxide ionic conduction is found to influence the conductivity properties of the compounds. |
| Keywords | Mixed ionic-electronic conductivity, Stannate pyrochlores, Oxide ion conductors |
| Remark |
https://doi.org/10.1016/j.solidstatesciences.2019.105957 Link |
Fabrication and encapsulation of micro-SOFCs
ID=537| Author |
|
| Source |
Time of Publication: 2019
|
| Remark |
Tesi di Laurea Magistrale Link |
Protonic conductivity and thermal properties of cross-linked PVA/TiO2 nanocomposite polymer membranes
ID=536| Authors |
|
| Source |
Journal of Non-Crystalline Solids
Volume: 522
Time of Publication: 2019
|
| Abstract | Nanocomposite polymer membranes based on PVA/TiO2 were prepared by a solution casting method. Glutaraldehyde solution (GA) was used as linking agent to improve the chemical, thermal and physical properties of the membranes. The degree of cross-linking was varied by changing the reaction time. The phase behavior of the membranes was examined by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). High resolution SEM micrographs show that the TiO2 nanoparticles are homogeneously dispersed, whilst the PVA crosslinks with the inorganic phase and fill in the gap between the nanoparticles. The ionic conductivity measurements were studied by impedance spectroscopy in the radio frequency range between 5 kHz to 5 MHz. Proton conductivity increases by several orders of magnitude with increasing cross-linking reaction time, reaching a maximum of 0.016 Scm−1 at 130 °C for the PVA/TiO2 composition of 1:12%, which was cross-linked for 42 h and then immersed in a 32 wt% KOH solution for 24 h. The ionic activation energy of the prepared membranes ranged from 0.038 KeV to 0.121 KeV. This result was carried out to obtain an estimation of the desorption time of water in the range from room temperature to the decomposition temperature around 500 °C. |
| Remark | Link |
Ultrahigh temperature platinum microheater encapsulated by reduced-TiO2 barrier layer
ID=535| Authors |
|
| Source |
Sensors and Actuators A: Physical
Volume: 296,
Pages: 286-291 Time of Publication: 2019 |
| Abstract | Thermal stability and adhesion of the Pt/barrier interface were investigated herein. Reduced-TiO2, or TiO2-δ, was found to offer stronger adhesion and greater thermal stability as a barrier layer for Pt than that of TiN and stoichiometric TiO2. It enables a long-term high-temperature operation. No voids or peeling was seen after annealing at a temperature of 700 °C in a stacked layer of Pt/ TiO2-δ; whereas, voids and peeling inevitably appeared in Pt layers on TiN and TiO2, respectively. A microhotplate composed of a Pt/TiO2-δ microheater was confirmed to perform at 800 °C at a heating power of 120 mW. The heating response time was below 20 ms between 150 °C and 800 °C. Ten million cycles of temperature modulation between room temperature and 550 °C did not cause any performance deterioration. |
| Remark | Link |
Synthesis and Study of (Sr,La)2FeCo0.5Mo0.5O6 − δ Oxides with Double Perovskite Structure
ID=534| Authors |
|
| Source |
Russian Journal of Inorganic Chemistry
Volume: 64,
Issue: 6,
Pages: 696–704 Time of Publication: 2019 |
| Abstract | Complex oxides Sr2 − xLaxFeCo0.5Mo0.5O6 − δ, (x = 0.2, 0.4; δ ≈ 0.03–0.15) have been first synthesized by the sol-gel method. Their crystal structures have been refined by the Rietveld method; the refinement showed that the complex oxides have the structure of cubic double perovskite (a ≈ 2aper, space group Fm3̄m) with partial ordering of Fe(Co) and Mo in the B positions. Based on the 57Fe Mössbauer measurements, the average formal oxidation state of iron has been found to decrease from +3.20 (x = 0.0) to +3.04 (x = 0.4). Our study of the behavior of perovskites in a reducing Ar/H2 atmosphere (8%) revealed a decrease in the reduction resistance with decreasing La content (x = 0.4 → 0). The combination of the properties studied, namely chemical stability with respect to the reaction with Ce1 − xGdxO2 − x/2 and Zr1 − xYxO2 − x/2, high-temperature thermal expansion, and electrical conductivity in air and Ar/H2, shows that Sr1.6La0.4Fe-Co0.5Mo0.5O6 − δ (δ ≈ 0.03) perovskite is more attractive as an electrode material for medium-temperature symmetric solid oxide fuel cells than Sr2FeCo0.5Mo0.5O6 − δ. |
| Remark | Link |
Influence of Lanthanum Doping on Structural and Electrical/Electrochemical Properties of Double Perovskite Sr2CoMoO6 as Anode Materials for Intermediate-Temperature Solid Oxide Fuel Cells
ID=532| Authors |
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| Source |
ACS Appl. Mater. Interfaces
Volume: 11,
Issue: 27,
Pages: 24659-24667 Time of Publication: 2019 |
| Abstract | Lanthanum (La3+)-doped double perovskites Sr2CoMoO6 (Sr2–xLaxCoMoO6, 0.00 ≤ x ≤ 0.03) were synthesized via the citrate–nitrate autocombustion route. The Reitveld refinement analysis of X-ray diffraction reveals the tetragonal symmetry as the main phase with space group I4/m and also confirms the presence of some peaks corresponding to extra phase SrMoO4. The SEM micrograph images reflect that grains are in irregular shape and sizes for all samples. Average grain size gradually decreases with the increase of the SrMoO4 phase. The X-ray photoelectron spectroscopy (XPS) analysis confirms the presence of mixed valence states of Mo5+/Mo6+, Co2+/Co3+, and O-lattice/O-chemisorbed/O-physisorbed species. Coefficient of thermal expansion (CTE) analysis shows that the particular composition Sr1.97La0.03CoMoO6 has the lowest CTE value among the compositions studied. The electrical conductivity of Sr2CoMoO6 is enhanced effectively by doping La at Sr sites. The measured area-specific resistance (ASR) for the composition Sr1.97La0.03CoMoO6 (SLCM03) is found to be appreciably low, ∼0.053 Ohm cm–2 at 800 °C. The obtained highest electrical conductivity with the lowest activation energy and low ASR value for the composition Sr1.97La0.03CoMoO6 encompasses it as a promising candidate for anode material in the intermediate-temperature solid oxide fuel cell (IT-SOFC) application. |
| Remark | Link |
Scheelite type Sr1−xBaxWO4 (x = 0.1, 0.2, 0.3) for possible application in Solid Oxide Fuel Cell electrolytes
ID=531| Authors |
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| Source |
Scientific Reports
Volume: 9
Time of Publication: 2019
|
| Abstract | Polycrystalline scheelite type Sr1−xBaxWO4 (x = 0.1, 0.2 & 0.3) materials were synthesized by the solid state sintering method and studied with respect to phase stability and ionic conductivity under condition of technological relevance for SOFC applications. All compounds crystallized in the single phase of tetragonal scheelite structure with the space group of I41/a. Room temperature X-ray diffraction and subsequent Rietveld analysis confirms its symmetry, space group and structural parameters. SEM illustrates the highly dense compounds. Significant mass change was observed to prove the proton uptake at higher temperature by TG-DSC. All compound shows lower conductivity compared to the traditional BCZY perovskite structured materials. SBW with x = 0.3 exhibit the highest ionic conductivity among all compounds under wet argon condition which is 1.9 × 10−6 S cm−1 at 1000 °C. Since this scheelite type compounds show significant conductivity, the new series of SBW could serve in IT-SOFC as proton conducting electrolyte. |
| Remark |
Article number: 9173 (2019) Link |
Surface Reconstruction under the Exposure of Electric Fields Enhances the Reactivity of Donor-Doped SrTiO3
ID=530| Authors |
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| Source |
J. Phys. Chem. C
Volume: 123,
Issue: 27,
Pages: 16883-16892 Time of Publication: 2019 |
| Abstract | In the present work, we show how exposure to electric fields during a high-temperature treatment can be used to manipulate surface properties of donor-doped ceramics and thus improve their reactivity. La0.1Sr0.9TiO3 (LSTO) nanoparticles, prepared by hydrothermal synthesis, were consolidated under air with and without external electric fields. Although neither approaches caused grain growth upon consolidation, the treatment under the influence of the electric field (i.e., flash sintering) remarkably enhanced the segregation of Sr on the material’s surface. In addition, a high concentration of O– defects both in bulk as well as on the material surface was demonstrated by spectroscopic methods. This enhanced defect concentration along with the nanoscopic grain size of the field-consolidated materials is probably one of the triggering factors of their improved charge carrier mobility, as observed by impedance spectroscopy. The effect of such a perturbed defect structure on the reactivity of the materials was evaluated by the total oxidation of methane. For materials treated under the influence of electric fields, the catalytic reaction rate improved by a factor of 3 with respect to that of conventionally treated LSTO, along with a remarkable decrease of the activation energy. Thus, electric-field-assisted processes, usually known for their energy-saving character, can also be deemed as an attractive, forward-looking strategy for improving functional properties of ceramics. |
| Remark | Link |
Metal oxides for thermoelectrics
ID=529| Author |
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| Source |
Time of Publication: 2019
|
| Remark |
Dissertation Link |
Mixed proton and electron conducting double perovskite anodes for stable and efficient tubular proton ceramic electrolysers
ID=528| Authors |
|
| Source |
Nature Materials
Volume: 18,
Pages: 752–759 Time of Publication: 2019 |
| Abstract | Hydrogen production from water electrolysis is a key enabling energy storage technology for the large-scale deployment of intermittent renewable energy sources. Proton ceramic electrolysers (PCEs) can produce dry pressurized hydrogen directly from steam, avoiding major parts of cost-driving downstream separation and compression. However, the development of PCEs has suffered from limited electrical efficiency due to electronic leakage and poor electrode kinetics. Here, we present the first fully operational BaZrO3-based tubular PCE, with 10 cm2 active area and a hydrogen production rate above 15 Nml min−1. The novel steam anode Ba1−xGd0.8La0.2+xCo2O6−δ exhibits mixed p-type electronic and protonic conduction and low activation energy for water splitting, enabling total polarization resistances below 1 Ω cm2 at 600 °C and Faradaic efficiencies close to 100% at high steam pressures. These tubular PCEs are mechanically robust, tolerate high pressures, allow improved process integration and offer scale-up modularity. |
| Remark | Link |
Long-term stability of iron-doped calcium titanate CaTi0.9Fe0.1O3−δ oxygen transport membranes under non-reactive and reactive atmospheres
ID=527| Authors |
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| Source |
Journal of Membrane Science
Volume: 583,
Pages: 171-179 Time of Publication: 2019 |
| Abstract | Oxygen transport membranes (OTM) are widely considered as a possible solution to limit the carbon footprint, but are notoriously afflicted by performance issues due to chemical instability observed during long-term operation. This paper reports on the stability of an OTM made of CaTi0.9Fe0.1O3−δ (CTF), and addresses its applicability. The redox stability of CTF was investigated using thermal gravimetry up to 1000 °C under air and H2, coupled with XRD and Mössbauer analyses. The redox potential of iron was measured using an electrochemical potential relaxation as a function of temperature. The baseline oxygen semi-permeability flux of dense CTF membranes was measured in inert atmospheres (air/argon or air/helium), and the long-term stability established for up to 1600 h under simulated operation atmospheres containing CO, CO2, H2 and CH4. CTF shows a remarkable performance stability and post mortem XRD, SEM-EDS and Raman analyses show no evidence of decomposition or reaction byproducts. |
| Remark |
https://doi.org/10.1016/j.memsci.2019.04.049 Link |
Inkjet Printing Functionalization of SOFC LSCF Cathodes
ID=526| Authors |
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| Source |
Nanomaterials
Time of Publication: 2019
|
| Abstract | An important segment of the future renewable energy economy is the implementation of novel energy generation systems. Such electrochemical systems are solid oxide fuel cells, which have the advantage of direct conversion of the chemical energy stored in the fuel to electrical energy with high effciency. Improving the performance and lowering the cost of solid oxide fuel cells (SOFCs) are strongly dependent on finding commercially viable methods for nano-functionalization of their electrodes via infiltration. Inkjet printing technology was proven to be a feasible method providing scalability and high-resolution ink delivery. LaxSr1-xCoyFe1-yO3 cathodes were modified using inkjet printing for infiltration with two different materials: Gd-doped ceria (CGO) commonly used as ion-conductor and La0.6Sr0.4CoO3 (LCO) commonly used as a mixed ionic electronic conductor. As-modified surface structures promoted the extension of the three-phase boundary (TPB) and enhanced the mechanisms of the oxygen reduction reaction. Electrochemical impedance measurements revealed significantly lowered polarization resistances (between 2.7 and 3.7 times) and maximum power output enhancement of 24% for CGO infiltrated electrodes and 40% for LCO infiltrated electrodes. |
| Remark | Link |
AlTiN based thin films for degradation protection of tetrahedrite thermoelectric material
ID=525| Authors |
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| Source |
Journal of Alloys and Compounds
Volume: 792,
Pages: 953-959 Time of Publication: 2019 |
| Abstract | Efficient protection against degradation process of tetrahedrite-based thermoelectric materials was obtained employing AlTiN based thin films. The coatings were deposited via reactive direct current physical vapour deposition magnetron sputtering. The composition, thermal and electrical behaviour of thin films were investigated by X-ray diffraction, energy dispersive spectroscopy associated to field emission scanning electron microscopy, thermogravimetric analyses and electrical conductivity measurements. The barrier features for oxygen protection during thermal treatment in air at 500 °C were qualitatively evaluated, studying the coating behaviour over the higher operating temperature of tetrahedrite based thermoelectric devices. |
| Remark |
https://doi.org/10.1016/j.jallcom.2019.04.116 Link |
Barium-induced effects on structure and properties of β-Ca3(PO4)2-type Ca9Bi(VO4)7
ID=524| Authors |
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| Source |
Journal of Alloys and Compounds Volume: 793, Pages: 56-64 Time of Publication: 2019 |
| Abstract | Ca9–xBaxBi(VO4)7 (0 ≤ x ≤ 1.5) solid solutions with the β-Ca3(PO4)2-type structure were prepared by a solid-state method. Powder X-ray diffraction study of 0 ≤ x ≤ 0.7 showed that Bi3+ and Ba2+ cations were completely incorporated into the β-TCP-type host framework up to x = 0.7. Ca9-xBaxBi(VO4)7 (x = 0.25, 0.5) structures were refined by the Rietveld method using powder synchrotron X-ray diffraction data. DSC, SHG and dielectric properties measurements of Ca9-xBaxBi(VO4) (x = 0, 0.25, 0.5) revealed two reversible first-order phase transitions (PT1 and PT2). Increase of Ba2+ content in Ca9-xBaxBi(VO4)7 leads to lowering PT1 and PT2 phase transitions temperatures due to the increase of cell volume and the structure looseness. Nonlinear optical activity of Ca9–xBaxBi(VO4)7 reaches its maximum response at x = 0.5. The amount of (M1–(M3)–M2) dipoles in Ca9–xBaxBi(VO4)7 (0 < x ≤ 0.7) structures increases with increasing Ba2+ content from 0.25 to 0.5 and decreases with changing x from 0.5 to 0.7. |
| Remark |
https://doi.org/10.1016/j.jallcom.2019.03.365 Link |
Comparative Study of Electrical Conduction and Oxygen Diffusion in the Rhombohedral and Bixbyite Ln6MoO12 (Ln = Er, Tm, Yb) Polymorphs
ID=523| Authors |
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| Source |
Inorg. Chem.
Volume: 58,
Issue: 7,
Pages: 4275-4288 Time of Publication: 2019 |
| Abstract | Electrical conduction and oxygen diffusion mobility in the bixbyite (Ia3̅) and rhombohedral (R3̅) polymorphs of the Ln6MoO12−Δ (Ln = Er, Tm, Yb; Δ = δ, δ1, δ2; δ1 > δ2) heavy lanthanide molybdates, belonging to new, previously unexplored classes of potential mixed (ionic–electronic) conductors, have been studied in the range of 200–900 °C. The oxygen self-diffusion coefficient in bixbyite (Ia3̅) Yb6MoO12−δ phase estimated by the temperature-programmed heteroexchange with C18O2 was shown to be much higher than that for rhombohedral (R3̅) RI (with large oxygen deficiency) and (R3̅) RII (with small oxygen deficiency) Ln6MoO12−Δ (Ln = Tm, Yb; Δ = δ1; δ1 > δ2) oxides. According to the activation energy for total conduction in ambient air, 0.99, 0.93, and 1.01 eV in Er6MoO12−δ, Tm6MoO12−δ, and Yb6MoO12−δ bixbyites, respectively, oxygen ion conductivity prevails in the range ∼200–500 °C. Oxygen mobility data for the rhombohedral Ln6MoO12−Δ (Ln = Er, Tm, Yb; Δ = δ1, δ2) phases RI and RII indicate that the oxygen in these phases exhibits mobility at much higher temperatures, such as those above 600–700 °C. Accordingly, below 600–700 °C they have predominantly electronic conductivity. As shown by total conductivity study of Ln6MoO12−δ (Ln = Er, Tm, Yb) bixbyites (Ia3̅) and rhombohedral phases Ln6MoO12−Δ (Ln = Er, Tm, Yb; Δ = δ1, δ2) (R3̅) in dry and wet air, the proton conductivity contribution exists only in Ln6MoO12−δ (Ln = Er, Tm, Yb) bixbyites up to 450–600 °C and decreases with a decreasing of the lanthanide ionic radius. The obtained data on the mobility of oxygen and the presence of proton contribution in bixbyites in the 300–600 °C temperature range make it possible to confirm unequivocally that Ln6MoO12−δ (Ln = Er, Tm, Yb) bixbyites are mixed electron–proton conductors at these temperatures. |
| Remark | Link |
Processing of high performance composite cathodes for protonic ceramic fuel cells by exsolution
ID=522| Authors |
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| Source |
J. Mater. Chem. A
Volume: 7,
Pages: 8609-8619 Time of Publication: 2019 |
| Abstract | La0.5Ba0.5CoO3−δ–BaZrO3 (LB–BZ)-based composite materials were prepared by a modified Pechini sol–gel method combined with exsolution. Two different LB–BZ composites were prepared through two alternative thermal treatments of the precursor gel. A metastable single phase with a perovskite crystal structure was first obtained upon annealing the precursor in an inert atmosphere, and it was further transformed into a two-phase composite by in situ exsolution in air. Comparatively, direct calcination of the LB–BZ gel in air resulted in a two-phase composite with different microstructures and compositions of the two phases. The composite cathode formed by exsolution consisted of a matrix of BZ-phase with ∼45 nm grain size embedding ∼20 nm grains of LB-phase, while the composite cathode obtained by direct calcination consisted of a mixture of both phases with 50–60 nm grain size. Electrodes of symmetric half-cells were spray-coated on the BaZr0.9Y0.1O2.95 electrolyte to examine the electrochemical performance by impedance spectroscopy. The lowest area specific resistance (ASR) was obtained for the composite cathode produced by exsolution with an excellent ASR of 1.54 Ω cm2 at 600 °C and 18 Ω cm2 at 400 °C and an activation energy (Ea) of 0.60 eV in 3% moist synthetic air. This work demonstrates the potential of fabricating high performance nanocomposite cathodes with tailored chemical composition by a novel exsolution method. |
| Remark |
DOI: 10.1039/C8TA10950H Link |
Optimization of laser-patterned YSZ-LSM composite cathode-electrolyte interfaces for solid oxide fuel cells
ID=521| Authors |
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| Source |
Journal of the European Ceramic Society
Volume: 39,
Issue: 12,
Pages: 3466-3474 Time of Publication: 2019 |
| Abstract | Patterned cathode/electrolyte interfaces formed by a hexagonal array of ∼22 μm deep wells with 24 μm lattice parameter have been prepared by pulsed laser machining to enlarge the contact surface and, consequently, to reduce the cathode polarization of Solid Oxide Fuel Cells. These new interfaces have been tested in YSZ-LSM/YSZ/YSZ-LSM symmetrical cells, where the cathode is deposited by dip-coating. Appropriate ceramic suspensions have been formulated to penetrate into deep wells without presenting interfacial delamination after sintering. We analyse their applicability by comparing their rheology with the microstructure and electrochemical performance of the cells. The activation component of the polarization resistance is reduced by ∼50% using ethanol-based suspensions with 20 wt% solids loading, although the gas diffusion component increases due to excessive densification. Alternative ceramic suspensions with 17.5 wt% solids loading provide optimum electrode gas diffusion but lower activation components, resulting in an overall decrease of ∼20% in polarization resistance. |
| Remark |
https://doi.org/10.1016/j.jeurceramsoc.2019.02.049 Link |
The effect of Fe‐acceptor doping on the electrical properties of Na1/2Bi1/2TiO3 and 0.94 (Na1/2Bi1/2)TiO3–0.06 BaTiO3
ID=520| Authors |
|
| Source |
J. of American Ceramic Society
Volume: 102,
Issue: 9,
Pages: 5295-5304 Time of Publication: 2019 |
| Abstract | Na1/2Bi1/2TiO3 (NBT) based ceramics are amongst the most promising lead‐free ferroelectric materials. It was expected that the defect chemistry and the effect of doping of NBT would be similar to that observed for lead based materials, however, acceptor doping does not lead to ferroelectric hardening. Instead, high oxygen ionic conductivity is induced. Nevertheless, for solid solutions with BaTiO3 (BT), which are more relevant with respect to ferroelectric applications, such a drastic change of electrical properties has not been observed so far. To rationalize the difference in defect chemistry between NBT and its solid solution 94(Na1/2Bi1/2TiO3)–0.06 BaTiO3 (NBT–6BT) compositions with different concentrations of Fe‐dopant were investigated. The study illustrates that the materials exhibit very similar behavior to NBT, and extraordinarily high oxygen ionic conductivity could also be induced in NBT–6BT. The key difference between NBT–6BT and NBT is the range of the dependence of ionic conductivity with dopant concentration. Previous studies of NBT–6BT have not reached sufficiently high dopant concentrations to observe high conductivity. In consequence, the same defect chemical model can be applied to both NBT and its solid solutions. This will help to rationalize the effect of doping on ferroelectric properties of NBT‐ceramics and defect chemistry related degradation and fatigue. |
| Remark |
https://doi.org/10.1111/jace.16401 Link |
SOFC cathodic layers using wet powder spraying technique with self synthesized nanopowders
ID=519| Authors |
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| Source |
International Journal of Hydrogen Energy
Volume: 44,
Issue: 14,
Pages: 7555-7563 Time of Publication: 2019 |
| Abstract | In this work, a wet powder spraying method has been investigated as a facile low cost route to deposit electrode layer on SOFC electrolyte support. A particular focus has been examining the interfacial stability of the deposited layers, and determining the influence of the thickness of the different layers, as well as the ball milling regime used to produce the electrode inks. The developed system consist of an yttria stabilized zirconia electrolyte support, a La0.6Sr0.4FeO3 (LSF) cathode, a Sm0.2Ce0.8O1.9 (SDC) barrier layer between the electrolyte and the cathode, and LaNi0.6Fe0.4O3 (LNF) as a contact layer, for a future integration with the SOFC interconnector. The electrolyte supports (300 μm thickness and 9 mm diameter) supports were prepared by uniaxial pressing, while the deposition of thin barrier layers, cathode and contact layer were carried out by manual spray coating. |
| Remark |
https://doi.org/10.1016/j.ijhydene.2019.01.220 Link |
Crystal structure, dielectric, and optical properties of β-calcium orthophosphates heavily doped with ytterbium
ID=518| Authors |
|
| Source |
Journal of Alloys and Compounds
Volume: 787,
Pages: 1301-1309 Time of Publication: 2019 |
| Abstract | Solid solution of Ca10.5–1.5xYbx(PO4)7 (0 ≤ x ≤ 1) was synthesized in the β-Са3(РО4)2-type structure by a standard solid-state method. Second-harmonic generation, differential scanning calorimetry, and dielectric measurements showed the presence of a reversible first-order phase transition of ferroelectric type between the room-temperature polar R3c structure to centrosymmetry. The temperature of the phase transition decreases from 1203 K for x = 0 to 788 K for x = 1, while the second-harmonic generation response decreases from 1.4 to 0.17 α-SiO2 powder standard units. The luminescence spectra of Ca10.5–1.5xYbx(PO4)7 point to two structural Yb3+ positions in full agreement with the structural data. The intensity of the luminescence emission line at ∼975 nm due to the 2F5/2 → 2F7/2 transition reaches the maximum at x = 0.667 in Ca10.5–1.5xYbx(PO4)7. The Yb3+ luminescence spectra studied as a function of the chemical composition 0 < x ≤ 1 are compared with the corresponding crystallographic data obtained from the powder diffraction of both X-Ray and synchrotron radiation. Although the overwhelming majority of the Yb3+ cations are located in the pseudosymmetry in M5 position, their smaller number is located in an acentric manner in M1 and M2. A structural mechanism for the transition between the polar (ferroelectric, space group R3c) and centrosymmetric (paraelectric, space group R-3c) phases is proposed. |
| Remark |
https://doi.org/10.1016/j.jallcom.2019.02.103 Link |
Surface reactivity and cation non-stoichiometry in BaZr1−xYxO3−δ (x = 0–0.2) exposed to CO2 at elevated temperature
ID=517| Authors |
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| Source |
J. Mater. Chem. A
Volume: 7,
Pages: 3848-3856 Time of Publication: 2019 |
| Abstract | The reactivity of BaZr1−xYxO3−δ (x = 0–0.2) ceramics under 1 atm CO2 at 650 °C for up to 1000 h was investigated in order to elucidate possible degradation processes occurring when the material is applied as a proton-conducting electrolyte in electrochemical devices. The annealed ceramics were characterized by a range of techniques (SEM, TEM, GIXRD, XPS and SIMS) with respect to changes in the phase composition and microstructure. Formation of BaCO3 was observed on the surfaces of the annealed samples and the amount increased with time and was higher for the Y-doped compositions. The subsurface regions were found to be deficient in Ba and, in the case of the Y-doped compositions, enriched in Y in two distinct chemical states as identified by XPS. First-principles calculations showed that they were Y residing on the Zr and Ba-sites, respectively, and that local enrichment of Y both in bulk and on the surface attained a structure similar to Y2O3. Overall, it was substantiated that the reaction with CO2 mainly proceeded according to a defect chemical reaction involving transfer of Y to the Ba-site and consumption of BaZrO3 formula units. It was suggested that a similar degradation mechanism may occur in the case of Ba(OH)2 formation under high steam pressure conditions. |
| Remark | Link |
Superprotonic CsH2PO4 in dry air
ID=516| Authors |
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| Source |
Journal of Physics and Chemistry of Solids Volume: 129, Pages: 324-328 Time of Publication: 2019 |
| Abstract | The first observation of a stable superprotonic CsH2PO4 (CDP) phase in the absence of high humidity and high pressure is reported. Temperature- and time-resolved impedance spectroscopy data show that the superprotonic conductivity of a CDP pellet measured in dry air (22%rh) in a hermetically sealed chamber holds at σ∼1.5 × 10−2 S cm−1 over a timespan t = 50 h at a temperature T = 260 °C. Nyquist plots confirm the superprotonic nature of the conduction and x-ray diffraction data reveal that no dehydration of the CDP superprotonic phase occurs under the above-mentioned conditions. |
| Remark | Link |
Synthesis of Li4+xSi1−xFexO4 solid solution by dry ball milling and its highly efficient CO2 chemisorption in a wide temperature range and low CO2 concentrations
ID=515| Source |
J. Mater. Chem. A
Volume: 7,
Pages: 4153-4164 Time of Publication: 2019 |
| Abstract | To be considered a good CO2 capture material for industrial applications, alkaline ceramics have to present several properties such as fast sorption and desorption kinetics, large sorption capacities, regenerability and stability, and a wide operating temperature range. In this sense, Li4SiO4 fulfills some of these features, although it has some kinetic disadvantages at temperatures lower than 500 °C and under low CO2 partial pressures. Herein, we show an easy an efficient way to synthesize a Fe-containing Li4SiO4 solid solution (Li4+xSi1−xFexO4, with x ≤ 0.5); by a dry ball milling synthesis, with high CO2 capture capacities. A synergic effect, between the microstructural features given by the proposed synthesis method and the iron content, improves the CO2 capture exhibited by the material in different ways: (1) Li4+xSi1−xFexO4 solid solution samples are able to trap large amounts of CO2 between 200 and 650 °C. At 200 °C, the solid solution chemisorbs 11 wt% of CO2, the largest amount of CO2 captured reported so far in the literature at this temperature; (2) iron containing samples diminish the CO2 capture dependence on temperature; (3) CO2 capture was considerably improved under low partial pressures of CO2 and (4) iron redox properties enhanced the CO2 capture, by using a low partial pressure of O2. |
| Remark | Link |
Tuning the optical and thermoelectric properties of SrTi0.8−x Sn0.2FexO3
ID=514| Authors |
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| Source |
Materials Research Express
Volume: 6,
Issue: 4
Time of Publication: 2019
|
| Abstract | Effect of Fe doping on the structure, optical and thermoelectric properties of SrTi0.8Sn0.2O3 sample has been investigated. The SrTi0.8−xSn0.2FexO3 (x = 0, 0.1, 0.3) samples are fabricated using solid-state synthesis route. It is observed that Fe doping helps in reducing the densification temperature of SrTi0.8Sn0.2O3 during spark plasma sintering. Precipitation of Sn has been observed in SrTi0.8−xSn0.2FexO3 (x = 0, 0.1) samples while the SrTi0.8−xSn0.2FexO3 (x = 0.3) sample is of purely single cubic perovskite phase. All the samples consist of nanocrystalline grains and the grain size varies between 150 to 200 nm. Fourier transform infrared spectroscopy (FTIR) analysis reveals the distortion of TiO6 octahedra due to the increase in Fe content. Raman spectroscopy analysis has shown that perovskite cubic structure is stable from room temperature to 873 K. From thermophysical measurements, it is shown that the Fermi band gap reduces from 2.87 to 0.66 eV with increase in Fe in the investigated samples. The Seebeck co-efficient is found to change the sign from n –type to p-type with the increase of Fe concentration in SrTi0.8Sn0.2O3, which is an interesting observation to obtain p-type SrTiO3 based thermoelectric materials. The optical and thermoelectric properties show that Fe doping improves the thermoelectric properties of SrTi0.8Sn0.2O3 ceramics by altering the Seebeck co-efficient and thermal conductivity. |
| Remark | Link |
Template-free mesoporous La0.3Sr0.7Ti1-xFexO3±δ for CH4 and CO oxidation catalysis
ID=513| Authors |
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| Source |
Applied catalysis B: Enviromental
Volume: 245,
Pages: 536-545 Time of Publication: 2019 |
| Abstract | The design of perovskite oxides with improved textural properties in combination with tunable composition variations is a forward-looking strategy for the preparation of next generation catalytic converter. In the present work we report the template-free synthesis of mesoporous solid solutions of La0.3Sr0.7Ti1-xFexO3±δ (0 ≤ x ≤ 0.5) and the study of their catalytic performance towards CH4 and CO oxidation. Using an innovative polymer complex route, phase pure perovskite solid solutions with specific surface area of 65 m2 g−1 and average pore size of 15 nm were prepared. The iron concentration increase led to a progressive enhancement of not only both concentration and transport of the charge carriers but also reducibility and oxygen desorption capability on the catalyst. As a result, we observed almost complete conversion of CH4 and CO at 600 °C and 300 °C, respectively. Kinetic studies on methane oxidation showed that competing suprafacial and intrafacial reaction mechanisms coexist, and that the concentration of 30% of Fe maximizes the suprafacial contribution. Under reducing conditions at 600 °C the materials retained their structural and morphological integrity, showing superior stability. Finally, the reaction rate of CH4 and CO conversion evidenced that our systems are by a maximum of 90 times more performing than other bulk and nanoporous Fe-based perovskites in literature (e.g. La0.66Sr0.34Co0.2Fe0.8O3-δ), as a result their large surface area, intimate gas-solid contact and short intragrain oxygen diffusion pathways induced by the mesoporous structure. |
| Remark | Link |
Versatile Application of Redox Processes for REBaCoMnO5+δ (RE: La, Pr, Nd, Sm, Gd, and Y) Oxides
ID=512| Authors |
|
| Source |
J. Phys. Chem. C
Volume: 123,
Issue: 1,
Pages: 48-61 Time of Publication: 2019 |
| Abstract | Belonging to the not fully explored REBaCo2-xMnxO5+δ system, a series of REBaCoMnO5+δ (RE: selected rare earth elements) oxides having perovskite-type structure is synthesized and studied in terms of their structural properties, oxygen content, stability, thermal expansion, and transport properties. Impact of RE3+ on physicochemical properties of the compounds is derived, with smaller cations causing a decrease of the unit cell volume, lowering of the total oxygen content and thermal expansion, but also suppressing electrical conductivity. It is shown that a proper chemical modification enables to successfully utilize REBaCoMnO5+δ in applications, in which redox processes associated with oxygen reduction/oxidation and transport determine the effectiveness of the working material. In particular, NdBaCoMnO5+δ (with larger Nd3+) shows good chemical stability in relation to Ce0.8Gd0.2O2−δ and La0.8Sr0.2Ga0.8Mg0.2O3-δ solid electrolytes and moderate thermal expansion, 20.04(4)·10–6 K–1 in 300–900 °C. In symmetrical configuration with La0.8Sr0.2Ga0.8Mg0.2O3-δ electrolyte its cathodic polarization resistance is found to be only 0.036 Ω cm2 at 900 °C, making it an excellent candidate cathode for solid oxide fuel cells. At the same time, YBaCoMnO5+δ (with small and cheap Y3+) delivers reversible oxygen storage capacity surpassing 3.4 wt % during the oxygen partial pressure swing process between air and 5 vol % H2 in Ar at 500 °C. |
| Remark | Link |
Unraveling bulk and grain boundary electrical properties in La0.8Sr0.2Mn1−yO3±δ thin films
ID=511| Authors |
|
| Source |
APL Materials Volume: 7, Pages: 013205 Time of Publication: 2019 |
| Abstract | Grain boundaries in Sr-doped LaMnO3±δthin films have been shown to strongly influence the electronic and oxygen mass trans-port properties, being able to profoundly modify the nature of the material. The unique behavior of the grain boundaries canbe correlated with substantial modifications of the cation concentration at the interfaces, which can be tuned by changing theoverall cationic ratio in the films. In this work, we study the electronic properties of La0.8Sr0.2Mn1−yO3±δthin films with variableMn content. The influence of the cationic composition on the grain boundary and grain bulk electronic properties is elucidatedby studying the manganese valence state evolution using spectroscopy techniques and by confronting the electronic propertiesof epitaxial and polycrystalline films. Substantial differences in the electronic conduction mechanism are found in the presenceof grain boundaries and depending on the manganese content. Moreover, the unique defect chemistry of the nanomaterial is elu-cidated by measuring the electrical resistance of the thin films as a function of oxygen partial pressure, disclosing the importanceof the cationic local non-stoichiometry on the thin film behavior. |
| Remark | Link |
Effect of magnetron sputtered anode functional layer on the anode-supported solid oxide fuel cell performance
ID=510| Authors |
|
| Source |
International Journal of Hydrogen Energy
Time of Publication: 2018
|
| Abstract | Nickel oxide-yttria stabilized zirconia (NiO-YSZ) thin films were reactively sputter-deposited by pulsed direct current magnetron sputtering from the Ni and ZrY targets onto heated commercial NiO-YSZ substrates. The microstructure and composition of the deposited films were investigated with regard to application as thin anode functional layers (AFLs) for solid oxide fuel cells (SOFCs). The pore size, microstructure and phase composition of both as-deposited and annealed at 1200 °C for 2 h AFLs were studied by scanning electron microscopy and X-ray diffractometry and controlled by changing the deposition process parameters. The results show that annealing in air at 1200 °C is required to improve structural homogeneity of the films. NiO-YSZ films have pores and grains of several hundred nanometers in size after reduction in hydrogen. Adhesion of deposited films was evaluated by scratch test. Anode-supported solid oxide fuel cells with the magnetron sputtered anode functional layer, YSZ electrolyte and La0.6Sr0.4Co0.2Fe0.8O3/Ce0.9Gd0.1O2 (LSCF/CGO) cathode were fabricated and tested. Influence of thin anode functional layer on performance of anode-supported SOFCs was studied. It was shown that electrochemical properties of the single fuel cells depend on the NiO volume content in the NiO-YSZ anode functional layer. Microstructural changes of NiO-YSZ layers after nickel reduction-oxidation (redox) cycling were studied. After nine redox cycles at 750 °C in partial oxidation conditions, the cell with the anode NiO-YSZ layer showed stable open circuit voltage values with the power density decrease by 11% only. |
| Remark |
In Press, https://doi.org/10.1016/j.ijhydene.2018.11.193 Link |
Engineering Transport in Manganites by Tuning Local Nonstoichiometry in Grain Boundaries
ID=509| Authors |
|
| Source |
Advanced Materials
Volume: 31,
Issue: 4,
Pages: 1805360 Time of Publication: 2019 |
| Abstract | Interface‐dominated materials such as nanocrystalline thin films have emerged as an enthralling class of materials able to engineer functional properties of transition metal oxides widely used in energy and information technologies. In particular, it has been proven that strain‐induced defects in grain boundaries of manganites deeply impact their functional properties by boosting their oxygen mass transport while abating their electronic and magnetic order. In this work, the origin of these dramatic changes is correlated for the first time with strong modifications of the anionic and cationic composition in the vicinity of strained grain boundary regions. We are also able to alter the grain boundary composition by tuning the overall cationic content in the films, which represents a new and powerful tool, beyond the classical space charge layer effect, for engineering electronic and mass transport properties of metal oxide thin films useful for a collection of relevant solid‐state devices. |
| Remark | Link |
Improved CO2 flux by dissolution of oxide ions into the molten carbonate phase of dual-phase CO2 separation membranes
ID=508| Authors |
|
| Source |
Separation and Purification Technology
Volume: 212,
Pages: 723-727 Time of Publication: 2019 |
| Abstract | In a solid-liquid dual-phase CO2 separation membrane, the native ions in the molten alkali carbonate, including carbonate anions and metal cations can transport CO2 in a process that is charge-compensated by electronic species (electrons or holes), oxide ions, or hydroxide ions, depending on materials and conditions. This strongly affects the design of experiments for assessing the performance of these membranes, and further determines the routes for integration of these membranes in industrial applications. Here we report how dissolved oxides in the liquid carbonate improve the CO2 flux of the membrane due to an enhanced charge-compensating oxygen ion transport. A qualitative understanding of the magnitude and role of oxide ion conductivity in the molten phase and in the solid support as a function of the temperature is provided. Employing a solid matrix of ceria, and dissolving CsVO3 and MoO3 oxides in the molten carbonate phase led to an almost doubled CO2 flux at 550 °C under dry ambient conditions. When the sweep gas contained 2.5% H2O, the CO2 flux was increased further due to formation of hydroxide ions in the molten carbonate acting as charge compensating species. Also, as a consequence of permeation controlled by ions in the liquid phase, the CO2 flux increased with the pore volume of the solid matrix. |
| Remark | Link |
Influence of the Initial Powder’s Specific Surface Area on the Properties of Sm-Doped Ceria Thin Films
ID=507| Authors |
|
| Source |
Crystals
Time of Publication: 2018
|
| Remark | Link |
Synthesis, Structure, and Conductivity of Alluaudite‐Related Phases in the Na2MoO4–Cs2MoO4–CoMoO4 System
ID=506| Authors |
|
| Source |
Europian Journal of Inorganic Chemistry
Volume: 2019,
Pages: 277-286 Time of Publication: 2018 |
| Abstract | Phase formation study of the Na2MoO4–Cs2MoO4–CoMoO4 system resulted in new cesium‐containing alluaudite‐related phases. The solid solution Na4–2x‐yCsyCo1+x(MoO4)3 (0 ≤ x, y ≤ 0.30), based on the alluaudite‐type Na4–2xCo1+x(MoO4)3, and triple molybdate Na10(Cs4‐xNax)Co5(MoO4)12 (0 ≤ x ≤ 0.30) were found, and their structures were solved. In the structure of Na3.21Cs0.37Co1.21(MoO4)3 (a = 13.0917(8) Å, b = 13.5443(8) Å, c = 7.1217(4) Å, space group C2/c, β = 112.331(2), Z = 4), the cesium ions partially substitute the Na+ in the channels running along the c‐axis. The structure of Na10(Cs3.77Na0.23)Co5(MoO4)12 (a = 13.6572(3) Å, b = 11.5063(3) Å, c = 27.9898(5) Å, space group Pbca, Z = 4) was proved to be the aristotype for the pseudo orthorhombic Na25Cs8R5(MoO4)24 (R = Fe, Sc, In). The compounds contain alluaudite‐like layers of MoO4 tetrahedra and pairs of edge‐shared (Co, Na)O6 or (R, Na)O6 and NaO6 octahedra, which are connected by bridging MoO4 tetrahedra to form 3D frameworks differing from the alluaudite type. The frameworks contain channels along the c‐axis filled by Cs+ and Na+ ions. Bond valence sum (BVS) maps show that the alluaudite‐related molybdates can have a 2D sodium‐ion conductivity at elevated temperatures in contrast to the alluaudite‐type cathode material Na2+2xFe2‐x(SO4)3 with a 1D conductivity. The measured ionic conductivity of Na4–2xCo1+x(MoO4)3, Na4–2x‐yCsyCo1+x(MoO4)3, and Na10Cs4Co5(MoO4)12 reaches 10–3–10–2 S cm–1 at 500 °C. Abstract The phase relations, structures, ionic conductivity, and Na‐ion migration pathways for alluaudite‐related Na4–2x‐yCsyCo1+x(MoO4)3 and Na10(Cs4‐xNax)Co5(MoO4)12 (new type) were determined. Introducing Cs+ blocks 1D Na‐conductivity in the former phase, but it leads to possible 2D conductivity for the latter and the highest Na+ mobility among known alluaudite‐related molybdates at elevated temperatures. |
| Remark |
https://doi.org/10.1002/ejic.201801307 Link |
Large-area and adaptable electrospun silicon-based thermoelectric nanomaterials with high energy conversion efficiencies
ID=505| Authors |
|
| Source |
Nature Communications
Volume: 9
Time of Publication: 2018
|
| Abstract | Large amounts of waste heat generated in our fossil-fuel based economy can be converted into useful electric power by using thermoelectric generators. However, the low-efficiency, scarcity, high-cost and poor production scalability of conventional thermoelectric materials are hindering their mass deployment. Nanoengineering has proven to be an excellent approach for enhancing thermoelectric properties of abundant and cheap materials such as silicon. Nevertheless, the implementation of these nanostructures is still a major challenge especially for covering the large areas required for massive waste heat recovery. Here we present a family of nano-enabled materials in the form of large-area paper-like fabrics made of nanotubes as a cost-effective and scalable solution for thermoelectric generation. A case study of a fabric of p-type silicon nanotubes was developed showing a five-fold improvement of the thermoelectric figure of merit. Outstanding power densities above 100 W/m2 at 700 °C are therefore demonstrated opening a market for waste heat recovery. |
| Remark |
Article number: 4759 (2018) |
A comprehensive study on improved power materials for high-temperature thermoelectric generators
ID=504| Authors |
|
| Source |
Journal of Power Sources
Volume: 410-411,
Pages: 143-151 Time of Publication: 2019 |
| Abstract | Dense Ca3Co4O9-NaxCoO2-Bi2Ca2Co2O9 (CCO-NCO-BCCO) nanocomposites were produced from sol-gel derived Ca2.25Na0.3Bi0.35Tb0.1Co4O9 powder by four methods: Hot-pressing (HP), spark plasma sintering (SPS) and pressureless sintering in air or O2 atmosphere. Nanocomposites from HP and SPS revealed nanosized grains and showed a thermoelectric power factor of 4.8 and 6.6 μW cm−1 K−2, respectively, at 1073 K in air. A dense 2D nanocomposite with structures on multiple length scales and enhanced thermoelectric properties was obtained from pressureless sintering in O2 atmosphere. The resulting 2D nanocomposite enabled the simultaneous increase in isothermal electrical conductivity σ and Seebeck coefficient α, and showed a thermoelectric power factor of 8.2 μW cm−1 K−2 at 1073 K in air. The impact of materials with enhanced electrical conductivity and power factor on the electrical power output of thermoelectric generators was verified in prototypes. A high electrical power output and power density of 22.7 mW and 113.5 mW cm−2, respectively, were obtained, when a hot-side temperature of 1073 K and a temperature difference of 251 K were applied. Different p- and n-type materials were used to verify the effect of the thermoelectric figure-of-merit and power factor on the performance of thermoelectric generators. |
| Remark | Link |
Triple-phase ceramic 2D nanocomposite with enhanced thermoelectric properties
ID=503| Authors |
|
| Source |
Journal of the European Ceramic Society
Volume: 39,
Issue: 4,
Pages: 1237-1244 Time of Publication: 2019 |
| Abstract | A thermoelectric triple-phase p-type Ca3Co4O9-NaxCoO2-Bi2Ca2Co2O9 (CCO–NCO–BCCO) 2D nanocomposite was obtained from pressureless sintering in air. The anisotropic thermoelectric properties of the nanocomposite exhibit a high electrical conductivity of 116 S cm−1 and a power factor of 6.5 μW cm−1 K−2 perpendicular to the pressing direction at 1073 K in air. A corresponding zT value of 0.35 was obtained. Three co-doped, thermoelectrically active misfit-layered materials were stacked to form a triple-phase nanocomposite, which combines the advantages of all three materials. The resulting nanocomposite enables simultaneous increases of the isothermal electrical conductivity σ and the Seebeck coefficient α by charge carrier concentration engineering and synergistic effects. The Bi2Ca2Co2O9 and NaxCoO2 phases were stabilized in a Ca3Co4O9 matrix at high temperatures. To evaluate the application of the nanocomposite in high-temperature thermoelectric generators, the representation of the electrical conductivity and power factor in a Ioffe plot was more appropriate than the zT value. |
| Remark | Link |
Effects of calcium doping to oxygen reduction activity on Pr2-xCaxNiMnO6 cathode
ID=502| Authors |
|
| Source |
Journal of Alloys and Compounds
Volume: 777,
Pages: 1319-1326 Time of Publication: 2019 |
| Abstract | Pr2-xCaxNiMnO6-δ (PCNMOx, x = 0.0–0.3) are prepared successfully by glycine-nitrate method. The effects of calcium doping to the crystal structure, the oxygen non-stoichiometry, and the cathode properties are evaluated by XRD, SEM, XPS and EIS. The double perovskite PCNMOx crystallize into a monoclinic structure with space group P21/n. The unit cell volumes and thermal expansion coefficients increase systematically with Ca2+ doping, due to the gradual generation of oxygen vacancies in the lattice. Pr2-xCaxNiMnO6-δ exhibits promising chemical compatibility with the electrolyte material Ce0.9Gd0.1O1.95 (GDC) at 1200 °C. The electrochemical characterization results indicate that both oxygen vacancy concentration and electrical conductivity play important roles to cathode properties. The optimum composition Pr1.8Ca0.2NiMnO6-δ shows the lowest polarization resistance of 0.18 Ω cm2 and highest peak power density of 0.3 W cm2 at 700 °C on GDC electrolyte supported fuel cell. The electrochemical impedance measurements under oxygen partial pressures, together with distribution of relaxation times analysis, identify three conjunctive elementary processes involved in the cathode reaction, and prove that the charge transfer process is the major rate-determining step of oxygen reduction reaction. |
| Remark | Link |
Metal-Doping of La5.4MoO11.1 Proton Conductors: Impact on the Structure and Electrical Properties
ID=501| Authors |
|
| Source |
Inorg. Chem.
Volume: 57,
Issue: 20,
Pages: 12811-12819 Time of Publication: 2018 |
| Abstract | La5.4MoO11.1 proton conductors with different metal doping (Ca2+, Sr2+, Ba2+, Ti4+, Zr4+, and Nb5+) have been prepared and structurally and electrically characterized. Different polymorphs are stabilized depending on the doping and cooling rate used during the synthesis process. The most interesting results are obtained for Nb-doping, La5.4Mo1–xNbxO11.1–x/2, where single compounds are obtained in the compositional range 0 ≤ x ≤ 0.2. These materials are fully characterized by structural techniques such as X-ray and neutron powder diffraction and transmission electron microscopy, which independently confirm the changes of polymorphism. Scanning electron microscopy and impedance spectroscopy measurements in dry/wet gases (N2, O2, and 5% H2–Ar) showed an enhancement of the sinterability and electrical properties of the materials after Nb-doping. Conductivity measurements under very reducing conditions revealed that these materials are mixed ionic-electronic conductors, making them potential candidates for hydrogen separation membranes. |
| Remark | Link |
Effect of B-site doping on electrical conductivity of YAlO3 based electrolytes for solid oxide fuel cells
ID=500| Authors |
|
| Source |
Journal of Electroceramics
Volume: 42,
Issue: 1-2,
Pages: 79–86 Time of Publication: 2019 |
| Abstract | Solid oxide fuel cells (SOFCs) have emerged as high temperature fuel cell technology operating at temperatures around 1000 °C. Lowering the operating temperature enables the use of cheaper materials while maintaining high power outputs. Electrolytes with ABO3-type perovskite structure are good ionic conductors and are promising materials for SOFCs. In this study, a systematic investigation on the synthesis and characterization of Mg- substituted YAlO3 system has been performed. The samples have been synthesized by wet chemical citrate gel route and the electrical conductivity measurements have been conducted in air between 300 and 800 °C. Effect of composition of the phases on total conductivity has been analyzed employing X-ray diffraction. The influence of microstructure on total conductivity has been studied using scanning electron microscopy and orientation imaging microscopy. |
| Keywords | Intermediate temperature SOFCs, Perovskites, Total conductivity, Citrate gel route, Doping |
| Remark | Link |
Invistigation of the role of gravitational attraction in the structure and the catalysis of the formation of particles and study of the catalytic hydrogenation of CO2 using supported ruthenium catalysts on different substrates
ID=499| Author |
|
| Source |
Time of Publication: 2018
|
| Remark |
Dissertation o obtain the Degree of Doctor of the University of Patras Link |
Investiagation of the role of gravitational attraction in the structure and the catalysis of the formation of particles and study of catalytic hydrogenation of CO2 using supported ruthenium catalysts on different substrates
ID=498| Author |
|
| Source |
Time of Publication: 2018
|
| Remark | Link |
Dy doped SrTiO3: A promising anodic material in solid oxide fuel cells
ID=496| Authors |
|
| Source |
International Journal of Hydrogen Energy
Volume: 43,
Issue: 41,
Pages: 19242-19249 Time of Publication: 2018 |
| Abstract | The perovskite-type oxides, having a general formula ABO3, are promising candidates for anode materials in solid oxide fuel cells. In particular, doped SrTiO3 based perovskites are potential mixed ionic-electronic conductors and they are known to have excellent thermal and chemical stability along with carbon and sulfur tolerance. In this work, DyxSr1-xTiO3-δ system with x = 0.03, 0.05, 0.08 and 0.10 is studied to understand the influence of Dy content on its structural and electrical behavior. Electrochemical properties are measured, both in air and hydrogen atmosphere, and structural characterizations are performed before and after electrochemical tests and compared each other to study the stability. Results show that DyxSr1-xTiO3-δ powders with x ≤ 0.05, are single phase, while for x ≥ 0.08 a small amount of secondary phases is formed. In air, the conductivity is predominantly mixed ionic-electronic type for x ≤ 0.05, becoming ionic for x ≥ 0.08. It is observed that conductivity, for each composition, increases passing from air to hydrogen and activation energy decreases. Dy0.05Sr0.95TiO3-δ shows the highest conductivity in air whereas Dy0.08Sr0.92TiO3-δ in H2 atmosphere. Degradation observed by XRD is negligible for x ≤ 0.05 but increases with higher Dy content. |
| Remark |
https://doi.org/10.1016/j.ijhydene.2018.08.160 Link |
Efficient intermediate-temperature steam electrolysis with Y : SrZrO3–SrCeO3 and Y : BaZrO3–BaCeO3 proton conducting perovskites
ID=495| Authors |
|
| Source |
J. Mater. Chem. A
Volume: 6,
Pages: 19113-19124 Time of Publication: 2018 |
| Abstract | Ceramic proton conductors have the potential to become important components in future clean and efficient energy technologies. In this manuscript, barium cerium yttrium zirconate (Ba(Zr0.5Ce0.4)8/9Y0.2O2.9) and strontium cerium yttrium zirconate (SrZr0.5Ce0.4Y0.1O2.95), proton conducting perovskites were employed as solid oxide electrolysis cell (SOEC) electrolytes for hydrogen production via intermediate temperature steam electrolysis at 550 and 600 °C. Cathode-supported button cells examined for a 12 μm Ba(Zr0.5Ce0.4)8/9Y0.2O2.9 electrolyte, with Ni–SrZr0.5Ce0.4Y0.1O2.95 as the H2-electrode, and porous Ba0.5La0.5CoO3 as the anode reached current densities of 0.2 and 0.5 A cm−2 with applied voltage of 1.45 V, at 550 and 600 °C, respectively. Moreover, a hydrogen evolution rate of 127 μmol cm−2 per minute was achieved at 0.5 A cm−2, translating to a current efficiency of 82%. In addition, excellent cell performance was obtained using SrZr0.5Ce0.4Y0.1O2.95 as an electrolyte. Current densities of 0.2 and 0.5 A cm−2 were obtained at 600 °C with applied voltages of 1.28 and 1.63 V, achieving faradaic current efficiencies of 88 and 85%. The NiO–SrZr0.5Ce0.4Y0.1O3−δ composite cathode was more favorable for the densification of the supported Ba(Zr0.5Ce0.4)8/9Y0.2O2.9 electrolyte during sintering and could be promising for use as a cathode substrate in proton-conducting SOECs. |
| Remark |
DOI: 10.1039/C8TA04019B Link |
Computational Prediction and Experimental Realization of p-Type Carriers in the Wide-Band-Gap Oxide SrZn1–xLixO2
ID=494| Authors |
|
| Source |
Inorg. Chem.
Volume: 57,
Issue: 19,
Pages: 11874-11883 Time of Publication: 2018 |
| Abstract | It is challenging to achieve p-type doping of zinc oxides (ZnO), which are of interest as transparent conductors in optoelectronics. A ZnO-related ternary compound, SrZnO2, was investigated as a potential host for p-type conductivity. First-principles investigations were used to select from a range of candidate dopants the substitution of Li+ for Zn2+ as a stable, potentially p-type, doping mechanism in SrZnO2. Subsequently, single-phase bulk samples of a new p-type-doped oxide, SrZn1–xLixO2 (0 < x < 0.06), were prepared. The structural, compositional, and physical properties of both the parent SrZnO2 and SrZn1–xLixO2 were experimentally verified. The band gap of SrZnO2 was calculated using HSE06 at 3.80 eV and experimentally measured at 4.27 eV, which confirmed the optical transparency of the material. Powder X-ray diffraction and inductively coupled plasma analysis were combined to show that single-phase ceramic samples can be accessed in the compositional range x < 0.06. A positive Seebeck coefficient of 353(4) μV K–1 for SrZn1–xLixO2, where x = 0.021, confirmed that the compound is a p-type conductor, which is consistent with the pO2 dependence of the electrical conductivity observed in all SrZn1–xLixO2 samples. The conductivity of SrZn1–xLixO2 is up to 15 times greater than that of undoped SrZnO2 (for x = 0.028 σ = 2.53 μS cm–1 at 600 °C and 1 atm of O2). |
| Remark | Link |
Microstructure and doping effect on the enhancement of the thermoelectric properties of Ni doped Dy filled CoSb3 skutterudites
ID=493| Authors |
|
| Source |
Sustainable Energy Fuels
Volume: 2,
Pages: 2687-2697 Time of Publication: 2018 |
| Abstract | The thermoelectric properties of nanostructured Ni doped Dy filled CoSb3 skutterudites (Dy0.4Co4−xNixSb12 (x = 0, 0.4, and 0.8)) have been reported. The samples are processed using a solid-state synthesis route. The structural analysis of the samples using X-ray diffraction reveals the existence of a single skutterudite phase in Ni doped samples irrespective of the Ni concentration. Microstructure studies using transmission electron microscopy and scanning electron microscopy show the existence of nanometer (∼60 nm) size equiaxed grains in the investigated samples. A few recrystallized elongated grains (∼200 nm) are observed in the Dy0.4Co3.2Ni0.8Sb12 sample. The power factor of the Dy0.4Co3.2Ni0.8Sb12 sample is enhanced to 5.2 mW mK−2, which is the highest power factor for the doped ternary skutterudites reported so far. The enhancement of the power factor is due to the substantial reduction in electrical resistivity with an increase in Ni concentration at higher temperature. The lattice thermal conductivity is drastically reduced to 0.3 W mK−1 at 773 K in the Dy0.4Co3.2Ni0.8Sb12 sample due to the enhanced phonon scattering from Ni induced point defects and grain boundaries. As a result, a huge increase in the figure of merit (ZT ∼ 1.4 ± 0.14) at 773 K is observed in the Dy0.4Co3.2Ni0.8Sb12 sample, the highest among those of the single element filled CoSb3 skutterudites reported so far at this temperature. Hence, Ni doping could enhance the thermoelectric efficiency of Dy filled CoSb3 skutterudites. This can be taken as a reference to synthesize CoSb3 skutterudite thermoelectric materials having a higher figure of merit. |
| Remark |
DOI: 10.1039/C8SE00395E Link |
Computational Prediction and Experimental Realization of p-Type Carriers in the Wide-Band-Gap Oxide SrZn1–xLixO2
ID=492| Authors |
|
| Source |
Inorg. Chem.
Time of Publication: 2018
|
| Abstract | It is challenging to achieve p-type doping of zinc oxides (ZnO), which are of interest as transparent conductors in optoelectronics. A ZnO-related ternary compound, SrZnO2, was investigated as a potential host for p-type conductivity. First-principles investigations were used to select from a range of candidate dopants the substitution of Li+ for Zn2+ as a stable, potentially p-type, doping mechanism in SrZnO2. Subsequently, single-phase bulk samples of a new p-type-doped oxide, SrZn1–xLixO2 (0 < x < 0.06), were prepared. The structural, compositional, and physical properties of both the parent SrZnO2 and SrZn1–xLixO2 were experimentally verified. The band gap of SrZnO2 was calculated using HSE06 at 3.80 eV and experimentally measured at 4.27 eV, which confirmed the optical transparency of the material. Powder X-ray diffraction and inductively coupled plasma analysis were combined to show that single-phase ceramic samples can be accessed in the compositional range x < 0.06. A positive Seebeck coefficient of 353(4) μV K–1 for SrZn1–xLixO2, where x = 0.021, confirmed that the compound is a p-type conductor, which is consistent with the pO2 dependence of the electrical conductivity observed in all SrZn1–xLixO2 samples. The conductivity of SrZn1–xLixO2 is up to 15 times greater than that of undoped SrZnO2 (for x = 0.028 σ = 2.53 μS cm–1 at 600 °C and 1 atm of O2). |
| Remark |
DOI: 10.1021/acs.inorgchem.8b00697 Link |
Thermoelectric Properties of (1-x)LaCoO3.(x)La0.95Sr0.05CoO3 composite
ID=491| Authors |
|
| Source |
Materials Research Express
Time of Publication: 2018
|
| Abstract | Thermopower in cobalt oxides has been a rich area of interest due to the existence of the different charge states along-with different spin states. In this report, we have systematically studied the structural and thermal transport properties of ($1-x$)LaCoO$_3$.($x$)La$_{0.95}$Sr$_{0.05}$CoO$_3$ composite. The Seebeck coefficient ($alpha$) values for the composite increases at high temperatures compared to the LaCoO$_3$ (LCO) and La$_{0.95}$Sr$_{0.05}$CoO$_3$ (LSCO) systems. The electrical conductivity ($sigma$) decreases with the increase in the LSCO fraction which may be attributed to the localization of charge carriers due to intersite diffusion. All the samples show increase in the value of $sigma$ with increase in temperature. The thermal conductivity ($kappa$) values decrease with the increase of LSCO content in the composite and the phonon thermal conductivity dominates over the total thermal conductivity. We observe a maximum value of figure of merit (ZT)$sim$0.06 at 640,K for $x=$0.05. |
| Remark | Link |
Wide bandgap oxides for low-temperature single-layered nanocomposite fuel cell
ID=490| Authors |
|
| Source |
Nano Energy
Volume: 53,
Pages: 391-397 Time of Publication: 2018 |
| Abstract | A composite of wide bandgap lithium-nickel-zinc-oxide (LNZ) and gadolinium-doped-cerium-oxide (GDC) was systematically analyzed for a low-temperature nanocomposite fuel cell in a so-called single-component configuration in which the electrodes and electrolyte form a homogenous mixture. We found that the operational principle of a single-layer fuel cell can be explained by electronic blocking by the oxide mixture with almost insulator-like properties in the operating voltage regime of the fuel cell, which will prevent short-circuiting, and by its catalytic properties that drive the fuel cell HOR and ORR reactions. The resistance to charge transport and leakage currents are dominant performance limiting factors of the single-component fuel cell. A test cell with Au as current collector reached a power density of 357 mWcm−2 at 550 °C. Changing the current collector to a Ni0.8Co0.15Al0.05LiO2 (NCAL) coated Ni foam produced 801 mWcm−2, explained by better catalytic properties. However, utilizing NCAL coated Ni foam may actually turn the 1-layer fuel cell device into a traditional 3-layer (anode-electrolyte-cathode) structure. This work will help in improving the understanding of the underlying mechanisms of a single-layer fuel cell device important to further develop this potential energy technology. |
| Keywords | Bandgap; Ceramic; Fuel cell; Ionic conductivity; Nanocomposite; Single-component |
| Remark |
https://doi.org/10.1016/j.nanoen.2018.08.070 Link |
Crystal Structure and Coordination of B-Cations in the Ruddlesden–Popper Phases Sr3−xPrx(Fe1.25Ni0.75)O7−δ (0 ≤ x ≤ 0.4)
ID=489| Authors |
|
| Source |
Inorganics
Volume: 6,
Issue: 3
Time of Publication: 2018
|
| Abstract | Compounds Sr3−xPrxFe1.25Ni0.75O7−δ with 0 ≤ x ≤ 0.4 and Ruddlesden–Popper n = 2 type structures were synthesized and investigated by X-ray and neutron powder diffraction, thermogravimetry, and Mössbauer spectroscopy. Both samples, prepared at 1300 °C under N2(g) flow and samples subsequently air-annealed at 900 °C, were studied. The structures contained oxygen vacancies in the perovskite layers, and the Fe/Ni cations had an average coordination number less than six. The oxygen content was considerably higher for air-annealed samples than for samples prepared under N2, 7 − δ = ~6.6 and ~5.6 per formula unit, respectively. Mössbauer data collected at 7 K, below magnetic ordering temperatures, were consistent with X-ray powder diffraction (XRD) and neutron powder diffraction (NPD) results. The electrical conductivity was considerably higher for the air-annealed samples and was for x = 0.1~30 S·cm−1 at 500 °C. The thermal expansion coefficients were measured in air between room temperature and 900 °C and was found to be 20–24 ppm·K−1 overall. |
| Keywords | Ruddlesden–Popper structure; oxygen non-stoichiometry; crystal structure; Mössbauer spectroscopy; electrical conductivity; thermal expansion |
| Remark | Link |
All-Oxide Thermoelectric Module with in Situ Formed Non-Rectifying Complex p–p–n Junction and Transverse Thermoelectric Effect
ID=488| Authors |
|
| Source |
ACS Omega
Volume: 3,
Issue: 8,
Pages: 9899–9906 Time of Publication: 2018 |
| Abstract | All-oxide thermoelectric modules for energy harvesting are attractive because of high-temperature stability, low cost, and the potential to use nonscarce and nontoxic elements. Thermoelectric modules are mostly fabricated in the conventional π-design, associated with the challenge of unstable metallic interconnects at high temperature. Here, we report on a novel approach for fabrication of a thermoelectric module with an in situ formed p–p–n junction made of state-of-the-art oxides Ca3Co4–xO9+δ (p-type) and CaMnO3–CaMn2O4 composite (n-type). The module was fabricated by spark plasma co-sintering of p- and n-type powders partly separated by insulating LaAlO3. Where the n- and p-type materials originally were in contact, a layer of p-type Ca3CoMnO6 was formed in situ. The hence formed p–p–n junction exhibited Ohmic behavior and a transverse thermoelectric effect, boosting the open-circuit voltage of the module. The performance of the module was characterized at 700–900 °C, with the highest power output of 5.7 mW (around 23 mW/cm2) at 900 °C and a temperature difference of 160 K. The thermoelectric properties of the p- and n-type materials were measured in the temperature range 100–900 °C, where the highest zT of 0.39 and 0.05 were obtained at 700 and 800 °C, respectively, for Ca3Co4–xO9+δ and the CaMnO3–CaMn2O4 composite. |
| Remark |
DOI: 10.1021/acsomega.8b01357 |
An operando calorimeter for high temperature electrochemical cells
ID=487| Authors |
|
| Source |
Time of Publication: 2018
|
| Abstract | Operando calorimetry has previously been utilized to study degradation, side reactions, and other electrochemical effects in electrochemical cells such as batteries at or near room temperature. Calorimetric data can provide important information on the lifetime and thermal properties of electrochemical cells and can be used in practical engineering applications such as thermal anagement. High temperature electrochemical cells such as solid oxide fuel cells or electrolyzers can also benefit from operando calorimetry, although to our knowledge no such unit has been eveloped commercially. Herein, we report an operando calorimeter capable of simultaneous calorimetry and electrochemistry at temperatures up to 1,000 °C and in both oxidizing and reducing atmospheres. The calorimeter is constructed by modifying a commercial apparatus originally designed to study high temperature electrochemical cells in various gas environments. We utilize a grey - box, nonlinear system identification model to analyze calorimetric data and achieve an electrochemical cell power sensitivity of 16.1±11.7 mW. This operando calorimeter provides the tools needed to study both the thermal and kinetic behavior of electrochemical cells at elevated temperatures. |
| Remark | Link |
Ohmically heated ceramic asymmetric tubular membranes for gas separation
ID=486| Authors |
|
| Source |
Journal of Membrane Science
Volume: 564,
Pages: 598-604 Time of Publication: 2018 |
| Abstract | Mixed conducting dense ceramic gas separation membranes can be used in air separation for oxy-fuel and pre-combustion processes in CO2 capture schemes for emission-free power plants and chemical industries. Such membranes operate at high temperatures, and the energy penalty associated with heating the membranes with external electrical heaters or burners via the feed or sweep gas can be significantly reduced by adopting direct ohmic heating of the membrane. We demonstrate that tubular asymmetric gas separation membranes of La2NiO4+δ and La0.87Sr0.13CrO3-δ can be heated to temperatures in excess of 800 °C by passing current through them, and that such ohmically heated tubular membranes can be operated in an oxygen potential gradient to selectively separate oxygen from a feed gas mixture. We highlight the associated challenges with heat transport and thermal gradients and undertake numerical simulations to investigate the effect of materials properties on heating power and heat distribution in the tubes. |
| Keywords | Membranes, ceramic, dense; Gas separation; Ohmic heating, La2NiO4; LaCrO3 |
| Remark |
https://doi.org/10.1016/j.memsci.2018.07.070 Link |
A novel anode for solid oxide fuel cells prepared from phase conversion of La0.3Sr0.7Fe0.7Cr0.3O3-δ perovskite under humid hydrogen
ID=485| Authors |
|
| Source |
Electrochimica Acta
Volume: 284,
Pages: 303-313 Time of Publication: 2018 |
| Abstract | A novel anode for solid oxide fuel cells (SOFCs), consisting of a Ruddlesden-Popper compound, La0.6Sr1.4Fe0.4Cr0.6O3.8, with in situ exsolved α-Fe nanoparticles (RP-LSF + Fe), is prepared from the phase conversion of the La0.3Sr0.7Fe0.7Cr0.3O3-δ (LSFCr-3) perovskite under humid H2 at 800 °C. On the surface of the RP-LSF + Fe anode, Fe cations are presented to be a mixture of Fe2+ and Fe3+, of which the average valence is lower than that in the bulk (Fe3+). The coverage of atomic hydrogen on the RP-LSF + Fe anode is over 0.8 in the pH2 range of 0.017–0.27 atm, implying a significant effect of these small amount (∼8 mol% on the surface) of exsolved Fe nanoparticles (∼200–300 nm) on promoting the dissociative absorption of H2. The charge transfer resistance is found to be closely related to the concentration of surface oxygen vacancies of the oxide matrix. The addition of catalytic amount of Ni (1–3 wt.%) greatly improves the fuel flexibility of the RP-LSF + Fe anode. Furthermore, it contributes to acceleration the phase conversion of the LSFCr-3 perovskite and reduced time for in situ preparation of the RP-LSF + Fe anode. The RP-LSF + Fe anode with 2.7 wt.% Ni exhibits a stable cell performance under 2.7%H2O+1:1-(H2:CO) and 2.7%H2O + CH4 for ∼30 h. It costs shortest time (30 h) to reach a stable cell voltage of 0.76 V at a galvanostatic current density of 0.25 A/cm2 under humid H2, which is clearly an active and stable anode material for SOFCs. |
| Keywords | Solid oxide fuel cell, Oxide anode, Phase conversion, Electrodics, Fuel flexibility |
| Remark |
https://doi.org/10.1016/j.electacta.2018.07.132 Link |
Assessment of layered La2-x(Sr,Ba)xCuO4-δ oxides as potential cathode materials for SOFCs
ID=484| Authors |
|
| Source |
International Journal of Hydrogen Energy
Volume: 43,
Issue: 32,
Pages: 15492-15504 Time of Publication: 2018 |
| Abstract | In this paper, selected layered cuprates with La2-x(Sr,Ba)xCuO4-δ formula are evaluated as candidate cathode materials for Solid Oxide Fuel Cells. Two synthesis routes, a typical solid state reaction and a sol-gel method yield well-crystallized La1.5Sr0.5CuO4-δ, La1.6Ba0.4CuO4-δ and La1.5Sr0.3Ba0.2CuO4-δ materials having tetragonal I4/mmm space group, but differing in morphology of the powder. Fine powders obtained using sol-gel route seem to be more suitable for preparation of the porous cathode layers having good adhesion on the solid electrolyte, but powders obtained after the solid state route can be also successfully utilized. Investigations of structural and transport properties, the oxygen nonstoichiometry and its change with temperature, thermal expansion, as well as chemical and thermal stability are systematically performed, to evaluate and compare basic physicochemical properties of the oxides. At room temperature the average valence state of copper is found to be in 2.2–2.35 range, indicating oxygen deficiency in all of the compounds, which further increases with temperature. The conducted high-temperature X-ray diffraction tests reveal moderate, but anisotropic thermal expansion of La2-x(Sr,Ba)xCuO4-δ, with higher expansion at temperatures above 400 °C occurring along a-axis, due to the oxygen release. However, the corresponding chemical expansion effect is small and the materials possess moderate thermal expansion in the whole studied temperature range. All compounds show relatively high electrical conductivity at the elevated temperatures, related to the Cu2+/Cu3+ charge transfer, with the highest values recorded for La1.5Sr0.5CuO4-δ. Comprehensive studies of chemical stability of the selected La1.5Sr0.5CuO4-δ material with La0.8Sr0.2Ga0.8Mg0.2O3-δ solid electrolyte revealed complex behavior, with stability being dependent apart from temperature, also on morphology of the powders. A model describing such behavior is presented. While it is possible to minimize reactivity and characterize electrochemical properties of the La1.5Sr0.5CuO4-δ-based cathode layer, usage of the buffer layer is indispensable to maintain full stability. It is shown that mutual chemical compatibility of La1.5Sr0.5CuO4-δ and commonly used La0.4Ce0.6O2-δ buffer layer material is excellent, with no reactivity even at 1000 °C for prolonged time. Laboratory-scale fuel cell with the La1.5Sr0.5CuO4-δ cathode sintered at the optimized temperature is able to deliver 0.16 W cm−2 at 800 °C while fueled with wet hydrogen. |
| Keywords | Layered cuprates, Cathodic polarization, Chemical stability, LSGM, Buffer layer, SOFC |
| Remark |
https://doi.org/10.1016/j.ijhydene.2018.06.119 Link |
Sol-gel Zn, Fe modified SnO2 powders for CO sensors and magnetic applications
ID=483| Authors |
|
| Source |
Process Safety and Environmental Protection
Volume: 117,
Pages: 722-729 Time of Publication: 2018 |
| Abstract | Zn, Fe modified SnO2 powders were prepared by sol-gel method using Tripropylamine as chelating agent and Polyvinylpyrrolidone K90 as dispersant and stabilizer. Two compositions were taken into account: Zn, Fe modified SnO2 – 20 mol% Zn, 10 mol% Fe and Zn, Fe modified SnO2 – 20 mol% Zn, 30 mol% Fe, denoted further as SZFe1and SZFe2 respectively. The properties and the influence of Fe amount on structure, morphology and surface chemistry, electrical and magnetic properties have been investigated. The X-ray diffraction analysis showed the formation of a polycrystalline mixture of cassiterite – SnO2, hematite – Fe2O3, franklinite – ZnFe2O4 and zincite – ZnO for the samples with different Fe content. The magnetization of SZFe2 sample was found to be composed of a ferromagnetic and a paramagnetic phase. The presence of Fe in the powders composition improved the electrical properties, demonstrating performant features in sensing characteristics (tested in CO gas concentrations varied from 50 to 1000 ppm). The magnetic investigations suggest their possible future applications as soft magnetic materials. |
| Keywords | Oxides, Sol-gel chemistry, Surface properties, Electrical properties, CO gas sensor |
| Remark |
https://doi.org/10.1016/j.psep.2018.06.010 Link |
Optimization and Electrochemical Properties of Double Perovskite NdBaCo2O6–δ ·LaBaCo2O5+δ as Cathode Material for Solid Oxide Fuel Cell
ID=482| Authors |
|
| Source |
Journal of Nanoelectronics and Optoelectronics
Volume: 13,
Issue: 5,
Pages: 749-757(9) Time of Publication: 2018 |
| Abstract | In this paper, the double perovskite structure NdBaCo2O6–δ ·LaBaCo2O5+δ was used as cathode material for solid oxide fuel cell (SOFC). The cathode material was prepared using sol in situ composite method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical measurements systems. The NdBaCo2O6–δ and (Ce, Gd, O) were prepared to get NdBaCo2O6–δ –xCe0.8Gd0.1O1.75 (x = 0–10 wt%) and with the increase of the compound (Ce, Gd, O), the electrode polarization surface resistance changes. The polarization resistance at 700 °C was only 0.032 Ω cm2. The output power of single battery was 0.363 W/cm2. The sol–gel method was used to replace Co with Fe and LaBaCo2–x Fe x O5+δ (x = 0.0, 0.3, 0.5, 0.8) was prepared. It was observed that under different Fe contents, the polarization resistance of the composite cathode material LaBaCo2–x Fe x O5+δ decreases first and then increases. When x = 0.3, the minimum polarization resistance can be obtained, however, with the increase of temperature, the polarization resistance of the composite cathode material further reduced. |
| Remark |
DOI: https://doi.org/10.1166/jno.2018.2320 Link |
Electrochemical and degradation study of Sr0.6Na0.4SiO3-δ
ID=481| Authors |
|
| Source |
Journal of Solid State Electrochemistry
Volume: 22,
Issue: 10,
Pages: 3009–3013 Time of Publication: 2018 |
| Abstract | The high ionic conductivity of Na-doped SrSiO3 (SNS) is a topic of interest due to contradictory reports on its conductivity and stability by various groups. From a recent NMR study, it is proposed that Na+ is mainly responsible for ionic conductivity in an amorphous Na2Si2O5 phase present in SNS. The present study further extends to determine experimentally the ion transport number as well as material characteristics after long time annealing at 600 °C. The conductivity behavior of as-sintered and annealed nominally Sr0.6Na0.4SiO3-δ is investigated and a sharp fall (~ 2 order magnitude) of the same at 800 °C is found. An XPS study is included for comprehensive understanding of conductivity and degradation behavior of SNS material. On basis of the collective results, we propose a rational description of the conduction and material degradation of SNS. |
| Keywords | SrSiO3, Transport number, SOFC, Ionic conductivity, Protonic conductivity |
| Remark | Link |
Novel ReBaCo1.5Mn0.5O5+δ (Re: La, Pr, Nd, Sm, Gd and Y) perovskite oxide: influence of manganese doping on the crystal structure, oxygen nonstoichiometry, thermal expansion, transport properties, and application as a cathode material in solid oxide f
ID=480| Authors |
|
| Source |
Journal of Materials Chemistry A
Issue: 6,
Pages: 13271-13285 Time of Publication: 2018 |
| Abstract | In this work, a novel series of Mn-containing ReBaCo1.5Mn0.5O5+δ (Re: selected rare earth elements) perovskite-type oxides is studied, with systematic measurements of physicochemical properties being reported. Comparison with the very well-studied, parent ReBaCo2O5+δ allows determination of the role of the introduced manganese concerning modification of the crystal structure at room temperature and its evolution at high temperatures, variation of the oxygen content, thermal stability of the materials, and total electrical conductivity, as well as thermal and chemical expansion. Generally, the presence of Mn cations does not affect the tendency for A-site cation ordering, resulting in an increased unit cell volume of the compounds, as well as causing an increase of the oxygen content. Reduced thermal expansion, together with high values of electrical conductivity and suitable thermal stability, makes the compounds containing larger Re3+ cations attractive from the point of view of application as cathode materials in solid oxide fuel cells. Chemical compatibility studies reveal the sufficient stability of the considered perovskites in relation to Ce0.8Gd0.2O2−δ solid electrolyte, while unexpected, somewhat increased reactivity towards La0.8Sr0.2Ga0.8Mg0.2O3−δ and La0.4Ce0.6O2−δ is also reported. Furthermore, the electrochemical tests of the symmetric cells show strong dependence of the polarization resistance of the electrode on the synthesis and sintering temperatures. For the selected and optimized NdBaCo1.5Mn0.5O5+δ layer employed in the electrolyte-supported (LSGM) symmetric cell with a CGO buffer layer, the cathodic polarization resistance is 0.043 Ω cm2 at 900 °C. A wet hydrogen-fuelled button-type cell with the NdBaCo1.5Mn0.5O5+δ-based cathode is also prepared, delivering the maximum power density exceeding 1.3 W cm−2 at 850 °C. |
| Remark |
DOI: 10.1039/C8TA03479F Link |
High performance ceramic nanocomposite fuel cells utilizing LiNiCuZn-oxide anode based on slurry method
ID=479| Authors |
|
| Source |
International Journal of Hydrogen Energy
Time of Publication: 2018
|
| Abstract | A multi-oxide material LiNiCuZn-oxide was prepared through a slurry method as an anode for ceramic nanocomposite fuel cell (CNFC). The CNFCs using this anode material, LSCF as cathode material and a composite electrolyte consisting of CaSm co-doped CeO2 and (NaLiK)2CO3 produced ∼1.03 W/cm2 at 550 °C due to efficient reaction kinetics at the electrodes and high ionic transport in the nanocomposite electrolyte. The electrochemical impedance spectroscopy revealed low ionic transport losses (0.238 Ω cm2) and low polarization losses (0.124 Ω cm2) at the electrodes. The SEM measurements revealed the porous microstructures of the composite materials at electrode and the dense mixture of CaSm co-doped CeO2 and (NaLiK)2CO3. The Brunauer-Emmett-Teller (BET) analysis revealed high surface areas, 4.1 m2/g and 3.8 m2/g, of the anode and cathode respectively. This study provides a promising material for high performance CNFCs. |
| Keywords | Ceramic, Conductivity, Fuel cell, Multi-oxide, Nanocomposite, Synthesis |
| Remark |
https://doi.org/10.1016/j.ijhydene.2018.03.232 Link |
Enhanced Performance of Gadolinia-Doped Ceria Diffusion Barrier Layers Fabricated by Pulsed Laser Deposition for Large-Area Solid Oxide Fuel Cells
ID=478| Authors |
|
| Source |
ACS Appl. Energy Mater.
Time of Publication: 2018
|
| Abstract | Diffusion barrier layers are typically introduced in solid oxide fuel cells (SOFCs) to avoid reaction between state-of-the-art cathode and electrolyte materials, La1–xSrxCo1–yFeyO3-δ and yttria-stabilized zirconia (YSZ), respectively. However, commonly used layers of gadolinia-doped ceria (CGO) introduce overpotentials that significantly reduce the cell performance. This performance decrease is mainly due to the low density achievable with traditional deposition techniques, such as screen printing, at acceptable fabrication temperatures. In this work, perfectly dense and reproducible barrier layers for state-of-the-art cells (∼80 cm2) were implemented, for the first time, using large-area pulsed laser deposition (LA-PLD). In order to minimize cation interdiffusion, the low-temperature deposited barrier layers were thermally stabilized in the range between 1100 and 1400 °C. Significant enhanced performance is reported for cells stabilized at 1150 °C showing excellent power densities of 1.25 W·cm–2 at 0.7 V and at a operation temperature of 750 °C. Improved cells were finally included in a stack and operated in realistic conditions for 4500 h revealing low degradation rates (0.5%/1000 h) comparable to reference cells. This approach opens new perspectives in manufacturing highly reproducible and stable barrier layers for a new generation of SOFCs. |
| Keywords | Cation diffusion at CGO/YSZ interface; diffusion barrier layer; gadolinia doped ceria (CGO); pulsed laser deposition (PLD); solid oxide fuel cells (SOFCs); SrZrO3 |
| Remark |
DOI: 10.1021/acsaem.8b00039 Link |
Solid oxide fuel cells incorporating doped lanthanum gallate films deposited by radio-frequency magnetron sputtering at various Ar/O2 ratios and annealing conditions
ID=477| Authors |
|
| Source |
Surface and Coatings Technology
Volume: 344,
Pages: 507-513 Time of Publication: 2018 |
| Abstract | In this study, we prepared solid oxide fuel cells (SOFCs) incorporating a dense La0.87Sr0.13Ga0.88Mg0.12O3−δ (LSGM) film deposited by radio-frequency (RF) magnetron sputtering on an NiO-Sm0.2Ce0.8O2−δ (NiO-SDC) anode substrate. The influences of the Ar-O2 deposition atmosphere and the subsequent annealing conditions on the characteristics of the LSGM film and on the performance of the resulting SOFCs was investigated. LSGM targets with La0.76Sr0.24Ga0.63Mg0.37O3−δ composition and a deposition atmosphere with Ar/O2 ratios ranging from 10/0 to 5/5 were used throughout the study. Owing to the amorphous nature of the as-deposited LSGM films, the film deposited in an Ar/O2 = 10/0 atm required post-annealing at 950 °C for 4 h for crystallization and removal of the SrLaGa2O7 content, while the films deposited at lower Ar/O2 ratios required higher crystallization temperatures: for instance, the films deposited at Ar/O2 = 6/4 had to be annealed at 1100 °C for 2 h. The anode-supported substrates were then screen-printed with a La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF)-LSGM cathode layer and fired to form SOFC cells. The single cell incorporating an LSGM film with La0.87Sr0.13Ga0.88Mg0.12O3−δ composition deposited in a pure Ar atmosphere exhibited the lowest cell resistance and thus the highest maximum power density (MPD) at all operating temperatures. The total resistance of the single cell incorporating a 4.3 μm-thick LSGM film decreased from 0.386 to 0.121 Ω cm2 as the temperature increased from 650 to 850 °C, and the open circuit voltages ranged from 0.941 to 0.861 V. The maximum power density of the single cell was 0.422, 0.736, and 1.105 W cm−2 at 650, 750, and 850 °C, respectively. |
| Keywords | Solid oxide fuel cell, Sputtering, Electrolyte, Doped lanthanum gallate |
| Remark |
https://doi.org/10.1016/j.surfcoat.2018.03.073 Link |
Influence of annealing at intermediate temperature on oxygen transport kinetics of Pr2NiO4+δ
ID=476| Authors |
|
| Source |
J. Mater. Chem. A
Volume: 6,
Pages: 8331-8339 Time of Publication: 2018 |
| Abstract | Electrical conductivity relaxation (ECR) and oxygen permeation measurements were conducted, at 750 °C, to assess the long-term oxygen transport characteristics of the mixed ionic–electronic conducting Pr2NiO4+δ with a K2NiF4 structure. The results show that the apparent values for the oxygen diffusion and surface exchange coefficients extracted from the data and the associated oxygen flux increase over 120 h by 1–2 orders of magnitude. The results of post-mortem X-ray diffraction analysis of the samples show partial to virtually complete decomposition of Pr2NiO4+δ under the conditions of the experiments to Pr4Ni3O10+δ, PrNiO3−δ, Pr6O11, and traces of NiO. Pulse 18O–16O isotopic exchange (PIE) measurements confirmed fast surface exchange kinetics of the higher-order Ruddlesden–Popper phase Pr4Ni3O10+δ and Pr6O11 formed upon decomposition. Additional factors related to the microstructure, however, need to be considered to explain the observations. |
| Remark | Link |
Thermoelectric properties of (1-x)LaCoO3.xLa0.7Sr0.3MnO3 composite
ID=475| Authors |
|
| Source |
Journal of Alloys and Compounds
Volume: 749,
Pages: 1092-1097 Time of Publication: 2018 |
| Abstract | We report the thermoelectric (TE) properties of (1-x)LaCoO3.xLa0.7Sr0.3MnO3 (0 < x < 0.50) composite in a temperature range 320–800 K. Addition of La0.7Sr0.3MnO3 to LaCoO3 in small amount (5 weight %) improves the overall Seebeck coefficient (α) at higher temperatures. The electrical conductivity however decreases due to a decrease in carrier concentration of the composite. The decrease in electrical conductivity of the composite at high temperature may be attributed to the insulating nature of the LSMO above room temperature. Thermal conductivity (κ) of all the samples increases with an increase in the temperature, but decreases with increasing LSMO content. We also report the local variation of Seebeck coefficient across the composite samples measured using a precision Seebeck measurement system. A maximum value of 0.09 for the figure of merit (ZT) is obtained for 0.95LaCoO3.0.05La0.7Sr0.3MnO3 at 620 K which is significantly higher than the ZT of either of LaCoO3 or La0.7Sr0.3MnO3 at 620 K. This suggests the potential for enhancement of operating temperatures of hitherto well known low temperature thermoelectric materials through suitable compositing approach. |
| Keywords | Thermal conductivity, Electrical conductivity, Perovskites, Manganites, Cobaltate, Composite |
| Remark |
https://doi.org/10.1016/j.jallcom.2018.03.347 Link |
Lanthanum doped strontium titanate - ceria anodes: deconvolution of impedance spectra and relationship with composition and microstructure
ID=474| Authors |
|
| Source |
Journal of Power Sources
Volume: 385,
Pages: 62-75 Time of Publication: 2018 |
| Abstract | Electrochemical performance of ceramic (Ni-free) SOFC anodes based on La0.2Sr0.7TiO3-δ (LST) and Gd0.1Ce0.9O1.95-δ (CGO) is thoroughly investigated. Microstructures and compositions are systematically varied around the percolation thresholds of both phases by modification of phase volume fractions, particle size distributions and firing temperature. Differential impedance spectroscopy was performed while varying gas composition, electrical potential and operating temperature, which allows determining four distinct electrode processes. Significant anode impedances are measured at low frequencies, which in contrast to the literature cannot be linked with gas concentration impedance. The dominant low frequency process (∼1 Hz) is attributed to the chemical capacitance. Combined EIS and microstructure investigations show that the chemical capacitance correlates inversely with the available surface area of CGO, indicating CGO surface reactions as the kinetic limitation for the dominant anode process and for the associated chemical capacitance. In anodes with a fine-grained microstructure this limitation is significantly smaller, which results in an impressive power output as high as 0.34 Wcm−2. The anodes show high redox stability by not only withstanding 30 isothermal redox cycles, but even improving the performance. Hence, compared to conventional Ni-cermet anodes the new LST-CGO material represents an interesting alternative with much improved redox-stability. |
| Keywords | SOFC, LST, Microstructure analysis, Electrochemical impedance, Spectroscopy, Redox Anodes |
| Remark |
https://doi.org/10.1016/j.jpowsour.2018.03.024 Link |
Influence of texture and grain misorientation on the ionic conduction in multilayered solid electrolytes – interface strain effects in competition with blocking grain boundaries
ID=473| Authors |
|
| Source |
Physical Chemistry Chemical Physics
Issue: 14
Time of Publication: 2018
|
| Abstract | Interface strain and its influence on the ionic transport along hetero-interfaces has gained a lot of attention over the last decade and is controversially discussed. We investigate the relaxation of mismatch induced interfacial strain as a function of the degree of orientation/texture of the columnar crystallites and assess the impact on the oxygen ion conductivity in Er2O3/YSZ multilayer systems. Results from X-ray diffraction clearly show, that the width of the strained hetero-interface region increases with an increasing degree of orientation of the crystallites. The combined impact of film texture and strain at the hetero-interfaces of the film on the ionic conductivity however is not easily deduced from these measurements. The samples with the highest degree of orientation, i.e. with only one azimuthal variant, show strong anisotropic electrical properties. In samples with a lower degree of orientation, i.e. samples with a fiber texture, anisotropic properties cannot be detected, possibly due to a geometrical averaging of the electrical properties. The expected strain induced monotonic increase of the ionic conductivity with decreasing layer thickness and thus increasing interfacial influence could only be detected for samples with a fiber texture and a considerable degree of crystallite misorientation. This leads to the important conclusion that the texture and therefore the nature of the grain boundaries and their network influence the ionic conductivity of the multilayer thin films in the same order of magnitude as the misfit induced interface strain. Thus, the potential design of strain-controlled ionic conductors requires additionally the control of the microstructure in terms of grain orientation. |
| Remark | Link |
Crystal Structure, Hydration, and Two-Fold/Single-Fold Diffusion Kinetics in Proton-Conducting Ba0.9La0.1Zr0.25Sn0.25In0.5O3−a Oxide
ID=472| Authors |
|
| Source |
Crystals
Volume: 8,
Issue: 3,
Pages: 136 Time of Publication: 2018 |
| Abstract | In this work, hydration kinetics related to the incorporation of water into proton-conducting Ba0.9La0.1Zr0.25Sn0.25In0.5O3−a perovskite-type oxide are presented, with a recorded transition on temperature from a single-fold to a two-fold behavior. This can be correlated with an appearance of the electronic hole component of the conductivity at high temperatures. The collected electrical conductivity relaxation data allowed to calculate chemical diffusion coefficient D and surface exchange reaction coefficient k, as well as respective activation energies of their changes on temperature. Presented results are supplemented with a systematic characterization of the structural properties of materials synthesized at different temperatures, amount of incorporated water after hydration in different conditions, influence of water content on the crystal structure, as well as electrical conductivity in dry, H2O- and D2O-containing air, which enabled to evaluate proton (deuterium) conductivity. |
| Keywords | Perovskite oxides; substituted barium indate; hydration; proton conductivity; relaxation experiments; coupled/decoupled ionic transport. |
| Remark |
doi:10.3390/cryst8030136 Link |
Sol-gel synthesis of ZnO/Zn2-xFexTiO4 powders: structural properties, electrical conductivity and dielectric behavior
ID=471| Authors |
|
| Source |
Journal of Sol-Gel Science and Technology
Volume: 86,
Issue: 1,
Pages: 151–161 Time of Publication: 2018 |
| Abstract | The aim of this work was an investigation of structural and electrical properties of ZnO/Zn2-xFexTiO4 (x = 0.7, 1, 1.4) powders. The compounds obtained by sol-gel method are characterized by several techniques: X-ray diffraction (XRD), N2 adsorption–desorption isotherms, scanning and transmission electron microscopy (SEM and TEM), X-ray photoelectron spectroscopy (XPS), electrical and dielectrical measurements. The XRD, SEM and XPS analysis confirmed the formation of ZnFeTiO4 inverse spinel structure. The electrical and dielectrical properties of ZnO/Zn2-xFexTiO4 (x = 0.7, 1, 1.4) were measured by impedance spectroscopy, revealing a decrease in the electrical conductivity and the dielectric constant with Fe content. |
| Keywords | Sol-gel, ZnO/ZnFeTiO4, dielectric constant, AC conductivity |
| Remark | Link |
p-Type/n-type behaviour and functional properties of KxNa(1-x)NbO3 (0.49 ≤ x ≤ 0.51) sintered in air and N2
ID=470| Authors |
|
| Source |
Journal of the European Ceramic Society
Volume: 38,
Issue: 9,
Pages: 3118-3126 Time of Publication: 2018 |
| Abstract | Potassium sodium niobate (KNN) is a potential candidate to replace lead zirconate titanate in sensor and actuator applications but there are many fundamental science and materials processing issues to be understood before it can be used commercially, including the influence of composition and processing atmosphere on the conduction mechanisms and functional properties. Consequently, KNN pellets with different K/Na ratios were sintered to 95% relative density in air and N2 using a conventional mixed oxide route. Oxygen vacancies (VO••) played a major role in the semi-conduction mechanism in low p(O2) for all compositions. Impedance spectroscopy and thermo-power data confirmed KNN to be n-type in low p(O2) in contradiction to previous reports of p-type behaviour. The best piezoelectric properties were observed for air- rather than N2-sintered samples with d33 = 125 pC/N and kp = 0.38 obtained for K0.51Na0.49NbO3. |
| Keywords | p-Type, n-Type, Low p(O2), Oxygen vacancies, Seebeck coefficient |
| Remark |
https://doi.org/10.1016/j.jeurceramsoc.2018.03.013 Link |
La1.8Sr0.2Ni0.8M0.2O4 (M = Fe, Co, or Cu) Complex Oxides: Synthesis, Structural Characterization, and Dielectric Properties
ID=469| Authors |
|
| Source |
Russian Journal of Inorganic Chemistry
Volume: 63,
Issue: 2,
Pages: 141–148 Time of Publication: 2018 |
| Abstract | New solid solutions La1.8Sr0.2Ni0.8M0.2O4 (M = Fe, Co, or Cu) have been prepared, and their crystal- chemical characteristics and electric properties studied. The studied materials have been shown to have activation-time conductivity. Structural distortions have been found to affect the dielectric properties of ceramic samples. La1.8Sr0.2Ni0.8M0.2O4 is observed to have the greatest distortion of АО9 coordination polyhedra and a higher dielectric constant. |
| Remark | Link |
Inter-diffusion across a direct p-n heterojunction of Li-doped NiO and Al-doped ZnO
ID=468| Authors |
|
| Source |
Solid State Ionics
Volume: 320,
Pages: 215-220 Time of Publication: 2018 |
| Abstract | We herein report inter-diffusion across the interface between p-type Ni0.98Li0.02O and n-type Zn0.98Al0.02O for various applications including p-n-heterojunction diodes and oxide thermoelectrics. Diffusion couples were made of polished surfaces of ceramic samples pre-sintered at 1250 and 1350 °C for Ni0.98Li0.02O and Zn0.98Al0.02O, respectively. The inter-diffusion couples were annealed at 900–1200 °C for 160 h in ambient air. Electron Probe Micro Analysis (EPMA) was used to acquire diffusion profiles, followed by fitting to Ficks second law and Whipple–Le Claires models for bulk and grain-boundary diffusion calculation, respectively. Zn2+ diffused into Ni0.98Li0.02O mainly by bulk diffusion with an activation energy of 250 ± 10 kJ/mol, whereas Ni2+ diffused into Zn0.98Al0.02O by both bulk and enhanced grain boundary diffusion with activation energies of 320 ± 120 kJ/mol and 245 ± 50 kJ/mol, respectively. The amount of Al3+ diffused from the Al-doped ZnO into the NiO phase was too small for a corresponding diffusion coefficient to be calculated. Li-ion distribution and diffusivity were not determined due to lack of analyzer sensitivity for Li. The bulk and effective diffusivities of Zn2+ and Ni2+ into NiO and ZnO enable prediction of inter-diffusion lengths as a function of time and temperature, allowing estimates of device performance, stability, and lifetimes at different operation temperatures. |
| Keywords | NiO, ZnO, Cation diffusion, Grain-boundary diffusion, p-n junction |
| Remark |
https://doi.org/10.1016/j.ssi.2018.03.011 Link |
Electrochemical promotion of nanodispersed Ru-Co catalysts for the hydrogenation of CO2
ID=467| Authors |
|
| Source |
Applied Catalysis B: Environmental
Volume: 232,
Pages: 60-68 Time of Publication: 2018 |
| Abstract | Electrochemical promotion of the CO2 hydrogenation to CH4 and CO on a nanodispersed Ru-Co catalyst has been achieved via slurry deposition of the nanodispersed catalyst on an interlayer Ru film deposited on a BZY (BaZr0.85Y0.15O3) proton conducting solid electrolyte disc. The effect of current is nonFaradaic, with Faradaic efficiency values as high as 60 and leads to a reversible variation of the selectivity to CH4 between 16% and 41%. Due to thermal spillover of protons on the Ru-Co catalyst surface, the open circuit selectivity to CO is quite high, i.e. up to 84% and similar values are obtained via negative potential application, i.e. proton supply to the Ru catalyst film deposited on BZY before the deposition of the nanodispersed catalyst. These results underline the similarity between electrochemical promotion and metal support interactions when using proton conducting supports. They also show the usefulness of electrochemical promotion for mechanistic investigations. The electrochemical promotion of nanodispersed catalysts is a promising step for the practical utilization of electrochemical promotion. |
| Keywords | Electrochemical promotion, EPOC, NEMCA effect, CO2 hydrogenation, Dispersed catalyst, BZY |
| Remark |
https://doi.org/10.1016/j.apcatb.2018.03.031 Link |
Structural transformations, water incorporation and transport properties of tin-substituted barium indate
ID=466| Authors |
|
| Source |
Journal of Solid State Chemistry
Volume: 262,
Pages: 58-67 Time of Publication: 2018 |
| Abstract | Incorporation of water into tin-substituted BaIn1-xSnxO3-δ (x = 0.1–0.3) is shown to influence crystal structure at room temperature, structural transformations at high temperatures and ionic transport properties of the materials. Increasing tin content stabilizes oxygen vacancy-disordered perovskite-type phase, which together with large changes of the unit cell volume occurring during hydration and dehydration processes, result in a complex structural behavior, as documented by high-temperature X-ray diffraction and thermogravimetric studies. Impedance spectroscopy measurements at elevated temperatures (350–800 °C) revealed very high proton conductivity in BaIn.8Sn.2O3-δ, exceeding 1.1·10−3 S cm−1 at 500 °C, with high values of the transference number in wet air. At the same time, relaxation kinetics of the electrical conductivity showed a monotonous nature, which indicates negligible component of the electronic hole conductivity in the hydrated material. The oxides are extremely moisture-sensitive, which results in a significant mechanical stability problems, affecting possibility to prepare electrolyte membranes. |
| Keywords | Barium indate, Hydration, Structural transformations, Proton conductivity, Relaxation experiments |
| Remark |
https://doi.org/10.1016/j.jssc.2018.03.004 Link |
Single-crystal x-ray diffraction and impedance spectroscopy investigations of the RbxCs1-xH2PO4 (0≤x≤1) proton conductor series
ID=465| Authors |
|
| Source |
Journal of Physics and Chemistry of Solids
Volume: 118,
Pages: 200-210 Time of Publication: 2018 |
| Abstract | We have used single-crystal x-ray diffraction to investigate the structural modifications induced by Rb-doping of the superprotonic conductor CsH2PO4. We found that the monoclinic P21/m CsH2PO4 modification persists within the RbxCs1-xH2PO4 (0 ≤ x ≤ 1) series upon Rb-doping from x = 0.1 to x = 0.7. Rb0.8Cs0.2H2PO4 (x = 0.8), however, exhibits a previously unreported P21/c monoclinic phase, where the mirror plane is lost and disorder is present in the PO4 tetrahedra even at room temperature. Higher levels of x display a tetragonal I-42d unit cell isomorphic with the known structure of RbH2PO4. The temperature dependence of the proton conductivity determined from impedance spectroscopy data collected within the 160⁰C-250 °C range is also markedly different at high Rb-doping levels, x ≥ 0.8. Finally, we found that Rb0.9Cs0.1H2PO4 undergoes a transition from its room-temperature tetragonal I-42d phase to an intermediate-temperature monoclinic P21/m modification at a significantly lower temperature (∼80 °C) than its RbH2PO4 counterpart (∼120 °C). |
| Remark |
https://doi.org/10.1016/j.jpcs.2018.03.011 Link |
Performance evaluation of Mn and Fe doped SrCo 0.9 Nb 0.1 O 3-δ cathode for IT-SOFC application
ID=464| Authors |
|
| Source |
IOP Conference Series: Materials Science and Engineering
Volume: 310
|
| Abstract | Cathode materials of Mn and Fe doped SrCo0.9Nb0.1O3-δ, are synthesized by solid state route for intermediate temperature fuel cell applications. Phase pure material is obtained after calcining the precursors at 1100oC. Phase compatibility is observed between this novel cathode material with gadolinia doped ceria (GDC)electrolyte material as reflected in the diffraction pattern. The state of art YSZ electrolyte is not compatible with this cathode material. Average thermal expansion coefficient of the material varies between 17 to 22 X 10-6 K-1 on doping, from room temperature to 800 oC. Increase in thermal expansion coefficient is observed with Mn and Fe doping associated with the loss of oxygen from the crystal. The electrical conductivity of the cathode material decreases with Fe and Mn doping. Mn doped samples show lowest conductivity. From the symmetric cell measurement lower area specific resistance (0.16 Ω-cm2) is obtained for un-doped samples, at 850 oC. From the initial results it can be inferred that Mn/Fe doping improves neither the thermal expansion coefficient nor the electrochemical activity. |
| Remark | Link |
Does the conductivity of interconnect coatings matter for solid oxide fuel cell applications?
ID=463| Authors |
|
| Source |
Journal of Power Sources
Volume: 383,
Pages: 110-114 Time of Publication: 2018 |
| Abstract | The present work aims to quantify the influence of typical interconnect coatings used for solid oxide fuel cells (SOFC) on area specific resistance (ASR). To quantify the effect of the coating, the dependency of coating thickness on the ASR is examined on Crofer 22 APU at 600 °C. Three different Co coating thicknesses are investigated, 600 nm, 1500 nm, and 3000 nm. Except for the reference samples, the material is pre-oxidized prior to coating to mitigate the outward diffusion of iron and consequent formation of poorly conducting (Co,Fe)3O4 spinel. Exposures are carried out at 600 °C in stagnant laboratory air for 500 h and subsequent ASR measurements are performed. Additionally the microstructure is investigated with scanning electron microscopy (SEM). On all pre-oxidized samples, a homogenous dense Co3O4 top layer is observed beneath which a thin layer of Cr2O3 is present. As the ASR values range between 7 and 12 mΩcm2 for all pre-oxidized samples, even though different Co3O4 thicknesses are observed, the results strongly suggest that for most applicable cases the impact of the coating on ASR is negligible and the main contributor is Cr2O3. |
| Keywords | Solid oxide fuel cell, Interconnect, Corrosion, Coating, Area specific resistance, Cr2O3 |
| Remark |
https://doi.org/10.1016/j.jpowsour.2018.02.060 Link |
Amorphous-cathode-route towards low temperature SOFC
ID=462| Authors |
|
| Source |
Volume: 2,
Pages: 862-875 Time of Publication: 2018 |
| Abstract | Lowering the operating temperature of solid oxide fuel cell (SOFC) devices is one of the major challenges limiting the industrial breakthrough of this technology. In this study we explore a novel approach to electrode preparation employing amorphous cathode materials. La0.8Sr0.2CoO3−δ dense films have been deposited at different temperatures using pulsed laser deposition on silicon substrates. Depending on the deposition temperature, textured polycrystalline or amorphous films have been obtained. Isotope exchange depth profiling experiments reveal that the oxygen diffusion coefficient of the amorphous film increased more than four times with respect to the crystalline materials and was accompanied by an increase of the surface exchange coefficient. No differences in the surface chemical composition between amorphous and crystalline samples were observed. Remarkably, even if the electronic conductivities measured by the Van Der Pauw method indicate that the conductivity of the amorphous material was reduced, the overall catalytic properties of the cathode itself were not affected. This finding suggests that the rate limiting step is the oxygen mobility and that the local electronic conductivity in the amorphous cathode surface is enough to preserve its catalytic properties. Different cathode materials have also been tested to prove the more general applicability of the amorphous-cathode route. |
| Remark |
DOI: 10.1039/C7SE00606C Link |
Stability of the superprotonic conduction of (1-x)CsH2PO4/xSiO2 (0 ≤ x ≤ 0.3) composites under dry and humid environments
ID=461| Authors |
|
| Source |
Materials Today Communications
Volume: 15,
Pages: 11-17 Time of Publication: 2018 |
| Abstract | We have used temperature- and time-resolved electrochemical impedance spectroscopy, x-ray diffraction, and thermal analysis methods to investigate the effect of mixing CsH2PO4 with nano-silica on the superprotonic conduction of this solid acid. We collected data on (1-x)CsH2PO4/xSiO2 (0 ≤ x ≤ 0.3) composites in dry (air) and humid (PH2O ∼ 0.38 atm) environments at temperatures below and above the superprotonic transition of CsH2PO4 (TSP ∼ 234 °C). We first observed that a three-order-of-magnitude proton conductivity jump occurred in the unmixed sample (x = 0) at TSP, even under dry conditions and despite chemical changes (dehydration). We also found that the proton conductivity of the x = 0.1, 0.2 and 0.3 composites measured at T = 260 °C in air is nearly one order of magnitude greater than that of the unmixed phosphate (x = 0). Even more significantly, we found that humid sample environments have no effect on the stability of the proton conductivity of the x = 0.2 composite measured over a 10 h timespan at temperatures above TSP. This is contrary to the behavior of the x = 0 sample, which is known [31] to be stable under humid conditions, but undergoes a three-order-of-magnitude proton conductivity drop in air. |
| Keywords | Superprotonic phase, Composite materials, X-ray diffraction, Impedance spectroscopy |
| Remark |
https://doi.org/10.1016/j.mtcomm.2018.02.021 Link |
Co-deficient PrBaCo2−xO6−δ perovskites as cathode materials for intermediate-temperature solid oxide fuel cells: Enhanced electrochemical performance and oxygen reduction kinetics
ID=460| Authors |
|
| Source |
International Journal of Hydrogen Energy
Volume: 43,
Issue: 7,
Pages: 3761-3775 Time of Publication: 2018 |
| Abstract | Co-deficient PrBaCo2−xO6−δ perovskites (x = 0, 0.02, 0.06 and 0.1) are synthesized by a solid-state reaction, and the effects of Co-deficiency on the crystal structure, oxygen nonstoichiometry and electrochemical properties are investigated. The PrBaCo2−xO6−δ samples have an orthorhombic layered perovskite structure with double c axis. The degree of oxygen nonstoichiometry increases with decreasing Co content (0 ≤ x ≤ 0.06) and then slightly decreases at x = 0.1. All the samples exhibit the electrical conductivity values of >300 S cm−1 in the temperature range of 100–800 °C in air, which match well the requirement of cathode. With significantly enhanced electrochemical performance and good chemical compatibility between PrBaCo2−xO6−δ and CGO, this system of Co-deficient perovskite is promising cathode material for IT-SOFCs. Among all these components, PrBaCo1.94O6−δ gives lowest polarization resistance of 0.059 Ω cm2 at 700 °C in air. When tested as cathode in fuel cell, the anode-supported Ni-YSZ|YSZ|CGO|PrBaCo1.94O6−δ cell delivers a maximum peak power density of 889 mW cm−2 at 650 °C, which is higher than that of PrBaCoO6−δ cathode-based cell (764 mW cm−2). The oxygen reduction kinetics at the PrBaCo1.94O6−δ cathode interface is also explored, and the rate-limiting steps for oxygen reduction reaction are determined. |
| Keywords | Intermediate-temperature solid oxide fuel cells, Cathode material, Layered perovskite, Electrochemical performance, Oxygen reduction kinetics |
| Remark |
https://doi.org/10.1016/j.ijhydene.2018.01.018 Link |
Deposition of nickel oxide-yttria stabilized zirconia thin films by reactive magnetron sputtering
ID=459| Authors |
|
| Source |
International Journal of Hydrogen Energy
Time of Publication: 2018
|
| Abstract | Nickel oxide-yttria stabilized zirconia (NiO-YSZ) thin films were reactively sputter-deposited by pulsed direct current magnetron sputtering from the Ni and Zr-Y targets onto heated commercial NiO-YSZ substrates. The microstructure and composition of the deposited films were investigated with regard to application as thin anode functional layers (AFLs) for solid oxide fuel cells (SOFCs). The porosity and microstructure of both as-deposited and annealed at 1200 °C for 2 h AFLs were studied by scanning electron microscopy and X-ray diffractometry and controlled by changing the deposition process parameters. The results show that annealing in air at 1200 °C is required to improve film crystallinity and structural homogeneity. NiO-YSZ films have pores and grains of several hundred nanometers in size after reduction in hydrogen. Adhesion of deposited films was evaluated by scratch test. Anode-supported solid oxide fuel cells with the magnetron sputtered anode functional layer, YSZ electrolyte and La0.6Sr0.4Co0.2Fe0.8O3/Ce0.9Gd0.1O2 (LSCF/CGO) cathode were fabricated and tested. Influence of thin anode functional layer on performance of anode-supported SOFCs was studied. It was shown that electrochemical properties of the single fuel cells depend on the NiO volume content in the NiO-YSZ anode functional layer. Microstructural changes of NiO-YSZ layers after nickel reduction-oxidation (redox) cycling were studied. After nine redox cycles at 750 °C in partial oxidation conditions, the cell with the anode NiO-YSZ layer showed stable open circuit voltage values with the power density decrease by 11% only. |
| Keywords | Solid oxide fuel cells, Magnetron sputtering, Thin-film anode, Microstructure, Redox cycling |
| Remark |
Available online 7 February 2018, https://doi.org/10.1016/j.ijhydene.2018.01.076 Link |
Solid oxide fuel cells with apatite-type lanthanum silicate-based electrolyte films deposited by radio frequency magnetron sputtering
ID=458| Authors |
|
| Source |
Journal of Power Sources
Volume: 381,
Pages: 101-106 Time of Publication: 2018 |
| Abstract | In this study, solid oxide fuel cells (SOFCs) containing high-quality apatite-type magnesium doped lanthanum silicate-based electrolyte films (LSMO) deposited by RF magnetron sputtering are successfully fabricated. The LSMO film deposited at an Ar:O2 ratio of 6:4 on an anode supported NiO/Sm0.2Ce0·8O2-δ (SDC) substrate followed by post-annealing at 1000 °C reveals a uniform and dense c-axis oriented polycrystalline structure, which is well adhered to the anode substrate. A composite SDC/La0·6Sr0·4Co0·2Fe0·8O3-δ cathode layer is subsequently screen-printed on the LSMO deposited anode substrate and fired. The SOFC fabricated with the LSMO film exhibits good mechanical integrity. The single cell with the LSMO layer of ≈2.8 μm thickness reports a total cell resistance of 1.156 and 0.163 Ωcm2, open circuit voltage of 1.051 and 0.982 V, and maximum power densities of 0.212 and 1.490 Wcm−2 at measurement temperatures of 700 and 850 °C, respectively, which are comparable or superior to those of previously reported SOFCs with yttria stabilized zirconia electrolyte films. The results of the present study demonstrate the feasibility of deposition of high-quality LSMO films by RF magnetron sputtering on NiO-SDC anode substrates for the fabrication of SOFCs with good cell performance. |
| Keywords | Solid oxide fuel cell, Sputtering, Electrolyte Doped lanthanum silicate |
| Remark |
https://doi.org/10.1016/j.jpowsour.2018.02.007 Link |
Electrical conductivity of NiMo–based double perovskites under SOFC anodic conditions
ID=457| Authors |
|
| Source |
International Journal of Hydrogen Energy
Volume: 43,
Issue: 9,
Pages: 4528-4533 Time of Publication: 2018 |
| Abstract | Three different materials are prepared by chemical reaction route, Sr2NiMoO6 (SNM00), Sr1.96La004NiMoO6 (SLNM04) and Sr1.99Ce0.01NiMoO6 (SCNM01) and conductivity is measured under reducing atmosphere, in order to study their suitability as anode materials in SOFC application. Selected materials correspond to compositions reported with highest conductivity in air at operative temperatures of a SOFC among the systems SLNM (Sr2−xLaxNiMoO6, 0.02 ≤ x ≤ 0.10) and SCNM (Sr2−xCexNiMoO6, 0.01 ≤ x ≤ 0.05). The end member Sr2NiMoO6 (SNM) is also considered as reference. Their conductivities considerably increase in wet hydrogen and follow Arrhenius behavior with lower activation energy. Effects of reduction on microstructure and phase stability are also studied by scanning electron microscopy and X–ray diffraction. The enhancement in conductivity is discussed in terms of defects chemistry. Amongst all measured samples, SLNM04 shows the highest conductivity in reducing atmosphere without phase degradation, which makes it a promising anode material for Solid Oxide Fuel Cells (SOFC). |
| Keywords | Double perovskite Reduction Electrical conductivity Anodic materials SOFC |
| Remark |
https://doi.org/10.1016/j.ijhydene.2018.01.066 Link |
Effect of sintering temperature on the performance of composite La0.6Sr0.4Co0.2Fe0.8O3–Ce0.9Gd0.1O2 cathode for solid oxide fuel cells
ID=456| Authors |
|
| Source |
Journal of Electroceramics
Time of Publication: 2018
|
| Abstract | Studied here are the effects of sintering temperature of La0.6Sr0.4Co0.2Fe0.8O3-Ce0.9Gd0.1O2 (LSCF–CGO) cathodes on their microstructure and performance of intermediate-temperature solid oxide fuel cells (IT-SOFC). Phase composition, microstructure and electrochemical properties were investigated by X-ray powder diffraction (XRD), scanning electron microscopy and current-voltage characteristics measurement, respectively. The electrochemical performances of Ni–YSZ anode-supported SOFC having YSZ electrolyte (4 μm) with CGO interlayer (2 μm) are studied with LSCF–CGO (50:50 wt%) cathodes in the temperature range 600–800 °C using H2 as fuel and air as oxidant. The cathode microstructure was found to be less dense and to contain smaller grains as the sintering temperature was decreased in the range 1250–1150 °C. Results reveal that sintering temperature and electrode morphology have strong influence on electrochemical performances of the IT-SOFC. Highest maximum power density of ∼1.26 W/cm2 is achieved during cell testing at 800 °C with a cathode sintered at 1200 °C. However, cells with in-situ sintered LSCF–CGO cathode showed highest power density at 600 °C (0.48 W/cm2) because there is no particle coarsening at low sintering temperatures. |
| Keywords | LSCF–CGO, Composite cathode, Microstructure,, Performanc, Intermediate-temperature solid oxide fuel cells |
| Remark |
https://doi.org/10.1007/s10832-018-0114-5, First Online: 29 January 2018 Link |
Proton and oxygen ion conductivity in the pyrochlore/fluorite family of Ln2−xCaxScMO7−δ (Ln = La, Sm, Ho, Yb; M = Nb, Ta; x = 0, 0.05, 0.1) niobates and tantalates
ID=455| Authors |
|
| Source |
Dalton Transaction
Volume: 47,
Pages: 2376-2392 Time of Publication: 2018 |
| Abstract | The tolerance factor is a good criterion to understand the structural transitions in Ln2−xCaxScMO7−δ (Ln = La, Sm, Ho, Yb; M = Nb, Ta; x = 0, 0.05, 0.1). Decreasing the Ln ionic radius in Ln2ScNb(Ta)O7 leads to a morphotropic transition from a pyrochlore to a fluorite-like structure. Ca2+-doping leads to a pyrochlore-to-fluorite transition in Ln2−xCaxScMO7−δ (Ln = La, Sm) and a fluorite-to-pyrochlore transition in Ho2−xCaxScNbO7−δ. Proton contribution to the total conductivity was observed for Ln2−xCaxScNb(Ta)O7−δ (Ln = La, Sm; x = 0, 0.05, 0.1) 3+/5+ pyrochlores and the maximum proton contribution was shown by Sm1.9Ca0.1ScMO6.95 (M = Nb, Ta), which are located at the boundary between pyrochlores and fluorites (comparative study of electrical conduction and oxygen diffusion). Proton conduction of Sm1.9Ca0.1ScNbO6.95 and Sm1.9Ca0.1ScTaO6.95 pyrochlores persists up to 800 and 850 °C, respectively. The conductivity of fluorite-like Ho2−xCaxScNbO7−δ (x = 0, 0.05) and Yb2ScNbO7 is dominated by the oxygen ion transport, in accordance with their energy activation values 1.09–1.19 eV. The dielectric permittivity and TG studies were used for the investigation of oxygen vacancy dynamics and water incorporation into the Ln2−xCaxScNb(Ta)O7−δ (Ln = La, Sm, Ho, Yb; x = 0, 0.05, 0.1) lattice. It is shown that oxygen vacancy-related dielectric relaxation in the range of 550–650 °C (ambient air), typical of pyrochlores and fluorites with pure oxygen ion conductivity, decreases and disappears for proton-conducting oxides. |
| Keywords | Proton and oxygen ion conductivity, Pyrochlore/fluorite family |
| Remark |
DOI: 10.1039/C7DT03912C Link |
Iono-molecular Separation with Composite Membranes
ID=454| Authors |
|
| Source |
REV.CHIM.
Volume: 9
Time of Publication: 2016
|
| Abstract |
The fast development of these methods in the recent years has been possible due to new materials developing, the boom of nanomaterials in the development of composite and hybrid materials and also due to developing of new techniques and technologies. This paper presents the composite membranes based on polysulfone and performance nanomaterials: polyaniline and magnetic nanoparticles synthesis and characterization. Composite membranes (PSf-PANI and PSf-magnetite) have been produced by phase inversion by immersion - precipitation from a polysulfone in N-methyl pyrrolidone dispersion solution in which were dispersed polyaniline or magnetic nanoparticles. The prepared composite membranes were morphologically and structurally characterized using techniques and specific measurments: FT-IR, SEM, AFM, UV VIS, DSC, dielectric spectroscopy, solvents permeation and bovine serum albumin retention.Membranes pore size indicate their use in micro and ultrafiltration (12% in the case of PSF membrane and 12% for PSf - PANI) or in the field of microfiltration and membrane sensor, 12% for magnetite - PSF membrane. The results show that water flows at 3-4 bar pressure, are increasing in the order: PSf membrane < PSf –magnetite membrane |
| Remark | Link |
Structural and electrochemical characterization of BaCe0.7Zr0.2Y0.05Zn0.05O3 as an electrolyte for SOFC-H
ID=453| Authors |
|
| Source |
IOP Conf. Series: Materials Science and Engineering
Volume: 121
Time of Publication: 2016
|
| Abstract | As a potential electrolyte for proton-conducting solid oxide fuel cells (SOFC-Hs)and to get better protonic conductivity and stability, zinc doped BCZY material has been found to be promising. In this study, we report a new composition of proton conductors BaCe0.7Zr0.2Y0.05Zn0.05O3 (BCZYZn5) which was investigated using XRD, SEM and conductivity measurements. Rietveld refinement of the XRD data revel a cubic perovskite structure with Pm-3m space group. BaCe0.7Zr0.2Y0.05Zn0.05O3 shows cell parameter a = 4.3452(9) Å. Scanning electron microscopy images shows that the grain sizes are large and compact which gives the sample high density and good protonic conductivity. The total conductivity in wet atmosphere is significantly higher than that of dry condition and the conductivity was found to be 0.276 x 10-3 Scm-1 and 0.204 x 10-3 Scm-1 at 600°C in wet and dry Ar, respectively. This study indicated that perovskite electrolyte BCZYZn5 is a promising material for the next generation intermediate temperature solid oxide fuel cells (IT-SOFCs). |
| Remark | Link |
Enhanced O2 Flux of CaTi0.85Fe0.15O3−δ Based Membranes by Mn Doping
ID=452| Authors |
|
| Source |
Journal of the American Ceramic Society
Volume: 99,
Issue: 3,
Pages: 1071–1078 Time of Publication: 2016 |
| Abstract | Dense symmetric membranes of CaTi0.85−xFe0.15MnxO3−δ (x = 0.1, 0.15, 0.25, 0.4) are investigated in order to determine the optimal Mn dopant content with respect to highest O2 flux. O2 permeation measurements are performed as function of temperature between 700°C–1000°C and as function of the feed side math formula ranging between 0.01 and 1 bar. X-ray photoelectron spectroscopy is utilized to elucidate the charge state of Mn, and synchrotron radiation X-ray powder diffraction (SR-XPD) is employed to investigate the structure symmetry and cell volume of the perovskite phase at temperatures up to 800°C. The highest O2 permeability is found for x = 0.25 over the whole temperature and math formula ranges, followed by x = 0.4 above 850°C. The O2 permeability for x = 0.25 reaches 0.01 mL(STP) min−1 cm−1 at 925°C with 0.21 bar feed side math formula and Ar sweep gas. X-ray photoelectron spectroscopy indicates that the charge state of Mn changes from approx. +3 to +4 when x > 0.1, which implies that Mn mainly improves electronic conductivity for x > 0.1. The cell volume is found to decrease linearly with Mn content, which coincides with an increase in the activation energy of O2 permeability. These results are consistent with the interpretation of the temperature and math formula dependency of O2 permeation. The sintering behavior and thermal expansion properties are investigated by dilatometry, which show improved sinterability with increasing Mn content and that the thermal expansion coefficient decreases from 12.4 to 11.9 × 10−6 K−1 for x = 0 and x = 0.25, respectively. |
Fabrication and characterization of La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF)-Ce0.9Gd0.1O1.95 (GDC) composite thick film for anode supported solid oxide fuel cells
ID=451| Authors |
|
| Source |
Journal of Materials Science: Materials in Electronics
Volume: 27,
Issue: 1,
Pages: 795–799 Time of Publication: 2016 |
| Abstract | Nowadays, the commercialization of solid oxide fuel cell (SOFC) is impeded by the chemical compatibility and polarization losses in association with electrode/electrolyte interface. Thus, to minimize these difficulties, the thick film of LSCF-GDC (50:50 wt%) composite was deposited onto GDC electrolyte to form perfect LSCF-GDC/GDC structure. The chemically compatibility of LSCF-GDC upon sintering of 1000 °C was confirmed from the X-ray diffraction studies. Typically, the film with 15 μm thickness possesses the porous structure, availing the free path for oxygen diffusion. The electrochemical impedance analysis of symmetric cell with LSCF-GDC as an electrode implies the relaxation of charge transfer and electrochemical reduction reaction with temperature. The NiO-GDC (30:70 wt%) supported SOFC with GDC and LSCF-GDC as an electrolyte and cathode, respectively was tested for their performance. The cell generates the maximum powder density of 315 μWcm−2 at 500 °C. |
| Remark | Link |
Materials development: general discussion
ID=450| Authors |
|
| Source |
Faraday Discussions
Volume: 182,
Pages: 307 Time of Publication: 2015 |
| Remark | Link |
The Band Gap of BaPrO3 Studied by Optical and Electrical Methods
ID=449| Authors |
|
| Source |
Journal of the American Ceramic Society
Volume: 99,
Issue: 2,
Pages: 492–498 Time of Publication: 2016 |
| Abstract | We report on measurements of the electrical and optical properties of BaPrO3. The temperature dependences of the electrical conductivity σ and the Seebeck coefficient α of polycrystalline samples were studied over a wide temperature range (300°C–1050°C). At lower temperatures, the observed charge transport can be described as thermally activated hopping of electron-based small polarons with an activation energy of 0.37 eV. An observed change in temperature dependence of both σ and α around 700°C was observed and interpreted as a transition from extrinsic to intrinsic carrier transport. The intrinsic conduction can be modeled with an apparent electrical band gap of ~2 eV. Optical absorption and emission spectroscopy in the UV–VIS–NIR range revealed a series of characteristic absorption thresholds and the type of optical transitions was identified by combining transmittance and diffuse-reflectance spectroscopy methods. An absorption edge of indirect type with onset at 0.6 eV is attributed to small polaron effects. The higher lying absorption thresholds of direct origin positioned at around 1.8 and 3.8 eV are correlated with thermal activation parameters from electrical measurements and discussed in terms of the band gap of BaPrO3. |
| Remark |
DOI: 10.1111/jace.13961 Link |
Copper Iron Conversion Coating for Solid Oxide Fuel Cell Interconnects
ID=448| Authors |
|
| Source |
Journal of Power Sources
Volume: 297,
Pages: 534-539 Time of Publication: 2015 |
| Abstract | A conversion coating of iron and copper was investigated with the purpose of increasing the performance of Sanergy HT as a potential SOFC interconnect material. Samples were exposed to a simulated cathode atmosphere (air, 3 % H2O) for durations of up to 1000 h at 850 °C. Their performance in terms of corrosion, chromium evaporation and electrical resistance (ASR) was monitored and compared to uncoated and cobalt-coated Sanergy HT samples. The copper iron coating had no negative effects on corrosion protection and decreased chromium evaporation by about 80%. An Area Specific Resistance (ASR) of 10 mΩcm2 was reached after 1000 h of exposure. Scanning Electron Microscopy revealed well adherent oxide layers comprised of an inner chromia layer and an outer spinel oxide layer. |
| Remark |
https://doi.org/10.1016/j.jpowsour.2015.06.139 Link |
New alluaudite-related triple molybdates Na25Cs8R5(MoO4)24 (R = Sc, In): synthesis, crystal structures and properties
ID=447| Authors |
|
| Source |
New Journal of Chemistry
Volume: 41,
Pages: 5450 Time of Publication: 2017 |
| Abstract | New triple molybdates Na25Cs8R5(MoO4)24 (R = Sc, In) were prepared as powders and ceramics by solid state reactions, and their single crystals were also obtained from melts by spontaneous сrystallization. The structures were determined by single crystal XRD analysis. The electrical conductivity of ceramics was measured by impedance spectroscopy. The crystal structures were determined in monoclinic sp. gr. P21/c, a = 14.0069(3) Å,b = 12.6498(3) Å, c = 28.6491(6) Å, b = 90.007(1)1 (Sc) and a = 14.0062(2) Å, b = 12.6032(2) Å, c = 28.7138(4) Å,b = 90.001(1)1 (In). Together with triclinic Na25Cs8Fe5(MoO4)24, the titled compounds form a distinctive family of pseudo-orthorhombic alluaudite-related structures with the parent sp. gr. Pbca. Its structural features are alluaudite-like polyhedral layers composed of pairs of edge-shared (R, Na)O6 and NaO6 octahedra connected by bridging MoO4 tetrahedra. The layers are joined together by means of interlayer MoO4 tetrahedra, thus forming open 3D frameworks with cavities filled with Cs+ and Na+ ions. The manner of stacking layers is somewhat different from the alluaudite type. The compounds undergo phase transitions at 668 (Sc) and 725 (In) K accompanied by an abrupt increase of electrical conductivity presumably Na+-ionic in nature. Above these transitions, the conductivity is as high as 10(3) Scm(-1), which makes Na25Cs8R5(MoO4)24 (R = Sc, In) promising solid state electrolytes. |
| Remark |
DOI: 10.1039/c7nj00202e Link |
Enhanced Flexible Thermoelectric Generators Based on Oxide–Metal Composite Materials
ID=446| Authors |
|
| Source |
Journal of Electronic Materials
Volume: 46,
Issue: 4,
Pages: 2356–2365 Time of Publication: 2017 |
| Abstract | The thermoelectric performance of flexible thermoelectric generator stripes was investigated in terms of different material combinations. The thermoelectric generators were constructed using Cu-Ni-Mn alloy as n-type legs while varying the p-type leg material by including a metallic silver phase and an oxidic copper phase. For the synthesis of Ca3Co4O9/CuO/Ag ceramic-based composite materials, silver and the copper were added to the sol–gel batches in the form of nitrates. For both additional elements, the isothermal specific electronic conductivity increases with increasing amounts of Ag and CuO in the samples. The amounts for Ag and Cu were 0 mol.%, 2 mol.%, 5 mol.%, 10 mol.%, and 20 mol.%. The phases were confirmed by x-ray diffraction. Furthermore, secondary electron microscopy including energy dispersive x-ray spectroscopy were processed in the scanning electron microscope and the transmission electron microscope. For each p-type material, the data for the thermoelectric parameters, isothermal specific electronic conductivity σ and the Seebeck coefficient α, were determined. The p-type material with a content of 5 mol.% Ag and Cu exhibited a local maximum of the power factor and led to the generator with the highest electric power output Pel. |
| Remark | Link |
Protonic Conduction in TiP2O7
ID=445| Authors |
|
| Source |
Solid State Ionics: Advanced Materials for Emerging Technologies
|
| Remark | Link |
Crystal structure and proton conductivity of BaSn 0.6 Sc 0.4 O 3 d : insights from neutron powder di ff raction and solid-state NMR spectroscopy
ID=444| Authors |
|
| Source |
J.Mater.Chem.A
Volume: 4,
Issue: 14,
Pages: 5088-5101 Time of Publication: 2016 |
| Abstract | The solid-state synthesis and structural characterisation of perovskite BaSn1−xScxO3−δ (x = 0.0, 0.1, 0.2, 0.3, 0.4) and its corresponding hydrated ceramics are reported. Powder and neutron X-ray diffractions reveal the presence of cubic perovskites (space group Pm[3 with combining macron]m) with an increasing cell parameter as a function of scandium concentration along with some indication of phase segregation. 119Sn and 45Sc solid-state NMR spectroscopy data highlight the existence of oxygen vacancies in the dry materials, and their filling upon hydrothermal treatment with D2O. It also indicates that the Sn4+ and Sc3+ local distribution at the B-site of the perovskite is inhomogeneous and suggests that the oxygen vacancies are located in the scandium dopant coordination shell at low concentrations (x ≤ 0.2) and in the tin coordination shell at high concentrations (x ≥ 0.3). 17O NMR spectra on 17O enriched BaSn1−xScxO3−δ materials show the existence of Sn–O–Sn, Sn–O–Sc and Sc–O–Sc bridging oxygen environments. A further room temperature neutron powder diffraction study on deuterated BaSn0.6Sc0.4O3−δ refines the deuteron position at the 24k crystallographic site (x, y, 0) with x = 0.579(3) and y = 0.217(3) which leads to an O–D bond distance of 0.96(1) Å and suggests tilting of the proton towards the next nearest oxygen. Proton conduction was found to dominate in wet argon below 700 °C with total conductivity values in the range 1.8 × 10−4 to 1.1 × 10−3 S cm−1 between 300 and 600 °C. Electron holes govern the conduction process in dry oxidizing conditions, whilst in wet oxygen they compete with protonic defects leading to a wide mixed conduction region in the 200 to 600 °C temperature region, and a suppression of the conductivity at higher temperature. |
| Remark |
DOI: 10.1039/c5ta09744d Link |
Microstructural design of CaMnO3 and its thermoelectric proprieties.
ID=443| Author |
|
| Source |
dissertation
Time of Publication: 2015
|
| Remark |
Norwegian University of Science and Technology, Department of Materials Science and Engineering Link |
Effect of Firing Temperature on the Kinetics of Oxygen Reduction in La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) Cathodes for Solid Oxide Fuel Cells
ID=442| Author |
|
| Source |
dissertation
Time of Publication: 2015
|
| Remark |
Norwegian University of Science and Technology, Department of Materials Science and Engineering Link |
DC-bias dependent impedance spectroscopy of BaTiO3–Bi(Zn1/2Ti1/2)O3 ceramics
ID=441| Authors |
|
| Source |
J. Mater. Chem. C
Volume: 4,
Pages: 1782-1786 Time of Publication: 2016 |
| Remark |
DOI: 10.1039/C5TC04247J Link |
Surface Protonics Promotes Catalysis
ID=440| Authors |
|
| Source |
Nature Scientific Reports 6
Time of Publication: 2016
|
| Abstract | Catalytic steam reforming of methane for hydrogen production proceeds even at 473 K over 1 wt% Pd/CeO2 catalyst in an electric field, thanks to the surface protonics. Kinetic analyses demonstrated the synergetic effect between catalytic reaction and electric field, revealing strengthened water pressure dependence of the reaction rate when applying an electric field, with one-third the apparent activation energy at the lower reaction temperature range. Operando–IR measurements revealed that proton conduction via adsorbed water on the catalyst surface occurred during electric field application. Methane was activated by proton collision at the Pd–CeO2 interface, based on the inverse kinetic isotope effect. Proton conduction on the catalyst surface plays an important role in methane activation at low temperature. This report is the first describing promotion of the catalytic reaction by surface protonics. |
| Remark |
doi:10.1038/srep38007 Link |
Structural- and Compositional Investigations of Grain Boundaries in Y-Doped BaZrO3 A proton-conducting electrolyte for electrochemical applications
ID=439| Author |
|
| Source |
Master’s Thesis
Time of Publication: 2016
|
| Remark |
University of Oslo Link |
Comparative study of the electrochemical promotion of CO2 hydrogenation on Ru using Na+, K+, H+ and O2 − conducting solid electrolytes
ID=438| Authors |
|
| Source |
Surface Science
Volume: 646,
Pages: 194-203 Time of Publication: 2016 |
| Abstract | The kinetics and the electrochemical promotion of the hydrogenation of CO2 to CH4 and CO are compared for Ru porous catalyst films deposited on Na+, K+, H+ and O2 − conducting solid electrolyte supports. It is found that in all four cases increasing catalyst potential and work function enhances the methanation rate and selectivity. Also in all four cases the rate is positive order in H2 and exhibits a maximum with respect to CO2. At the same time the reverse water gas shift reaction (RWGS) which occurs in parallel exhibits a maximum with increasing and is positive order in CO2. Also in all cases the selectivity to CH4 increases with increasing and decreases with increasing . These results provide a lucid demonstration of the rules of chemical and electrochemical promotion which imply that (∂r/∂Φ)(∂r/∂pD) > 0 and (∂r/∂Φ)(∂r/∂pA) < 0, where r denotes a catalytic rate, Φ is the catalyst work function and pD and pA denote the electron donor and electron acceptor reactant partial pressures respectively. |
| Keywords | Electrochemical promotion of catalysis, Ion conducting support, Hydrogenation of CO2, Ruthenium catalyst, Rules of promotion, Metal–support interactions |
| Remark |
https://doi.org/10.1016/j.susc.2015.09.011 Link |
Defect mechanisms in BaTiO3-BiMO3 ceramics
ID=437| Authors |
|
| Source |
Journal of the American Ceramic Society Time of Publication: 2018 |
| Abstract | Often, addition of BiMO3 to BaTiO3 (BT) leads to improvement in resistivity with a simultaneous shift to n-type conduction from p-type for BT. In considering one specific BiMO3 composition, that is, Bi(Zn1/2Ti1/2)O3 (BZT), several prospective candidates for the origin of this n-type behavior in BT-BZT were studied—loss of volatile cations, oxygen vacancies, bismuth present in multiple valence states and precipitation of secondary phases. Combined x-ray and neutron diffraction, prompt gamma neutron activation analysis and electron energy loss spectroscopy suggested much higher oxygen vacancy concentration in BT-BZT ceramics (>4%) as compared to BT alone. X-ray photoelectron spectroscopy and x-ray absorption spectroscopy did not suggest the presence of bismuth in multiple valence states. At the same time, using transmission electron microscopy, some minor secondary phases were observed, whose compositions were such that they could result in effective donor doping in BT-BZT ceramics. Using experimentally determined thermodynamic parameters for BT and slopes of Kröger-Vink plots, it has been suggested that an ionic compensation mechanism is prevalent in these ceramics instead of electronic compensation. These ionic defects have an effect of shifting the conductivity minimum in the Kröger-Vink plots to higher oxygen partial pressure values in BT-BZT ceramics as compared to BT, resulting in a significantly higher resistivity values in air atmosphere and n-type behavior. This provides an important tool to tailor transport properties and defects in BT-BiMO3 ceramics, to make them better suited for dielectric or other applications. |
| Remark |
DOI: 10.1111/jace.15403, Version of Record online: 8 JAN 2018 Link |
The Effect of Ni Doping on the Performance and Electronic Structure of LSCF Cathodes Used for IT-SOFCs
ID=436| Authors |
|
| Source |
J. Phys. Chem.: C
Time of Publication: 2017
|
| Abstract | We investigated the effect of nickel doping on the electronic structure and performance of nanostructured La0.6Sr0.4Co0.2Fe0.8–0.03Ni0.03O3−δ prepared by the one-pot sol–gel method. The commercial undoped La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF0.8) was used as reference. Moreover, for comparison, Ni (3 mol %) was deposited by wetness impregnation over the La0.6Sr0.4Co0.2Fe0.8O3−δ. We show by in situ X-ray absorption spectroscopy at 900 °C under air flow that nickel enters the B perovskite site of the material and favors the stabilization of the cobalt oxidation state, as evidenced by the delay in the decrease of the average Co valence with respect to undoped samples. Our results are further supported by in situ X-ray Raman spectroscopy (XRS) that allowed us to monitor the temperature evolution of the O K-edge. XRS evidences that nickel-doped LSCF shows unmodified O2p-TM3d density of states, which proves that the Co oxidation state is preserved. Electrochemical impedance spectroscopy measurements were carried out over half-cell systems consisting of LSCF-based materials deposited onto a Ce0.8Gd0.2O2−δ electrolyte. The improvement of the electrochemical performances of the Ni-doped La0.6Sr0.4Co0.2Fe0.8–0.03Ni0.03O3−δ sample with respect to a reference Ni-impregnated LSCF is attributed to the stabilization of the TM-O6 structural units, which were recently proposed as the functional units for oxygen reduction. |
| Remark |
DOI: 10.1021/acs.jpcc.7b07626 Link |
Protonic Conductors for Intermediate Temperature Fuel Cell Electrolytes: Superprotonic CsH2PO4 Stabilization and in-Doped SnP2O7 Structure Study
ID=435| Author |
|
| Source |
Dissertation
Time of Publication: 2017
|
| Remark |
The University of Texas at El Paso Link |
Optimisation of growth parameters to obtain epitaxial Y-doped BaZrO3 proton conducting thin films
ID=434| Authors |
|
| Source |
Volume: 314,
Pages: 9–16 Time of Publication: 2018 |
| Abstract | We hereby report developments on the fabrication and characterization of epitaxial thin films of proton conducting Y-doped BaZrO3 (BZY) by pulsed laser deposition (PLD) on different single crystal substrates (MgO, GdScO3, SrTiO3, NdGaO3, LaAlO3 and sapphire) using Ni-free and 1% Ni-containing targets. Pure, high crystal quality epitaxial films of BZY are obtained on MgO and on perovskite-type substrates, despite the large lattice mismatch. The deposition conditions influence the morphology, cell parameters and chemical composition of the film, the oxygen partial pressure during film growth being the most determining. Film characterization was carried out using X-ray diffraction, transmission electron and atomic force microscopies, wavelength dispersive X-ray spectroscopy and angle-resolved X-ray photoelectron spectroscopy. All films show a slight tetragonal distortion that is not directly related to the substrate-induced strain. The proton conductivity of the films depends on deposition conditions and film thickness, and for the optimised conditions its total conductivity is slightly higher than the bulk conductivity of the target material (3 mS/cm at 600 °C, in wet 5% H2/Ar). The conductivities are, however, more than one order of magnitude lower than the highest reported in literature and possible reasoning is elucidated in terms of local and extended defects in the films. |
| Keywords | BaZrO3; Thin film; Electrolyte; Proton conductivity; SOFC; PC-SOFC |
| Remark |
https://doi.org/10.1016/j.ssi.2017.11.002 Link |
Improvement of thermoelectric properties of lanthanum cobaltate by Sr and Mn co-substitution
ID=433| Authors |
|
| Source |
Journal of Alloys and Compounds
Volume: 735,
Pages: 1787–1791 Time of Publication: 2018 |
| Abstract | We report thermoelectric (TE) properties of Sr and Mn co-substituted LaCoO3 system from room temperature to 700 K. Sr-substitutions at La and Mn at Co site in LaCoO3 improves the electrical conductivity (σ). Thermal conductivity (κ) of all the samples increases with the increase in temperature but decreases with the substitution in LaCoO3. An estimation of the electronic thermal conductivity (κe) suggests a dominant phonon contribution to thermal conductivity in this system. A maximum value of the figure of merit is 0.14 at 480 K for La0.95Sr0.05Co0.95Mn0.05O3. |
| Keywords | Powders: solid-state reaction; Thermal conductivity; Electrical conductivity; Perovskites |
| Remark |
https://doi.org/10.1016/j.jallcom.2017.11.334 Link |
Microstructural engineering and use of efficient poison resistant Au-doped Ni-GDC ultrathin anodes in methane-fed solid oxide fuel cells
ID=432| Authors |
|
| Source |
International Journal of Hydrogen Energy
Volume: 43,
Issue: 2,
Pages: 885–893 Time of Publication: 2018 |
| Abstract | Ultrathin porous solid oxide fuel cell (SOFC) anodes consisting of nickel-gadolinia-doped-ceria (Ni-GDC) cermets with a unique porous micro-columnar architecture with intimate contact between the GDC and the Ni phases were made by magnetron sputtering at an oblique deposition angle and characterised in detail by a variety of methods prior to use in hydrogen or methane-fuelled SOFCs. These Ni-GDC anodes exhibited excellent transport properties, were robust under thermal cycling and resistant to delamination from the underlying yttria-stabilised zirconia electrolyte. Similarly prepared Au-doped Ni-GDC anodes exhibited the same morphology, porosity and durability. The gold associated exclusively with the Ni component in which it was present as a surface alloy. Strikingly, whatever their treatment, a substantial amount of Ce3+ persisted in the anodes, even after operation at 800 °C under fuel cell conditions. With hydrogen as fuel, the un-doped and Au-doped Ni-GDC anodes exhibited identical electrochemical performances, comparable to that of much thicker commercial state-of-the-art Ni-GDC anodes. However, under steam reforming conditions with CH4/H2O mixtures the behaviour of the Au-doped Ni-GDC anodes were far superior, exhibiting retention of good power density and dramatically improved resistance to deactivation by carbon deposition. Thus two distinct beneficial effects contributed to overall performance: persistence of Ce3+ in the working anodes could induce a strong metal-support interaction with Ni that enhanced the catalytic oxidation of methane, while formation of a Nisingle bondAu surface alloy that inhibited carbonisation and poisoning of the active nickel surface. |
| Keywords | SOFC; Ultrathin film anodes; Magnetron sputtering; Gadolinia doped ceria; Carbon-tolerant; Gold doping |
| Remark |
https://doi.org/10.1016/j.ijhydene.2017.11.020 Link |
Electrical properties of polycrystalline materials from the system Cu-As-Ge-Se under high pressure condition
ID=431| Authors |
|
| Source |
Journal of Physics: Conference Series
Volume: 917
Time of Publication: 2017
|
| Abstract | The paper deals with electrical properties of polycrystalline materials (GeSe)x(CuAsSe2)1-x(x= 0.5 and 0.7) under high pressure (up to 45 GPa) conditions. The phenomenon of negative magnetoresistance was observed for studied materials. |
| Remark |
doi :10.1088/1742-6596/917/8/082009 Link |
Asymmetric tubular CaTi0.6Fe0.15Mn0.25O3-δ membranes: Membrane architecture and long-term stability
ID=430| Authors |
|
| Source |
Journal of Membrane Science
Volume: 548,
Pages: 372-379 Time of Publication: 2018 |
| Abstract | Three architectures of asymmetric tubular oxygen transport membranes (OTM) based on CaTi0.6Fe0.15Mn0.25O3-δ were fabricated with various thicknesses of the tubular porous supports and the dense membrane layers. This was achieved by a two-step firing method combining water based extrusion and dip-coating. The oxygen flux of the tubular membranes was characterized as a function of temperature and oxygen partial pressure on both feed and sweep sides for the different architectures. The flux exhibits different functional dependencies with respect to the oxygen partial pressure gradient and the membrane architecture. Numerical simulations using a Dusty-gas model were conducted to evaluate the effect of the porous support microstructure and thickness on oxygen partial pressure gradient inside the porous media. Results from this work were used to establish dependency of the flux with respect to bulk transport properties of the material, surface kinetics and architecture of the porous support. Furthermore, long-term stability of the produced tubular asymmetric membrane operated in CO2-containing atmospheres was assessed over half a year. The membrane exhibited a stable oxygen flux without showing significant flux degradation. |
| Keywords | OTM, Asymmetric tubular membrane, Oxygen flux, CaTiO3, Long-term stability |
| Remark |
https://doi.org/10.1016/j.memsci.2017.11.042 Link |
Three-dimensional printed yttria-stabilized zirconia self-supported electrolytes for solid oxide fuel cell applications
ID=429| Authors |
|
| Source |
Journal of the European Ceramic Society
Time of Publication: 2017
|
| Abstract | Additive manufacturing represents a revolution due to its unique capabilities for freeform fabrication of near net shapes with strong reduction of waste material and capital cost. These unfair advantages are especially relevant for expensive and energy-demanding manufacturing processes of advanced ceramics such as Yttria-stabilized Zirconia, the state-of-the-art electrolyte in Solid Oxide Fuel Cell applications. In this study, self-supported electrolytes of yttria-stabilized zirconia have been printed by using a stereolithography three-dimensional printer. Printed electrolytes and complete cells fabricated with cathode and anode layers of lanthanum strontium manganite- and nickel oxide-yttria-stabilized zirconia composites, respectively, were electrochemical characterized showing full functionality. In addition, more complex configurations of the electrolyte have been printed yielding an increase of the performance entirely based on geometrical aspects. Complementary, a numerical model has been developed and validated as predictive tool for designing more advanced configurations that will enable highly performing and fully customized devices in the next future. |
| Keywords | Solid oxide fuel cell, 3D printing, Stereolithography, Yttria-stabilized zirconia, Electrolyte |
| Remark |
Available online 15 November 2017, https://doi.org/10.1016/j.jeurceramsoc.2017.11.033 Link |
Characteristics of LaCo0.4Ni0.6-xCuxO3-δ ceramics as a cathode material for intermediate-temperature solid oxide fuel cells
ID=428| Authors |
|
| Source |
Journal of the European Ceramic Society
Time of Publication: 2017
|
| Abstract | In this study, the effects of Cu-ion substitution on the densification, microstructure, and physical properties of LaCo0.4Ni0.6-xCuxO3-δ ceramics were investigated. The results indicate that doping with Cu ions not only enhances the densification but also promotes the grain growth of LaCo0.4Ni0.6-xCuxO3-δ ceramics. The Cu substitution at x ≤ 0.2 can suppress the formation of La4Ni3O10, while the excess Cu triggers the formation of La2CuO4.032 phase. The p-type conduction of LaCo0.4Ni0.6O3-δ ceramic was significantly raised by Cu substitution because the acceptor doping () triggered the formation of hole carriers; this effect was maximized in the case of LaCo0.4Ni0.4Cu0.2O3-δ composition (1480 S cm−1 at 500 °C). Thermogravimetric data revealed a slight weight increase of 0.29% for LaCo0.4Ni0.4Cu0.2O3-δ compact up to 871 °C; this is due to the incorporation of oxygen that creates metal vacancies and additional carriers, partially compensating the conductivity loss due to the spin-disorder scattering. As the temperature of the LaCo0.4Ni0.4Cu0.2O3-δ compacts rose above 871 °C, significant weight loss with temperature was observed because of the release of lattice oxygen to the ambient air as a result of Co (IV) thermal reduction accompanied by the formation of oxygen vacancies. A solid oxide fuel cell (SOFC) single cell with Sm0.2Ce0.8O2-δ (electrolyte) and LaCo0.4Ni0.4Cu0.2O3-δ (cathode) was built and characterized. The Ohmic (0.256 Ω cm2) and polarization (0.434 Ω cm2) resistances of the single cell at 700 °C were determined; and the maximum power density was 0.535 W cm−2. These results show that LaCo0.4Ni0.4Cu0.2O3-δ is a very promising cathode material for SOFC applications. |
| Keywords | Solid oxide fuel cells, Cell performance, Impedance Cathode |
| Remark |
Available online 8 November 2017, https://doi.org/10.1016/j.jeurceramsoc.2017.11.019 Link |
Influence of processing on stability, microstructure and thermoelectric properties of Ca3Co4 − xO9 + δ
ID=427| Authors |
|
| Source |
Journal of the European Ceramic Society
Time of Publication: 2017
|
| Abstract | Due to high figure of merit, Ca3Co4 − xO9 + δ (CCO) has potential as p-type material for high-temperature thermoelectrics. Here, the influence of processing including solid state sintering, spark plasma sintering and post-calcination on stability, microstructure and thermoelectric properties is reported. By a new post-calcination approach, single-phase materials were obtained from precursors to final dense ceramics in one step. The highest zT of 0.11 was recorded at 800 °C for CCO with 98 and 72% relative densities. In situ high-temperature X-ray diffraction in air and oxygen revealed a higher stability of CCO in oxygen (∼970 °C) than in air (∼930 °C), with formation of Ca3Co2O6 which also showed high stability in oxygen, even at 1125 °C. Since achievement of phase pure high density CCO by post-calcination method in air is challenging, the phase stability of CCO in oxygen is important for understanding and further improvement of the method. |
| Keywords | Ca3Co4 − xO9 + δ, Post calcination, Phase stability, Microstructure, Thermoelectric performance |
| Remark |
Available online 6 November 2017, https://doi.org/10.1016/j.jeurceramsoc.2017.11.011 Link |
Analysis of potential materials for single component fuel cells
ID=426| Authors |
|
| Source |
FUNCTIONAL NANOSTRUCTURES PROCEEDINGS
Time of Publication: 2017
|
| Abstract | The following paper summarizes the results of systematic analysis on single component fuel cell. This recent technology in the solid oxide fuel cell field consists of a unique layer in place of the conventional three-layers structure. The single layer is a mixture of ionic and semi-conductor material. Surprisingly, the expected short circuit has not shown up. On the contrary, the performance is even higher, as reported in literature [1]. This work aims to compare different combinations of materials in terms of performance. La0.6Sr0.4Co0.2Fe0.8O3-δ(LSCF), LiNi0.8Co0.15Al0.05O2 (NCAL), La0.8Sr0.2CoO3(LSC), LiNiZn oxide (LNZ) and a new kind of material, CuFe2O4 are analysed as semi-conductor material. As ionic conductor, CeO2/Gd (GDC) is mainly tilised. Also, CeO2/Sm (SDC) and CeO2/Sm/Ca SCDC are considered too. |
| Remark | Link |
Thermoelectrochemical Heat Converter
ID=425| Source |
Time of Publication: 2017
|
| Abstract | A direct thermoelectrochemical heat-to-electricity converter includes two electrochemical cells at hot and cold temperatures, each having a gas-impermeable, electron-blocking membrane capable of transporting an ion I, and a pair of electrodes on opposite sides of the membrane. Two closed-circuit chambers A and B each includes a working fluid, a pump, and a counter-flow heat exchanger. The chambers are connected to opposite sides of the electrochemical cells and carry their respective working fluids between the two cells. The working fluids are each capable of undergoing a reversible redox half-reaction of the general form R→O+I+e−, where R is a reduced form of an active species in a working fluid and O is the oxidized forms of the active species. One of the first pair of electrodes is electrically connected to one the second pair of electrodes via an electrical load to produce electricity. The device thereby operates such that the first electrochemical cell runs a forward redox reaction, gaining entropy, and the second electrochemical cell runs a reverse redox reaction, expelling entropy. |
| Remark |
United States Patent Application 20170288253 Link |
High-temperature properties of (La,Ca)(Fe,Mg,Mo)O3-δ perovskites as prospective electrode materials for symmetrical SOFC
ID=424| Authors |
|
| Source |
Journal of Solid State Chemistry
Volume: 258,
Pages: 1-10 Time of Publication: 2018 |
| Abstract | La1−yCayFe0.5+x(Mg,Mo)0.5−xO3-δ oxides with the orthorhombic GdFeO3-type perovskite structure have been synthesized at 1573 K. Transmission electron microscopy study for selected samples shows the coexistence of domains of perovskite phases with ordered and disordered B-cations. Mössbauer spectroscopy studies performed at 300 K and 573 K show that while compositions with low Ca-content (La0.55Ca0.45Fe0.5Mg0.2625Mo0.2375O3-δ and La0.5Ca0.5Fe0.6Mg0.175Mo0.225O3-δ) are nearly oxygen stoichiometric, La0.2Ca0.8Fe0.5Mg0.2625Mo0.2375O3-δ is oxygen deficient with δ ≈ 0.15. Oxides are stable in reducing atmosphere (Ar/H2, 8%) at 1173 K for 12 h. No additional phases have been observed at XRPD patterns of all studied perovskites and Ce1−xGdxO2−x/2 electrolyte mixtures treated at 1173–1373K, while Fe-rich compositions (x≥0.1) react with Zr1−xYxO2−x/2 electrolyte above 1273 K. Dilatometry studies reveal that all samples show rather low thermal expansion coefficients (TECs) in air of 11.4–12.7 ppm K−1. In reducing atmosphere their TECs were found to increase up to 12.1–15.4 ppm K−1 due to chemical expansion effect. High-temperature electrical conductivity measurements in air and Ar/H2 atmosphere show that the highest conductivity is observed for Fe- and Ca-rich compositions. Moderate values of electrical conductivity and TEC together with stability towards chemical interaction with typical SOFC electrolytes make novel Fe-containing perovskites promising electrode materials for symmetrical solid oxide fuel cell. |
| Keywords | Symmetrical solid oxide fuel cell, Perovskites, Crystal structure, High-temperature electrical conductivity |
| Remark |
https://doi.org/10.1016/j.jssc.2017.10.005 Link |
New Solid Electrolyte Na9Al(MoO4)6: Structure and Na+ Ion Conductivity
ID=423| Authors |
|
| Source |
Chem. Mater.
Volume: 29,
Issue: 20,
Pages: 8901–8913 Time of Publication: 2017 |
| Abstract | Solid electrolytes are important materials with a wide range of technological applications. This work reports the crystal structure and electrical properties of a new solid electrolyte Na9Al(MoO4)6. The monoclinic Na9Al(MoO4)6 consists of isolated polyhedral [Al(MoO4)6]9– clusters composed of a central AlO6 octahedron sharing vertices with six MoO4 tetrahedra to form a three-dimensional framework. The AlO6 octahedron also shares edges with one Na1O6 octahedron and two Na2O6 octahedra. Na3–Na5 atoms are located in the framework cavities. The structure is related to that of sodium ion conductor II-Na3Fe2(AsO4)3. High-temperature conductivity measurements revealed that the conductivity (σ) of Na9Al(MoO4)6 at 803 K equals 1.63 × 10–2 S cm–1. The temperature behavior of the 23Na and 27Al nuclear magnetic resonance spectra and the spin-lattice relaxation rates of the 23Na nuclei indicate the presence of fast Na+ ion diffusion in the studied compound. At T<490 K, diffusion occurs by means of Na+ ion jumps exclusively through the sublattice of Na3–Na5 positions, whereas Na1 and Na2 become involved in the diffusion processes (through chemical exchange with the Na3–Na5 sublattice) only at higher temperatures. |
| Remark |
DOI: 10.1021/acs.chemmater.7b03989 Link |
Alkali and Alkaline Earth Oxoacid Salts; Synthesis, Hydration, Stability, and Electrical Conductivity
ID=422| Author |
|
| Source |
Time of Publication: 2017
|
| Abstract | Proton-conducting electrolytes are sough after for use in various applications within the field of electrochemistry. Pure and high proton conductivity has been found in many perovskite-type oxides like BaZrO3 (BZY) and BaCeO3, with BaCeO3-based materials being among the best proton-conducting oxides. In the intermediate temperature range of 400 to 800 C, BZY has been established as one of the most promising materials, exhibiting a protonic conductivity higher than 1 102 S cm1 over the whole temperature range. However, it is difficult to process, and the resulting materials are usually grainy and possess highly resistive grain-boundaries [1]. For low-temperature regions, compounds like CsHSO4 and CsH2PO4 show great potential with respect to protonic conductivity, even displaying superprotonic transitions that immensely increase their conductivity, however their stability is lacking with respect to temperature and solubility in water [2]. With this project, the aim is to broaden the horizon and investigate compounds that fall outside the common perovskite-definition. In this work, various solid acids (E.g. KBaPO4, NaCaHSiO4 and BaH2SiO4), in which the cations are alkali and alkaline earth metals and the anionic groups are separated XO4 tetrahedra, are synthesized and subsequently characterized by X-Ray Diffraction (XRD), Thermogravimetric Analysis (TG), as well as electrical characterization by Impedance Spectroscopy (IS). The work on KBaPO4 culminated in a submitted paper [3]. KBaPO4 has been proposed to transform into a great protonic conductor upon hydration at low temperatures. Effectively, hydration through steam at 80 C is said to give the compound a protonic conductivity of 1 102 S cm1 just below 100 C [4]. This is a remarkable result and, if it can be reproduced, it can become a viable rival to BZY. For this reason, KBaPO4 was chosen as a topic for this work. Here, we synthesize KBaPO4 through a high-temperature solid state reaction, and subsequently characterize the system with respect to thermal stability and its inherent electrical conductivity. Through electrical measurements, we found that the conductivity of pure KBaPO4 was very low, around 2 106 S cm1 at 600 C, with an activation energy exceeding 1 eV. The compound is indifferent to the presence of humidity, and results indicate that the charge carrier in the compound is not protonic, but rather it is theorized to be potassium ions, with potassium Frenkel defects being the predominating defect, however this has not been explicitly confirmed. All in all, we propose a defect model for KBaPO4 with Frenkel defects as the predominating defects. Through attempts at hydrating KBaPO4 in accordance to the method proposed by Goodenough, we found that it does not transform into a high-conductivity phase, but rather decomposes into potassium doped Ba3(PO4)2, and that the resulting system shows similar properties, such as thermal stability (Decomposing at 300 C) and protonic conductivity (1:6 106 S cm1 at 250 C), to the system Ba3-xKxHx(PO4)2 previously investigated by Haile et al. [5], albeit with a significantly lower potassium content than the systems they have characterized, possibly indicating that a saturation of K in Ba3(PO4)2 has been reached. By subsequently heating Ba3-xKxHx(PO4)2 to high temperatures, the system is found to expel potassium and form a two-phase system of Ba3(PO4)2 and a secondary phase of KBaPO4, showing similarities to the system Ba3(1-x)K3x(PO4)2-x previously investigated by Iwahara et al. [6]. Through impedance spectroscopy of said system, we found evidence that points toward the system being a protonic conductor, with a bulk conductivity slightly higher than 1 103 S cm1 at 600 C, and an activation energy of around 0:67 eV. This is one order of magnitude higher than the one previously reported by Iwahara et al., and only one order of magnitude lower than that of BaZrO3. Parallelly, NaCaHSiO4 and related compounds ABHXO4 (A Li, Na or K. B Ca, Sr or Ba. X Si, Ge or Sn) were synthesized hydrothermally and subsequently characterized. Electrical characterization of NaCaHSiO4 gave low conductivities, although protonic, of 1:8 108 S cm1 at 250 C, with an activation energy of 0:9 eV. Based on the results, we propose a defect model in which interstitial hydroxide ions and interstitial protons str significant defects in the compound. However, although NaCaHSiO4 could be successfully synthesized and subsequently characterized, the other syntheses did not yield the desired results. In fact, the only synthesis that yielded a pure product was that which gave Sr2SiO4, possibly providing a hydrothermal approach to synthesizing a compound previously produced by a hightemperature solid state reaction. Lastly, the compound BaH2SiO4 was synthesized, according to a hydrothermal route, and characterized with respect to thermal stability and electrical conductivity. It was found to exhibit a conductivity of 2:5 108 S cm1 at 200 C with an activation energy of 0:88 eV, comparable to that of NaCaHSiO4. Due to BaH2SiO4 showing similar response to various atmospheres as NaCaHSiO4, a defect model containing hydroxide and hydrogen interstitials is proposed for BaH2SiO4 as well. Compared to earlier reports, a discrepancy was found in that the BaH2SiO4 decomposes prior to temperature regions in which data on electrical conductivity has been previously reported. Another, separate investigation into BaH2SiO4 is therefore recommended. |
| Remark |
Thesis for the degree of ’Master of Science’, Depertment of Chemistry, University of Oslo Link |
Defect chemistry and electrical properties of BiFeO3
ID=421| Authors |
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| Source |
Journal of Materials Chemistry C
Issue: 38
Time of Publication: 2017
|
| Abstract | BiFeO3 attracts considerable attention for its rich functional properties, including room temperature coexistence of magnetic order and ferroelectricity and more recently, the discovery of conduction pathways along ferroelectric domain walls. Here, insights into the defect chemistry and electrical properties of BiFeO3 are obtained by in situ measurements of electrical conductivity, σ, and Seebeck coefficient, α, of undoped, cation-stoichiometric BiFeO3 and acceptor-doped Bi1−xCaxFeO3−δ ceramics as a function of temperature and oxygen partial pressure pO2. Bi1−xCaxFeO3−δ exhibits p-type conduction; the dependencies of σ and α on pO2 show that Ca dopants are compensated mainly by oxygen vacancies. By contrast, undoped BiFeO3 shows a simultaneous increase of σ and α with increasing pO2, indicating intrinsic behavior with electrons and holes as the main defect species in almost equal concentrations. The pO2-dependency of σ and α cannot be described by a single point defect model but instead, is quantitatively described by a combination of intrinsic and acceptor-doped characteristics attributable to parallel conduction pathways through undoped grains and defect-containing domain walls; both contribute to the total charge transport in BiFeO3. Based on this model, we discuss the charge transport mechanism and carrier mobilities of BiFeO3 and show that several previous experimental findings can readily be explained within the proposed model. |
| Remark | Link |
Performance and stability in H2S of SrFe0.75Mo0.25O3-δ as electrode in proton ceramic fuel cells
ID=420| Authors |
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| Source |
Journal of the European Ceramic Society
Volume: 38,
Issue: 1,
Pages: 163-171 Time of Publication: 2018 |
| Abstract | The H2S-tolerance of SrFe0.75Mo0.25O3-δ (SFM) electrodes has been investigated in symmetric proton ceramic fuel cells (PCFC) with BaZr0.8Ce0.1Y0.1O3-δ (BZCY81) electrolyte. The ionic conductivity of the electrolyte under wet reducing conditions was found to be insignificantly affected in the presence of up to 5000 ppm H2S. The fuel cell exhibited an OCV of about 0.9 V at 700 °C, which dropped to about 0.6 V and 0.4 V upon exposure to 500 and 5000 ppm H2S, respectively, on the fuel side. Post characterization of the fuel cell revealed significant degradation of the anode in terms of microstructure and chemical composition due to formation of sulfides such as SrS, MoS2 and Fe3S4. Nevertheless, the fuel cell was still functional due to the sufficient electronic conductivity of some of these sulfides. |
| Keywords | Proton ceramic fuel cells (PCFC), Sulfur tolerance, H2S, Strontium ferrite, Barium zirconate |
| Remark |
https://doi.org/10.1016/j.jeurceramsoc.2017.08.020 Link |
Improvement of thermoelectric properties of lanthanum cobaltate by Sr and Mn co-substitution
ID=419| Authors |
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| Source |
Journal of Alloys and Compounds
Volume: 735,
Pages: 1787–1791 Time of Publication: 2017-12 |
| Abstract | We report thermoelectric (TE) properties of Sr and Mn co-substituted LaCoO3 system from room temperature to 700 K. Sr-substitutions at La and Mn at Co site in LaCoO3 improves the electrical conductivity (σ). Thermal conductivity (κ) of all the samples increases with the increase in temperature but decreases with the substitution in LaCoO3. An estimation of the electronic thermal conductivity (κe) suggests a dominant phonon contribution to thermal conductivity in this system. A maximum value of the figure of merit is 0.14 at 480 K for La0.95Sr0.05Co0.95Mn0.05O3. |
| Keywords | Seebsys, Powders: solid-state reaction, Thermal conductivity, Electrical conductivity, Perovskites |
| Remark | Link |
Fabrication and testing of unileg oxide thermoelectric device
ID=418| Authors |
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| Source |
API Conference Proceedings
Time of Publication: 2017
|
| Abstract | A prototype of oxide thermoelectric unileg device was fabricated. This device was based on only n-legs made of La doped calcium manganate. The powder was synthesized, characterised and consolidated in rectangular thermoelements. A 3×3 device was fabricated by fitting 9 rectangular bars in alumina housing and connected by silver strips. The device has been tested under large temperature difference (ΔT=480°C) using an indegenous system. An open circuit voltage of 468 mV was obtained for a nine leg unileg device. The device exhibits a internal resistance of ∼1Ω. The maximum power output for this nine leg device reached upto 50 mW in these working condition |
| Keywords | Seebsys |
| Remark | Link |
On the formation of phases and their influence on the thermal stability and thermoelectric properties of nanostructured zinc antimonide
ID=417| Authors |
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| Source |
Journal of Physics D: Applied Physics
Volume: 50,
Issue: 1
Time of Publication: 2016-11
|
| Abstract | To investigate the thermal reliability of the structure and thermoelectric properties of the zinc antimony compounds, undoped (Zn4Sb3) and doped (Zn4Sb2.95Sn0.05 and Co0.05Zn3.95Sb3) zinc antimonide samples were processed using the powder metallurgy route. It was observed that the as-prepared undoped sample contains a pure β-Zn4Sb3 phase, whereas the doped samples consist of Ω-ZnSb as the major phase and β-Zn4Sb3 as the minor phase. Differential scanning calorimetry analysis confirms the stability of the β-Zn4Sb3 phase up to 600 K. X-ray diffraction data of the undoped and doped samples show that the nanocrystallinity of the as-prepared samples is retained after one thermal cycle. The thermal bandgap, thermopower and thermal conductivity are not affected by the thermal cycle for the doped samples. A maximum power factor of 0.6 mW m−1 K−2 was achieved in the Sn-doped sample (Zn4Sb2.95Sn0.05). This is enhanced to 0.72 mW m−1 K−2 after one thermal cycle at 650 K under Ar atmosphere and slightly decreases after the third thermal cycle. In the case of the Co-doped sample (Co0.05Zn3.95Sb3), the power factor increases from 0.4 mW m−1 K−2 to 0.7 mW m−1 K−2 after the third thermal cycle. A figure of merit of ~0.3 is achieved at 573 K in the Zn4Sb2.95Sn0.05 sample. The results from the nanoindentation experiment show that Youngs modulus of the Sn-doped sample (Zn4Sb2.95Sn0.05) after the thermal cycle is enhanced (96 GPa) compared to the as-prepared sample (~76 GPa). These important findings on the thermal stability of the thermoelectric and mechanical properties of Sn-doped samples (Zn4Sb2.95Sn0.05) confirm that Sn-doped zinc antimonide samples can be used as efficient thermoelectric materials for device applications. |
| Keywords | Seebsys |
| Remark | Link |
The effect of Cu2O nanoparticle dispersion on the thermoelectric properties of n-type skutterudites
ID=416| Authors |
|
| Source |
Journal of Physics D: Applied Physics
Volume: 48,
Issue: 45
Publisher: IOP Publishing Ltd,
Time of Publication: 2015-11
|
| Abstract | We report the thermoelectric properties of Ba0.4Co4Sb12 and Sn0.4Ba0.4Co4Sb12 skutterudites dispersed with Cu2O nanoparticles. The samples were synthesized by ball milling and consolidated by spark plasma sintering. Dispersion of Cu2O is found to significantly influence the electrical resistivity and thermopower at high temperatures with a more pronounced effect on the electrical resistivity due to the energy filtering effect at the interface between Cu2O nanoparticles and a Ba0.4Co4Sb12 and Sn0.4Ba0.4Co4Sb12 matrix. At 573 K, the electrical resistivity of Ba0.4Co4Sb12 decreases from 5.01 × 10−5 Ohmm to 2.98 × 10−5 Ohmm upon dispersion of Cu2O. The dispersion of Cu2O reduces the thermal conductivity of the samples from 300 K and above by increasing the phonon scattering. The lowest observed thermal conductivity at 573 K is found to be 2.001 W mK−1 in Cu2O dispersed Ba0.4Co4Sb12 while it is 2.91 W mK−1 in the Ba0.4Co4Sb12 sample without Cu2O dispersion. Hence Cu2O dispersion plays a significant role in the thermoelectric properties and a maximum figure of merit (ZT ) ~ 0.92 is achieved in Cu2O dispersed Ba0.4Co4Sb12 at 573 K which is more than 200% compared to the pure Ba0.4Co4Sb12 sample. The results from nanoindentation experiments show that the Cu2O dispersed sample (Cu2O + Sn0.4Ba0.4Co4Sb11.6) has a higher reduced Youngs modulus (~139 GPa) than the pure Sn0.4Ba0.4Co4Sb11.6 sample (~128 GPa). |
| Keywords | Seebsys |
| Remark | Link |
Phase stability and thermoelectric properties of Cu10.5Zn1.5Sb4S13 tetrahedrite
ID=415| Authors |
|
| Source |
Journal of Alloys and Compounds
Volume: 667,
Pages: 323-328 Time of Publication: 2016-05 |
| Abstract | Cu10.5Zn1.5Sb4S13 tetrahedrite compound was prepared by mechanical milling of Cu2S, ZnS and Sb2S3 powders and spark plasma sintered (SPS) to dense samples. The phase formation, chemical homogeneity, thermal stability of the compound and the thermoelectric properties of the sintered samples were evaluated. Single phase tetrahedrite with the crystallite size of 40 nm was obtained after 30 h of milling followed by annealing at 573 K for 6 h in an argon atmosphere. In-situ high-temperature X-ray diffraction studies revealed that the phase is stable up to 773 K. The Seebeck coefficient of the sintered samples of density >98% shows p-type behavior with maximum thermopower of 170 μV/K at 573 K. The electrical resistivity (ρ) decreases with temperature up to 475 K and then increases. A low thermal conductivity of 0.5 W/(m⋅K), in combination with moderate power factor gave a maximum ZT of ∼0.038 at 573 K in Cu10.5Zn1.5Sb4S13 sample having a grain size of ∼200 nm. |
| Keywords | Seebsys, Thermoelectric, Tetrahedrite, Solid state reactions, Spark plasma sintering, Figure of merit |
| Remark |
Cu10.5Zn1.5Sb4S13 Link |
Study of novel proton conductors for high temperature Solid Oxide Cells
ID=414| Author |
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| Source |
Time of Publication: 2015
|
| Abstract | The main objective of the present work was the systematic study of several groups of materials: Gd3-xMexGaO6-δ (Me = Ca2+, Sr2+), Ba2Y1+xNb1-xO6-δ , and BaZr0.85Y0.15O3-δ (BZY15) as proton conductors. We developed a synthesis route for each group of materials such as microwave- assisted citric acid combustion method, freezedrying synthesis and modified citrate-EDTA complexing method. Pure nanopowders and dense ceramics were obtained after these syntheses plus a classical sintering process. The structure and composition of the obtained products were characterized by X-Ray diffraction (XRD) and scanning electron microscopy (SEM). The temperature dependences of the conductivity were investigated by impedance spectroscopy as a function of pO2 and pH2O. For the family of Gd3-xMexGaO6-δ (Me = Ca2+, Sr2+), we studied the influence of dopant nature and content on the structural and electrical properties. Results indicate that the substitution possible till 10 % of doping content. According to the SEM observations, the grain size is increased with increasing dopant content. Concerning electrical properties, we found an increase of conduction with increasing dopant content. All compounds present a good stability in humid, hydrogen and CO2 containing atmosphere. In case of Ba2Y1+xNb1-xO6-δ materials, the physico-chemical properties of synthesized materials have been characterized by the XRD and SEM techniques. The average grain size increased significantly with increasing amount of Y3+. Conduction properties were slightly improved with the partial substitution of niobium by yttrium. The stability of Ba2Y1+xNb1-xO6-δ compounds was investigated under different atmospheres and conditions. The ionic conduction in this case is quite low, which has been explained by futher molecular dynamics simulations. Finally, we studied the influence of an ZnO and NiO additives on the sintering of BZY15, being these sintering aids used to lower the sintering temperature. Zinc oxide as a sintering aid lowers the sintering temperature by 300 °C and slightly increases the bulk and total conductivity of BZY15. |
| Remark |
THESE DE DOCTORAT |
Advanced low-temperature ceramic nanocomposite fuel cells using ultra high ionic conductivity electrolytes synthesized through freeze-dried method and solid-route
ID=413| Authors |
|
| Source |
Materials Today Energy
Volume: 5,
Pages: 338-346 Time of Publication: 2017 |
| Abstract | Low ionic conductivity and slow reaction kinetics often limit the performance of a ceramic nanocomposite fuel cell (CNFC). Here, we report a novel synthesis method, freeze-dried method, to achieve a record high ionic conductivity for nanocomposite electrolytes (>0.5 S/cm) based on Ce0.85Sm0.15O2 (SDC) and a eutectic mixture of Na2CO3, Li2CO3, K2CO3 (NLK). The highest ionic conductivity (0.55 S/cm) was reached by increasing the carbonate content of the electrolyte to 35 wt%. For the sake of comparison, the nanocomposite electrolytes were also prepared through solid-route. Composite anodes and cathodes for complete fuels were prepared from NiO and La0.6Sr0.4Co0.2Fe0.8O3 (LSCF), respectively using both solid-route and freeze-dried nanocomposite electrolytes. Complete fuel cells manufactured from these nanocomposite materials produced ∼1.1 W/cm2 at 550 °C. The EIS measurements revealed low ohmic losses (0.18 Ω cm2) and even lower charge transfer resistance (0.05 Ω cm2). In addition, it was found that the open-circuit-voltage (OCV) of the CNFCs improved from 1.1 V to 1.2 V when a mixture of air and CO2 was supplied as compared to the case when only air was supplied at the cathode. Finally, high temperature X-ray diffraction (HT-XRD) revealed stable structures of SDC, NiO and LSCF up to 600 °C, which shows the thermal stability of these fuel cell materials. |
| Keywords | Fuel cells, Ceramic, Nanocomposite, Carbonate, Ionic conductivity, Perovskite |
| Remark |
https://doi.org/10.1016/j.mtener.2017.07.017 Link |
Stability and range of the type II Bi1 − xWxO1.5 + 1.5x solid solution
ID=412| Authors |
|
| Source |
Solid State Ionics
Volume: 308,
Pages: 173-180 Time of Publication: 2017 |
| Abstract | We have established the stability and range of the cubic type II phase of Bi1 − xWxO1.5 + 1.5x using a combination of X-ray diffraction, neutron diffraction and X-ray absorption spectroscopy. Type II is a high temperature modification that can be obtained by quenching/rapid cooling of samples with compositions between x = 0.148 to x = 0.185. Slower cooling rates yield the stable low temperature polymorph, the tetragonal type Ib phase (Bi rich samples), and mixtures of type Ib and Aurivillius phase (W-rich samples). Throughout the entire solid solution range, type II exhibits a (3 + 3) dimensional incommensurate modulation with modulation vectors slightly smaller than 1/3 based on a cubic fluorite type subcell (δ-Bi2O3). The main structural motifs are well-defined tetrahedra of WO6 octahedra in a δ-Bi2O3-matrix, with additional W being incorporated on corners and face centers of the approximate commensurate 3 × 3 × 3 supercell in octahedral coordination, confirmed by XANES analysis of the W L3-edge. Impedance measurements reveal oxide ionic conductivities comparable to those of yttria-stabilised zirconia even after a decrease in ionic conductivity of about half an order of magnitude on thermal cycling due to transition to the tetragonal type Ib phase. |
| Keywords | Oxide ionic conductors, Solid solution, Bismuth oxide, Incommensurately modulated structures, Neutron diffraction, XANES |
| Remark |
https://doi.org/10.1016/j.ssi.2017.07.015 Link |
High performance novel gadolinium doped ceria/yttria stabilized zirconia/nickel layered and hybrid thin film anodes for application in solid oxide fuel cells
ID=411| Authors |
|
| Source |
Journal of Power Sources
Volume: 363,
Pages: 251-259 Time of Publication: 2017 |
| Abstract | Magnetron sputtering under oblique angle deposition was used to produce Ni-containing ultra thin film anodes comprising alternating layers of gadolinium doped ceria (GDC) and yttria stabilized zirconia (YSZ) of either 200 nm or 1000 nm thickness. The evolution of film structure from initial deposition, through calcination and final reduction was examined by XRD, SEM, TEM and TOF-SIMS. After subsequent fuel cell usage, the porous columnar architecture of the two-component layered thin film anodes was maintained and their resistance to delamination from the underlying YSZ electrolyte was superior to that of corresponding single component Ni-YSZ and Ni-GDC thin films. Moreover, the fuel cell performance of the 200 nm layered anodes compared favorably with conventional commercially available thick anodes. The observed dependence of fuel cell performance on individual layer thicknesses prompted study of equivalent but more easily fabricated hybrid anodes consisting of simultaneously deposited Ni-GDC and Ni-YSZ, which procedure resulted in exceptionally intimate mixing and interaction of the components. The hybrids exhibited very unusual and favorable IV characteristics, along with exceptionally high power densities at high currents. Their discovery is the principal contribution of the present work. |
| Keywords | Magnetron sputtering, Oblique angle deposition, Thin film anodes, Layered and hybrid structures, SOFC |
| Remark |
https://doi.org/10.1016/j.jpowsour.2017.07.085 Link |
Relating defect chemistry and electronic transport in the double perovskite Ba1−xGd0.8La0.2+xCo2O6−δ (BGLC)
ID=410| Authors |
|
| Source |
Journal of Materials Chemistry A
Volume: 5,
Pages: 15743-15751 Time of Publication: 2017 |
| Abstract | Rare earth double perovskites comprise a class of functional oxides with interesting physiochemical properties both for low- and high-temperature applications. However, little can be found relating electrical properties with equilibrium thermodynamics of non-stoichiometry and defects. In the present work, a comprehensive and generally applicable defect chemical model is developed to form the link between the defect chemistry and electronic structure of partially substituted BGLC (Ba1−xGd0.8La0.2+xCo2O6−δ, 0 ≤ x ≤ 0.5). The equilibrium oxygen content of 4 different compositions is determined as a function of pO2 and temperature by thermogravimetric analysis, and combined with defect chemical modelling to obtain defect concentrations and thermodynamic parameters. Oxidation enthalpies determined by TG-DSC become increasingly exothermic (−50 to −120 kJ mol−1) with increased temperature and oxygen non-stoichiometry for all compositions, in excellent agreement with the thermodynamic parameters obtained from the defect chemical model. All compositions display high electrical conductivities (500 to 1000 S cm−1) with shallow pO2-dependencies and small and positive Seebeck coefficients (3 to 15 μV K−1), indicating high degree of degeneracy of the electronic charge carriers. The complex electrical properties of BGLC at elevated temperatures is rationalized by a two-band conduction model where highly mobile p-type charge carriers are transported within the valence band, whereas less mobile “n-type” charge carriers are located in narrow Co 3d band. |
| Remark |
DOI: 10.1039/C7TA02659E Link |
Formation of NiO/YSZ functional anode layers of solid oxide fuel cells by magnetron sputtering
ID=409| Authors |
|
| Source |
Russian Journal of Electrochemistry
Volume: 53,
Issue: 6,
Pages: 670–676 Time of Publication: 2017 |
| Abstract | The decrease in the polarization resistance of the anode of solid-oxide fuel cells (SOFCs) due to the formation of an additional NiO/(ZrO2 + 10 mol % Y2O3) (YSZ) functional layer was studied. NiO/YSZ films with different NiO contents were deposited by reactive magnetron sputtering of Ni and Zr–Y targets. The elemental and phase composition of the films was adjusted by regulating oxygen flow rate during the sputtering. The resulting films were studied by scanning electron microscopy and X-ray diffractometry. Comparative tests of planar SOFCs with a NiO/YSZ anode support, NiO/YSZ functional nanostructured anode layer, YSZ electrolyte, and La0.6Sr0.4Co0.2Fe0.8O3/Ce0.9Gd0.1O2 (LSCF/CGO) cathode were performed. It was shown that the formation of a NiO/YSZ functional nanostructured anode leads to a 15–25% increase in the maximum power density of fuel cells in the working temperature range 500–800°C. The NiO/YSZ nanostructured anode layers lead not only to a reduction of the polarization resistance of the anode, but also to the formation of denser electrolyte films during subsequent magnetron sputtering of electrolyte. |
| Keywords | SOFC, magnetron sputtering, nanostructured electrode, thin-film anode, polarization resistance |
| Remark | Link |
Tailoring the electrode-electrolyte interface of Solid Oxide Fuel Cells (SOFC) by laser micro-patterning to improve their electrochemical performance
ID=408| Authors |
|
| Source |
Journal of Power Sources
Volume: 360,
Pages: 336-344 Time of Publication: 2017 |
| Abstract | Cathode activation polarisation is one of the main contributions to the losses of a Solid Oxide Fuel Cell. To reduce this loss we use a pulsed laser to modify the surface of yttria stabilized zirconia (YSZ) electrolytes to make a corrugated micro-patterning in the mesoscale. The beam of the laser source, 5 ns pulse width and emitting at λ = 532 nm (green region), is computer-controlled to engrave the selected micro-pattern on the electrolyte surface. Several laser scanning procedures and geometries have been tested. Finally, we engrave a square array with 28 μm of lattice parameter and 7 μm in depth on YSZ plates. With these plates we prepare LSM-YSZ/YSZ/LSM-YSZ symmetrical cells (LSM: La1-xSrxMnO3) and determine their activation polarisation by Electrochemical Impedance Spectroscopy (EIS). To get good electrode-electrolyte contact after sintering it is necessary to use pressure-assisted sintering with low loads (about 5 kPa), which do not modify the electrode microstructure. The decrease in polarisation with respect to an unprocessed cell is about 30%. EIS analysis confirms that the reason for this decrease is an improvement in the activation processes at the electrode-electrolyte interface. |
| Keywords | SOFC, Laser machining, Corrugated surface, Electrode polarisation, Cathode activation, Electrode/electrolyte interface |
| Remark |
https://doi.org/10.1016/j.jpowsour.2017.05.106 Link |
Suppression of electrical conductivity and switching of conduction mechanisms in ‘stoichiometric’ (Na0.5Bi0.5TiO3)1−x(BiAlO3)x (0 ≤ x ≤ 0.08) solid solutions
ID=407| Authors |
|
| Source |
Journal of Materials Chemistry C
Volume: 5,
Pages: 7243-7252 Time of Publication: 2017 |
| Abstract | (Na0.5Bi0.5TiO3)1−x(BiAlO3)x (0 ≤ x ≤ 0.08) solid solutions were prepared by a solid state reaction and their electrical properties were established by ac impedance spectroscopy and electromotive force transport number measurements. Incorporation of BiAlO3 (BA) decreases the electrical conductivity of Na0.5Bi0.5TiO3 (NBT) and sequentially changes the conduction mechanism with increasing x from predominant oxide-ion conduction to mixed ionic–electronic conduction and finally to predominant electronic conduction. The suppressed oxide-ion conduction by BA incorporation significantly reduces the dielectric loss at elevated temperatures and produces excellent high-temperature dielectric materials for high BA contents. The possible reasons for the suppressed oxide-ion conduction in the NBT–BA solid solutions have been discussed and we propose that the local structure, especially trapping of oxygen vacancies by Al3+ on the B-site, plays a key role in oxide-ion conduction in these apparently ‘stoichiometric’ NBT-based solid-solution perovskite materials. |
| Remark |
DOI: 10.1039/C7TC02519J Link |
High conductive (LiNaK)2CO3Ce0.85Sm0.15O2 electrolyte compositions for IT-SOFC applications
ID=406| Authors |
|
| Source |
International Journal of Hydrogen Energy
Volume: 42,
Issue: 32,
Pages: 20904-20909 Time of Publication: 2017 |
| Abstract | Composite electrolytes of lithium, sodium, and potassium carbonate ((LiNaK)2CO3), and samarium doped ceria (SDC) have been synthesized and the carbonate content optimized to study conductivity and its performance in intermediate-temperature solid oxide fuel cell (IT-SOFC). Electrolyte compositions of 20, 25, 30, 35, 45 wt% (LiNaK)2CO3–SDC are fabricated and the physical and electrochemical characterization is carried out using X-ray diffraction, scanning electron microscopy, electrochemical impedance spectroscope, and current–voltage measurements. The ionic conductivity of (LiNaK)2CO3–SDC electrolytes increases with increasing carbonate content. The best ionic conductivity is obtained for 45 wt% (LiNaK)2CO3–SDC composite electrolyte (0.72 S cm−1 at 600 °C) followed by the 35 wt% (LiNaK)2CO3–SDC composite electrolyte (0.55 S cm−1 at 600 °C). The symmetrical cell of the 35 wt% (LiNaK)2CO3–SDC composite electrolyte with lanthanum strontium cobalt ferrite (LSCF) electrode in air gives an area specific resistance of 0.155 Ω cm2 at 500 °C. The maximum power density of the fuel cell using 35 wt% (LiNaK)2CO3–SDC composite electrolyte, composite NiO anode and composite LSCF cathode is found to be 801 mW cm−2 at 550 °C. |
| Keywords | IT-SOFC, Ternary carbonate–SDC electrolyte, Carbonate loading, Composite electrolytes |
| Remark |
https://doi.org/10.1016/j.ijhydene.2017.05.152 Link |
Mixed ionic–electronic conduction in K1/2Bi1/2TiO3
ID=405| Authors |
|
| Source |
J. Mater. Chem. C
Volume: 5,
Pages: 6300-6310 Time of Publication: 2017 |
| Abstract | Recently, it has been reported that the Pb-free piezoelectric perovskite Na1/2Bi1/2TiO3 (NBT) can be compositionally tuned by close control of the A-site starting stoichiometry to exhibit high levels of oxide-ion conduction. The related K1/2Bi1/2TiO3 (KBT) perovskite has also drawn considerable interest as a promising Pb-free piezoelectric material; however, its conduction properties have been less extensively investigated. Here we report on the influence of the K/Bi ratio in the starting composition on the electrical properties using a combination of impedance spectroscopy and ion-transport property measurements. KBT ceramics exhibit mixed ionic–electronic (oxide-ion) conduction with tion ∼ 0.5 at 600–800 °C and although variations in the A-site starting stoichiometry can create a ∼1 order of magnitude difference in the bulk conductivity at >500 °C, the conductivity is low (ca. 0.1 to 1 mS cm−1 at 700 °C) and the activation energy for bulk conduction remains in the range ∼1.2 to 1.5 eV. The high temperature electrical transport properties of KBT are therefore much less sensitive to the starting A-site stoichiometry as compared to NBT. However, KBT ceramics exhibit non-negligible proton conduction at lower temperatures (<300 °C). For K/Bi ≥ 1 the total conductivity of KBT ceramics at room temperature can be as high as ∼0.1 mS cm−1 under wet atmospheric conditions. This study demonstrates ionic conduction to be a common feature in A1/2Bi1/2TiO3 perovskites, where A = Na, K. |
| Remark |
DOI: 10.1039/C7TC01786C Link |
Effect of plasma spraying power on LSGM electrolyte of metal-supported solid oxide fuel cells
ID=404| Authors |
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| Source |
Ceramics International
Volume: 43,
Issue: 1,
Pages: S591-S597 Time of Publication: 2017 |
| Abstract | Four nickel-iron metal-supported solid oxide fuel cells with a diameter of 2.4 cm and a cathode active area of 1.76 cm2 are fabricated by atmospheric plasma spraying (APS) and heat-treated in air at 850 °C and 500 g cm−2 pressure for 4 h. These cells with the same functional layer materials have electrolyte layers produced by different APS torch powers, but the APS fabrication parameters for other functional layers of these cells are kept the same. XRD data show that there is a LaSrGaO4 impurity phase in the prepared dense LSGM electrolyte produced at 54 kW torch power. According to experimental data on the current-voltage-power and AC impedance measurements at temperatures ranging from 550 to 800 °C, the cell with dense LSGM electrolyte produced at 52 kW torch power has the best power performance and the lowest electrolyte resistance and the corresponding delivered power densities at 0.7 V for 550, 600, 650, 700, 750 and 800 °C temperatures are 0.147, 0.271, 0.426, 0.585, 0.716 and 0.796 W cm−2, respectively. |
| Keywords | Metal-supported, Solid oxide fuel cell, Atmospheric plasma spraying, LSGM electrolyte |
| Remark | Link |
Composite mixed ionic-electronic conducting ceramic for intermediate temperature oxygen transport membrane
ID=403| Authors |
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| Source |
Ceramics International
Volume: 43,
Issue: 1,
Pages: S628-S632 Time of Publication: 2017 |
| Abstract | The dense ceramic substrate formed by a mixed ionic-electronic conducting (MIEC) material can be used as an oxygen transport membrane (OTM), enabling the transport of high flux oxygen with certain selectivity and gas separation at high temperatures (800 ~ 900 °C). In recent years, Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) has been reported to be a promising MIEC material for oxygen permeation due to its relatively high oxygen ion conductivity at high temperatures. However, the catalytic efficiency of BSCF is relatively low among the MIEC materials, resulting in the dramatic decrease of oxygen permeation at temperatures below 800 °C. In the present study, a composite MIEC ceramic consisting of a BSCF substrate and the catalytic La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) layer has been proposed. A simple method of laser surface melting is executed to fabricate the composite oxygen transport membrane. The scanning electron microscope (SEM) investigations show that LSCF powders can be well-adherent to the BSCF surface after laser scanning melting process. The oxygen permeation flux reaches 0.5 ml min−1 cm−2 for pure BSCF membrane with thickness of 420 µm, while the BSCF membrane substrate with laser scanning LSCF exhibits substantial improvement on oxygen permeation up to 60% at 700 °C. The result suggests that the composite MIEC ceramic has significant potential for intermediate temperature oxygen transport membrane. |
| Keywords | Membranes, Composites, Laser surface melting |
| Remark |
https://doi.org/10.1016/j.ceramint.2017.05.222 Link |
The Effect of Metallic Co-Coating Thickness on Ferritic Stainless Steels Intended for Use as Interconnect Material in Intermediate Temperature Solid Oxide Fuel Cells
ID=402| Authors |
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| Source |
Oxidation of Metals
Pages: 1–18 Time of Publication: 2017 |
| Abstract | The effect of metallic Co-coating thickness on ferritic stainless steels is investigated. This material is suggested to be used as interconnect material in intermediate temperature solid oxide fuel cells. Uncoated, 200-, 600-, 1000-, and 1500-nm Co-coated Sanergy HT is isothermally exposed for up to 500 h in air at 650 °C. Mass gain is recorded to follow oxidation kinetics, and area-specific resistance (ASR) measurements are conducted on samples exposed for 168 and 500 h. The microstructure of the thermally grown oxide scales is characterized utilizing scanning electron microscopy and energy-dispersive X-ray analysis on broad ion beam-milled cross sections. A clear increase in ASR as a function of Co-coating thickness is observed. However, the increase in ASR, as an effect of a thicker Co-coating, is correlated with thicker (Cr,Fe)2O3 scales formed on these materials and not to an increase in Co spinel top layer thickness. |
| Keywords | Solid oxide fuel cell, Interconnect, Coating, Area-specific resistance, Corrosion |
| Remark |
DOI 10.1007/s11085-017-9782-9 Link |
Porous Ca3Co4O9 with enhanced thermoelectric properties derived from Sol–Gel synthesis
ID=401| Authors |
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| Source |
Journal of the European Ceramic Society
Time of Publication: 2017
|
| Abstract | Highly porous Ca3Co4O9 thermoelectric oxide ceramics for high-temperature application were fabricated by sol–gel synthesis and subsequent conventional sintering. Growth mechanism of misfit-layered Ca3Co4O9 phase, from sol–gel synthesis educts and upcoming intermediates, was characterized by in-situ X-ray diffraction, scanning electron microscopy and transmission electron microscopy investigations. The Ca3Co4O9 ceramic exhibits a relative density of 67.7%. Thermoelectric properties were measured from 373 K to 1073 K. At 1073 K a power factor of 2.46 μW cm−1 K−2, a very low heat conductivity of 0.63 W m−1 K−1 and entropy conductivity of 0.61 mW m−1 K−2 were achieved. The maintained figure of merit ZT of 0.4 from sol–gel synthesized Ca3Co4O9 is the highest obtained from conventional, non-doped Ca3Co4O9. The high porosity and consequently reduced thermal conductivity leads to a high ZT value. |
| Keywords | Thermoelectricity; Thermal conductivity; Porosity; Oxide; Ca3Co4O9 |
| Remark |
https://doi.org/10.1016/j.jeurceramsoc.2017.04.059 Link |
Electrochemical performance of Co3O4/CeO2 electrodes in H2S/H2O atmospheres in a proton-conducting ceramic symmetrical cell with BaZr0.7Ce0.2Y0.1O3 solid electrolyte
ID=400| Authors |
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| Source |
Solid State Ionics
Time of Publication: 2017
|
| Abstract | The electrochemical performance of Co3O4/CeO2 mixed oxide materials as electrodes, when exposed to H2S/H2O atmospheres, was examined employing a proton conducting symmetrical cell, with BaZr0.7Ce0.2Y0.1O3 (BZCY72) as the solid electrolyte. The impact of temperature (700–850 °C) and H2S concentration (0–1 v/v%) in steam-rich atmospheres (90 v/v% H2O) on the overall cell performance was thoroughly assessed by means of electrochemical impedance spectroscopy (EIS) studies. The performance of the Co3O4/CeO2 electrode was significantly enhanced by increasing the H2S concentration and temperature. The obtained results were interpreted on the basis of EIS results and physicochemical characterization (XRD, SEM) studies of fresh and used electrodes. Notably, it was found that the mass transport processes, mainly associated with the adsorption and diffusion of the intermediate species resulting by the chemical and half-cell reactions taking place during cell operation, dominate the electrode polarization resistance compared with the charge transfer processes. Upon increasing temperature and H2S concentration, the electrode resistance is substantially lowered, due to the in situ activation and morphological modifications of the electrode, induced by its interaction with the reactants (H2S/H2O) and products (H2/SO2) mixtures. |
| Keywords | H2S-tolerant electrodes; Cobalt-ceria oxides; BZCY72 |
| Remark |
https://doi.org/10.1016/j.ssi.2017.04.010 Link |
Thermal stability and enhanced thermoelectric properties of the tetragonal tungsten bronzes Nb8−xW9+xO47 (0 < x < 5)
ID=399| Authors |
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| Source |
Journal of Materials Chemistry A
Time of Publication: 2017
|
| Abstract | Thermoelectric materials are believed to play a fundamental role in the energy field over the next years thanks to their ability of directly converting heat into usable electric energy. To increase their integration in the commercial markets, improvements of the efficiencies are needed. At the same time, cheap and non-toxic materials are required along with easily upscalable production cycles. Compounds of the tetragonal tungsten bronze (TTB) series Nb8−xW9+xO47 fulfill all these requirements and are promising materials. Their adaptive structure ensures glass-like values of the thermal conductivity, and the substitution on the cation side allows a controlled manipulation of the electronic properties. In this contribution we report the stability study of the two highly substituted samples of the series, Nb5W12O47 (x = 3) and Nb4W13O47 (x = 4), when subjected to thermal cycling. Moreover, we show the results of the thermoelectric characterization of these samples. The two compounds have not been affected by the thermal treatment and showed an improvement of the thermoelectric performances up to a zT = 0.2 above 1000 K. |
| Remark | Link |
Influence of (Zn,Co)O/ZnO) interface amounts on ionic conduction performance of (Zn1-x,Cox)O (x=0.01, 0.05 and 0.10)
ID=398| Authors |
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| Source |
Composites Part B: Engineering
Time of Publication: 2017
|
| Abstract | We investigated the effect of dopant Co atoms into ZnO lattice, on ionic conduction at internal grain and/or through the grain boundary. Influence of dopant Co amount on resistivity was associated with enhanced activation energies of ionic conductivity through the grain boundaries. The change in the activation energy indicated that the mechanism of ionic conduction through the boundaries can be manipulated with Co amount in the lattice. Three conductance mechanisms were identified from the Cole-Cole Plots in order to understand the relaxation mechanism and activation energies of ionic transportations. Formed activation energy, 395 meV, by increasing Co dopant amount up to 10 mol% was attributed to enhanced ionic conductivity through enhancing (Zn,Co)O/ZnO) interface amounts at the grain boundaries. Furthermore, increased activation energy were also enhanced the electronic stability at high temperatures due to decrease in electronic conductivity compared to undoped ZnO. |
| Keywords | Ionic activation energy; Oxide semiconductors; Impedance spectroscopy |
| Remark |
https://doi.org/10.1016/j.compositesb.2017.04.020 Link |
Development of novel metal-supported proton ceramic electrolyser cell with thin film BZY15–Ni electrode and BZY15 electrolyte
ID=397| Authors |
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| Source |
International Journal of Hydrogen Energy
Volume: 42,
Issue: 19,
Pages: 13454–13462 Time of Publication: 2017 |
| Abstract | Metal supports for planar MS-PCEC were manufactured using tape-casting of low-cost ferritic stainless steel. A coating protecting the metal support against oxidation was applied by vacuum infiltration and a buffer layer of La0.5Sr0.5Ti0.75Ni0.25O3–δ (LSTN) was further deposited to smoothen the surface. The BaZr0.85Y0.15O3–δ–NiO (BZY15–NiO) cathode and the BaZr0.85Y0.15O3–δ (BZY15) electrolyte were applied by pulsed laser deposition (PLD) at elevated substrate temperatures (at 700 °C and 600 °C, respectively). The main challenges are related to the restrictions in sintering temperature and atmosphere induced by the metal support, as well as strict demands on the roughness of substrates used for PLD. Reduction treatment of the half cells confirmed that NiO in the BZY15–NiO layer was reduced to Ni, resulting in increased porosity of the BZY15–Ni cathode, while keeping the columnar and dense microstructure of the BZY15 electrolyte. Initial electrochemical testing with a Pt anode showed a total resistance of 40 Ω·cm2 at 600 °C. Through this work important advances in using metal supports and thin films in planar PCEC assemblies have been made. |
| Keywords | Proton ceramic electrolyser cell (PCEC); Tape casting; Thin film deposition; Metal supports |
| Remark |
https://doi.org/10.1016/j.ijhydene.2017.03.028 Link |
Energetically benign synthesis of lanthanum silicate through “silica garden” route and its characterization
ID=396| Authors |
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| Source |
Materials Chemistry and Physics
Volume: 194,
Pages: 147–152 Time of Publication: 2017 |
| Abstract | Lanthanum silicate synthesis through “silica garden” route has been reported as an alternative to energy intensive milling procedure. Under optimum conditions lanthanum chloride crystals react with water glass (sodium silicate) to produce self generating hollow lanthanum silicate precipitation tube(s) (LaSPT). The micro tubes are irregular, thick, white coloured and amorphous but are hierarchically built from smaller tubules of 10–20 nm diameters. They retain their amorphous nature on being heated up to 600 °C beyond which crystallization starts. The major phase in the LaSPT heated at 900 °C is La2Si2O7. “As synthesized” LaSPT is heterogeneous and comprises non stoichiometric phases. The exterior and interior surfaces of these tubes are remarkably different in their morphology and chemical composition. LaSPT sintered at 1200 and 1300 °C show fair amount of ionic conductivity. |
| Keywords | Silica garden; Lanthanum silicate; Synthesis; Characterization |
| Remark |
https://doi.org/10.1016/j.matchemphys.2017.03.021 Link |
Effect of Pt catalyst and external circuit on the hydrogen permeation of Mo and Nb co-doped lanthanum tungstate
ID=395| Authors |
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| Source |
Journal of Membrane Science
Volume: 553,
Pages: 336–341 Time of Publication: 2017 |
| Abstract | In this contribution, the hydrogen permeation properties of 30% Mo and 15% Nb co-doped La5.4WO11.1-δ (LWNM30) with/without Pt catalyst and external circuit were investigated. It was found that the surface reaction was the limiting factor in the hydrogen permeation process of LWNM30, and could be improved by using Pt as catalyst. The applied external circuit could also increase the hydrogen flux of LWNM30, and two followed effects might be responsible: the external circuit could transfer the electrons and promote the diffusion process; the external circuit could remove the charge layer on the surface and enhance the surface reaction rate. |
| Keywords | Lanthanum tungstate; Hydrogen permeation; Pt catalyst; Mo and Nb; External circuit |
| Remark | Link |
Magnetron-sputtered La0.6Sr0.4Co0.2Fe0.8O3 nanocomposite interlayer for solid oxide fuel cells
ID=394| Authors |
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| Source |
Journal of Nanoparticle Research
Time of Publication: 2017
|
| Abstract | A thin layer of a La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) is deposited between the electrolyte and the La0.6Sr0.4Co0.2Fe0.8O3/Ce0.9Gd0.1O2 (LSCF/CGO) cathode layer of a solid oxide fuel cell (SOFC) by pulsed magnetron sputtering using an oxide target of LSCF. The films were completely dense and well adherent to the substrate. The effects of annealing in temperature range from 200 to 1000 °C on the crystalline structure of the LSCF films have been studied. The films of nominal thickness, 250–500 nm, are crystalline when annealed at temperatures above 600 °C. The crystalline structure, surface topology, and morphology of the films were determined using X-ray diffraction (XRD), atomic force microscopy (AFM), and scanning electron microscopy (SEM), respectively. To study the electrochemical characteristics of the deposited-film, solid oxide fuel cells using 325-nm LSCF films as interlayer between the electrolyte and the cathode have been fabricated. The LSCF interlayer improves the overall performance of the SOFC by increasing the interfacial area between the electrolyte and cathode. The electrolyte-supported cells with the interlayer have 30% greater, overall power output compared to that achieved with the cells without interlayer. The LSCF interlayer could also act as a transition layer that improves adhesion and relieves both thermal stress and lattice strain between the cathode and the electrolyte. Our results demonstrate that pulsed magnetron sputtering provides a low-temperature synthesis route for realizing ultrathin nanocrystalline LSCF film layers for intermediate- or low-temperature solid oxide fuel cells. |
| Keywords | (La,Sr)(Co,Fe)O3 Magnetron sputtering Nanocomposite Interlayer Solid oxide fuel cells Nanostructured thin films Energy conversion |
| Remark |
DOI: 10.1007/s11051-017-3791-0 Link |
Ferroelectric crystal Ca9Yb(VO4)7 in the series of Ca9R(VO4)7 non-linear optical materials (R = REE, Bi, Y)
ID=393| Authors |
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| Source |
Journal of Materials Chemistry C
Time of Publication: 2017
|
| Abstract | The crystal structure, thermal, dielectric and second harmonic generation (SHG), and nonlinear optical activity data for whitlockite-type Ca9Yb(VO4)7 single crystals were obtained on one and the same sample produced by means of the Czochralski method. The crystal structure refinement has revealed that Yb3+ cations substitute for Ca2+ ions only in the M1, M2 and M5 positions of the whitlockite-type structure. Dielectric, differential thermal analysis and SHG data have shown that Ca9Yb(VO4)7 belongs to the family of high-temperature Ca3(VO4)2 ferroelectrics with Curie temperature Tc = 1221 K, where the symmetry changes from R3c to R[3 with combining macron]c. At higher temperatures a previously unknown complementary phase transition is discovered at T2 = 1276 K and is associated with the symmetry change during heating from R[3 with combining macron]c to R[3 with combining macron]m. Unlike other whitlockites, two phase transitions in Ca9Yb(VO4)7 are separated by a broad interval (ΔT = 55 K) which allows one to register two phase transitions by DSC and dielectric measurements. According to the thermal type both transitions are classified as first-order transformations and their structural mechanisms are considered. Inhomogeneity in the cation distribution is argued to have a crucial influence on the optical quality and ferroelectric domain structures of Ca9Yb(VO4)7 and other whitlockite-type laser crystals. |
| Remark | Link |
Status report on high temperature fuel cells in Poland – Recent advances and achievements
ID=392| Authors |
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| Source |
International Journal of Hydrogen Energy
Volume: 42,
Issue: 7,
Pages: 4366–4403 Time of Publication: 2017 |
| Abstract | The paper presents recent advances in Poland in the field of high temperature fuel cells. The achievements in the materials development, manufacturing of advanced cells, new fabrication techniques, modified electrodes and electrolytes and applications are presented. The work of the Polish teams active in the field of solid oxide fuel cells (SOFC) and molten carbonate fuel cell (MCFC) is presented and discussed. The review is oriented towards presenting key achievements in the technology at the scale from microstructure up to a complete power system based on electrochemical fuel oxidation. National efforts are covering wide range of aspects both in the fundamental research and the applied research. The review present the areas of (i) novel materials for SOFC including ZrO2-based electrolytes, CeO2-based electrolytes, Bi2O3 based electrolytes and proton conducting electrolytes, (ii) cathode materials including thermal shock resistant composite cathode material and silver-containing composites, (iii) anode materials, (iv) metallic interconnects for SOFC, (v) novel fabrication techniques, (vi) pilot scale SOFC, including electrolyte supported SOFC (ES-SOFC) and anode supported SOFC (AS-SOFC), (vii) metallic supported SOFC (MS-SOFC), (viii) direct carbon SOFC (DC-SOFC), (ix) selected application of SOFC, (x) advances in MCFC and their applications, (xi) advances in numerical methods for simulation and optimization of electrochemical systems. |
| Keywords | SOFC; MCFC; Experiments; Simulations; Fabrication techniques |
| Remark |
https://doi.org/10.1016/j.ijhydene.2016.12.087 Link |
Surface Protonics Promotes Catalysis
ID=391| Authors |
|
| Source |
Nature Scientific Reports
Volume: 6,
Pages: Article number: 38007 Time of Publication: 2016 |
| Abstract | Catalytic steam reforming of methane for hydrogen production proceeds even at 473 K over 1 wt% Pd/CeO2 catalyst in an electric field, thanks to the surface protonics. Kinetic analyses demonstrated the synergetic effect between catalytic reaction and electric field, revealing strengthened water pressure dependence of the reaction rate when applying an electric field, with one-third the apparent activation energy at the lower reaction temperature range. Operando–IR measurements revealed that proton conduction via adsorbed water on the catalyst surface occurred during electric field application. Methane was activated by proton collision at the Pd–CeO2 interface, based on the inverse kinetic isotope effect. Proton conduction on the catalyst surface plays an important role in methane activation at low temperature. This report is the first describing promotion of the catalytic reaction by surface protonics. |
| Keywords | Catalytic mechanisms, Energy, Heterogeneous catalysis, Surface spectroscopy |
| Remark |
doi:10.1038/srep38007 Link |
Sm6-xMoO12-δ (x = 0, 0.5) and Sm6WO12 – Mixed electron-proton conducting materials
ID=390| Authors |
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| Source |
Solid State Ionics
Time of Publication: 2017
|
| Abstract | Samarium molybdates Sm6-xMoO12-δ (x = 0, 0.5) and samarium tungstate Sm6WO12 – potential mixed electron-proton conductors have been studied by X-ray diffraction, Raman spectroscopy, SEM and impedance spectroscopy (in ambient air and in dry and wet air). Solid solutions differing in structure have been obtained in the Sm2O3-MoO3 system at 1600 °C. The samarium molybdate Sm6MoO12 has the fluorite structure (Fm¯3m). The less samarium rich solid solution Sm5.5MoO11.25 crystallizes in a rhombohedral (View the MathML sourceR3¯) structure. The morphotropic transformation is due to the change in the chemical composition of the solid solution with decreasing Sm3 + concentration. The total conductivity of the cubic fluorite phase Sm6MoO12 at 750 °C in air (1.48 × 10− 3 S/cm, Ea = 1.22 eV) is an order of magnitude higher than that of rhombohedral Sm5.5MoO11.25 (2.34 × 10− 4 S/cm, Ea = 1.11 eV). At low temperatures (T < 500 °C), the Arrhenius plot of total conductivity for Sm6MoO12 and Sm5.5MoO11.25 in air deviates from linearity, suggesting that there is a proton contribution to its conductivity at these temperatures, like in the case of the Sm5.4Zr0.6MoO12.3 zirconium-doped molybdate. Below ~ 500 °C, Sm6MoO12 fluorite and fluorite-like Sm6WO12 have identical Arrhenius plots of conductivity in ambient air. The region of dominant proton conductivity is wider for Sm6WO12 than Sm6MoO12, reaching temperatures as high as 750 °С for the former. The absolute values of total conductivity obtained for samarium tungstate and molybdate at 400 °С in wet air are virtually identical and close to 3 × 10− 6 S/cm, which suggests the conductivity of both compounds is dominated by protons at low temperatures and the proton transport numbers are similar. |
| Keywords | Phase transition; Fluorite; Fluorite-like phase; Proton-conducting membranes; Proton conductivity; Electron conductivity |
| Remark |
http://dx.doi.org/10.1016/j.ssi.2017.01.020 Link |
The effect of Zr-substitution in La1‐xSrxCo0.2M0.6Zr0.2O3‐δ (M = Fe, Mn) on the crystal structure, thermal expansion and electronic transport properties
ID=389| Authors |
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| Source |
Solid State Ionics
Volume: 301,
Pages: 53–58 Time of Publication: 2017 |
| Abstract | The effect of Zr-substitution on the evolution of crystal structure, thermal expansion and the electronic transport properties is reported for La1‐xSrxCo0.2Fe0.6Zr0.2O3‐δ (0.1 ≤ x ≤ 1.0) and La1‐xSrxCo0.2Mn0.6Zr0.2O3-δ (x = 0.1, 0.2, 0.25, 0.3). La1‐xSrxCo0.2Fe0.6Zr0.2O3‐δ was found to be single-phase for the compositions investigated. The electrical conductivity of La1‐xSrxCo0.2Fe0.6Zr0.2O3‐δ demonstrated a maximum for x = 0.5, while the area specific resistance was shown to decrease significantly with increasing Sr-content due to an increased concentration of oxygen vacancies. No signs of oxygen vacancy ordering were observed. The area specific resistance of La0.3Sr0.7Co0.2Fe0.6Zr0.2O3‐δ at 600 °C is close to an order of magnitude lower than reported values for La0.4Sr0.6Co0.2Fe0.8O3‐δ. The series La1‐xSrxCo0.2Mn0.6Zr0.2O3‐δ was found as multiphase materials. The stability of both series is discussed with respect to the red-ox properties of the transition metals. |
| Keywords | Perovskite; Zr-substitution; X-ray diffraction; Electrical conductivity; Thermal expansion |
| Remark |
http://dx.doi.org/10.1016/j.ssi.2017.01.011 Link |
Co- and Ce/Co-coated ferritic stainless steel as interconnect material for Intermediate Temperature Solid Oxide Fuel Cells
ID=388| Authors |
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| Source |
Journal of Power Sources
Volume: 343,
Pages: 1-10 Time of Publication: 2017 |
| Abstract | Chromium species volatilization, oxide scale growth, and electrical scale resistance were studied at 650 and 750 °C for thin metallic Co- and Ce/Co-coated steels intended to be utilized as the interconnect material in Intermediate Temperature Solid Oxide Fuel Cells (IT-SOFC). Mass gain was recorded to follow oxidation kinetics, chromium evaporation was measured using the denuder technique and Area Specific Resistance (ASR) measurements were carried out on 500 h pre-exposed samples. The microstructure of thermally grown oxide scales was characterized using Scanning Electron Microscopy (SEM), Scanning Transmission Electron Microscopy (STEM), and Energy Dispersive X-Ray Analysis (EDX). The findings of this study show that a decrease in temperature not only leads to thinner oxide scales and less Cr vaporization but also to a significant change in the chemical composition of the oxide scale. Very low ASR values (below 10 mΩ cm2) were measured for both Co- and Ce/Co-coated steel at 650 and 750 °C, indicating that the observed change in the chemical composition of the Co spinel does not have any noticeable influence on the ASR. Instead it is suggested that the Cr2O3 scale is expected to be the main contributor to the ASR, even at temperatures as low as 650 °C. |
| Keywords | Interconnect; Solid oxide fuel cell; Corrosion; Cr vaporization; Area specific resistance; Coating |
| Remark |
http://dx.doi.org/10.1016/j.jpowsour.2017.01.045 Link |
Characterization of laser-processed thin ceramic membranes for electrolyte-supported solid oxide fuel cells
ID=387| Authors |
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| Source |
International Journal of Hydrogen Energy
Time of Publication: 2017
|
| Abstract | By laser machining we have prepared thin and self-supported yttria stabilized zirconia (YSZ) electrolytes that can be used in electrolyte-supported solid oxide fuel cells for reducing the operation temperature. The membranes, which are supported by thicker areas of the same material, have an active area of ∼20 μm in thickness and up to 8 mm in diameter. Buckling limits the maximum size of the thin areas to below 1 mm, the overall effective active area being formed by multiple thin areas bounded by ribs. Electron Backscattering Diffraction experiments determined that there are not significant strains inside the membranes and that the heat-affected zone is confined to a shallow layer of ∼1–2 μm. The bending strength of the membranes decreases by ∼26% as a result of the surface microcracking produced by the laser machining. The membranes have a roughness of ∼2.5 μm and are coated by a layer of nanoparticles produced by the laser ablation. This coating and small roughness is not detrimental for the cathodic polarization of the cells. Conversely, the cathode polarization resistance decreases ∼5% in the 650–850 °C temperature range. |
| Keywords | SOFC; Solid electrolytes; Laser machining; Self-supporting ceramic membranes |
| Remark |
http://dx.doi.org/10.1016/j.ijhydene.2016.12.112 Link |
Tuning of nonlinear optical and ferroelectric properties via the cationic composition of Ca9.5–1.5xBixCd(VO4)7 solid solutions
ID=386| Authors |
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| Source |
Materials & Design Volume: 116, Pages: 515–523 Time of Publication: 2017 |
| Abstract | Ca9.5–1.5xBixCd(VO4)7 (0 ≤ x ≤ 1) solid solutions with the whitlockite-type structure (SG R3c) were synthesized by a standard solid-state method in air. Structures of Ca9.5–1.5xBixCd(VO4)7 (x = 0.167, 0.5, 0.833) were refined by the Rietveld method from synchrotron powder X-ray diffraction data. Nonlinear optical properties of the whitlockite-type compounds can be designed and increased by an order of magnitude through appropriate isovalent and aliovalent substitutions for Ca2+ cations. Dielectric and temperature second harmonic generation investigations revealed the presence of a reversible ferroelectric phase transition in the range from 1331 K to 1055 K. The phase transition temperature monotonically decreases while nonlinear optical activity of Ca9.5–1.5xBixCd(VO4)7 strongly increases with increasing Bi3+ content. |
| Keywords | Vanadates; Ferroelectric properties; Nonlinear optical properties; Crystal structure |
| Remark |
http://dx.doi.org/10.1016/j.matdes.2016.11.107 Link |
The structural and electrical properties of samarium doped ceria films formed by e-beam deposition technique
ID=385| Authors |
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| Source |
Solid State Ionics
Time of Publication: 2016
|
| Abstract | Sm2O3-doped CeO2 (Sm0.15Ce0.85O1.925, SDC) thin films were formed by e-beam evaporation method. Thin films were formed evaporating micro powders (particle size varied from 0.3 to 0.5 μm). The influence of deposition rate on formed thin film structures and surface morphology were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersion spectrometry (EDS), and atomic force microscopy (AFM). The deposition rate of formed SDC thin films was changed from 2 to 16 Å/s. The electrical properties were investigated as a function of frequency (0.1–106 Hz) at different temperatures (473–873 K). The formed SDC thin ceramic films repeat the crystallographic orientation of the initial powders using different substrates and different deposition rate. It was determined that crystallites size and samarium concentration are decreasing by increasing the deposition rate. The crystallites size decreased from 17.0 nm to 10.4 nm when SDC thin films were deposited on Alloy 600 (Fe-Ni-Cr), and decreased from 13.7 nm to 8.9 nm when were used optical quartz substrate. The best ionic conductivity σtot = 1.66 Sm− 1 at 873 K temperature, activation energy ΔEa = 0.87 eV (σg = 1.66 Sm− 1, σgb = 1.66 Sm− 1) was achieved when 2 Å/s deposition rate was used. The grain size (in the formed SDC thin films) was ~ 83 nm in this case. |
| Keywords | Electron beam deposition; Samarium doped ceria oxide (SDC); Solid oxide fuel cells (SOFC); Ionic conductivity |
| Remark |
http://dx.doi.org/10.1016/j.ssi.2016.12.003 Link |
Interstitial oxygen as a source of p-type conductivity in hexagonal manganites
ID=384| Authors |
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| Source |
Nature Communications
Time of Publication: 2016
|
| Abstract | Hexagonal manganites, h-RMnO3 (R=Sc, Y, Ho–Lu), have been intensively studied for their multiferroic properties, magnetoelectric coupling, topological defects and electrically conducting domain walls. Although point defects strongly affect the conductivity of transition metal oxides, the defect chemistry of h-RMnO3 has received little attention. We use a combination of experiments and first principles electronic structure calculations to elucidate the effect of interstitial oxygen anions, Oi, on the electrical and structural properties of h-YMnO3. Enthalpy stabilized interstitial oxygen anions are shown to be the main source of p-type electronic conductivity, without reducing the spontaneous ferroelectric polarization. A low energy barrier interstitialcy mechanism is inferred from Density Functional Theory calculations to be the microscopic migration path of Oi. Since the Oi content governs the concentration of charge carrier holes, controlling the thermal and atmospheric history provides a simple and fully reversible way of tuning the electrical properties of h-RMnO3. |
| Remark |
doi:10.1038/ncomms13745 Link |
Oxygen ion conductivity in samarium and gadolinium stabilized cerium oxide heterostructures
ID=383| Authors |
|
| Source |
Solid State Ionics
Time of Publication: 2016
|
| Abstract | Gadolinium (GDC) and samarium (SDC) doped ceria were investigated in terms of multilayer systems, evaporated by e-beam technique on optical quartz, Alloy600 and sapphire substrate. GDC-SDC heterostructures of 1.3 μm thicknesses, composed of 1, 2, 3, 5 and 7 layers and they were investigated by structural and ionic conductivity techniques. Bragg peaks show nanocrystalline state of Gd and Sm doped ceria thin films. XRD patterns show fluorite type structure with space group Fm3m. The XRD analysis of thin films, deposited on quartz substrate, reveals the increase of (220) peak with increasing number of layers. The decrease of (111) peak is slightly notable, also. Thin film heterostructures have a face-centered cubic cell with the following lattice parameters, such as 5.4180 nm for GDC of and of 5.4245 nm for SDC. The scanning electron microscopy cross sectional analysis of three-layered structure clearly indicates the interfaces of different material. There are no visually distinct discontinuities in higher layer structures (5–7 layers). Total conductivity increases linearly with increasing of temperature, but decreases with the increase of number of layers. The highest total ionic conductivity at 1214 K temperature for SDC and GDC thin monolayers was 1.62 S/m and 1.02 S/m, respectively. The activation energy increases with the increase of number of layer as well. |
| Keywords | Multilayer electrolyte; SDC; GDC; e-Beam deposition |
| Remark |
http://dx.doi.org/10.1016/j.ssi.2016.11.025 Link |
A multistep model for the kinetic analysis of the impedance spectra of a novel mixed ionic and electronic conducting cathode
ID=382| Authors |
|
| Source |
Electrochimica Acta
Time of Publication: 2016
|
| Abstract | A one-dimensional, heterogeneous and dynamic model is applied to kinetically analyze impedance experiments performed on a novel NdBa0.9Co2O5.6 (NBC) MIEC cathode. The model simulates the spectra in the time domain by accounting for the gas diffusion inside the electrode pores, and for the solid state diffusion of oxygen vacancies inside the bulk of the cathodic material. A detailed kinetic scheme is applied to describe the oxygen reduction mechanism, which includes steps for adsorption and desorption, first and second electronation at the gas/electrode interface, and ion transfer at the electrode/electrolyte interface. The kinetic investigation is based on impedance spectra collected on symmetric NBC/GDC/NBC cells, at open circuit voltage, between 550 and 700°C, and 5–100% O2 molar fraction. The vacancies diffusion coefficient and the kinetic parameters of the reaction steps are fitted to describe the data. At the highest temperatures, a sensitivity analysis reveals that the rate determining step is the first electronation of the oxygen adatom, while the second electronation and the interfacial ion transport are kinetically irrelevant. Overall, the model allows to individuate the key parameters for capturing the kinetics of a MIEC cathode. |
| Keywords | EIS; perovskites; kinetics; modeling |
| Remark |
http://dx.doi.org/10.1016/j.electacta.2016.11.072 Link |
Stability of NASICON materials against water and CO2 uptake
ID=381| Authors |
|
| Source |
Solid State Ionics
Time of Publication: 2016
|
| Abstract | The stability in ambient conditions of a scandium-based NASICON material, Na3.4Sc2Si0.4P2.6O12, was investigated using impedance spectroscopy, thermogravimetry/differential scanning calorimetry (TG/DSC) and multinuclear magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR). The presence of H2O and CO2 in samples stored in ambient air could be evidenced as well as its impact on the ionic conductivity of the samples. The detected amounts of water and CO2 in the samples had no influence on the measured conductivities at room temperature, which confirmed the absence of protonic conduction in hydrated samples. A loss of conductivity during heating of hydrated samples was due to a loss of contact between the ceramic and the electrode used for the conductivity measurement. The recommendation for handling of NASICON-type materials is therefore: samples require storage in an Ar-filled glove box or in a dry environment to avoid artefacts during high temperature measurements. Nevertheless, the stability of the NASICON-type materials is confirmed since their conductivity is not affected by the moisture. |
| Keywords | Ionic conductivity; NASICON; Sodium; Scandium; ProGasMix |
| Remark |
http://dx.doi.org/10.1016/j.ssi.2016.11.006 Link |
AgI thin films prepared by laser ablation
ID=380| Authors |
|
| Source |
Solid State Ionics
Volume: 297,
Pages: 64–67 Time of Publication: 2016 |
| Abstract | High quality and uniform morphology AgI films consisting of crystal grains about 30 nm in size were obtained by the laser (XeCl) ablation method. The designed silver iodide films have crystalline structure, optical and electrical properties corresponding to stoichiometric compound films. We have demonstrated that the laser ablation method commonly used for the preparation of thin films and nanolayered structures with the defined thickness can be successfully used for the deposition of AgI superionic conductor layers as well. The films were studied by XRD, EDA, optical absorption, photoluminescence, and impedance spectroscopies. |
| Keywords | Thin films; Laser ablation; Conductivity; Optical band gap; Luminescence; Morphology; Excitons; XRD; Electron microscopy |
| Remark |
http://dx.doi.org/10.1016/j.ssi.2016.10.004 Link |
Development of Temperature - Stable Relaxor Dielectrics for High Energy Density Capacitor Applications
ID=379| Author |
|
| Source |
Time of Publication: 2016
|
| Remark |
THESIS Link |
Magnetron-Sputtered YSZ and CGO Electrolytes for SOFC
ID=378| Authors |
|
| Source |
Journal of Electronic Materials
Volume: 45,
Issue: 8,
Pages: 3921-3928 Time of Publication: 2016 |
| Solid oxide fuel cell, CGO, YSZ, bilayer electrolyte, magnetron sputtering, pulse electron-beam treatment | |
| Remark | Link |
Thermodynamic properties of the Ba0.75Sr0.25TiO3 nanopowders obtained by hydrothermal synthesis
ID=377| Authors |
|
| Source |
Journal of Alloys and Compounds
Volume: 693,
Pages: 1000–1010 Time of Publication: 2017 |
| Abstract | The paper is devoted to the investigation of the thermodynamic properties of nanostructured Ba0.75Sr0.25TiO3 perovskite material synthesized by hydrothermal method. The thermodynamic parameters obtained by a couple of measurements in both isothermal and dynamic regimes (drop calorimetry, solid-oxide electromotive force measurements, differential scanning calorimetry and thermogravimetry), allow for the investigations of the thermodynamic stability in a large temperature range from room temperature to 1273 K. The influence of the oxygen stoichiometry on the thermodynamic properties was examined using a coulometric titration technique coupled with electromotive force measurements. The results are discussed based on the strong correlation between the thermodynamic parameters and the charge compensation of the material system. X-ray powder diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM) were used for the microstructure and morphology analyses. The variation of the thermal expansion and electrical conductivity associated with the structural changes has been evidenced by thermomechanical measurements and impedance spectroscopy, respectively. Through a combined analysis of all the results, new features related to the understanding of the strong interplay between the thermodynamic properties, microstructure, thermal expansion and electrical conductivity in the hydrothermally prepared Ba0.75Sr0.25TiO3 perovskite material have been revealed. |
| Keywords | Nanostructured materials; Chemical synthesis; Thermodynamic properties; Electromotive force, EMF; Calorimetry; X-ray diffraction |
| Remark |
http://dx.doi.org/10.1016/j.jallcom.2016.09.215 Link |
Enhanced bulk conductivity of A-site divalent acceptor-doped non-stoichiometric sodium bismuth titanate
ID=376| Author |
|
| Source |
Fan Yang, Patrick Wu, Derek C. Sinclair
Time of Publication: 2016
|
| Abstract | Bismuth-deficient sodium bismuth titanate (nominally Na0.5Bi0.49TiO2.985, NB0.49T) is a good oxide-ion conductor. Here we report the influence of A-site divalent ions, M2 + = Ca2 +, Sr2 + and Ba2 +, on the electrical properties of NB0.49T. A-site divalent doping for Bi3 + enhances the bulk (grain) conductivity by ~ one order of magnitude without changing the conduction mechanism, which is attributed to an increase in the oxygen vacancy concentration based on the doping mechanism Bi3 + + ½ O2 − → M2 +. Among these three dopants, Sr2 + is the most effective in increasing the bulk conductivity due to a combination of its smaller mismatch in ion size with Bi3 +, its intermediate polarisability and lower bond strength to oxygen compared to Ca2 + and Ba2 +. Doping strategies for further improvements to bulk conductivity of NBT materials are discussed based on these results. Comparison with other oxide-ion conductors and initial stability test under reducing atmosphere show the doped non-stoichiometric NBT materials are promising for low and intermediate temperature applications. |
| Keywords | Sodium bismuth titanate; Oxide-ion conductors; Doping; Non-stoichiometry |
| Remark |
http://dx.doi.org/10.1016/j.ssi.2016.09.016 Link |
Effect of high pressures and temperatures on the structure and properties of CaCu3Ti4O12
ID=375| Authors |
|
| Source |
Inorganic Materials
Volume: 52,
Issue: 10,
Pages: 1051–1054 Time of Publication: 2016 |
| Abstract | We have prepared ceramic CaCu3Ti4O12 samples by solid-state reaction and investigated the effect of high-pressure/high-temperature processing (p = 8.0 GPa, t = 1100°C) on the structure and electrical properties of CaCu3Ti4O12. |
| Keywords | High pressures and temperatures, microstructure, dielectric properties, CaCu3Ti4O12 |
| Remark |
DOI: 10.1134/S0020168516100083 Link |
Evaluation of La0.75Sr0.25Cr0.5Mn0.5O3 protective coating on ferritic stainless steel interconnect for SOFC application
ID=374| Authors |
|
| Source |
International Journal of Hydrogen Energy
Time of Publication: 2016
|
| Abstract | Ferritic stainless steel (SS) interconnect used for intermediate temperature solid oxide fuel cell has issues associated with the growth of oxide scale on the surface and evaporation of chromium species to the cathode leading to increase in polarization resistance and hence, overall cell resistance. Protective coating is essentially applied over the SS surface to restrict the above phenomena. In the present investigation, strontium doped lanthanum manganese chromite (LSCM) of composition La0.75Sr0.25Cr0.5Mn0.5O3 has been explored as a possible protective coating material on ferritic SS interconnect surface. For this application, fine LSCM powder was synthesized by solution polymerization method. Terpineol based slurry of LSCM was formulated and used for coating on ferritic SS surface by screen printing. LSCM coated ferritic SS was exposed to moist oxygen at 800 °C for 300 h and area specific resistance (ASR) of the coating was found to be as low as 2.0 mΩ cm2 after exposure. Microstructure of LSCM coating and the chromium oxide film was investigated using SEM and EDS. The results indicate that LSCM can form an effective protective coating on ferritic stainless steel for SOFC interconnect application. |
| Keywords | Interconnect; Protective coating; LSCM; SOFC |
| Remark |
http://dx.doi.org/10.1016/j.ijhydene.2016.08.143 Link |
Solid oxide carbonate composite fuel cells: Size effect on percolation
ID=373| Authors |
|
| Source |
International Journal of Hydrogen Energy
Time of Publication: 2016
|
| Abstract | In the studies of solid oxide carbonate composite fuel cell, percolation behaviour of the two phases was investigated as a function of particle size of the oxide phase. The ratio of amount of samarium doped ceria (SDC; Sm0.2Ce0.8O) to Na2CO3 was varied to determine an optimum ionic conductivity as function of oxide particle size. The roles of both phases in the composite electrolyte were investigated. SDC particles were mixed in different amounts of Na2CO3 to obtain composites with carbonate ratios from 1 wt% to 50 wt%. Micro-structural investigations showed that Na2CO3 phase served as the matrix in the micro-structure gluing the oxide particles together. The lowest and the highest carbonate ratios caused low conductivities in the composite as in these samples the 3D connectivity of both phases were disrupted. Low conductivity at both ends of the mixture composition could be interpreted as none of the components of the composite dominated the ionic conductivity. The highest conductivity was obtained at 10 wt% Na2CO3 amount in the composite electrolyte when nano-sized SDC (5–10 nm) oxide powders were used. Two different particle sizes of SDC powders were used to show that the optimum phase ratio, i.e. percolation of both phases, is function of particle size as well. The conductivity in the composite showed percolation behaviour with respect to the two constituent phases. |
| Keywords | Composite electrolyte; SOFC; Interface; Percolation; Carbonate; Impedance |
| Remark |
http://dx.doi.org/10.1016/j.ijhydene.2016.07.208, in press Link |
Insights into the enhancement of oxygen mass transport properties of strontium-doped lanthanum manganite interface-dominated thin films
ID=372| Authors |
|
| Source |
Solid State Ionics
Time of Publication: 2016
|
| Abstract | Strontium-doped lanthanum manganite thin films were deposited by pulsed laser deposition on yttria-stabilized zirconia single crystals for a comprehensive electrochemical characterization of the material acting as a cathode. A physically-meaningful electrical model was employed to fit the electrochemical impedance spectroscopy results in order to extract the main oxygen mass transport parameters as a function of the temperature and oxygen partial pressure. The oxygen diffusion and surface exchange coefficients extracted from the analysis showed several orders of magnitude of enhancement with respect to the bulk values reported in the literature and an unexpectedly low dependence with the oxygen partial pressure. Different observations were combined to propose a mechanism for the enhanced incorporation of oxygen in interface-dominated thin films mainly based on the high concentration of oxygen vacancies expected in the grain boundaries. |
| Remark |
http://dx.doi.org/10.1016/j.ssi.2016.08.009 Link |
Formation of solid solutions in the CdSe–PbSe system under the action of high pressures and temperatures
ID=371| Authors |
|
| Source |
Russian Journal of Inorganic Chemistry
Volume: 61,
Issue: 8,
Pages: 1013–1018 Time of Publication: 2016 |
| Abstract | A method was proposed for producing solid solutions in the CdSe–PbSe systems, which is based on heat and high pressure treatment. X-ray powder diffraction analysis showed the formation of substitutional solid solutions CdxPb1–xSe with the NaCl structure, which contained 20, 40, 60, and 80 mol % cadmium selenide. The solid solutions were characterized by scanning electron microscopy, impedance spectroscopy, gas pycnometry, and Raman spectroscopy. |
| Remark |
DOI: 10.1134/S0036023616080052 Link |
Comparison of characteristics of solid oxide fuel cells with YSZ and CGO film solid electrolytes formed using magnetron sputtering technique
ID=370| Authors |
|
| Source |
Russian Journal of Electrochemistry
Volume: 52,
Issue: 7,
Pages: 662–668 Time of Publication: 2016 |
| Abstract | The work describes the methods of manufacturing single cells of solid oxide fuel cell (SOFC) with thin–film YSZ and CGO electrolytes and also with the bilayer YSZ/CGO electrolyte. Formation of YSZ and CGO films on the supporting NiO–YSZ anode of SOFC was carried out using the combined electron–ionic–plasma deposition technique. The microstructure and phase composition of the formed coatings are studied and also comparative analysis of electrochemical characteristics of single fuel cells with different electrolytes is performed. It is shown that the maximum power density of 1.35 W/cm2 at the temperature of 800°C is obtained for the cell with bilayer YSZ/CGO electrolyte. However, the highest performance at lower working temperatures (650–700°C) is characteristic for the fuel cell with single–layer CGO electrolyte; its power density is 600–650 mW/cm2. |
| Keywords | Solid oxide fuel cell, CGO, YSZ, bilayer electrolyte, magnetron sputtering, pulsed electron–beam treatment |
| Remark |
DOI: 10.1134/S102319351607017X Link |
Nanolayered solid electrolyte (GeSe2)30(Sb2Se3)30(AgI)40/AgI: A new hypothesis for the conductivity mechanism in layered AgI
ID=369| Authors |
|
| Source |
Solid State Ionics
Volume: 294,
Pages: 82–89 Time of Publication: 2016 |
| Abstract | Using the laser ablation method, films comprised of alternating layers of AgI and (GeSe2)30(Sb2Se3)30(AgI)40 glass were obtained. Individual layer thickness amounts to 10 ÷ 15 nm, and the total number of layers is about 100. X-ray diffraction (XRD) and film conductivity measurements were carried out during several cycles of heating up to 200 °C and cooling to room temperature. It was established that after three cycles of thermal processing specific lateral conductivity of the film is equal to 0.3 S cm− 1 and conductivity activation energy is equal to 0.07 eV at room temperature. Attempts to explain such a high conductivity value based on XRD results did not yield satisfactory results. However, our first-principle calculations within the density functional theory (DFT) showed that in the free layer composed of four AgI planes a rearrangement occurs, resulting in formation of the stable structure of two silver planes on the inside and two iodine planes on the outside (I–Ag–Ag–I). Rearrangement of similar stack of eight or twelve atomic planes results in formation of two or three I–Ag–Ag–I layers loosely bound to each other, accordingly. This suggests that increase in specific conductivity growth of multilayer film as a consequence of cyclic heating and cooling may be connected with AgI stratification on its boundary with chalcogenide glass and following stabilization of layered phases mentioned above. The existence of an empty space between the layers that is constrained by iodine ion planes should facilitate silver ion diffusion along the layers. |
| Keywords | Glass-composite; Laser-ablation method; Ionic conductivity; AgI polymorphs; DFT calculations |
| Remark |
doi:10.1016/j.ssi.2016.07.004 Link |
Tin–Zinc oxide composite ceramics for selective CO sensing
ID=368| Authors |
|
| Source |
Ceramics International
Time of Publication: 2016
|
| Abstract | Composite metal oxide gas sensors were intensely studied over the past years having superior performance over their individual oxide components in detecting hazardous gases. A series of pellets with variable amounts of SnO2 (0–50 mol%) was prepared using wet homogenization of the component oxides leading to the composite tin-zinc ceramic system formation. The annealing temperature was set to 1100 °C. The samples containing 2.5 mol% SnO2 and 50 mol% SnO2 were annealed also at 1300 °C, in order to observe/to investigate the influence of the sintering behaviour on CO detection. The sensor materials were morphologically characterized by scanning electron microscopy (SEM). The increase in the SnO2 amount in the composite ceramic system leads to higher sample porosity and an improved sensitivity to CO. It was found that SnO2 (50 mol%) - ZnO (50 mol%) sample exhibits excellent sensing response, at a working temperature of 500 °C, for 5 ppm of CO, with a fast response time of approximately 60 s and an average recovery time of 15 min. Sensor selectivity was tested using cross-response to CO, methane and propane. The results indicated that the SnO2 (50 mol%)-ZnO (50 mol%) ceramic compound may be used for selective CO sensing applications. |
| Keywords | SnO2–ZnO; Composites; Sensors; Selective detection of CO |
| Remark |
doi:10.1016/j.ceramint.2016.07.102 Link |
Synthesis and electrical properties of new perovskite-like AMn3V4O12 (A = Ca, Ce, and Sm) compounds
ID=367| Authors |
|
| Source |
Bulletin of the Russian Academy of Sciences: Physics
Volume: 80,
Issue: 6,
Pages: 620–623 Time of Publication: 2016 |
| Abstract | AMn3V4O12 (A = Ca, Ce, and Sm) compounds with a perovskite structure are synthesized at high pressures and temperatures. The crystalline structure of these compounds (space group Im3¯Z = 2) is determined via X-ray analysis. If ions in the A sublattice are changed in the order Ca2+–Sm3+–Ce3+, the valence is redistributed from Ca2+Mn32+V44+O12 to Sm3+Mn32+V43.75+O12, and to Ce3+Mn32+V43.75+O12. The temperature dependences of the electrical resistivity are studied. |
| Remark | Link |
Tailoring transport properties through nonstoichiometry in BaTiO3–BiScO3 and SrTiO3–Bi(Zn1/2Ti1/2)O3 for capacitor applications
ID=366| Authors |
|
| Source |
Journal of Materials Science
Volume: 51,
Issue: 20,
Pages: 9404–9414 Time of Publication: 2016 |
| Abstract | The ceramic perovskite solid solutions BaTiO3–BiScO3 (BT–BS) and SrTiO3–Bi(Zn1/2Ti1/2)O3 (ST–BZT) are promising candidates for high-temperature and high-energy density dielectric applications. A-site cation nonstoichiometry was introduced in these two ceramic systems to investigate their effects on the dielectric and transport properties using temperature- and oxygen partial pressure-dependent AC impedance spectroscopy. For p-type BT–BS ceramics, the addition of excess Bi led to effective donor doping along with a significant improvement in insulation properties. A similar effect was observed on introducing Ba vacancies onto the A-sublattice. However, Bi deficiency registered an opposite effect with effective acceptor doping and a deterioration in the bulk resistivity values. For n-type intrinsic ST–BZT ceramics, the addition of excess Sr onto the A-sublattice resulted in a decrease in resistivity values, as expected. Introduction of Sr vacancies or addition of excess Bi on A-site did not appear to affect the insulation properties in air. These results indicate that minor levels of nonstoichiometry can have an important impact on the material properties, and furthermore it demonstrates the difficulties encountered in trying to establish a general model for the defect chemistry of Bi-containing perovskite systems. |
| Remark |
DOI: 10.1007/s10853-016-0186-z Link |
Leaching effect in gadolinia-doped ceria aqueous suspensions for ceramic processes
ID=365| Authors |
|
| Source |
Journal of Power Sources
Volume: 326,
Issue: 15,
Pages: 70–77 Time of Publication: 2016 |
| Abstract | Gadolinium doped ceria (CGO) is a commonly used electrolytic material for Solid Oxide Fuel Cells (SOFCs) and for this reason different shaping methods for its deposition are reported in literature. Most of these processes are based on the use of organic-based CGO suspensions, but water-based processes are acquiring increasingly interest for their economical and environmental friendly properties. In this paper we reported how the components of water-based suspension and some unexpected process parameters can deeply affect the functional properties of the final powder. In particular, we observed that CGO powders are strongly affected by ionic leaching induced by furoic acid used as dispersant: the extent of this leaching was related to the dispersant concentration and suspension’s ball-milling-time; the phenomenon was confirmed by ICP-AES analyses on suspensions surnatant. Most importantly, ionic leaching affected the electrical properties of CGO: leached powder showed a higher ionic conductivity as a consequence of a partial removal of Gd ions at the grain boundaries. This work is therefore pointing out that when considering water-based suspensions, it is extremely important to carefully consider all the process parameters, including the organic components of the ceramic suspension, as these could lead to unexpected effects on the properties of the powder, affecting the performance of the final shaped material. |
| Keywords | Gadolinium doped ceria; Water-based suspensions; Furoic acid; Ionic leaching; Electrical conductivity |
| Remark |
doi:10.1016/j.jpowsour.2016.06.069 Link |
Structural, textural, surface chemistry and sensing properties of mesoporous Pr, Zn modified SnO2–TiO2 powder composites
ID=364| Authors |
|
| Source |
Ceramics International
Volume: 43,
Issue: 13,
Pages: 14992–14998 Time of Publication: 2016 |
| Abstract | Mesoporous Zn and Pr modified SnO2-TiO2 mixed powders (Sn:Ti:Zn:Pr contents 60:20:15:5) have been prepared by a modified sol–gel method involving Tripropylamine (TPA) as chelating agent, TritonX100 as template and Polyvinylpyrrolidone as dispersant and stabilizer, respectively. The obtained gels have been dried at different temperatures and calcined in air at 600 and 800 °C, respectively. Phase identification of the synthesized samples and their evolution with the calcination temperature has been performed by X-ray diffraction. N2 adsorption/desorption isotherms were found to be characteristic for mesoporous materials, showing relatively low values for the specific surface area (15–32 m2 g−1) and nanometric sized pores. In case of the sample calcined at 800 °C, a bimodal pore size distribution can be observed, with maxima at 20 and 60 nm. SEM results demonstrate a porous nanocrystalline morphology stable up to 800 °C. The surface chemistry investigated by XPS reveals the presence of the elements on the surface as well as the oxidation states for the detected elements. At 800 °C a diffusion process of Sn from surface to the subsurface/bulk region accompanied by a segregation of Ti and Zn to the surface is noticed, while Pr content is unchanged. The sensing properties of the prepared powders for CO detection have been tested in the range of 250–2000 ppm and working temperatures of 227–477 °C. |
| Keywords | SnO2; TiO2; Sol–gel; Mesoporous materials; CO detection |
| Remark |
doi:10.1016/j.ceramint.2016.06.146 Link |
New promising NASICON material as solid electrolyte for sodium-ion batteries: Correlation between composition, crystal structure and ionic conductivity of Na3 + xSc2SixP3 − xO12
ID=363| Authors |
|
| Source |
Solid State Ionics
Volume: 293,
Pages: 18–26 Time of Publication: 2016 |
| Abstract | In the search for novel sodium-ion conductors to be used in batteries for grid application, the thoroughly studied class of NASICON materials is of great interest due to compositional diversity and high ionic conductivity. The solid solution Na3 + xSc2(SiO4)x(PO4)3 − x with 0.05 ≤ x ≤ 0.8 was investigated for the first time. The various compositions were synthesized by solid state reaction and their crystallographic and electrical properties were measured. As a result, one of the best sodium-conductive NASICON materials to date was obtained for x = 0.4 (σNa,Total = 6.9 × 10− 4 S cm− 1 at 25 °C). Furthermore, the importance of the sodium concentration and size of lattice parameters on the ionic conductivity were investigated. The bulk ionic conductivity was correlated with the structural parameters along the conduction pathway of the sodium ions and confirm the key influence of the interatomic Na–O distances on sodium ion transport. |
| Keywords | Ionic conductivity; NASICON; Sodium; Scandium; Solid electrolyte; Battery |
| Remark |
doi:10.1016/j.ssi.2016.06.005 Link |
Effect of Nb Doping on Hydration and Conductivity of La27W5O55.5−δ
ID=362| Authors |
|
| Source |
J. Am. Ceram. Soc.
Time of Publication: 2016
|
| Abstract | Hydration properties and electrical characteristics of the high-temperature proton conductor La27(W0.85Nb0.15)5O55.5−δ are investigated by means of thermogravimetry, impedance spectroscopy, and the electromotive force (EMF) method as a function of temperature, water vapor, and oxygen partial pressures, as well as isotope exchange measurements in order to elucidate the mechanism and thermodynamics of protons formation and transport. The highest proton conductivity, 1.3 × 10-3 S/cm, is achieved at 700°C in wet O2. Proton self-diffusion coefficients are estimated from thermogravimetric measurements of hydration and conductivity data. Comparison of the conductivity characteristics between nominally pure and Nb-substituted materials reveals that the ionic conductivity increases and the activation energy decreases with Nb doping. These differences are discussed to reflect changes in the structure promoting ionic transport rather than changing the concentration of defects to any large extent. |
| Keywords | Lanthanum tungstate; proton concentration; proton conductivity; H/D isotope effect |
| Remark |
doi:10.1111/jace.14346 Link |
Synthesis, characterization and performance of robust poison-resistant ultrathin film yttria stabilized zirconia – nickel anodes for application in solid electrolyte fuel cells
ID=361| Authors |
|
| Source |
Journal of Power Sources
Volume: 324,
Pages: 679–686 Time of Publication: 2016 |
| Abstract | We report on the synthesis of undoped ∼5 μm YSZ-Ni porous thin films prepared by reactive pulsed DC magnetron sputtering at an oblique angle of incidence. Pre-calcination of the amorphous unmodified precursor layers followed by reduction produces a film consisting of uniformly distributed tilted columnar aggregates having extensive three-phase boundaries and favorable gas diffusion characteristics. Similarly prepared films doped with 1.2 at.% Au are also porous and contain highly dispersed gold present as Ni-Au alloy particles whose surfaces are strongly enriched with Au. With hydrogen as fuel, the performance of the undoped thin film anodes is comparable to that of 10–20 times thicker typical commercial anodes. With a 1:1 steam/carbon feed, the un-doped anode cell current rapidly falls to zero after 60 h. In striking contrast, the initial performance of the Au-doped anode is much higher and remains unaffected after 170 h. Under deliberately harsh conditions the performance of the Au-doped anodes decreases progressively, almost certainly due to carbon deposition. Even so, the cell maintains some activity after 3 days operation in dramatic contrast with the un-doped anode, which stops working after only three hours of use. The implications and possible practical application of these findings are discussed. |
| Keywords | Magnetron sputtering; Oblique angle deposition; Thin film anodes; Carbon-tolerant; SOFC |
| Remark |
doi:10.1016/j.jpowsour.2016.05.124 Link |
Electrical characterization of amorphous LiAlO2 thin films deposited by atomic layer deposition
ID=360| Authors |
|
| Source |
RSC Advances
Volume: 6,
Issue: 65,
Pages: 60479-60486 Time of Publication: 2016 |
| Abstract | LiAlO2 thin films deposited by atomic layer deposition (ALD) have a potential application as an electrolyte in three-dimensional (3D) all-solid-state microbatteries. In this study, Li-ion conductivity of such films is investigated by both in-plane and cross-plane methods. LiAlO2 thin films with a Li composition of [Li]/([Li] + [Al]) = 0.46 and an amorphous structure were grown by ALD with thicknesses of 90, 160 and 235 nm on different substrates. The electrical characterization was conducted by impedance spectroscopy using inert electrodes over a temperature range of 25–200 °C in an inert atmosphere. In-plane conductivities were obtained from films on insulating sapphire substrates, whereas cross-plane conductivities were measured from films on conducting titanium substrates. For the first time, comparison of the in-plane and cross-plane conductivities in these ALD LiAlO2 films has been achieved. More comparable results are obtained using a cross-plane method, whereas in-plane conductivity measurements demonstrate a considerable thickness-dependence with thinner film thickness. The room-temperature conductivity of the LiAlO2 films has been determined to be in the order of 10−10 S cm−1 with an activation energy of ca. 0.8 eV. |
| Remark |
DOI: 10.1039/C6RA03137D Link |
Thin film YSZ-based limiting current-type oxygen and humidity sensor on thermally oxidized silicon substrates
ID=359| Author |
|
| Source |
Sensors and Actuators B: Chemical
Volume: 236,
Pages: 499–505 Time of Publication: 2016 |
| Abstract | In this paper, we propose a thin film yttria-stabilized-zirconia (YSZ)-based limiting current-type oxygen and humidity sensor. These sensors were fabricated from layers of thin films on thermally oxidized silicon substrates, with the intention of installing such sensors onto microheaters. Sputtered porous Pt cathode are situated beneath the YSZ films, and are designed to provide a gas diffusion layer as well as function as electrodes. The porous Pt layer exhibits good performance as a gas diffusion layer because of its small pore size. Optimized YSZ sputtering growth conditions result in in-plane densification without the presence of cracks. The temperature dependence of the oxygen sensor’s level of limiting current was T −0.5. This result was attributed to the shrinkage of the extremely small pores in the gas diffusion layer. Between 450 and 550 °C, following the application of a voltage of 1.1 V, the time response measurements show a rapid response of a few seconds. The oxygen concentration and water vapor pressure correspond to the level of the limiting current at 1.1 V and 1.8 V, respectively. |
| Keywords | Yttria-stabilized-zirconia; Limiting current; Oxygen sensor; Humidity sensor; Thin film; Silicon substrate |
| Remark |
doi:10.1016/j.snb.2016.06.025 Link |
Conduction Mechanisms in BaTiO3–Bi(Zn1/2Ti1/2)O3 Ceramics
ID=358| Authors |
|
| Source |
J. Am. Ceram. Soc.
Time of Publication: 2016
|
| Abstract | Polycrystalline BaTiO3–Bi(Zn1/2Ti1/2)O3 (BT–BZT) ceramics have superior dielectric properties for high-temperature and high-energy density applications as compared to the existing materials. While it has been shown that the addition of BZT to BT leads to an improvement in resistivity by two orders of magnitude, in this study impedance spectroscopy is used to demonstrate a novel change in conduction mechanism. While nominally undoped BT exhibits extrinsic-like p-type conduction, it is reported that BT–BZT ceramics exhibit intrinsic n-type conduction using atmosphere-dependent conductivity measurements. Annealing studies and Seebeck measurements were performed and confirmed this result. For BT, resistivity values were higher for samples annealed in nitrogen as compared to oxygen, whereas the opposite responses were observed for BZT-containing solid solutions. This suggests a fundamental change in the defect equilibrium conditions upon the addition of BZT to the solid solution that lowered the carrier concentration and changed the sign of the majority charge carrier. This is then also linked to the observed improvement in resistivity in BT–BZT ceramics as compared to undoped BT. |
| Remark |
doi:10.1111/jace.14313 Link |
Effect of Nd-deficiency on electrochemical properties of NdBaCo2O6−δ cathode for intermediate-temperature solid oxide fuel cells
ID=357| Authors |
|
| Source |
International Journal of Hydrogen Energy
Volume: 41,
Issue: 24,
Pages: 10228–10238 Time of Publication: 2016 |
| Abstract | Nd1−xBaCo2O6−δ (N1−xBCO) is evaluated as cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The effects of Nd-deficiency on the crystal structure, thermal expansion behavior, electrical conductivity and electrochemical performance are studied. N1−xBCO oxides crystallize in the orthorhombic symmetry with Pmmm space group. A good chemical compatibility between N1−xBCO and CGO electrolyte is found at 1100 °C in air. Introducing Nd-deficiency promotes the formation of oxygen vacancy, and significantly improves the electrochemical performance of N1−xBCO cathodes. The lowest area specific resistance (ASR) value of 0.043 Ω cm2 is obtained on the N0.96BCO cathode at 700 °C in air. The rate limiting step for electrochemical oxygen reduction reaction (ORR) is charge transfer process at the interface. The power output of the electrolyte supported cell Ni-CGO/CGO/N0.96BCO reaches 0.6 W cm−2 at 700 °C. |
| Keywords | Solid oxide fuel cell; Double perovskite; Nd-deficiency; Cathode; Electrode reaction |
| Remark |
doi:10.1016/j.ijhydene.2016.04.248 Link |
Controlling mixed conductivity in Na1/2Bi1/2TiO3 using A-site non-stoichiometry and Nb-donor doping
ID=356| Authors |
|
| Source |
J. Mater. Chem. C
Volume: 4,
Pages: 5779-5786 Time of Publication: 2016 |
| Abstract | Precise control of electronic and/or ionic conductivity in electroceramics is crucial to achieve the desired functional properties as well as to improve manufacturing practices. We recently reported the conventional piezoelectric material Na1/2Bi1/2TiO3 (NBT) can be tuned into a novel oxide-ion conductor with an oxide-ion transport number (tion) > 0.9 by creating bismuth and oxygen vacancies. A small Bi-excess in the nominal starting composition (Na0.50Bi0.50+xTiO3+3x/2, x = 0.01) or Nb-donor doping (Na0.50Bi0.50Ti1−yNbyO3+y/2, 0.005 ≤ y ≤ 0.030) can reduce significantly the electrical conductivity to create dielectric behaviour by filling oxygen vacancies and suppressing oxide ion conduction (tion ≤ 0.10). Here we show a further increase in the starting Bi-excess content (0.02 ≤ x ≤ 0.10) reintroduces significant levels of oxide-ion conductivity and increases tion ∼ 0.4–0.6 to create mixed ionic/electronic behaviour. The switch from insulating to mixed conducting behaviour for x > 0.01 is linked to the presence of Bi-rich secondary phases and we discuss possible explanations for this effect. Mixed conducting behaviour with tion ∼ 0.5–0.6 can also be achieved with lower levels of Nb-doping (y ∼ 0.003) due to incomplete filling of oxygen vacancies without the presence of secondary phases. NBT can now be compositionally tailored to exhibit three types of electrical behaviour; Type I (oxide-ion conductor); Type II (mixed ionic-electronic conductor); Type III (insulator) and these results reveal an approach to fine-tune tion in NBT from near unity to zero. In addition to developing new oxide-ion and now mixed ionic/electronic NBT-based conductors, this flexibility in control of oxygen vacancies allows fine-tuning of both the dielectric/piezoelectric properties and design manufacturing practices for NBT-based multilayer piezoelectric devices. |
| Remark |
DOI: 10.1039/C6TC01719C Link |
Influence of cathode functional layer composition on electrochemical performance of solid oxide fuel cells
ID=355| Authors |
|
| Source |
Journal of Solid State Electrochemistry
Time of Publication: 2016
|
| Abstract | In this work, anode-supported solid oxide fuel cells (SOFC) were tested with a yttria-stabilized zirconia (YSZ) (8 mol% Y2O3-ZrO2)/gadolinium-doped ceria (GDC) (Ce0.9Gd 0.1O1.95) bilayer electrolyte and two lanthanum strontium cobalt ferrite (LSCF) composition as functional cathode layer: La0.6Sr0.4Co0.8Fe0.2O3-δ (LSCF 1) and La0.60Sr0.40Co0.2Fe0.8O3-δ (LSCF 2). The functional cathode layers were made of 50 % (w/w) LSCF and 50 % (w/w) GDC. Microstructural characterization was performed by scanning electron microscopy and X-ray diffraction. Electrochemical impedance spectroscopy (EIS) and power measurements were performed under oxygen and hydrogen atmospheres. The microscopy studies showed that the LSCF 2 functional layer is more uniform and adherent to the electrolyte and the cathode collector than the LSCF 1 functional layer, which has cracks, chips, and lower adhesion. The use of the LSCF 2 layer allowed an approximately 25-fold reduction in ohmic resistance (0.06 Ω cm−2) compared with the LSCF 1 layer (1.5 Ω cm−2). The power measurements showed a considerable increase in the power cell using LSCF 2 (approximately 420 mW cm−2) compared with the power cell using LSCF 1 (approximately 180 mW cm−2). |
| Keywords | SOFC, LSCF, Interface, Electrochemical performance, Cathode, Functional layer |
| Remark |
First Online: 20 May 2016. DOI: 10.1007/s10008-016-3241-4 Link |
Mechanical degradation under hydrogen of yttrium doped barium zirconate electrolyte material prepared with NiO additive
ID=354| Authors |
|
| Source |
Journal of Power Sources
Volume: 321,
Pages: 226–232 Time of Publication: 2016 |
| Abstract | Recently, a novel process was presented to fabricate dense yttrium-doped barium zirconate electrolytes with high proton conductivity. This process was based on the use of a NiO additive during reactive sintering. We show here that materials made from this process present a fast degradation of mechanical properties when put in hydrogen-rich conditions, while material made from conventional sintering without NiO aid remains intact in the same conditions. The fast degradation of samples made from reactive sintering, leading to sample failure under highly compressive conditions, is due to the reduction of NiO nanoparticles at grain boundaries as shown from structural and chemical analyses using Transmission Electron Microscopy. By the present study, we alert about the potential risk of cell failure due to this mechanical degradation. |
| Keywords | PCFCs; Mechanical properties; BZY; Solid state reactive sintering |
| Remark |
doi:10.1016/j.jpowsour.2016.05.001 Link |
Electrochemical Property Assessment of Pr2CuO4 Submicrofiber Cathode for Intermediate-Temperature Solid Oxide Fuel Cells
ID=353| Authors |
|
| Source |
Journal of Electrochemical Energy Conversion and Storage
Volume: 13,
Issue: 1,
Pages: 011006 Time of Publication: 2016 |
| Abstract | The Pr2CuO4 (PCO) submicrofiber precursors are prepared by electrospinning technique and the thermo-decomposition procedures are characterized by thermal gravity (TG), X-ray diffraction (XRD), Fourier transform infrared spectoscopy (FT-IR), and scanning electron microscopy (SEM), respectively. The fibrous PCO material was formed by sintering the precursors at 900 °C for 5 hrs. The highly porous PCO submicrofiber cathode forms good contact with the Ce0.9Gd0.1O1.95 (CGO) electrolyte after heat-treated at 900 °C for 2 hrs. The performance of PCO submicrofiber cathode is comparably studied with the powder counterpart at various temperatures. The porous microstructure of the submicrofiber cathode effectively increases the three-phase boundary (TPB), which promotes the surface oxygen diffusion and/or adsorption process on the cathode. The PCO submicrofiber cathode exhibits an area specific resistance (ASR) of 0.38 Ω cm2 at 700 °C in air, which is 30% less than the PCO powder cathode. The charge transfer process is the rate limiting step of the oxygen reduction reaction (ORR) on the submicrofiber cathode. The maximum power densities of the electrolyte-support single cell PCO|CGO|NiO-CGO reach 149 and 74.5 mW cm−2 at 800 and 700 °C, respectively. The preliminary results indicate that the PCO submicrofiber can be considered as potential cathode for intermediate temperature solid fuel cells (IT-SOFCs). |
| Remark |
doi: 10.1115/1.4033526 Link |
Direct conversion of methane to aromatics in a catalytic co-ionic membrane reactor
ID=352| Authors |
|
| Source |
Science
Volume: 353,
Issue: 6299,
Pages: 563-566 Publisher: American Association for the Advancement of Science (AAAS), ISBN: Print ISSN:0036-8075 Online ISSN:1095-9203, Time of Publication: 2016-08 |
| Abstract | Nonoxidative methane dehydroaromatization (MDA: 6CH4 ↔ C6H6 + 9H2) using shape-selective Mo/zeolite catalysts is a key technology for exploitation of stranded natural gas reserves by direct conversion into transportable liquids. However, this reaction faces two major issues: The one-pass conversion is limited by thermodynamics, and the catalyst deactivates quickly through kinetically favored formation of coke. We show that integration of an electrochemical BaZrO3-based membrane exhibiting both proton and oxide ion conductivity into an MDA reactor gives rise to high aromatic yields and improved catalyst stability. These effects originate from the simultaneous extraction of hydrogen and distributed injection of oxide ions along the reactor length. Further, we demonstrate that the electrochemical co-ionic membrane reactor enables high carbon efficiencies (up to 80%) that improve the technoeconomic process viability. Methane gas is expensive to ship. It is usually converted into carbon monoxide and hydrogen and then liquefied. This is economically feasible only on very large scales. Hence, methane produced in small amounts at remote locations is either burned or not extracted. A promising alternative is conversion to benzene and hydrogen with molybdenumzeolite catalysts. Unfortunately, these catalysts deactivate because of carbon buildup; plus, hydrogen has to be removed to drive the reaction forward. Morejudo et al. address both of these problems with a solid-state BaZrO3 membrane reactor that electrochemically removes hydrogen and supplies oxygen to suppress carbon buildup. |
| Keywords | CMR, MDA, catalytic membrane reactor, ZSM-5, MCM-22, FBR, FBR-PolyM, Pd-CMR, Co-ionic CMR, FT, ProboStat CMR base unit (NORECS) |
| Remark |
http://science.sciencemag.org/highwire/filestream/682540/field_highwire_adjunct_files/0/Morejudo.SM.pdf BaZrO3 BaZrO3 Link |
Magnetron-Sputtered YSZ and CGO Electrolytes for SOFC
ID=351| Authors |
|
| Source |
Journal of Electronic Materials
Time of Publication: 2016
|
| Abstract | Reactive magnetron sputtering has been used for deposition of yttria-stabilized ZrO2 (YSZ) and gadolinium-doped CeO2 (CGO) layers on NiO-YSZ commercial anodes for solid oxide fuel cells. To increase the deposition rate and improve the quality of the sputtered thin oxide films, asymmetric bipolar pulse magnetron sputtering was applied. Three types of anode-supported cells, with single-layer YSZ or CGO and YSZ/CGO bilayer electrolyte, were prepared and investigated. Optimal thickness of oxide layers was determined experimentally. Based on the electrochemical characteristics of the cells, it is shown that, at lower operating temperatures of 650°C to 700°C, the cells with single-layer CGO electrolyte are most effective. The power density of these fuel cells exceeds that of the cell based on YSZ single-layer electrolyte at the same temperature. Power densities of 650 mW cm−2 and 500 mW cm−2 at 700°C were demonstrated by cells with single-layer YSZ and CGO electrolyte, respectively. Significantly enhanced maximum power density was achieved in a bilayer-electrolyte single cell, as compared with cells with a single electrolyte layer. Maximum power density of 1.25 W cm−2 at 800°C and 1 W cm−2 at 750°C under voltage of 0.7 V were achieved for the YSZ/CGO bilayer electrolyte cell with YSZ and CGO thickness of about 4 μm and 1.5 μm, respectively. This signifies that the YSZ thin film serves as a blocking layer to prevent electrical current leakage in the CGO layer, leading to the overall enhanced performance. This performance is comparable to the state of the art for cells based on YSZ/CGO bilayer electrolyte. |
| Keywords | Solid oxide fuel cell CGO YSZ bilayer electrolyte magnetron sputtering pulse electron-beam treatment |
| Remark | Link |
Characteristics of Cu and Mo-doped Ca3Co4O9−δ cathode materials for use in solid oxide fuel cells
ID=350| Authors |
|
| Source |
Ceramics International
Time of Publication: 2016
|
| Abstract | In this study, Cu and Mo ions were doped in Ca3Co4O9−δ to improve the electrical conductivity and electrochemical behavior of Ca3Co4O9−δ ceramic and the performance of a solid oxide fuel cell (SOFC) single cell based on NiO-SDC/SDC/doped Ca3Co4O9−δ-SDC were examined. Cu substitution in the monoclinic Ca3Co4O9−δ ceramic effectively enhanced the densification, slightly increased the grain size, and triggered the formation of some Ca3Co2O6; however, no second phase was found in porous Mo-doped Ca3Co4O9−δ ceramics even when the sintering temperature reached 1050 °C. Substitution of Cu ions caused slight increase in the Co3+ and Co4+ contents and decrease in the Co2+ content; however, doping with Mo ions showed the opposite trend. Doping the Ca3Co4O9−δ ceramic with a small amount of Cu or Mo increased its electrical conductivity. The maximum electrical conductivity measured was 218.8 S cm−1 for the Ca3Co3.9Cu0.1O9−δ ceramic at 800 °C. The Ca3Co3.9Cu0.1O9−δ ceramic with a coefficient of thermal expansion coefficient of 12.1×10−6 K−1 was chosen as the cathode to build SOFC single cells consisting of a 20 μm SDC electrolyte layer. Without optimizing the microstructure of the cathode or hermetically sealing the cell against the gas, a power density of 0.367 Wcm−2 at 750 °C was achieved, demonstrating that Cu-doped Ca3Co4O9−δ can be used as a potential cathode material for IT-SOFCs. |
| Keywords | Solid oxide fuel cell; Cathode; Impedance; Cell performance |
| Remark |
In Press, doi:10.1016/j.ceramint.2016.04.037 Link |
Synthesis and characterization of robust, mesoporous electrodes for solid oxide fuel cells
ID=349| Authors |
|
| Source |
Journal of Materials Chemistry A
Time of Publication: 2016
|
| Abstract | The use of mesoporous electrodes in solid oxide cells would lead to a significant enhancement of the performance due to their high surface area and large number of active sites for electrochemical reactions. However, their application in real devices is still hindered by the potential instability of the mesostructure and morphology at high temperatures required for device fabrication and under severe conditions for high-current, long-term operation. Here we report our findings on the preparation and characterization of mesoporous electrodes based on ceria infiltrated with catalysts: an anode consisting of a Ce0.8Sm0.2O1.9 (SDC) scaffold infiltrated with Ni and a cathode consisting of an SDC scaffold infiltrated with Sm0.5Sr0.5CoO3−δ (SSC). In particular, a doped-zirconia electrolyte supported cell with a mesoporous Ni–SDC anode and a mesoporous SSC–SDC cathode demonstrates an excellent peak power density of 565 mW cm−2 at 750 °C (using humidified hydrogen as the fuel). More importantly, both mesoporous electrodes display remarkable stability, yielding a combined electrode virtual non-degradation for the last 500 hours of the test at a constant current density of 635 mA cm−2 at 750 °C, demonstrating the potential of these mesoporous materials as robust electrodes for solid oxide fuel cells or other high-temperature electrochemical energy storage and conversion devices. |
| Remark |
DOI: 10.1039/C6TA00321D Link |
Fluorite-like compounds with high anionic conductivity in Nd2MoO6 – Bi2O3 system
ID=348| Authors |
|
| Source |
International Journal of Hydrogen Energy
Time of Publication: 2016
|
| Abstract | A wide range of (Bi2O3)x(Nd2O3)(1−x)/2(MoO3)(1−x)/2 solid solutions with the structure of the anion-conducting bismuth oxide was found in the Bi2O3–Nd2MoO6 join of ternary Bi2O3–MoO3–Nd2O3 system at 0.5 ≤ x ≤ 1. In said concentration range the compounds with large (0.92 ≤ x ≤ 0.98) and small (0.5 ≤ x < 0.6) bismuth content are tetragonal at room temperature. In the intermediate concentration range (0.67 ≤ x ≤ 0.9) cubic δ-Bi2O3 structure is stabilized at room temperature. It is shown that two tetragonal phases observed at different bismuth concentrations differ from each other in their polymorphism and behavior of the unit cell parameters. All the obtained compounds show high conductivity that reaches 0.1 S/cm (for a cubic sample with x = 0.8 at 800 °C). |
| Keywords | Bi2O3; Nd2O3; MoO3; Polymorphism; Oxygen conductivity |
| Remark |
In press, doi:10.1016/j.ijhydene.2016.03.046 Link |
Structural study and proton conductivity in BaCe0.7Zr0.25−xYxZn0.05O3 (x = 0.05, 0.1, 0.15, 0.2 & 0.25)
ID=347| Authors |
|
| Source |
International Journal of Hydrogen Energy
Time of Publication: 2016
|
| Abstract | Solid oxide fuel cell (SOFC) has been considered to generate power represented by conductivity. Zinc doped Barium Cerium Zirconium Yttrium oxide (BCZYZn) has been found to offer high protonic conductivity and high stability as being electrolyte for proton-conducting SOFCs. In this study, we report a new series of proton conducting materials, BaCe0.7Zr0.25−xYxZn0.05O3 (x = 0.05, 0.1, 0.15, 0.2 and 0.25). The materials were synthesized by solid state reaction route and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermal expansion, particle size and impedance spectroscopy (IS). Rietveld analysis of the XRD data reveal a cubic perovskite structure with Pm-3m space group up to composition x = 0.15. For x = 0.15 and 0.20, the materials have structural phase change to orthorhombic in the Pbnm space group. Scanning electron microscopy images show high density materials. Thermal expansion measurements show that the thermal expansion coefficient is in the range 10.0–11.0 × 10−6/°C. Impedance spectroscopy shows higher ionic conduction under wet condition compared to dry condition. Y content of 25% (BCZYZn25) exhibits highest conductivity of 1.84 × 10−2 S/cm in wet Argon. This study indicated that perovskite electrolyte BCZYZn is promising material for the next generation of intermediate temperature solid oxide fuel cells (IT-SOFCs). |
| Keywords | Proton conductor; Sinterability; Rietveld refinement; Conductivity; SOFC electrolyte |
| Remark |
In Press, doi:10.1016/j.ijhydene.2016.02.135 Link |
Ca-doped fluorite-like compounds based on Nd5Mo3O16
ID=346| Authors |
|
| Source |
Journal of Alloys and Compounds
Time of Publication: 2016
|
| Abstract | We have studied phase relations in a molybdenum oxide-rich region of the ternary system CaO–Nd2O3–MoO3. Using polycrystalline samples prepared by solid-state reactions in air, the system has been shown to contain a rather broad region of cubic fluorite-like phases isostructural with Nd5Mo3O16. The atomic structure of a calcium-doped fluorite-like Nd5Mo3O16+δ single crystal grown from an off-stoichiometric melt has been studied by X-ray diffraction. The peculiarities of the structure of calcium-doped fluorite-related compounds were revealed. Experimental structural data demonstrate partial mutual substitutions of Nd and Mo cations, splitting of the O2 position into several additional positions, and the presence of excess oxygen, which occupies octahedral sites in the voids of the structure. Some of the fluorite-like samples have high electrical conductivity, on the order of 10−2 S/cm at 800 °C. |
| Keywords | Ceramics; Oxides; Crystal growth; Crystal structure; Ionic conductivity |
| Remark |
doi:10.1016/j.jallcom.2016.03.013 Link |
Crystal structure and proton conductivity of BaSn0.6Sc0.4O3-δ: Insights from neutron powder diffraction and solid state NMR
ID=345| Authors |
|
| Source |
Journal of Materials Chemistry A
Time of Publication: 2016
|
| Remark |
DOI: 10.1039/C5TA09744D Link |
Optically-transparent and electrically-conductive AgI–AgPO3–WO3 glass fibers
ID=344| Authors |
|
| Source |
RSC Advances
Volume: 5,
Pages: 40236-40248 Time of Publication: 2015 |
| Abstract | In this study, we report to our knowledge the first optically-transparent and electrically-conductive optical glass fiber belonging to the system AgI–AgPO3–WO3. The addition of tungsten oxide (WO3) into the phosphate glassy network allowed the adjustment of the glass transition temperature, thermal expansion coefficient, refractive index, optical band edge, and electrical conductivity, which are all very important parameters in view of drawing glass fibers with a desired set of electrical and optical properties. Furthermore, the addition of WO3 can improve considerably glass stability against water and humidity in the environment. AgI–AgPO3–WO3 glass fibers with 15 mol% WO3 showed 2 dB m−1 optical propagation loss from 800 to 950 nm wavelength range, and 10−3 S cm−1 electrical conductivity at 1 MHz AC frequency. Complex impedance spectra and thermal activation energies ranging from 0.15 to 0.30 eV are indicative of a dominant conductivity mechanism being ionic in nature within the range of AC frequencies from 1 Hz to 1 MHz. Fibers exhibited higher electrical conductivities than the bulk glasses. Glasses in the AgI–AgPO3–WO3 system can be used for fibers that require a set of adjustable properties pertaining to electrical conductivity, optical transparency, and environmental stability. |
| Remark |
DOI: 10.1039/C5RA00681C Link |
Phase Relations and Physical Properties of Layered Pb-Containing Nd2MoO6 Compounds
ID=343| Authors |
|
| Source |
European Journal of Inorganic Chemistry
Volume: 2016,
Issue: 7,
Pages: 1022-1029 Time of Publication: 2016 |
| Abstract | The phase relations along the Nd2MoO6–PbO join of the ternary Nd2O3–MoO3–PbO system have been studied by means of solid-state synthesis in air. The samples with high Pb content underwent a reversible first-order phase transition near 820 °C. XRD analysis revealed two tetragonal phases, the high-temperature centric phase (I41/acd) and the low-temperature acentric phase (Iequation image2m). In the region of the phase transition, the permittivity of the Pb-containing samples show a strong lambda-type anomaly and electrical conductivity increases sharply by one and half orders of magnitude. The conductivities of the Pb-containing samples reach 10–2 S/cm at 850 °C, which is two orders of magnitude greater than the conductivity of pure Nd2MoO6. The conductivity in such compounds may be due to oxygen ions. A permittivity anomaly, existence of a piezoelectric effect, and the symmetry change from acentric Iequation image2m to centric I41/acd may indicate an antiferroelectric nature of the phase transition. |
| Keywords | Conducting materials;Layered compounds;Lead;Rare earths;Solid-phase synthesis |
| Remark |
DOI: 10.1002/ejic.201501167 Link |
Phase stability and thermoelectric properties of Cu10.5Zn1.5Sb4S13 tetrahedrite
ID=342| Authors |
|
| Source |
Journal of Alloys and Compounds
Volume: 667,
Pages: 323–328 Time of Publication: 2016 |
| Abstract | Cu10.5Zn1.5Sb4S13 tetrahedrite compound was prepared by mechanical milling of Cu2S, ZnS and Sb2S3 powders and spark plasma sintered (SPS) to dense samples. The phase formation, chemical homogeneity, thermal stability of the compound and the thermoelectric properties of the sintered samples were evaluated. Single phase tetrahedrite with the crystallite size of 40 nm was obtained after 30 h of milling followed by annealing at 573 K for 6 h in an argon atmosphere. In-situ high-temperature X-ray diffraction studies revealed that the phase is stable up to 773 K. The Seebeck coefficient of the sintered samples of density >98% shows p-type behavior with maximum thermopower of 170 μV/K at 573 K. The electrical resistivity (ρ) decreases with temperature up to 475 K and then increases. A low thermal conductivity of 0.5 W/(m⋅K), in combination with moderate power factor gave a maximum ZT of ∼0.038 at 573 K in Cu10.5Zn1.5Sb4S13 sample having a grain size of ∼200 nm. |
| Keywords | Thermoelectric; Tetrahedrite; Solid state reactions; Spark plasma sintering; Figure of merit |
| Remark |
doi:10.1016/j.jallcom.2016.01.094 Link |
New ferroelastic K2Sr(MoO4)2: Synthesis, phase transitions, crystal and domain structures, ionic conductivity
ID=341| Authors |
|
| Source |
Journal of Solid State Chemistry
Volume: 237,
Pages: 64–71 Time of Publication: 2016 |
| Abstract | K2Sr(MoO4)2 crystals were synthesized and their properties examined. The distortive polymorphic transformations at 421 K (α (LT)→ β(MT)) and 744 K (β(MT)→γ (HT)) of K2Sr(MoO4)2 were studied. It has been shown that the transitions go in sequence from the high-temperature palmierite K2Pb(SO4)2-type γ-phase (R View the MathML source3¯m) to an intermediate β-phase with a probable incommensurate structure and then to a low-temperature α-phase. Domain structures peculiarities in ferroelastic α-K2Sr(MoO4)2 have been investigated. The electrical conductivity of K2Sr(MoO4)2 rises tenfold in the vicinity of the phase transition at 744 K that may be associated with a change conductivity path from quasi-one-dimensional to two-dimensional. The crystal structure of the α-phase (sp. gr. С2/c, а=14.318(3) Å, b=5.9337(12) Å, с=10.422(2) Å, β=105.83(3)°, Z=4, R=0.0219) is similar to that of α-Pb3(PO4)2. Sr-atoms are mainly located at site with the coordination number CN=8 (a tetragonal antiprism with bond lengths of 2.578(2)–2.789(2) Å) and K atoms are located at site with CN=9+1. |
| Keywords | Potassium; Strontium; molybdates; Phase transitions; Ferroelastics; Crystal structure; Crystal optics analysis; Domain structure; Ionic conductivity |
| Remark |
doi:10.1016/j.jssc.2016.01.011 Link |
New methods for the preparation and dielectric properties of Lа2 − xSrxNiO4 (х = 1/8) ceramic
ID=340| Authors |
|
| Source |
Materials Research Bulletin
Volume: 77,
Pages: 190–198 Time of Publication: 2016 |
| Abstract | The perovskite-type oxide La2−xSrxNiO4 (x = 1/8) was prepared by a new precursor route. The reaction proceeds in the self-ignition mode. Single-phase powder and gas-tight ceramic samples can be produced by single annealing of decomposition products. It was shown that as a result of thermobaric treatment of La2−xSrxNiO4 (x = 1/8) the solid solution La2−xSrxNiO4 with a higher concentration of strontium and the second phase La3Ni2O7 are formed. Short-term (5 min) thermobaric treatment (P = 2.5 GPa) at t° = 900 °С changes the unit cell parameters, but is not accompanied by structural transitions. At the same time, morphological restructuring of the sample occurs—the agglomerates delaminate into thin plates crystals. It was established that the permittivity of the material exposed to thermobaric treatment is much higher compared to that of the sample annealed at atmospheric pressure and virtually does not depend on frequency in a wide temperature range. |
| Keywords | Oxides; X-ray diffraction; High pressure; Impedance spectroscopy; Dielectric properties |
| Remark |
doi:10.1016/j.materresbull.2016.01.023 Link |
Chemical stability and H2 flux degradation of cercer membranes based on lanthanum tungstate and lanthanum chromite
ID=339| Authors |
|
| Source |
Journal of Membrane Science
Volume: 503,
Pages: 42–47 Time of Publication: 2016 |
| Abstract | Ceramic–ceramic composite (cercer) membranes of (Mo-doped) lanthanum tungstate, La27(W,Mo)5O55.5−δ, and lanthanum chromite, La0.87Sr0.13CrO3−δ, have recently been shown to exhibit H2 permeabilities among state-of-the-art. The present work deals with the long-term stability of these cercer membranes in line with concern of flux degradation and phase instability observed in previous studies. The H2 permeability of disc shaped membranes with varying La/W ratio in the lanthanum tungstate phase (5.35≤La/W≤5.50) was measured at 900 and 1000 °C with a feed gas containing 49% H2 and 2.5% H2O for up to 1500 h. It was observed that the H2 permeability decreased by a factor of up to 5.3 over 1500 h at 1000 °C. Post-characterization of the membranes and similarly annealed samples was performed by SEM, STEM and XRD, and segregation of La2O3 was observed. The decrease in H2 permeability was ascribed to the compositional instability of the cation-disordered lanthanum tungstate under the measurement conditions. Equilibration of the La/W ratio by segregation of La2O3 leads to a lower ionic conductivity according to the materials inherent defect chemistry. Partial decomposition and reduction of the lanthanum tungstate phase, presumably to metallic tungsten, was also observed after exposure to nominally dry hydrogen. |
| Keywords | Hydrogen separation; Dense ceramic membrane; Ceramic–ceramic composite; Lanthanum tungstate; Lanthanum chromite |
| Remark |
doi:10.1016/j.memsci.2015.12.054 Link |
Nb-doped TiO2 sol–gel films for CO sensing applications
ID=338| Authors |
|
| Source |
Materials Science in Semiconductor Processing
Volume: 42,
Issue: 3,
Pages: 397–404 Time of Publication: 2016 |
| Abstract | Nb doped titania (TiO2:Nb) multilayered films (1–10 layers) with anatase structure were obtained by the low-cost sol–gel and dipping method on microscope glass substrates, followed by thermal treatment at 450 °C for 1 h. After each layer deposition, an intermediate annealing step was performed at 300 °C for 30 min. Doping TiO2 sol–gel films with a low amount of Nb (0.8 at%) allows obtaining an improved CO sensor able to operate under environmental atmosphere (air). It was found that the sensor sensitivity is less dependent on the film thickness but is significantly influenced by Nb doping at the optimal working temperature of 400 °C. Good recovery characteristics were obtained for a wide CO detection range, between 0 and 2000 ppm. The gas-sensing behavior of the films was correlated with the structural, chemical and morphological properties of the multi-layered structures. |
| Keywords | Sol–gel method; Nb-doped TiO2 films; Microstructure; CO sensor |
| Remark |
doi:10.1016/j.mssp.2015.11.004 Link |
Synthesis and properties of La0.05Ba0.95Ti1 −xMyO3 (M = Mn, Ce) as anode materials for solid oxide fuel cells
ID=337| Authors |
|
| Source |
Solid State Ionics
Volume: 283,
Pages: 21–29 Time of Publication: 2015 |
| Abstract | Stoichiometric and sub-stoichiometric lanthanum barium titanates (LBT) of perovskite structure type, substituted or not with Mn and/or Ce at the Ti-site, were prepared by sol–gel route with heat treatment in air. All the compounds display a cubic Pm-3m symmetry, which remains stable in reducing atmosphere. Whereas Mn substitution highly promotes the reducibility of the material, the electrical and electrochemical performance of Mn-doped compounds is decreased with respect to non-doped sub-stoichiometric LBT. In contrast, the electrical conductivity and resistance polarization of Ce-substituted LBT are close to those of non-doped LBT and Ce-substituted LBT appears especially efficient in improving the catalytic properties for methane steam reforming and avoiding carbon formation. |
| Keywords | SOFC; Anode; Perovskite; Barium titanate; Impedance electrochemical spectroscopy; Methane steam reforming |
| Remark |
doi:10.1016/j.ssi.2015.11.005 Link |
Molybdenum doped Pr0.5Ba0.5MnO3−δ (Mo-PBMO) double perovskite as a potential solid oxide fuel cell anode material
ID=336| Authors |
|
| Source |
Journal of Power Sources
Volume: 301,
Pages: 237–241 Time of Publication: 2016 |
| Abstract | A layered Mo doped Pr0.5Ba0.5MnO3−δ (Mo-PBMO) double perovskite oxide was prepared by a modified sol–gel method and the properties of the fabricated material are characterized by various technologies. The results of X-ray diffraction (XRD), H2-temperature programmed reduction (H2-TPR), NH3-temperature programmed desorption (NH3-TPD), and thermogravimetric analysis (TGA) demonstrate that the treatment in reducing atmosphere at high temperature lead to a significant phase transformation of the material to a single cubic phase as well as with the Mo in multiple oxidized states. Such character leads to the production of large amount of oxygen deficiency with facilitated oxygen diffusion. The electrochemical performance tests of half-cell and single cell SOFCs exhibit the promoted effect of Mo on catalytic activity for the oxidation of H2 and CH4, indicating that Mo-PBMO could serve as an anode material candidate for SOFCs. |
| Keywords | Mo; Pr0.5Ba0.5MnO3−δ; Double perovskite; Anode; SOFC |
| Remark |
doi:10.1016/j.jpowsour.2015.09.127 Link |
Experimental and molecular dynamics study of thermo-physical and transport properties of ThO2-5wt.%CeO2 mixed oxides
ID=335| Authors |
|
| Source |
Journal of Nuclear Materials
Volume: 467,
Issue: 2,
Pages: 644–659 Time of Publication: 2015 |
| Abstract | We have determined the thermo-physical (elastic modulus, specific heat, thermal expansion and thermal conductivity) and transport (ionic conductivity) properties of ThO2-5wt.%CeO2 mixed oxide (MOX) using a combined experimental and theoretical methodology. The specific heat, ionic conductivity and elastic properties of ThO2-5wt.%CeO2 pellets prepared by conventional powder metallurgy (POP) and coated agglomerate pelletization (CAP) routes (sintered in both air and Ar-8%H2 atmosphere) are compared with respect to homogeneity (CeO2 distribution in ThO2 matrix), microstructure, porosity and oxygen to metal ratio. The effects of inhomogeneity and pore distribution on thermal expansion and thermal conductivity of the mixed-oxide pellets are identified. Molecular dynamics (MD) simulations using the Coulomb-Buckingham-Morse-many-body model based interatomic potentials are used to predict elastic properties in the temperature range between 300 and 2000 K and thermodynamic properties, viz., enthalpy increment and specific heats of ThO2. Finally, the thermal expansion coefficient and thermal conductivity of ThO2 and (Th,Ce)O2 mixed-oxides obtained from MD are compared with available experimental results. |
| Keywords | ThO2-5%CeO2 MOX; Specific heat; Ionic conductivity; Temperature dependent elastic properties; Molecular dynamics simulation |
| Remark |
doi:10.1016/j.jnucmat.2015.10.053 Link |
Effect of Cerium on the Electrical Properties of a Cobalt Conversion Coating for Solid Oxide Fuel Cell Interconnects – A Study Using Impedance Spectroscopy
ID=334| Authors |
|
| Source |
Electrochimica Acta
Volume: 184,
Pages: 301–307 Time of Publication: 2015 |
| Abstract | Coatings of metallic cobalt, which convert into a cobalt manganese spinel oxide are known to improve the properties of interconnects for solid oxide fuel cells (SOFCs). The addition of cerium to the cobalt coating further improves the corrosion properties of the material. For this study traditional four-point DC measurements at high temperatures were combined with impedance spectroscopy at low temperatures in order to investigate the effect of cerium on the electrical properties of a cobalt conversion coating. It was found that combination-coatings of cerium and cobalt exhibit superior electrical properties compared to pure cobalt coatings. Cerium slows down the growth of chromia and prevents the outward diffusion of iron into the cobalt spinel layer. Both effects are beneficial for the electrical properties of the interconnect. Impedance spectroscopy measurements revealed that even after more than 3000 h of exposure the outer cobalt manganese spinel layer still has a higher electrical conductivity when cerium was present. |
| Remark |
doi:10.1016/j.electacta.2015.10.111 Link |
Lithium Polymer Electrolytes Based on Sulfonated Poly(ether ether ketone) for Lithium Polymer Batteries
ID=333| Authors |
|
| Source |
European Journal of Inorganic Chemistry
Volume: 2015,
Issue: 32,
Pages: 5395–5404 Time of Publication: 2015 |
| Abstract | We studied a lithium-ion conducting polymer based on sulfonated poly(ether ether ketone) (SPEEK) doped with lithium bis(trifluoromethane)sulfonimide (LiTFSI). Self-standing membranes were prepared by the solvent-casting technique with a LiTFSI loading of 0 to 30 wt.-%. The thermogravimetric analysis curves showed that the SO3H groups decompose earlier in the SPEEK–LiTFSI membranes than in pure SPEEK, owing to interactions between the Li+ ions and the SO3H groups. X-ray diffraction and differential scanning calorimetry studies showed that the addition of LiTFSI decreased the crystallinity and the glass-transition temperature of the polymer, which revealed the plasticizing effect of the lithium salt on the polymer matrix. The 7Li NMR spectroscopy results showed a single central transition line at around δ = –1.2 ppm, which indicated the presence of free mobile lithium ions. Dynamic mechanical analysis of the membrane showed it to be mechanically stable up to 100 °C, a prerequisite for flexible lithium polymer batteries. The highest room-temperature conductivity in the order of 10–5 S cm–1 was observed for the 20 wt.-% LiTFSI-doped SPEEK membrane, which increased to 5 × 10–4 S cm–1 at 100 °C. |
| Keywords | Lithium batteries;Polymer electrolytes;Dynamic mechanical analysis;Raman spectroscopy;Ion pairs |
| Remark |
DOI: 10.1002/ejic.201500649 Link |
Exceptional hydrogen permeation of all-ceramic composite robust membranes based on BaCe0.65Zr0.20Y0.15O3−δ and Y- or Gd-doped ceria
ID=332| Authors |
|
| Source |
Energy Environ. Sci.
Volume: 8,
Pages: 3675-3686 Time of Publication: 2015 |
| Abstract | Mixed proton and electron conductor ceramic composites were examined as hydrogen separation membranes at moderate temperatures (higher than 500 °C). In particular, dense ceramic composites of BaCe0.65Zr0.20Y0.15O3−δ (BCZ20Y15) and Ce0.85M0.15O2−δ (M = Y and Gd, hereafter referred to as YDC15 and GDC15), as protonic and electronic conducting phases respectively, were successfully prepared and tested as hydrogen separation membranes. The mixture of these oxides improved both chemical and mechanical stability and increased the electronic conductivity in dual-phase ceramic membranes. The synthetic method and sintering conditions were optimized to obtain dense and crack free symmetric membranes. The addition of ZnO as a sintering aid allowed achieving robust and dense composites with homogeneous grain distribution. The chemical compatibility between the precursors and the influence of membrane composition on electrical properties and H2 permeability performances were thoroughly investigated. The highest permeation flux was attained for the 50 : 50 volume ratio BCZ20Y15–GDC15 membrane when the feed and the sweep sides of the membrane were hydrated, reaching values of 0.27 mL min−1 cm−2 at 755 °C on a 0.65 mm thick membrane sample, currently one of the highest H2 fluxes obtained for bulk mixed protonic–electronic membranes. Increasing the temperature to 1040 °C, increased the hydrogen flux up to 2.40 mL min−1 cm−2 when only the sweep side was hydrated. The H2 separation process is attributed to two cooperative mechanisms, i.e. proton transport through the membrane and H2 production via the water splitting reaction coupled with oxygen ion transport. Moreover, these composite systems demonstrated a very good chemical stability under a CO2-rich atmosphere such as catalytic reactors for hydrogen generation. |
| Remark |
DOI: 10.1039/C5EE01793A Link |
The effect of Cu2O nanoparticle dispersion on the thermoelectric properties of n-type skutterudites
ID=331| Authors |
|
| Source |
Journal of Physics D: Applied Physics
Volume: 48,
Issue: 45
Time of Publication: 2015
|
| Abstract | We report the thermoelectric properties of Ba0.4Co4Sb12 and Sn0.4Ba0.4Co4Sb12 skutterudites dispersed with Cu2O nanoparticles. The samples were synthesized by ball milling and consolidated by spark plasma sintering. Dispersion of Cu2O is found to significantly influence the electrical resistivity and thermopower at high temperatures with a more pronounced effect on the electrical resistivity due to the energy filtering effect at the interface between Cu2O nanoparticles and a Ba0.4Co4Sb12 and Sn0.4Ba0.4Co4Sb12 matrix. At 573 K, the electrical resistivity of Ba0.4Co4Sb12 decreases from 5.01 × 10−5 Ωm to 2.98 × 10−5 Ωm upon dispersion of Cu2O. The dispersion of Cu2O reduces the thermal conductivity of the samples from 300 K and above by increasing the phonon scattering. The lowest observed thermal conductivity at 573 K is found to be 2.001 W mK−1 in Cu2O dispersed Ba0.4Co4Sb12 while it is 2.91 W mK−1 in the Ba0.4Co4Sb12 sample without Cu2O dispersion. Hence Cu2O dispersion plays a significant role in the thermoelectric properties and a maximum figure of merit (ZT ) ~ 0.92 is achieved in Cu2O dispersed Ba0.4Co4Sb12 at 573 K which is more than 200% compared to the pure Ba0.4Co4Sb12 sample. The results from nanoindentation experiments show that the Cu2O dispersed sample (Cu2O + Sn0.4Ba0.4Co4Sb11.6) has a higher reduced Youngs modulus (~139 GPa) than the pure Sn0.4Ba0.4Co4Sb11.6 sample (~128 GPa). |
| Remark | Link |
Oxygen permeation and creep behavior of Ca1−xSrxTi0.6Fe0.15Mn0.25O3−δ (x=0, 0.5) membrane materials
ID=329| Authors |
|
| Source |
Journal of Membrane Science
Volume: 449,
Pages: 172–178 Time of Publication: 2016 |
| Abstract | Oxygen permeation measurements were performed on dense symmetric samples of Ca0.5Sr0.5Ti0.6Fe0.15Mn0.25O3−δ and compared to CaTi0.6Fe0.15Mn0.25O3−δ in order to assess the influence of the perovskite lattice volume on oxygen permeation. Oxygen flux measurements were performed in the temperature range 700–1000 °C and as function of feed side pO2pO2 from 10−2 to 1 bar, and at high pressures up to 4 bar with a pO2pO2 of 3.36 bar. The O2 permeability of the Sr-doped sample was significantly lower than that of the Sr-free sample, amounting to 3.9×10−3 mL min−1 cm−1 at 900 °C for a feed side pO2pO2 of 0.21 bar. The O2 permeability of CaTi0.6Fe0.15Mn0.25O3−δ shows little variation with increased feed side pressures and reaches 1.5×10−2 mL min−1 cm−1 at 900 °C for a feed side pO2pO2 of 3.36 bar. This is approximately 1.5 times higher than the O2 permeability with a feed side pO2pO2 of 0.21 bar. Furthermore, in order to assess the applicability of CaTi0.6Fe0.15Mn0.25O3−δ as an oxygen membrane material, creep tests were performed under compressive loads of 30 and 63 MPa, respectively, in air in the temperature range 700–1000 °C; the results indicate a high creep resistance for this class of materials. The measured O2 permeabilities and creep rates are compared with other state-of-the-art membrane materials and their performance for relevant applications is discussed in terms of chemical and mechanical stability. |
| Keywords | Dense ceramic oxygen membrane; Ambipolar transport; Creep; CaTiO3; Calcium titanate |
| Remark |
doi:10.1016/j.memsci.2015.10.016 Link |
Comparative study of the electrochemical promotion of CO2 hydrogenation on Ru using Na+, K+, H+ and O2 − conducting solid electrolytes
ID=328| Authors |
|
| Source |
Surface Science
Time of Publication: 2015
|
| Abstract | The kinetics and the electrochemical promotion of the hydrogenation of CO2 to CH4 and CO are compared for Ru porous catalyst films deposited on Na+, K+, H+ and O2 − conducting solid electrolyte supports. It is found that in all four cases increasing catalyst potential and work function enhances the methanation rate and selectivity. Also in all four cases the rate is positive order in H2 and exhibits a maximum with respect to CO2. At the same time the reverse water gas shift reaction (RWGS) which occurs in parallel exhibits a maximum with increasing pH2pH2 and is positive order in CO2. Also in all cases the selectivity to CH4 increases with increasing pH2pH2 and decreases with increasing pCO2pCO2. These results provide a lucid demonstration of the rules of chemical and electrochemical promotion which imply that (∂r/∂Φ)(∂r/∂pD) > 0 and (∂r/∂Φ)(∂r/∂pA) < 0, where r denotes a catalytic rate, Φ is the catalyst work function and pD and pA denote the electron donor and electron acceptor reactant partial pressures respectively. |
| Keywords | Effect of Ru catalyst support and potential on product selectivity. |
| Remark |
In Press, doi:10.1016/j.susc.2015.09.011 Link |
Electrochemical promotion of the hydrogenation of CO2 on Ru deposited on a BZY proton conductor
ID=327| Authors |
|
| Source |
Journal of Catalysis
Volume: 331,
Pages: 98–109 Time of Publication: 2015 |
| Abstract | he kinetics and the electrochemical promotion of the hydrogenation of CO2 on polycrystalline Ru deposited on BZY (BaZr0.85Y0.15O3−α + 1 wt% NiO), a proton conductor in wet atmospheres, with α ≈ 0.075, was investigated at temperatures 300–450 °C and atmospheric pressure. Methane and CO were the only detectable products and the selectivity to CH4 could be reversibly controlled between 15% and 65% by varying the catalyst potential by less than 1.2 V. The rate and the selectivity to CH4 are very significantly enhanced by proton removal from the catalyst via electrochemically controlled spillover of atomic H from the catalyst surface to the proton-conducting support. The effect is strongly non-Faradaic and the apparent Faradaic efficiency of methanation takes values up to 500 and depends strongly on the porous Ru catalyst film thickness. The observed strong promotional effect, in conjunction with the observed reaction kinetics, is in good agreement with the rules of electrochemical and chemical promotion. |
| Keywords | Hydrogenation of CO2; CO2 methanation; Ru catalyst; RWGS reaction; BZY proton conducting support; Selectivity modification; Electrochemical promotion of catalysis (EPOC); Non-faradaic electrochemical modification of catalytic activity (NEMCA effect) |
| Remark |
doi:10.1016/j.jcat.2015.08.023 Link |
Electrochemical Promotion of Ir0.5Pt0.5O2/YSZ
ID=326| Authors |
|
| Source |
Topics in Catalysis
Volume: 58,
Issue: 18,
Pages: 1270-1275 Time of Publication: 2015 |
| Abstract | A high surface area, nanostructured bimetallic oxide catalyst, Ir0.5Pt0.5O2, deposited on YSZ was studied for the electrochemical promotion of ethylene oxidation. The catalyst was synthesized using the modified Adams fusion method and was characterized regarding its structure, morphology and specific surface area via XPS, XRD, HRTEM, SEM and BET. Regarding the performance for electrochemical promotion, it was found that the rate of ethylene oxidation can be enhanced significantly and in a strongly non-faradaic manner via positive potential application, exhibiting strongly electrophobic behaviour. |
| Keywords | Electrochemical promotion, EPOC, Ir0.5Pt0.5O2, Adams fusion method |
| Remark | Link |
Enhanced Carbon Deposition Tolerance of SOFC Anodes Under Triode Operation
ID=325| Authors |
|
| Source |
Topics in Catalysis
Volume: 58,
Issue: 18,
Pages: 1303-1310 Time of Publication: 2015 |
| Abstract | The triode fuel cell design and operation concept was applied as an alternative means for controlling and enhancing the carbon tolerance of state-of-the-art solid oxide fuel cell (SOFC) anodes. The triode cell configuration entails the introduction of a third electrode in addition to the anode and cathode, driven by an auxiliary circuit which is run in electrolytic mode. In this way the cell is forced to operate at controlled potential differences that are inaccessible under standard operation, and thus introduces a controllable variable into fuel cell operation. In the present study, the effectiveness of the triode approach was evaluated for the in situ control of the rate of carbon deposition in commercial multilayer NiO–GDC and NiO–YSZ SOFC anodes. The study involved typical and triode operation of SOFC button cells under CH4 steam reforming conditions, and it was found that the application of a small electrolytic current under triode operation resulted in significantly less carbon built-up on the anode compared to the standard SOFC operation. |
| Keywords | SOFC Triode fuel cell operation, Anode degradation, Carbon formation, CH4 steam reforming |
| Remark | Link |
Development of a Coking-Resistant NiSn Anode for the Direct Methane SOFC
ID=324| Authors |
|
| Source |
Fuel Cells
Volume: 15,
Issue: 5,
Pages: 711–717 |
| Abstract | The present work reports on the development of a coking-resistant NiSn-based membrane electrode assembly (MEA) for internal CH4 reforming in solid oxide fuel cells (SOFCs). Catalyst powder was prepared in a centrifugal casting oven by melting stoichiometric amounts of Ni and Sn under vacuum. The formation of Ni3Sn2 intermetallic phase was confirmed by XRD analysis. Catalytic activity for CH4 reforming and stability of the NiSn powder were first evaluated in a quartz glass reactor for 4 h at 600–1,000 °C. The main reaction products H2 and CO were detected by gas chromatography while no carbon formation was detected during the experiments. Then, 3YSZ electrolyte-supported MEAs were fabricated with a Ni3Sn2/YSZ anode and LSM/YSZ cathode and characterized under SOFC conditions. The MEA showed an excellent stability under CH4 atmosphere (3% H2O) at 850 °C over more than 650 h. No substantial decrease in cell potential was observed during this period. |
| Keywords | Anode Material;Intermetallic Phase;Internal Reforming;Methane;Nickel-Tin Alloy;Ni3Sn2;SOFC;Solid Oxide Fuel Cell |
| Remark |
DOI: 10.1002/fuce.201400187 Link |
Hardening in non-stoichiometric (1−x)Bi0.5Na0.5TiO3–xBaTiO3 lead-free piezoelectric ceramics
ID=323| Authors |
|
| Source |
Journal of Materials Science
Volume: 51,
Issue: 1,
Pages: 476-486 Time of Publication: 2016 |
| Abstract | The role of A-site non-stoichiometry was investigated in lead-free piezoelectric ceramics based on compositions in the 1 − x(Bi0.5Na0.5TiO3)–xBaTiO3 system near the morphotropic phase boundary, where x = 0.055, 0.06, and 0.07. Donor doping was introduced through the addition of excess Bi, however, there were no changes in the crystal structure. In contrast, acceptor doping was introduced through the addition of excess Na and was found to promote rhombohedral distortions. A significant improvement of dielectric properties was observed in donor-doped compositions and, in contrast, a degradation in properties was observed in acceptor-doped compositions. Compared to the stoichiometric composition, the acceptor-doped compositions displayed a significant increase in coercive field (E c) which is an indication of domain wall pinning as found in hard Pb(Zr x Ti1−x )O3. This result was further confirmed via remanent polarization hysteresis analyses. Moreover, all A-site acceptor-doped compositions also exhibited an increase in mechanical quality factor (Q m) as well as a decrease in piezoelectric coefficient (d 33), dielectric loss (tan δ), remanent polarization (P r), and dielectric permittivity, which are all the typical characteristics of the effects of “hardening.” The mechanism for the observed hardening in A-site acceptor-doped BNT-based systems is linked to changes in the long-range domain structure and defect chemistry. |
| Remark | Link |
Copper Iron Conversion Coating for Solid Oxide Fuel Cell Interconnects
ID=322| Authors |
|
| Source |
Journal of Power Sources
Volume: 297,
Pages: 534–539 Time of Publication: 2015 |
| Abstract | A conversion coating of iron and copper was investigated with the purpose of increasing the performance of Sanergy HT as a potential SOFC interconnect material. Samples were exposed to a simulated cathode atmosphere (air, 3 % H2O) for durations of up to 1000 h at 850 °C. Their performance in terms of corrosion, chromium evaporation and electrical resistance (ASR) was monitored and compared to uncoated and cobalt-coated Sanergy HT samples. The copper iron coating had no negative effects on corrosion protection and decreased chromium evaporation by about 80%. An Area Specific Resistance (ASR) of 10 mΩcm2 was reached after 1000 h of exposure. Scanning Electron Microscopy revealed well adherent oxide layers comprised of an inner chromia layer and an outer spinel oxide layer. |
| Keywords | Interconnect; Corrosion; Chromium volatilization; Sanergy HT; SOFC; Area specific resistance |
| Remark |
doi:10.1016/j.jpowsour.2015.06.139 Link |
Atomic structure and ionic conductivity of glassy materials based on silver sulfide
ID=321| Authors |
|
| Source |
Volume: 79,
Issue: 6,
Pages: 719-722 Time of Publication: 2015 |
| Abstract | The effect of the composition of glassy ionic conductors AgGe1 + x As1–x S3 and the composites based on these materials containing single-walled carbon nanotubes (CNT) AgGe1+x As1–x (S + CNT)3, on the atomic structure and ionic conductivity is analyzed. |
| Remark | Link |
Protons in piezoelectric langatate; La3Ga5.5Ta0.5O14
ID=320| Authors |
|
| Source |
Solid State Ionics
Volume: 278,
Pages: 275–280 Time of Publication: 2015 |
| Abstract | This contribution reports the hydration and electrical transport properties of effectively acceptor doped single crystalline and polycrystalline langatate, La3Ga5.5Ta0.5O14. The electrical properties are investigated over wide ranges of pH2OpH2O, pD2OpD2O and pO2pO2 in the temperature range 400 to 1000 °C. Acceptor doped langatate is dominated by oxygen vacancies in dry atmospheres and at high temperatures, and by protonic defects in wet atmospheres and at lower temperatures. The corresponding standard hydration enthalpy and entropy are − 90 ± 5 kJ/mol and − 130 ± 5 J/mol K, respectively. Further, all compositions display pure proton conductivity in wet atmospheres below 700 °C with a proton mobility enthalpy in the range of 70–75 kJ/mol, depending on doping level and crystallographic direction. Hence, protons are important for the physiochemical properties of langatate even at 1000 °C, and could therefore influence the behavior of langatate-based resonator devices. The proton conductivity is slightly anisotropic, being higher in the X- and Y- than in the Z-direction. At high temperatures and under dry conditions, electron holes and oxide ions dominate the conductivity, and the enthalpy of mobility of vacancies is 140 ± 5 kJ/mol. |
| Keywords | Langatate; Piezoelectric; Defects; Protons; Conductivity |
| Remark |
doi:10.1016/j.ssi.2015.06.024 Link |
Tetragonal tungsten bronzes Nb8−xW9+xO47−δ: optimization strategies and transport properties of a new n-type thermoelectric oxide
ID=319| Authors |
|
| Source |
Materials Horizons
Issue: 5,
Pages: 519-527 Time of Publication: 2015 |
| Abstract | Engineering of nanoscaled structures may help controlling the electrical and thermal transport in solids, in particular for thermoelectric applications that require the combination of low thermal conductivity and low electrical resistivity. The tetragonal tungsten bronzes Nb8−xW9+xO47 (TTB) allow a continuous variation of the charge carrier concentration while fulfilling at the same time the concept of a “phonon-glass electron-crystal” through a layered nanostructure defined by intrinsic crystallographic shear planes. The thermoelectric properties of the tetragonal tungsten bronzes Nb8−xW9+xO47−δ (0 < x < 2) were studied in the temperature range from 373 to 973 K. Structural defects and the thermal stability under various oxygen partial pressure pO2 were investigated by means of thermogravimetry, HR-TEM, and XRD. Nb8W9O47−δ was found stable at 973 K and a pO2 of ≈10−15 atm. The oxygen nonstoichiometry δ can reach up to 0.3, depending on the applied atmosphere. By increasing the substitution level x, the electrical resistivity ρ and the Seebeck coefficient S decreased. For x = 2, ρ reached 20 mΩ cm at 973 K, combined with a Seebeck coefficient of approximately −120 μV K−1. The thermal conductivity was low for all samples, ranging from 1.6 to 2.0 W K−1 m−1, attributed to the complex crystal structure. The best thermoelectric figure of merit zT of the investigated samples was 0.043, obtained for x = 2 at 973 K, but it is expected to increase significantly upon a further increase of x. The control of the oxygen non-stoichiometry δ opens a second independent optimization strategy for tetragonal tungsten bronzes. |
| Remark |
DOI: 10.1039/C5MH00033E Link |
EuBaCo2O5+δ-Ce0.9Gd0.1O2−δ composite cathodes for intermediate-temperature solid oxide fuel cells: high electrochemical performance and oxygen reduction kinetics
ID=318| Authors |
|
| Source |
Electrochimica Acta
Volume: 174,
Pages: 608–614 Time of Publication: 2015 |
| Abstract | The characteristics and electrochemical performance of double perovskite EuBaCo2O5+δ (EBCO) have been investigated as a composite cathode for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The thermal expansion coefficients can be effectively reduced in the case of EBCO-Ce0.9Gd0.1O2−δ (CGO) composite cathodes. No chemical reactions between EBCO cathode and CGO electrolyte are observed after sintering at 1000 °C for 24 h. The maximum electrical conductivities of EBCO-CGO materials reach 28-77 S cm−1 with the change of CGO weight ratio from 40 wt. % to 5 wt. %. Among all these components, the EBCO-10 wt. % CGO (EBCO-10CGO) composite cathode gives the lowest area-specific resistance of 0.055 and 0.26 Ω cm2 in air at 700 and 600 °C, respectively. The maximum power density of Ni-CGO anode-supported single cell consisted of the EBCO-10CGO composite cathode and CGO electrolyte achieves 0.81 W cm−2 at 700 °C. These results indicate that the EBCO-10CGO composite materials can be used as a promising cathode candidate for IT-SOFCs. Furthermore, the rate-limiting steps for the oxygen reduction reaction at the EBCO-10CGO composite cathode interface are determined to be the charge transfer and dissociation of adsorbed molecule oxygen processes. |
| Keywords | Intermediate-temperature solid oxide fuel cells; cathode materials; electrochemical performance; oxygen reduction kinetics |
| Remark |
doi:10.1016/j.electacta.2015.06.059 Link |
Multilayer ceramic capacitors based on relaxor BaTiO3-Bi(Zn1/2Ti1/2)O3 for temperature stable and high energy density capacitor applications
ID=317| Authors |
|
| Source |
Applied Physics Letters
Volume: 106,
Pages: 252901 Time of Publication: 2015 |
| Abstract | The need for miniaturization without compromising cost and performance continues to motivate research in advanced capacitor devices. In this report, multilayerceramiccapacitors based on relaxor BaTiO3-Bi(Zn1/2Ti1/2)O3 (BT-BZT) were fabricated and characterized. In bulk ceramic embodiments, BT-BZT has been shown to exhibit relative permittivities greater than 1000, high resistivities (ρ > 1 GΩ-cm at 300 °C), and negligible saturation up to fields as high as 150 kV/cm. Multilayercapacitor embodiments were fabricated and found to exhibit similar dielectric and resistivity properties. The energy density for the multilayerceramics reached values of ∼2.8 J/cm3 at room temperature at an applied electric field of ∼330 kV/cm. This represents a significant improvement compared to commercially available multilayercapacitors. The dielectric properties were also found to be stable over a wide range of temperatures with a temperature coefficient of approximately −2000 ppm/K measured from 50 to 350 °C, an important criteria for high temperature applications. Finally, the compatibility of inexpensive Ag-Pd electrodes with these ceramics was also demonstrated, which can have implications on minimizing the device cost. |
| Remark |
http://dx.doi.org/10.1063/1.4922947 Link |
Electrical conductivity of Zn-doped high temperature proton conductor LaNbO4
ID=316| Authors |
|
| Source |
Solid State Ionics
Volume: 278,
Pages: 152–156 Time of Publication: 2015 |
| Abstract | Zn-doped LaNbO4 (La1 − xZnxNbO4 − δ, LZ100x) was prepared by a solid-state reaction method with x = 0, 0.005, 0.01, 0.015, 0.03 and 0.05 and investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and conductivity measurement. There were no XRD and TEM evidences of formed secondary phases in the composition range of x ≤ 0.03 due to the sensitivity. However, the solubility of Zn, less than 1.0 mol.%, was reasonable, according the variety of the grain sizes, conductivity, as well as the activation energy for the conductivity, with the increasing concentration of Zn. The conductivity of LaNbO4 was improved by one to two orders of magnitude with Zn doping in the research range; and the highest conductivity of 9.8 × 10− 4 S cm− 1 was obtained with LZ0.5 at 900 °C in wet air. |
| Keywords | LaNbO4; Conductivity; Zn doping; Grain size |
| Remark |
doi:10.1016/j.ssi.2015.06.011 Link |
Gd- and Pr-based double perovskite cobaltites as oxygen electrodes for proton ceramic fuel cells and electrolyser cells
ID=315| Authors |
|
| Source |
Solid State Ionics
Volume: 278,
Pages: 120–132 Time of Publication: 2015 |
| Abstract | Double perovskite oxides BaGd0.8La0.2Co2O6−δ (BGLC), BaGdCo1.8Fe0.2O6−δ (BGCF), BaPrCo2O6−δ (BPC) and BaPrCo1.4Fe0.6O6−δ (BPCF) were investigated as oxygen electrodes on mixed conducting BaZr0.7Ce0.2Y0.1O3 (BZCY72) electrolyte using impedance spectroscopy vs temperature, pO2, and pH2O. We propose and have applied a novel approach to extract and parameterise the charge transfer and diffusion impedances of the electrode reactions in a system comprising charge transport of protons, oxide ions, and electrons. Given by the properties of the BZCY72, transport of protons dominates at lower temperatures and high pH2O, oxide ions at higher temperatures, and electron holes increasingly at high temperatures and high pO2. The electrodes showed good performance, with the lowest total apparent polarisation resistance for BGLC/BZCY72 being 0.05 and 10 Ωcm2 at 650 and 350 °C, respectively. The low temperature rate limiting reaction step is a surface related process, involving protonic species, with an activation energy of approximately 50 kJ mol−1 for BGLC/BZCY72. The oxide ion transport taking over at higher temperatures exhibits a higher activation energy typical of SOFC cathodes. Thermogravimetric studies revealed that BGLC exhibits considerable protonation at 300–400 °C, which may be interpreted as hydration with an enthalpy of approximately –50 kJ mol−1. The resulting mixed proton electron conduction may explain its good performance as electrode on BZCY72. |
| Keywords | PCFC; PCEC; P-MIEC; Proton conductor; Mixed conductivity; Double perovskite |
| Remark |
doi:10.1016/j.ssi.2015.05.014 Link |
Praseodymium-deficiency Pr0.94BaCo2O6-δ double perovskite: A promising high performance cathode material for intermediate-temperature solid oxide fuel cells
ID=313| Authors |
|
| Source |
Journal of Power Sources
Volume: 239,
Pages: 741–750 Time of Publication: 2015 |
| Abstract | Praseodymium-deficiency Pr0.94BaCo2O6-δ (P0.94BCO) double perovskite has been evaluated as a cathode material for intermediate-temperature solid oxide fuel cells. X-ray diffraction pattern shows the orthorhombic structure with double lattice parameters from the primitive perovskite cell in Pmmm space group. P0.94BCO has a good chemical compatibility with Ce0.9Gd0.1O1.95 (CGO) electrolyte even at 1000 °C for 24 h. It is observed that the Pr-deficiency can introduce the extra oxygen vacancies in P0.94BCO, further enhancing its electrocatalytic activity for oxygen reduction reaction. P0.94BCO demonstrates the promising cathode performance as evidenced by low polarization are-specific resistance (ASR), e. g. 0.11 Ω cm2 and low cathodic overpotential e. g. −56 mV at a current density of −78 mA cm−2 at 600 °C in air. These features are comparable to those of the benchmark cathode Ba0.5Sr0.5Co0.8Fe0.2O3-δ. The fuel cell CGO-Ni|CGO|P0.94BCO presents the attractive peak power density of 1.05 W cm−2 at 600 °C. Furthermore, the oxygen reduction kinetics of P0.94BCO material is also investigated, and the rate-limiting steps for oxygen reduction reaction are determined. |
| Keywords | Intermediate-temperature solid oxide fuel cell; Cathode material; Double perovskite; Electrochemical performance; Oxygen reduction reaction |
| Remark |
doi:10.1016/j.jpowsour.2015.06.007 Link |
Reduced long term electrical resistance in Ce/Co-coated ferritic stainless steel for solid oxide fuel cell metallic interconnects
ID=312| Authors |
|
| Source |
International Journal of Hydrogen Energy
Volume: 40,
Issue: 27,
Pages: 8579–8585 |
| Abstract | The present study is focused on the influence of selected coatings on a ferritic stainless steel (Sanergy HT™, Sandvik) on the evolution of the area specific resistance (ASR) as a function of time at high temperature. The samples are exposed in humidified air at 850 °C for up to 4200 h. It combines long-term ASR measurements with the thermogravimetric behavior and microstructural analysis of the cross sections by scanning electron microscopy. The results show that uncoated and Co-coated Sanergy HT™ exhibit similar oxidation kinetics and comparable ASRs, while a combined Ce/Co coating improves oxidation resistance and, consequently, reduces the ASR significantly. Other reports have earlier shown that Co- (and Ce/Co)-coated Sanergy HT™ reduces the evaporation of volatile chromium species. Overall, the study indicates that Ce/Co-coatings will render substantially improved performance for ferritic steel interconnects for solid oxide fuel cells. |
| Keywords | Metallic coating; SOFC; Interconnects; Stainless steel; Conductivity; ASR |
| Remark |
doi:10.1016/j.ijhydene.2015.04.147 Link |
Resistivity Enhancement and Transport Mechanisms in (1 − x)BaTiO3–xBi(Zn1/2Ti1/2)O3 and (1 − x)SrTiO3–xBi(Zn1/2Ti1/2)O3
ID=311| Author |
|
| Source |
Journal of the American Ceramic Society
Time of Publication: 2015
|
| Abstract | Ceramics of composition (1−x)BaTiO3–xBi(Zn1/2Ti1/2)O3 (BT-BZT) were prepared by solid-state synthesis; they have been shown to exhibit excellent properties suited for high-temperature dielectric applications. The X-ray diffraction data showed a single-phase perovskite structure for all the compositions prepared (x ≤ 0.1 BZT). The compositions with less than 0.075 BZT exhibited tetragonal symmetry at room temperature and pseudo-cubic symmetry above it. Most notably, a significant improvement in insulation properties was measured with the addition of BZT. Both low-field AC impedance and high-field direct DC measurements indicated an increase in resistivity of at least two orders of magnitude at 400°C with the addition of just 0.03 BZT (~107 Ω-cm) into the solid solution as compared to pure BT (~105 Ω-cm). This effect was also evident in dielectric loss data, which remained low at higher temperatures as the BZT content increased. In conjunction with band gap measurements, it was also concluded that the conduction mechanism transitioned from extrinsic for pure BT to intrinsic for 0.075 BZT suggesting a change in the fundamental defect equilibrium conditions. It was also shown that this improvement in insulation properties was not limited to BT-BZT, but could also be observed in the paraelectric SrTiO3–BZT system. |
| Remark |
DOI: 10.1111/jace.13666, Article first published online Link |
Triode operation for enhancing the performance of H2S-poisoned SOFCs operated under CH4–H2O mixtures
ID=310| Authors |
|
| Source |
Solid State Ionics
Volume: 277,
Pages: 65–71 Time of Publication: 2015 |
| Abstract | Performances of Solid Oxide Fuel Cells (SOFCs) were investigated in triode operation mode under methane steam reforming in the presence of H2S. Both the catalytic performances for methane steam reforming and the electrochemical properties for the electrochemical oxidation of hydrogen of a Ni/GDC anode drastically dropped in the presence of 1 ppm H2S. Poisoned catalytic sites are different from those for the hydrogen electrochemical oxidation. Triode operation, i.e. application of moderate negative currents between the anode and an auxiliary electrode, can improve electrochemical properties, as a result of a local production of H2 coming from H2O electrolysis. Some specific triode operations were found to achieve a thermodynamic efficiency close to the unity to avoid any energy overconsumption. |
| Keywords | SOFC; Triode operation; H2S poisoning; Ni/GDC anode |
| Remark |
doi:10.1016/j.ssi.2015.05.003 Link |
High-temperature anion and proton conduction in RE3NbO7 (RE = La, Gd, Y, Yb, Lu) compounds
ID=309| Authors |
|
| Source |
Journal of the European Ceramic Society
Volume: 35,
Issue: 11,
Pages: 3051–3061 Time of Publication: 2015 |
| Abstract | The oxide-ion and proton conduction properties of RE3NbO7 (RE = La, Gd, Y, Yb, Lu) compounds were investigated. For the bigger rare-earth cation, i.e. La3+, the compound crystallises in a weberite-type structure and the oxide-ion conductivity is low owing to the lack of intrinsic oxygen vacancies. Consequently, the resultant proton incorporation and conductivity in La3NbO7 are also low. For small rare-earth cations, i.e. from Gd3+ to Lu3+ and for RE = Y, materials adopt a fluorite-like structure confirmed from X-ray powder diffraction. In this latter case, materials include intrinsic oxygen vacancies leading to a higher oxygen conductivity. For these compounds, a proton incorporation takes place at low temperature under wet conditions giving rise to proton conductivity. Nevertheless, both oxygen and proton conductivities are low in these materials, which can be explained by the ordering of oxygen vacancies observed by Transmission Electron Microscopy. |
| Keywords | Protonic ceramic fuel cell; Rare-earth niobate; Combustion synthesis; Fluorite-type structure; Electrical properties |
| Remark |
doi:10.1016/j.jeurceramsoc.2015.04.014 Link |
Proton transport properties of the RE3Ga5MO14 (RE = La, Nd and M = Si, Ti, Sn) langasite family of oxides
ID=308| Authors |
|
| Source |
Solid State Ionics
Volume: 275,
Pages: 29–34 Time of Publication: 2015 |
| Abstract | Hydration and proton transport properties of novel, intrinsically acceptor doped compositions within the RE3Ga5MO14 family of oxides have been addressed by means of measurements of the electrical conductivity. Oxygen vacancies and protons charge compensate the acceptor in dry and wet atmospheres, respectively, and all compositions display significant proton conductivity below 1000 °C. The hydration thermodynamics is affected by M-ion substitution, and becomes more favorable in the order Si < Ti < Sn. The enthalpy of proton mobility is also strongly dependent on the M-ion; M = Si, Ti and Sn exhibit enthalpies of proton mobility of 76 ± 3, 61 ± 1 and 80 ± 2 kJ mol− 1, respectively. |
| Keywords | Langasites; Conductivity; Defects; Acceptor; Hydration; Protons |
| Remark |
doi:10.1016/j.ssi.2015.03.014 Link |
Diffusion of Nd and Mo in lanthanum tungsten oxide
ID=307| Authors |
|
| Source |
Solid State Ionics
Volume: 274,
Pages: 128–133 Time of Publication: 2015 |
| Abstract | Cation diffusion in functional oxides exposed to electrochemical gradients may lead to kinetic demixing or decomposition and, consequently, determine the life-time of the functional component. Here we present chemical diffusion coefficients of Nd and Mo in the mixed proton–electron conductor lanthanum tungsten oxide, La28 − xW4 + xO54 + 3x/2 (LWO), measured at 1000 to 1200 °C in both oxidizing and reducing atmospheres. The bulk diffusivities of Nd and Mo were similar at all temperatures investigated and did not change significantly from oxidizing to reducing conditions. On these bases it is suggested that bulk diffusion of both Nd and Mo occurs via the La2 site on which both cations reside. Based on the low activation energy for bulk transport (~ 200 kJ∙mol− 1) at temperatures below 1200 °C it is proposed that the cation defect concentrations are, in effect, frozen in. Preferential diffusion of Nd along the grain boundaries was rationalized based on space charge effects and depletion of W6 + and Mo6 + near the positively charged grain boundary core. Potential implications of kinetic demixing or decomposition of LWO membranes are also evaluated based on the present results. |
| Keywords | Lanthanum tungstate; Cation diffusion; SIMS; Degradation; Tracer diffusion |
| Remark |
doi:10.1016/j.ssi.2015.03.011 Link |
Crystal structure and high-temperature properties of the Ruddlesden–Popper phases Sr3−xYx(Fe1.25Ni0.75)O7−δ (0≤x≤0.75)
ID=306| Authors |
|
| Source |
Journal of Solid State Chemistry
Volume: 227,
Pages: 45–54 Time of Publication: 2015 |
| Abstract | Ruddlesden–Popper n=2 member phases Sr3−xYxFe1.25Ni0.75O7−δ, 0≤x≤0.75, have been investigated by X-ray and neutron powder diffraction, thermogravimetry and Mössbauer spectroscopy. Both samples as-prepared at 1300 °C under N2(g) flow and samples subsequently air-annealed at 900 °C were studied. The as-prepared x=0.75 phase is highly oxygen deficient with δ=1, the O1 atom site being vacant, and the Fe3+/Ni2+ ions having a square pyramidal coordination. For as-prepared phases with lower x values, the Mössbauer spectral data are in good agreement with the presence of both 5- and 4-coordinated Fe3+ ions, implying in addition a partial occupancy of the O3 atom sites that form the basal plane of the square pyramid. The air-annealed x=0.75 sample has a δ value of 0.61(1) and the structure has Fe/Ni ions in both square pyramids and octahedra. Mössbauer spectroscopy shows the phase to contain only Fe3+, implying that all Ni is present as Ni3+. Air-annealed phases with lower x values are found to contain both Fe3+ and Fe4+. For both the as-prepared and the air-annealed samples, the Y3+ cations are found to be mainly located in the perovskite block. The high-temperature thermal expansion of as-prepared and air-annealed x=0.75 phases were investigated by high-temperature X-ray diffraction and dilatometry and the linear thermal expansion coefficient determined to be 14.4 ppm K−1. Electrical conductivity measurements showed that the air-annealed samples have higher conductivity than the as-prepared ones. |
| Keywords | Ruddlesden–Popper structure; Oxygen non-stoichiometry; Crystal structure; Mössbauer spectroscopy; Electrical conductivity; Thermal expansion |
| Remark |
doi:10.1016/j.jssc.2015.03.018 Link |
Atmosphere dependence of anode reaction of intermediate temperature steam electrolysis using perovskite type proton conductor
ID=305| Authors |
|
| Source |
Journal of Solid State Electrochemistry
Volume: 19,
Issue: 6,
Pages: 1793-1798 Time of Publication: 2015 |
| Abstract | The effect of oxygen partial pressure on anode reaction of steam electrolysis using SrZr0.5Ce0.4Y0.1O3-α (SZCY-541) proton conducting electrolyte was investigated by AC impedance measurement in this work. The anode reaction was enhanced by increasing oxygen partial pressure, and this result was opposite to the expectation from the conventional anode reaction (water splitting reaction). The increase in the electrode reaction conductivity with oxygen chemical potential was proportional to PO21/4 at 600 °C and at higher oxygen partial pressure region of 700 and 800 °C, suggesting the possibility that the enhancement is caused by the increase in hole concentration on the electrolyte surface near the anode. |
| Remark | Link |
FD Electrolysis: Co-electrolysis of steam and CO2 in full-ceramic symmetrical SOECs: A strategy for avoiding the use of Hydrogen as a safe gas
ID=304| Authors |
|
| Source |
Faraday Discussions
Time of Publication: 2015
|
| Abstract | The use of cermets as fuel electrodes for solid oxide electrolysis cells requires permanent circulation of reducing gas, e.g. H2 or CO, so called safe gas, in order to avoid oxidation of the metallic phase. Replacing metallic based electrodes by pure oxides is therefore proposed as an advantage for the industrial application of solid oxide electrolyzers. In this work, full-ceramic symmetrical solid oxide electrolysis cells have been investigated for steam/CO2 co-electrolysis. Electrolyte supported cells with La0.75Sr0.25Cr0.5Mn0.5O3-δ reversible electrodes have been fabricated and tested in co-electrolysis mode using different fuel compositions, from pure H2O to pure CO2, at temperatures of 850°C – 900°C. Electrochemical impedance spectroscopy and galvanostatic measurements have been carried out for the mechanistic understanding of the symmetrical cells performance. The content of H2 and CO in the product gas has been measured by in-line gas micro-chromatography. The effect of employing H2 as a safe gas has been also investigated. Maximum density currents of 750 mA/cm2 and 620 mA/cm2 have been applied at 1.7 V for pure H2O and for H2O:CO2 ratios of 1:1, respectively. Remarkable results were obtained for hydrogen-free fuel compositions, which confirmed the interest of using ceramic oxides as a fuel electrode candidate to reduce or completely avoid the use of safe gas in operation minimizing the contribution of the reverse water shift reaction (RWSR) in the process. H2:CO ratios close to two were obtained for hydrogen-free tests fulfilling the basic requirements for synthetic fuel production. An important increase of the operation voltage was detected under continuous operation leading to a dramatic failure by delamination of the oxygen electrode. |
| Remark |
Accepted Manuscript, DOI: 10.1039/C5FD00018A Link |
Doping strategies for increased oxygen permeability of CaTiO3 based membranes
ID=303| Authors |
|
| Source |
Journal of Membrane Science
Volume: 482,
Pages: 137–143 Time of Publication: 2015 |
| Abstract | Oxygen permeation measurements are performed on dense samples of CaTi0.85Fe0.15O3−δ, CaTi0.75Fe0.15Mg0.05O3−δ and CaTi0.75Fe0.15Mn0.10O3−δ in combination with density functional theory (DFT) calculations and X-ray photoelectron spectroscopy (XPS) in order to assess Mg and Mn as dopants for improving the O2 permeability of CaTi1−xFexO3−δ based oxygen separation membranes. The oxygen permeation measurements were carried out at temperatures ranging between 700 and 1000 °C with feed side oxygen partial pressures between 0.01 and 1 bar. The O2 permeability was experimentally found to be highest for the Mn doped sample over the whole temperature range, reaching 4.2×10−3 ml min−1 cm−1 at 900 °C and 0.21 bar O2 in the feed which corresponds to a 40% increase over the Fe-doped sample and similar to reported values for x=0.2. While the O2 permeability of the Mg doped sample was also higher than the Fe-doped sample, it approached that of the Fe-doped sample above 900 °C. According to the DFT calculations, Mn introduces electronic states within the band gap and will predominately exist in the effectively negative charge state, as indicated by XPS measurements. Mn may therefore improve the ionic and electronic conductivity of CTF based membranes. The results are discussed in terms of the limiting species for ambipolar transport and O2 permeability, i.e., oxygen vacancies and electronic charge carriers. |
| Keywords | Dense ceramic oxygen membrane; Ambipolar transport; Mixed ionic-electronic conduction; CaTiO3; Calcium titanate |
| Remark |
doi:10.1016/j.memsci.2015.02.036 Link |
Coated stainless steel 441 as interconnect material for solid oxide fuel cells: Evolution of electrical properties
ID=302| Authors |
|
| Source |
Journal of Power Sources
Volume: 284,
Pages: 321–327 Time of Publication: 2015 |
| Abstract | AISI 441 coated with a double layer coating of 10 nm cerium (inner layer) and 630 nm cobalt was investigated and in addition the uncoated material was exposed for comparison. The main purpose of this investigation was the development of a suitable ASR characterization method. The material was exposed to a simulated cathode atmosphere of air with 3% water at 850 °C and the samples were exposed for up to 1500 h. We compared two methods of ASR measurements, an in-situ method where samples were measured with platinum electrodes for longer exposure times and an ex-situ method where pre-oxidized samples were measured for only very short measurement times. It was found that the ASR of ex-situ characterized samples could be linked to the mass gain and the electrical properties could be linked to the evolving microstructure during the different stages of exposure. Both the degradation of the electric performance and the oxygen uptake (mass gain) followed similar trends. After about 1500 h of exposure an ASR value of about 15 mΩcm2 was reached. The in-situ measured samples suffered from severe corrosion attack during measurement. After only 500 h of exposure already a value of 35 mΩcm2 was obtained. |
| Keywords | ASR; Interconnect; AISI 441; SOFC; Corrosion; Platinum |
| Remark |
doi:10.1016/j.jpowsour.2015.03.029 Link |
Steam-promoted CO2 flux in dual-phase CO2 separation membranes
ID=301| Authors |
|
| Source |
Journal of Membrane Science
Volume: 482,
Pages: 115–119 Time of Publication: 2015 |
| Abstract | Steam dissolving into molten carbonates through the formation of hydroxide ions could contribute to the permeation of CO2 in dual-phase membranes under certain conditions. In this work, ceria (CeO2) supported dual-phase membranes was fabricated and the effect of steam on the transport properties has been investigated by means of flux measurements. The results show an approximate 30% increase of the CO2 flux when 2.5% steam is introduced to the feed side, while an approximate 250–300% increase of the CO2 flux is observed when introducing the same amount of steam to the sweep side. These phenomena and transport mechanisms are explained by the theory of ambipolar permeation of CO2 via various combinations of charged species. |
| Keywords | Dual-phase; CO2 separation membrane; Steam; Flux |
| Remark |
doi:10.1016/j.memsci.2015.02.029 Link |
Electrical conductivity and thermopower of (1 − x) BiFeO3 – xBi0.5K0.5TiO3 (x = 0.1, 0.2) ceramics near the ferroelectric to paraelectric phase transition
ID=300| Authors |
|
| Source |
Physical Chemistry Chemical Physics
Volume: 17,
Issue: 14,
Pages: 9420-9428 Time of Publication: 2015 |
| Abstract | Ferroelectric BiFeO3 has attractive properties such as high strain and polarization, but a wide range of applications of bulk BiFeO3 are hindered due to high leakage currents and a high coercive electric field. Here, we report on the thermal behaviour of the electrical conductivity and thermopower of BiFeO3 substituted with 10 and 20 mol% Bi0.5K0.5TiO3. A change from p-type to n-type conductivity in these semi-conducting materials was demonstrated by the change in the sign of the Seebeck coefficient and the change in the slope of the isothermal conductivity versus partial pressure of O. A minimum in the isothermal conductivity was observed at [similar]10−2 bar O2 partial pressure for both solid solutions. The strong dependence of the conductivity on the partial pressure of O2 was rationalized by a point defect model describing qualitatively the conductivity involving oxidation/reduction of Fe3+, the dominating oxidation state of Fe in stoichiometric BiFeO3. The ferroelectric to paraelectric phase transition of 80 and 90 mol% BiFeO3 was observed at 648 ± 15 and 723 ± 15 °C respectively by differential thermal analysis and confirmed by dielectric spectroscopy and high temperature powder X-ray diffraction. |
| Remark |
DOI: 10.1039/C5CP00266D Link |
Structure and conductivity of acceptor doped La2BaZnO5 and Nd2BaZnO5
ID=299| Authors |
|
| Source |
Solid State Ionics
Volume: 272,
Pages: 160–165 Time of Publication: 2015 |
| Abstract | The effect of calcium substitution on the structure and electrical conductivity of Ln2 − xCaxBaZnO5 − δ, Ln = La and Nd, has been studied. Differing trends with respect to dependence of the unit cell volume were observed as a function of Ca substitution. For both series of materials the limit of Ca substitution was estimated to be x ≈ 0.2. The electrical conductivity was studied in the temperature range of 1000–350 °C using electrochemical impedance spectroscopy in argon and oxygen atmospheres and via isotherms between 400 and 1000 °C as function of oxygen pressure and the water vapour pressure. A marked increase in conductivity of approx. two orders of magnitude was explained by the presence of oxygen vacancies in the calcium doped samples. At pO2 < 10− 12 atm the x = 0.15 materials are predominantly oxygen ion conductors, and La1.85Ca0.15BaZnO5 − δ displays a peak conductivity of 0.002 S cm− 1 at 1000 °C. The materials display a rise in conductivity in oxidizing conditions, indicating a significant p-type contribution. |
| Keywords | Oxide ion conductor; Mixed conductor; Synthesis; Impedance spectroscopy; SOFC |
| Remark |
doi:10.1016/j.ssi.2015.02.001 Link |
Dual atmosphere study of the K41X stainless steel for interconnect application in high temperature water vapour electrolysis
ID=298| Authors |
|
| Source |
International Journal of Hydrogen Energy
Volume: 40,
Issue: 15,
Pages: 5305–5312 Time of Publication: 2015 |
| Abstract | High temperature water vapour electrolysis (HTE) is one of the most efficient technologies for mass hydrogen production. A major technical difficulty related to high temperature water vapour electrolysis is the development of interconnects working efficiently for a long period. Working temperature of 800 °C enables the use of metallic materials as interconnects. High temperature corrosion behaviour and electrical conductivity of a commercial stainless steel, K41X (AISI 441), were tested in HTE dual atmosphere (95%O2-5%H20/10%H2-90%H2O) at 800 °C. The alloy exhibits a very good oxidation resistance compared to single atmosphere tests. However, a supplied electrical current significantly changes the nature of the oxides that form during the test. A very good Area Specific Resistance (ASR) parameter was measured in dual atmosphere, much lower than the values obtained in single atmosphere tests. |
| Remark |
doi:10.1016/j.ijhydene.2015.01.116 Link |
Solid oxide fuel cells with (La,Sr)(Ga,Mg)O3-δ electrolyte film deposited by radio-frequency magnetron sputtering
ID=297| Authors |
|
| Source |
Journal of Power Sources
Volume: 281,
Pages: 258–264 Time of Publication: 2015 |
| Abstract | In this study, solid oxide fuel cells (SOFCs) containing a high quality La0.9Sr0.1Ga0.8Mg0.2O3-δ (LSGM) film deposited on anode supported substrate using RF magnetron sputtering are successfully prepared. The anode substrate is composed of two functional NiO/Sm0.2Ce0.8O2-δ (SDC) composite layers with ratios of 60/40 wt% and 50/50 wt% and a current collector layer of pure NiO. The as-deposited LSGM film appears to be amorphous in nature. After post-annealing at 1000 °C, a uniform and dense polycrystalline film with a composition of La0.87Sr0.13Ga0.85Mg0.15O3-δ and a thickness of 3.8 μm is obtained, which was well adhered to the anode substrate. A composite LSGM/La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) layer, with a ratio of 30/70 wt%, is used as the cathode. The SOFC prepared reveals a good mechanical integrity with no sign of cracking, delamination, or discontinuity among the interfaces. The total cell resistance of a single cell with LSGM electrolyte film declines from 0.60 to 0.10 Ω cm2 as the temperature escalates from 600 to 800 °C and the open circuit voltage (OCV) ranges from 0.85 to 0.95 V. The maximum power density (MPD) of the single cell is reported as 0.65, 1.02, 1.30, 1.42, and 1.38 W cm−2 at 600, 650, 700, 750, and 800 °C, respectively. The good cell performance leads to the conclusion that RF magnetron sputtering is a feasible deposition method for preparing good quality LSGM films in SOFCs. |
| Keywords | Solid oxide fuel cell; Sputtering; Electrolyte; Doped lanthanum gallate |
| Remark |
doi:10.1016/j.jpowsour.2015.01.185 Link |
Phase equilibria in the Cs2MoO4–ZnMoO4–Zr(MoO4)2 system, Crystal structures and properties of new triple molybdates Cs2ZnZr(MoO4)4 and Cs2ZnZr2(MoO4)6
ID=296| Authors |
|
| Source |
Volume: 81,
Pages: 93–99 Time of Publication: 2015 |
| Abstract | Subsolidus phase relations in the Cs2MoO4–ZnMoO4–Zr(MoO4)2 system were determined and two new compounds, Cs2ZnZr(MoO4)4 and Cs2ZnZr2(MoO4)6, were obtained. The structure of Cs2ZnZr(MoO4)4 (a=5.7919(1) Å, c=8.0490(3) Å; space group P View the MathML source3¯m1; Z=0.5; R=0.0149) belongs to the layered glaserite-like KAl(MoO4)2 structure type where the octahedral Al3+ positions are statistically occupied by 0.5 Zn2++0.5 Zr4+. The second triple molybdate, Cs2ZnZr2(MoO4)6 (a=13.366(1) Å, c=12.253(3) Å, space group R View the MathML source3¯, Z=3, R=0.0324), is isostructural to Cs2MnZr2(MoO4)6 and Cs2M2Zr(MoO4)6 (M=Al, Fe) and contains a mixed 3D framework built of МоO4 tetrahedra and (Zn, Zr)O6 octahedra sharing common vertices. Cesium cations are located in large channels of the framework. The latter compound undergoes a first-order phase transition at 723 K with considerable increasing its ionic conductivity. |
| Keywords | Cesium; Zinc; Zirconium; Triple molybdates; Crystal structure; X-ray diffraction; IR and Raman spectra; Conductivity |
| Remark |
doi:10.1016/j.jpcs.2015.01.015 Link |
Binder Jetting: A Novel Solid Oxide Fuel-Cell Fabrication Process and Evaluation
ID=295| Authors |
|
| Source |
JOM
Volume: 67,
Issue: 3,
Pages: 660-667 Time of Publication: 2015 |
| Abstract | With an ever-growing concern to find a more efficient and less polluting means of producing electricity, fuel cells have constantly been of great interest. Fuel cells electrochemically convert chemical energy directly into electricity and heat without resorting to combustion/mechanical cycling. This article studies the solid oxide fuel cell (SOFC), which is a high-temperature (100°C to 1000°C) ceramic cell made from all solid-state components and can operate under a wide range of fuel sources such as hydrogen, methanol, gasoline, diesel, and gasified coal. Traditionally, SOFCs are fabricated using processes such as tape casting, calendaring, extrusion, and warm pressing for substrate support, followed by screen printing, slurry coating, spray techniques, vapor deposition, and sputter techniques, which have limited control in substrate microstructure. In this article, the feasibility of engineering the porosity and configuration of an SOFC via an additive manufacturing (AM) method known as binder jet printing was explored. The anode, cathode and oxygen ion-conducting electrolyte layers were fabricated through AM sequentially as a complete fuel cell unit. The cell performance was measured in two modes: (I) as an electrolytic oxygen pump and (II) as a galvanic electricity generator using hydrogen gas as the fuel. An analysis on influence of porosity was performed through SEM studies and permeability testing. An additional study on fuel cell material composition was conducted to verify the effects of binder jetting through SEM–EDS. Electrical discharge of the AM fabricated SOFC and nonlinearity of permeability tests show that, with additional work, the porosity of the cell can be modified for optimal performance at operating flow and temperature conditions. |
| Remark |
DOI 10.1007/s11837-015-1296-9 Link |
Hydrogen separation membranes based on dense ceramic composites in the La27W5O55.5–LaCrO3 system
ID=294| Authors |
|
| Source |
Journal of Membrane Science
Volume: 479,
Pages: 39–45 Time of Publication: 2015 |
| Abstract | Some compositions of ceramic hydrogen permeable membranes are promising for integration in high temperature processes such as steam methane reforming due to their high chemical stability in large chemical gradients and CO2 containing atmospheres. In the present work, we investigate the hydrogen permeability of densely sintered ceramic composites (cercer) of two mixed ionic-electronic conductors: La27W3.5Mo1.5O55.5−δ (LWM) containing 30, 40 and 50 wt% La0.87Sr0.13CrO3−δ (LSC). Hydrogen permeation was characterized as a function of temperature, feed side hydrogen partial pressure (0.1–0.9 bar) with wet and dry sweep gas. In order to assess potentially limiting surface kinetics, measurements were also carried out after applying a catalytic Pt-coating to the feed and sweep side surfaces. The apparent hydrogen permeability, with contribution from both H2 permeation and water splitting on the sweep side, was highest for LWM70-LSC30 with both wet and dry sweep gas. The Pt-coating further enhances the apparent H2 permeability, particularly at lower temperatures. The apparent H2 permeability at 700 °C in wet 50% H2 was 1.1×10−3 mL min−1 cm−1 with wet sweep gas, which is higher than for the pure LWM material. The present work demonstrates that designing dual-phase ceramic composites of mixed ionic-electronic conductors is a promising strategy for enhancing the ambipolar conductivity and gas permeability of dense ceramic membranes. |
| Keywords | Hydrogen separation; Dense ceramic membrane; Ceramic–ceramic composite; Lanthanum tungstate; Lanthanum chromite |
| Remark |
doi:10.1016/j.memsci.2015.01.027 Link |
Bi1−xNbxO1.5+x (x=0.0625, 0.12) fast ion conductors: Structures, stability and oxide ion migration pathways
ID=293| Authors |
|
| Source |
Journal of Solid State Chemistry
Volume: 225,
Pages: 383–390 Time of Publication: 2015 |
| Abstract | A combined experimental and computational study of Bi1−xNbxO1.5+x (x=0.0625 and 0.12) has been carried out using laboratory X-ray, neutron and electron diffraction, impedance measurements and ab-initio molecular dynamics. We demonstrate that Bi0.9375Nb0.0625O1.5625, previously reported to adopt a cubic fluorite-type superstructure, can form two different polymorphs depending on the synthetic method: a metastable cubic phase is produced by quenching; while slower cooling yields a stable material with a tetragonal √2×√2×1 superstructure, which undergoes a reversible phase transition into the cubic form at ~680 °C on subsequent reheating. Neutron diffraction reveals that the tetragonal superstructure arises mainly from ordering in the oxygen sublattice, with Bi and Nb remaining disordered, although structured diffuse scattering observed in the electron diffraction patterns suggests a degree of short-range ordering. Both materials are oxide ion conductors. On thermal cycling, Bi0.88Nb0.12O1.62 exhibits a decrease in conductivity of approximately an order of magnitude due to partial transformation into the tetragonal phase, but still exhibits conductivity comparable to yttria-stabilised zirconia (YSZ). Ab-initio molecular dynamics simulations performed on Bi0.9375Nb0.0625O1.5625 show that oxide ion diffusion occurs by O2− jumps between edge- and corner-sharing OM4 groups (M=Bi, Nb) via tetrahedral □M4 and octahedral □M6 vacancies. |
| Keywords | Functional oxides; Fast ion conductors; Complex superstructures |
| Remark |
doi:10.1016/j.jssc.2015.01.006 Link |
Functional properties of La0.99X0.01Nb0.99Al0.01O4−δ and La0.99X0.01Nb0.99Ti0.01O4−δ proton conductors where X is an alkaline earth cation
ID=292| Authors |
|
| Source |
Journal of the European Ceramic Society
Volume: 35,
Issue: 4,
Pages: 1239–1253 Time of Publication: 2015 |
| Abstract | Lanthanum niobates with general formulas of La0.99X0.01Nb0.99Al0.01O4−δ and La0.99X0.01Nb0.99Ti0.01O4−δ (X = Mg, Ca, Sr or Ba) were synthesized via the conventional solid state reaction. Specimens with relative density above 96% were produced after sintering. Structural and phase composition studies revealed predominant monoclinic Fergusonite structure for the majority of samples. SEM and TEM studies elucidated the effect of the used dopant combinations on grain growth, micro-crack formation and secondary phase formation. Results from microstructural study were correlated to the grain interior and grain boundary conductivities for selected samples (La0.99Sr0.01Nb0.99Al0.01O4−δ and La0.99Sr0.01Nb0.99Ti0.01O4−δ). The majority of co-doped niobates exhibited appreciable protonic conductivity under humid atmospheres at intermediate temperatures. Sr- or Ca-doped compounds displayed the highest total conductivities with values for LSNA equal to 6 × 10−4 S/cm and 3 × 10−4 S/cm in wet air and in wet 4% H2–Ar (900 °C), respectively. Additionally, thermal expansion was studied to complete functional characterization of co-doped LaNbO4. |
| Keywords | Proton-conducting ceramic materials; Hydrogen transport ceramic membranes; Rare earth ortho-niobates; Acceptor-doped lanthanum niobates |
| Remark |
doi:10.1016/j.jeurceramsoc.2014.11.009 Link |
Hydrogen permeation, water splitting and hydration kinetics in Nd5.4Mo0.3W0.7O12−δ
ID=291| Authors |
|
| Source |
Journal of Membrane Science
Volume: 476,
Pages: 105–111 Time of Publication: 2015 |
| Abstract | To investigate transport properties of Mo-substituted Nd5.4Mo0.3W0.7O12−δ for hydrogen separation application, hydrogen fluxes of Nd5.4Mo0.3W0.7O12−δ have been measured in both dry and wet sweep gases. The fluxes in dry sweep gas show lower temperature dependence at high temperatures than at low temperatures. Comparing the hydrogen permeability among rare earth tungstates, it has been revealed that the larger the RE-site cation radius, the higher the hydrogen permeation. Water splitting effect for the wet sweep gas has been confirmed by mass spectrometry. Oxygen surface kinetics under oxidizing conditions has been studied by ToF-SIMS measurements, and is significantly faster under wet conditions than dry. Hydration kinetics has been studied by conductivity relaxation measurements under reducing conditions for the first time, showing a two-fold non-monotonic behavior. |
| Keywords | Hydrogen permeation; Hydration kinetics; Water splitting; Oxygen surface kinetics; Nd5.4Mo0.3W0.7O12−δ |
| Remark |
doi:10.1016/j.memsci.2014.11.013 Link |
Savitha Thayumanasundaram, Vijay Shankar Rangasamy, Niels De Greef, Jin Won Seo andJean-Pierre Locquet
ID=290| Author |
|
| Source |
European Journal of Inorganic Chemistry
Volume: 2015,
Issue: 7,
Pages: 1290–1299 Time of Publication: 2014 |
| Abstract | Polymer blends of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA) were prepared with different molar ratios by a solvent-casting technique. The XRD patterns of the blends show that the degree of crystallinity of the PVA membranes decreases with the addition of PAA owing to the formation of interpenetrating polymer chains. The vibrational spectra of the blend membranes reveal the formation of strong hydrogen bonding between PVA and PAA. Dynamic mechanical analysis (DMA) reveals that the storage modulus of a 25 mol-% PAA sample is comparable to that of pure PVA and, therefore, confirms the mechanical stability of the blend membranes. Significant changes in the peak areas and chemical shifts of the PVA hydroxyl signal (δ = 4–5 ppm) in the 1H NMR spectra of the blend membranes confirm the strong hydrogen bonding between the OH groups of PVA and PAA. The ionic liquid (IL) 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR14TFSI) with 0.2 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) was added to the polymer blend to prepare flexible, nonvolatile hybrid polymer electrolytes for lithium-ion batteries. A maximum ionic conductivity of 1 mS cm–1 is observed at 90 °C for the membrane with 70 mol-% IL. |
| Keywords | Polymers;Ionic liquids;Hybrid membranes;Hydrogen bonds;Lithium batteries |
| Remark |
DOI: 10.1002/ejic.201402603 Link |
Pure and Mn-doped La4SrTi5O17 layered perovskite as potential solid oxide fuel cell material: Structure and anodic performance
ID=289| Authors |
|
| Source |
Journal of Power Sources
Volume: 274,
Pages: 806–815 Time of Publication: 2015 |
| Abstract | Pure and 5% Mn doped layered perovskites La4SrTi5O17, members of the La4Srn-4(Ti,Mn)nO3n+2 series with n = 5, have been synthesized and investigated as anode materials for Solid Oxide Fuel Cells. The use of XRD, neutron and electron diffraction techniques allows clarifying some divergences concerning the structural characterization within the family, not only in air but also in anodic-like N2/H2(97/3) atmosphere. The electrical conductivity of both compounds is very low in air but those values increase by two orders of magnitude in diluted hydrogen. The study of catalytic properties for methane steam reforming as well as in-depth analysis of the SOFC anodic behaviour of both materials are described, for which a microstructure optimization of the electrode allows to demonstrate the potential interest of the lamellar materials upon the classical three-dimensional cubic-like LSTs. |
| Keywords | SOFC; Anode; Layered perovskite; Titanate; Methane steam reforming; Electrochemical impedance spectroscopy |
| Remark |
doi:10.1016/j.jpowsour.2014.10.131 Link |
Electrochemical performance and carbon deposition resistance of Ce-doped La0.7Sr0.3Fe0.5Cr0.5O3-δ anode materials for solid oxide fuel cells fed with syngas
ID=288| Authors |
|
| Source |
Journal of Power Sources
Volume: 254,
Pages: 483–487 Time of Publication: 2015 |
| Abstract | Ce-doped La0.7Sr0.3Fe0.5Cr0.5O3-δ (Ce-LSFC) perovskite anode catalysts for solid oxide fuel cells are successfully synthesized by a modified combustion method for the first time. The pure perovskite structure without formation of CeO2 is obtained when the content of Ce ≤ 10%. Compared with La0.7Sr0.3Fe0.5Cr0.5O3-δ anode, Ce-LSFC anode not only shows much higher catalytic activity towards the oxidation of syngas with less carbon deposition, but also displays better regeneration from coking. The enhanced performance is attributed to the more available oxygen vacancies in lattice and better oxygen mobility after doping with Ce. |
| Keywords | SOFC; Ce-doped LSFC; Perovskite |
| Remark |
doi:10.1016/j.jpowsour.2014.10.090 Link |
Visualization of conduction pathways in a lanthanum lithium titanate superionic conductor synthesized by rapid cooling
ID=287| Authors |
|
| Source |
Solid State Ionics
Volume: 268,
Issue: A,
Pages: 76-81 Time of Publication: 2014 |
| Abstract | Three-dimensional structure and conduction pathways of the lithium ions in 7Li0.4La0.53TiO3 quenched with liquid nitrogen were studied using reverse Monte Carlo modeling and the bond valence sum approach using neutron diffraction data. The lithium ions were primarily located in the region between the off-center positions of the A-sites and bottlenecks defined by four coordinating oxygen ions. The bottlenecks in the predicted conduction pathways of the lithium ions were classified into three types (I, II, and III) by their size. The type II bottlenecks were the most accessible to lithium-ion migration and more than 70% of the bottlenecks were type II. |
| Keywords | Lithium-ion conductor; Lanthanum lithium titanate; Local structure; Neutron diffraction; Reverse Monte Carlo modeling; Bond valence sum |
| Remark |
doi:10.1016/j.ssi.2014.09.030 Link |
Functional properties of La0.99X0.01Nb0.99Al0.01O4−δ and La0.99X0.01Nb0.99Ti0.01O4−δ proton conductors where X is an alkaline earth cation
ID=286| Authors |
|
| Source |
Journal of the European Ceramic Society
Time of Publication: 2014-12
|
| Abstract | Lanthanum niobates with general formulas of La0.99X0.01Nb0.99Al0.01O4−δ and La0.99X0.01Nb0.99Ti0.01O4−δ (X = Mg, Ca, Sr or Ba) were synthesized via the conventional solid state reaction. Specimens with relative density above 96% were produced after sintering. Structural and phase composition studies revealed predominant monoclinic Fergusonite structure for the majority of samples. SEM and TEM studies elucidated the effect of the used dopant combinations on grain growth, micro-crack formation and secondary phase formation. Results from microstructural study were correlated to the grain interior and grain boundary conductivities for selected samples (La0.99Sr0.01Nb0.99Al0.01O4−δ and La0.99Sr0.01Nb0.99Ti0.01O4−δ). The majority of co-doped niobates exhibited appreciable protonic conductivity under humid atmospheres at intermediate temperatures. Sr- or Ca-doped compounds displayed the highest total conductivities with values for LSNA equal to 6 × 10−4 S/cm and 3 × 10−4 S/cm in wet air and in wet 4% H2–Ar (900 °C), respectively. Additionally, thermal expansion was studied to complete functional characterization of co-doped LaNbO4. |
| Keywords | Proton-conducting ceramic materials, Hydrogen transport ceramic membranes, Rare earth ortho-niobates, Acceptor-doped lanthanum niobates, ProGasMix |
| Remark | Link |
Versatile apparatus for thermoelectric characterization of oxides at high temperatures
ID=285| Authors |
|
| Source |
Review of Scientific Instruments
Volume: 85,
Pages: 103906 Time of Publication: 2014 |
| Abstract | An apparatus for measuring the Seebeck coefficient and electrical conductivity is presented and characterized. The device can be used in a wide temperature range from room temperature to 1050 °C and in all common atmospheres, including oxidizing, reducing, humid, and inert. The apparatus is suitable for samples with different geometries (disk-, bar-shaped), allowing a complete thermoelectric characterization (including thermal conductivity) on a single sample. The Seebeck coefficient α can be measured in both sample directions (in-plane and cross-plane) simultaneously. Electrical conductivity is measured via the van der Pauw method. Perovskite-type CaMnO3 and the misfit cobalt oxide (Ca2CoO3) q (CoO2) are studied to demonstrate the temperature range and to investigate the variation of the electrical properties as a function of the measurement atmosphere. |
| Remark |
http://dx.doi.org/10.1063/1.4897489 Link |
Electrochemical behavior of the pyrochlore- and fluorite-like solid solutions in the Pr2O3–ZrO2 system. Part I
ID=284| Authors |
|
| Source |
Solid State Ionics
Time of Publication: 2014
|
| Abstract | We have studied the structure, microstructure, and electrochemical properties in air of (Pr2 − xZrx)Zr2O7 + x/2 (x = 0.15, 0.32, 0.78), Pr2Zr2O7, and Pr2(Zr2 − xPrx)O7 − x/2 (x = 0.1, 0.4, 1) materials. The solid solutions were prepared through coprecipitation followed by heat treatment of the precursors at 1550 °C for 4 h. According to XRD data, the extent of the pyrochlore-like Pr2 ± xZr2 ± xO7 ± x/2 solid solutions at 1550 °C is ~ 6 mol.%, which is considerably smaller than that in the NdZrO and SmZrO systems at this temperature. Among the pyrochlores, the highest bulk conductivity was offered by the (Pr2 − xZrx)Zr2O7 + x/2 (x = 0.15): 7.15 × 10− 3 S/cm at 800 °C (Ea = 0.66 eV). The pyrochlore-like Pr2(Zr2 − xPrx)O7 − x/2 (x = 0.1) had lower conductivity (3.97 × 10− 3 S/cm at 800 °C). The highest bulk conductivity among the materials studied was found in the Pr2O3-rich fluorite-like Pr2(Zr2 − xPrx)O7 − x/2 with x = 1: ~ 0.217 S/cm at 800 °C (Ea = 0.0.31 eV). The temperature-dependent conductivity of the Pr2O3-rich fluorite-like solid solutions Pr2(Zr2 − xPrx)O7 − x/2 with x = 0.4 and 1 had a break at 560 °C, suggesting a change in the mechanism of ion transport at this temperature. |
| Remark |
DOI: 10.1016/j.ssi.2014.09.035 Link |
Thermal Depolarization in the High-Temperature Ternary Piezoelectric System xPbTiO3–yBiScO3–zBi(Ni1/2Ti1/2)O3
ID=283| Authors |
|
| Source |
Journal of the American Ceramic Society
Time of Publication: 2014
|
| Abstract | In the high-temperature ternary perovskite piezoelectric system xPbTiO3–yBiScO3–zBi(Ni1/2,Ti1/2)O3 (PT–BS–BNiT), the addition of bismuth to the A site and nickel to the B site leads to compositions that exhibit diffuse relaxor-like behavior. For these, depolarization temperature, not Curie point, is the critical value of temperature. Depolarization temperature (Td) is defined as the temperature at which the steepest loss in polarization occurs. This temperature is observed in poled materials through two different methods: loss tangent measurements and in situ d33. Across the ternary system, multiple dielectric anomalies occurred which was observed in dielectric tests where the dielectric peak broadens and becomes frequency dependent as BNiT content increased. For different compositions, the value of Td ranged between 275°C–375°C. Values for the piezoelectric coefficient increased with temperature up to d33 = 1000 pC/N during in situ d33. High temperature (up to 190°C) and high field (up to 40 kV/cm) were also applied to test ferroelectric properties in these regimes. |
| Remark |
DOI: 10.1111/jace.13268 Link |
Characterization and Modeling of La 1 − x Sr x CoO 3 − δ Solid Oxide Fuel Cell Cathodes Using Nonlinear Electrochemical Impedance Techniques
ID=282| Author |
|
| Source |
Time of Publication: 2014
|
| Remark |
Dissertation Link |
Structural and electrical study of samarium doped cerium oxide thin films prepared by e-beam evaporation
ID=281| Authors |
|
| Source |
Solid State Ionics
Time of Publication: 2014
|
| Abstract | Samarium doped cerium oxide (Sm0.15Ce0.85O1.925, SDC) thin films were grown on the Alloy 600 (Fe–Ni–Cr) and optical quartz (SiO2) substrates using e-beam deposition technique. Formed SDC thin films were characterized using different X-ray diffraction (XRD) techniques, scanning electron microscope (SEM), energy-dispersive spectrometry (EDS) and impedance spectroscopy. The deposition rate of formed SDC thin films was changed from 2 Å/s to 16 Å/s. XRD analysis shows that all thin films have a cubic (FCC) structure and repeat the crystallographic orientation of the initial powders evaporated with different deposition rate and on different substrates. The crystallite size increases from 7.7 nm to 10.3 nm and from 7.2 nm to 9.2 nm on Alloy 600 substrate and optical quartz (SiO2) substrate respectively as the thin film deposition rate increases. SEM images indicate a dense and homogeneous structure of all formed SDC thin films. The ionic conductivity depends on thin films density and blocking factor. The best ionic conductivity (σg = 1.34 Sm− 1 and σgb = 2.29 Sm −1 at 873 K temperature, activation energy ΔEg = 0.91 eV and ΔEgb = 0.99 eV) was achieved for SDC thin films formed at 4 Å/s deposition rate. It was found that the highest density (5.25 g/cm3) and the lowest relaxation time in grain (τg = 9.83 × 10− 7 s), and the lowest blocking factor (0.39) is in SDC thin films formed at 4 Å/s deposition rate. The deposition rate influences the stoichiometry of the formed SDC thin ceramic films. |
| Keywords | Electron beam deposition; Samarium doped ceria oxide (SDC); Solid oxide fuel cells (SOFC); Ionic conductivity |
| Remark |
DOI: 10.1016/j.ssi.2014.09.036 Link |
Electrical conductivity and TG-DSC study of hydration of Sc-doped CaSnO3 and CaZrO3
ID=280| Authors |
|
| Source |
Solid State Ionics
Volume: 267,
Pages: 61–67 Time of Publication: 2014 |
| Abstract | Correlations linking hydration thermodynamics to materials parameters can be of vital importance for further development of proton conducting oxides. However, the currently proposed correlations are troubled by scattering limiting their predictive power. As such, the present contribution has investigated Sc-doped CaSnO3 and CaZrO3 in an attempt to further elucidate the trends in the thermodynamics of hydration for perovskites. Conductivity and impedance spectroscopy on 5 and 10% Sc-doped CaSnO3 demonstrated that it is primarily an oxygen ion conductor with a small protonic contribution at lower temperatures (below 500 °C) under wet conditions. Simultaneous thermogravimetry (TG) and differential scanning calorimetry (DSC), TG-DSC, was applied to measure the standard molar hydration enthalpy of CaSn1−xScxO3−δ and CaZr1−xScxO3−δ (x = 0.05, 0.10, 0.15 and 0.20) as a function of the Sc concentration. The hydration enthalpy becomes increasingly negative with increasing Sc substitution, which is discussed on the basis of changes in electronegativity, basicity and tolerance factor. |
| Keywords | Defects; Protons; Hydration; Thermodynamics; Perovskites |
| Remark |
DOI: 10.1016/j.ssi.2014.09.006 Link |
Synthesis, crystal structure and properties of alluaudite-like triple molybdate Na25Cs8Fe5(MoO4)24
ID=279| Authors |
|
| Source |
Journal of Solid State Chemistry
Volume: 220,
Pages: 217–220 Time of Publication: 2014 |
| Abstract | A new triple molybdate Na25Cs8Fe5(MoO4)24 was synthesized using solid state reactions and studied with X-ray powder diffraction, second harmonic generation (SHG) technique, differential scanning calorimetry, Mössbauer and dielectric impedance spectroscopy. Single crystals of Na25Cs8Fe5(MoO4)24 were obtained and its structure was solved (the space group P View the MathML source1¯, a=12.5814(5), b=13.8989(5), c=28.4386(9) Å, α=90.108(2), β=90.064(2), γ=90.020(2)°, V=4973.0(3) Å3, Z=2, R=0.0440). Characteristic features of the structure are polyhedral layers composed of pairs of edge-shared FeO6 and (Fe, Na)O6 octahedra, which are connected by bridging МоО4 tetrahedra. The layers share common vertices with bridging МоО4 tetrahedra to form an open 3D framework with the cavities occupied by the Cs+ and Na+ cations. The compound undergoes first-order phase transformation at 642 K and above this phase transition, electrical conductivity reaches 10−3–10−2 S cm−1. Thus, Na25Cs8Fe5(MoO4)24 may be considered as a promising compound for developing new materials with high ionic conductivity. |
| Keywords | Triple molybdate; Sodium; Synthesis; Crystal structure; Phase transition; Ionic conductivity |
| Remark |
DOI: 10.1016/j.jssc.2014.09.004 Link |
Hydrogen permeability of SrCe0.7Zr0.25Ln0.05O3−δ membranes (Ln=Tm and Yb)
ID=278| Authors |
|
| Source |
Journal of Membrane Science
Volume: 473,
Pages: 327–332 Time of Publication: 2015 |
| Abstract | Zr substituted acceptor doped SrCeO3 materials were synthesized by citric acid route and characterized by XRD and SEM. The hydrogen flux of the materials was measured as a function of temperature and hydrogen partial pressure on the feed side. The hydrogen permeability for SrCe0.7Zr0.25Tm0.05O3−δ and SrCe0.7Zr0.25Yb0.05O3−δ is similar under our measurement window and shows the same hydrogen partial pressure dependency. Under short circuit condition, the hydrogen permeability increased significantly by more than one order of magnitude indicating that the hydrogen transport is limited by electronic conduction under open circuit conditions. The observed data were discussed by applying defect chemistry and the conventional ambipolar transport theory. After the hydrogen permeation measurements, the indication of kinetic cation de-mixing was found by XRD analysis. |
| Keywords | Co-substitution of B site; Hydrogen flux; Permeability; Acceptor doping; SrCeO3 |
| Remark |
DOI: 10.1016/j.memsci.2014.09.027 Link |
Superior electrochemical performance and oxygen reduction kinetics of layered perovskite PrBaxCo2O5+δ (x = 0.90–1.0) oxides as cathode materials for intermediate-temperature solid oxide fuel cells
ID=277| Authors |
|
| Source |
International Journal of Hydrogen Energy
Time of Publication: 2014
|
| Abstract | The layered perovskite PrBaxCo2O5+δ (PBxCO, x = 0.90–1.0) oxides have been synthesized by a solid-state reaction technique, and evaluated as the potential cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). Room temperature X-ray diffraction patterns show the orthorhombic structures which double the lattice parameters from the perovskite cell parameter as a ≈ ap, b ≈ ap and c ≈ 2ap (ap is the cell parameter of the primitive perovskite) in the Pmmm space group. There is a good chemical compatibility between the PBxCO cathode and the Ce0.9Gd0.1O1.95 (CGO) electrolyte at 1000 °C. The electrical conductivity and thermal expansion coefficient of PBxCO are improved due to the increased amount of electronic holes originated from the Ba-deficiency. The results demonstrate the high electrochemical performance of PBxCO cathodes, as evidenced by the super low polarization resistances (Rp) over the intermediate temperature range. The lowest Rp value, 0.042 Ω cm2, and the cathodic overpotential, −15 mV at a current density of −25 mA cm−2, are obtained in the PrBa0.94Co2O5+δ cathode at 600 °C in air, which thus allow to be used as a highly promising cathode for IT-SOFCs. A CGO electrolyte fuel cell with the PrBa0.94Co2O5+δ cathode presents the attractive peak power density of ∼1.0 W cm−2 at 700 °C. Furthermore, the oxygen reduction kinetics of the PrBa0.94Co2O5+δ cathode is also studied, and the rate-limiting steps for oxygen reduction reaction are determined at different temperatures. |
| Remark |
DOI: 10.1016/j.ijhydene.2014.09.041 Link |
Organic–Inorganic Hybrid Membranes Based on Sulfonated Poly(ether ether ketone) and Tetrabutylphosphonium Bromide Ionic Liquid for PEM Fuel Cell Applications
ID=276| Authors |
|
| Source |
European Journal of Inorganic Chemistry
Time of Publication: 2014
|
| Abstract | Ionic liquids (ILs), with their inherent ionic conductivity and negligible vapor pressure, can be exploited in proton exchange membrane (PEM) fuel cells for which thermal management is a major problem and the cell operation temperature is limited by the boiling point of water. In this work, sulfonated poly(ether ether ketone) (SPEEK) membranes were modified by the incorporation of tetrabutylphosphonium bromide ([P4 4 4 4]Br) by solvent-casting. Electrochemical impedance spectroscopy (EIS) was used to study the electrical properties of the modified membranes. Simultaneous TGA and FTIR studies were used to evaluate the thermal stability and chemical structure of the modified membranes, respectively. 1H NMR spectroscopy was applied to probe the changes in the chemical environment due to the interaction between the ionic liquid and the polymer. Mechanical properties were studied by dynamic mechanical analysis. The temperature-dependent behavior of the viscosity of the [P4 4 4 4]Br ionic liquid was observed to obey the Vogel–Fulcher–Tammann (VFT) equation, and was correlated to the ion-conducting properties of the IL-doped SPEEK membranes. |
| Remark |
DOI: 10.1002/ejic.201402558 Link |
Crystal Structure and electrical properties of complex perovskite solid solutions based on (1-x) NaNbO3-xBi (Zn0.5Ti0.5) O3
ID=275| Authors |
|
| Source |
Journal of Electroceramics
Time of Publication: 2014
|
| Abstract | Ceramics based on the perovskite solid solution (1-x) NaNbO3-xBi (Zn0.5Ti0.5) O3 were prepared using conventional solid state synthesis. The crystal structure, electrical, and optical properties were examined. According to diffraction data, a single perovskite phase could be identified up to the composition x = 0.09. As the Bi (Zn0.5Ti0.5) O3 content increased the crystal structure transitioned from orthorhombic to pseudocubic symmetry. Furthermore, dielectric data showed that the dielectric maximum shifted to lower temperatures with the addition of Bi (Zn0.5Ti0.5) O3. Polarization hysteresis data revealed a slim linear loop across the whole range of solid solutions. Optical data also showed a decrease in the optical band gap from 3.4 eV for pure NaNbO3 to 2.9 eV for the x = 0.09 composition. Using impedance spectroscopy, an electrically inhomogeneous microstructure was observed for compositions with increased Bi (Zn0.5Ti0.5) O3 content. Finally, the substitution of Ta on the B-site was shown to shift the dielectric maximum to temperatures as low as 100 K. |
| Remark |
DOI 10.1007/s10832-014-9953-x Link |
A family of oxide ion conductors based on the ferroelectric perovskite Na0.5Bi0.5TiO3
ID=274| Authors |
|
| Source |
Nature Materials
Volume: 13,
Pages: 31-35 Time of Publication: 2014 |
| Abstract | Oxide ion conductors find important technical applications in electrochemical devices such as solid-oxide fuel cells (SOFCs), oxygen separation membranes and sensors1, 2, 3, 4, 5, 6, 7, 8, 9. Na0.5Bi0.5TiO3 (NBT) is a well-known lead-free piezoelectric material; however, it is often reported to possess high leakage conductivity that is problematic for its piezo- and ferroelectric applications10, 11, 12, 13, 14, 15. Here we report this high leakage to be oxide ion conduction due to Bi-deficiency and oxygen vacancies induced during materials processing. Mg-doping on the Ti-site increases the ionic conductivity to ~0.01 S cm−1 at 600 °C, improves the electrolyte stability in reducing atmospheres and lowers the sintering temperature. This study not only demonstrates how to adjust the nominal NBT composition for dielectric-based applications, but also, more importantly, gives NBT-based materials an unexpected role as a completely new family of oxide ion conductors with potential applications in intermediate-temperature SOFCs and opens up a new direction to design oxide ion conductors in perovskite oxides. |
| Remark |
doi:10.1038/nmat3782 Link |
Thermoelectric Properties of A-site Deficient Lanthanum Substituted Strontium Titanate
ID=273| Author |
|
| Source |
Time of Publication: 2014
|
| Remark | Link |
Grain Size Dependent Comparison of ZnO and ZnGa2O4 Semiconductors by Impedance Spectrometry
ID=272| Authors |
|
| Source |
Electrochimica Acta
Time of Publication: 2014
|
| Abstract | We investigated the electrical properties of ZnGa2O4 via AC (alternating current) Impedance Spectroscopy method comparing with ZnO reference material. Experimentally, AC electrical conductivity of ZnO and ZnGa2O4 were found to be a function of temperature and grain size; i.e., the increase in grain size of the ZnO led a decrease in room temperature conductivity from 1.35 × 10−7 S cm−1 to 9.9 × 10−8 S cm−1. The temperature dependent resistivity variation of ZnGa2O4 and ZnO were similar to each other with varied responding temperature. Likewise, the conductivity for ZnGa2O4 decrease from 2.2 × 10−8 S cm−1 to 3.8 × 10−9 S cm−1 upon an increase in grain size from ∼0.5 μm to 100 μm, accordingly. In addition, a rise in temperature caused an increase in conductivity and led to a corresponding shift in the relaxation time towards the lower values. The semicircles in Nyquist plots disappeared at temperature above 250 °C and 700 °C for ZnO and ZnGa2O4, respectively. The AC measurements were also correlated with the size dependent activation energies (171 meV for 0.5 μm ZnO and 1200 meV for 0.5 μm ZnGa2O4). |
| Keywords | Activation energy; Nyquist plots; AC Impedance spectrometry; Oxide semiconductors |
| Remark |
DOI: 10.1016/j.electacta.2014.08.084 Link |
Effect of thermobaric treatment on the structure and properties of CaCu3Ti4O12
ID=271| Authors |
|
| Source |
Bulletin of the Russian Academy of Sciences: Physics
Volume: 78,
Issue: 8,
Pages: 719-722 Time of Publication: 2014 |
| Abstract | CaCu3Ti4O12 is prepared by means of solid-state sintering. The effect of thermobaric treatment (P = 8.0 GPa and T = 1100°C) and partial replacement of titanium by vanadium on the microstructure and dielectric properties of CaCu3Ti4O12 are investigated. |
| Remark | Link |
Conductivity and oxygen reduction activity changes in lanthanum strontium manganite upon low-level chromium substitution
ID=270| Authors |
|
| Source |
Solid State Ionics
Volume: 266,
Pages: 19-24 Time of Publication: 2014 |
| Abstract | On the timescale of solid oxide fuel cell (SOFC) system lifetime requirements, the thermodynamically predicted low-level substitution of chromium on the B-site of (La,Sr)MnO3 could be a source of cathode degradation underlying more overt and well-known chromium poisoning mechanisms. To study this phenomenon in isolation, electronic conductivity (σ) and electrochemical oxygen reduction activity of the (La0.8Sr0.2)0.98CrxMn1−xO3 model series (x = 0, 0.02, 0.05 or 0.1) were measured in air between 850 and 650 °C. Depending on the extent of chromium substitution and the measurement temperature, electrochemical impedance spectroscopy (EIS) results could be deconvoluted into a maximum of three contributions reflecting possible limiting processes such as oxide ion transport and dissociative adsorption. Chromium substitution resulted in lowered σ (from 174 S cm− 1 (x = 0) to 89 S cm− 1 (x = 0.1) at 850 °C) and a steady rise in associated activation energy (Ea) (from 0.105 ± 0.001 eV (x = 0) to 0.139 ± 0.001 eV (x = 0.1)). From EIS analyses, ohmic and polarisation resistances increased, whilst Ea for the overall oxygen reduction reaction also increased from 1.39 ± 0.04 eV (x = 0) to 1.48–1.54 ± 0.04 eV upon chromium substitution. |
| Keywords | Solid oxide fuel cell; Lanthanum strontium manganite; Chromium poisoning; Electronic conductivity; Electrochemical impedance spectroscopy |
| Remark | Link |
The effect of calcination temperature on the electrochemical properties of La0.3Sr0.7Fe0.7Cr0.3O3−x (LSFC) perovskite oxide anode of solid oxide fuel cells (SOFCs)
ID=269| Authors |
|
| Source |
Sustainable Energy Technologies and Assessments
Volume: 8,
Pages: 92-98 Time of Publication: 2014 |
| Abstract | A series of perovskite structure anode materials, LSFC, was successfully prepared by a glycine combustion process and further calcined at different temperatures. The electrochemical properties of anodes prepared at various calcination temperatures (1100 °C, 1200 °C and 1300 °C) were investigated. The calcination temperature had no significant influence on the morphology of the material but showed obvious influences on the particle sizes and electrochemical properties of the materials. Higher calcination temperature results in sharper X-ray diffractometer (XRD) diffraction peaks of the materials with larger particle sizes and higher electrical conductivity. However materials calcined at higher temperature had much smaller BET surface area resulting in lower triple phase boundary (TPB). The electrochemical performance test exhibited that LSFC anode material sintered at 1100 °C exhibited the smallest area specific resistance (ASR) value in H2 at operating temperatures from 700 to 900 °C. For proton conducting SOFCs (PC-SOFCs) fed by syngas, the cell with anode calcined at 1100 °C also showed highest power density output of 120 mW/cm2 at 750 °C, which was almost three times higher than that of the cell with anode calcined at 1300 °C. |
| Keywords | Solid oxide fuel cell; Calcination temperature; Electrochemical properties; Perovskite |
| Remark | Link |
Oxygen interstitial and vacancy conduction in symmetric Ln2 ± x Zr2 ± x O7 ± x/2 (Ln = Nd, Sm) solid solutions
ID=268| Authors |
|
| Source |
Inorganic Materials
Volume: 50,
Issue: 10,
Pages: 1035-1049 Time of Publication: 2014 |
| Abstract | We have compared (Ln2 − x Zr x )Zr2O7 + x/2 (Ln = Nd, Sm) pyrochlore-like solid solutions with interstitial oxide ion conduction and Ln2(Zr2 − x Ln x )O7 − δ (Ln = Nd, Sm) pyrochlore-like solid solutions with vacancy-mediated oxide ion conduction in the symmetric systems Nd2O3-ZrO2 (NdZrO) and Sm2O3-ZrO2 (SmZrO). We have studied their structure, microstructure, and transport properties and determined the excess oxygen content of the (Sm2 − x Zr x )Zr2O7 + x/2 (x = 0.2) material using thermal analysis and mass spectrometry in a reducing atmosphere (H2/Ar-He). The Ln2 ± x Zr2 ± x O7 ± x/2 (Ln = Nd, Sm) solid solutions have almost identical maximum oxygen vacancy and interstitial conductivities: (3–4) × 10−3 S/cm at 750°C. The lower oxygen vacancy conductivity of the Ln2(Zr2 − x Ln x )O7 − δ (Ln = Nd, Sm; 0 < x ≤ 0.3) solid solutions is due to the sharp decrease in it as a result of defect association processes, whereas the interstitial oxide ion conductivity of the (Ln2 − x Zr x )Zr2O7 + x/2 (Ln = Nd, Sm; 0.2 ≤ x < 0.48) pyrochlore-like solid solutions is essentially constant in a broad range of Ln2O3 concentrations. |
| Remark | Link |
MICROWAVE SINTERING OF Sr AND Mg-DOPED LANTHANUM GALLATE (LSGM) SOLID ELECTROLYTES
ID=267| Authors |
|
| Source |
Romanian journal of materials
Time of Publication: 2014-01
|
| Abstract | Sr2+ and Mg2+ simultaneously doped lanthanum gallate (LSGM) powders, prepared by a modified Pechini route using polyvinyl alcohol (PVA) as polymeric alcohol, were densified using an activated microwave technique at 2.45 GHz, to develop a dense stable electrolyte for application in intermediate temperatures solid oxide fuel cells (IT-SOFC). Thermal behaviour of precursors was investigated by means of differential thermal analysis combined with thermogravimetric analysis (DTA/TGA). The powders and sintered samples were characterized using scanning electron microscopy and energy dispersive analysis (SEM-EDAX), X-ray diffraction (XRD) and infrared spectroscopy (FT-IR). The thermal expansion coefficient (TEC) and ionic conductivity of the sintered samples were also evaluated. Fine, homogeneous and high density pellets of almost pure LSGM phase were obtained after sintering at 14000C for a short period time in an activated microwave field. Using activated microwave field, due to the volumetric in situ heating, the sintering process is highly specific and instantaneous, leading to a faster kinetics compared to the conventional process (electric oven). With an optimized sintering schedule, a fine grained and dense microstructure of the samples were obtained. |
| Remark | Link |
Magnetron formation of Ni/YSZ anodes of solid oxide fuel cells
ID=266| Authors |
|
| Source |
Russian Journal of Electrochemistry
Volume: 50,
Issue: 7,
Pages: 647-655 Time of Publication: 2014 |
| Abstract | Physico-chemical and structural properties of nanocomposite NiO/ZrO2:Y2O3 (NiO/YSZ) films applied using the reactive magnetron deposition technique are studied for application as anodes of solid oxide fuel cells. The effect of oxygen consumption and magnetron power on the discharge parameters is determined to find the optimum conditions of reactive deposition. The conditions for deposition of NiO/YSZ films, under which the deposition rate is maximum (12 μm/h), are found and the volume content of Ni is within the range of 40–50%. Ni-YSZ films reduced in a hydrogen atmosphere at the temperature of 800°C have a nanoporous structure. However, massive nickel agglomerates are formed in the course of reduction on the film surface; their amount grows at an increase in Ni content in the film. Solid oxide fuel cells with YSZ supporting electrolyte and a LaSrMnO3 cathode are manufactured to study electrochemical properties of NiO/YSZ films. It is shown that fuel cells with a nanocomposite NiO/YSZ anode applied using a magnetron sputtering technique have the maximum power density twice higher than in the case of fuel cells with an anode formed using the high-temperature sintering technique owing to a more developed gas-anode-electrolyte three-phase boundary. |
| Remark | Link |
Full ceramic micro solid oxide fuel cells: towards more reliable MEMS power generators operating at high temperatures
ID=265| Authors |
|
| Source |
Energy Environ. Sci.
Time of Publication: 2014
|
| Abstract | Batteries, with a limited capacity, have dominated the power supply of portable devices for decades. Recently, the emergence of new types of highly efficient miniaturized power generators like micro fuel cells has opened up alternatives for continuous operation on the basis of unlimited fuel feeding. This work addresses for the first time the development of a full ceramic micro solid oxide fuel cell fabricated in silicon technology. This full-ceramic device represents a new generation of miniaturized power generators able to operate at high temperatures, and therefore able to work with a hydrocarbon fuel supply. Dense yttria-stabilized zirconia free-standing large-area membranes on micromachined silicon were used as the electrolyte. Thin-film porous electrodes of La0.6Sr0.4CoO3−δ and gadolinia-doped ceria were employed as cathode and anode materials, respectively. The electrochemical performance of all the components was evaluated by partial characterization using symmetrical cells, yielding excellent performance for the electrolyte (area specific resistance of 0.15 Ω cm2 at temperatures as low as 450 °C) and the electrodes (area specific resistance of the cathode and anode below 0.3 Ω cm2 at 700 °C). A micro solid oxide fuel cell with an active area of 2 mm2 and less than 1 micrometer in thickness was characterized under fuel cell conditions, using hydrogen as a fuel and air as an oxidant. A maximum power density of 100 mW cm−2 and 2 mW per single membrane was generated at 750 °C, having an open circuit voltage of 1.05 V. Impedance spectroscopy of the all-ceramic membrane showed a total area-specific resistance of [similar]3.5 Ω cm2. |
| Remark |
DOI: 10.1039/C4EE00748D Link |
Proton conductivity of hexagonal and cubic BaTi1−xScxO3−δ (0.1 ≤ x ≤ 0.8)
ID=264| Authors |
|
| Source |
Dalton Transactions
Time of Publication: 2014
|
| Abstract | BaTi1−xScxO3−δ (x = 0.1–0.8) was prepared via solid state reaction. High resolution X-ray powder diffraction was used to characterise the synthesised materials. It was found that low substitution (x = 0.1 and 0.2) of Ti4+ for Sc3+ gives a hexagonal perovskite structure, whereas high substitution (x = 0.5–0.7) results in a cubic perovskite structure. Thermogravimetric analysis revealed significant levels of protons in both as-prepared and hydrated samples. Electrical conductivity was measured by AC impedance methods under oxygen, argon and under dry and humid, both H2O and D2O, conditions for BaTi1−xScxO3−δ (x = 0.2, 0.6 and 0.7). In the temperature range of 150–600 °C, under humid conditions, the conductivity is significantly higher than that under the dry conditions. The increase in conductivity is especially prominent for the cubic phases, indicating that protons are the dominant charge carriers. The proton conductivity of hexagonal BaTi0.8Sc0.2O3−δ is approx. two orders of magnitude lower than that of the more heavily substituted cubic phases. Conductivity is also found to be higher in dry O2 than in Ar in the whole temperature range of 150–1000 °C, characteristic of a significant contribution from p-type charge carriers under oxidising atmospheres. Greater Sc3+ substitution leads to a higher proton concentration and the highest proton conductivity (σ [similar] 2 × 10−3 S cm−1 at 600 °C) is found for the BaTi0.3Sc0.7O3−δ composition. |
| Remark |
DOI: 10.1039/C4DT01280A Link |
Protons in acceptor doped langasite, La3Ga5SiO14
ID=263| Authors |
|
| Source |
Solid State Ionics
Volume: 264,
Pages: 76–84 Time of Publication: 2014 |
| Abstract | The electrical and defect chemical properties of acceptor doped langasite have been investigated over wide ranges of pH2O, pO2 and temperature. All compositions are pure proton conductors up to 800 °C in wet atmospheres and mixed oxide ion-p-type conductors at higher temperatures. The enthalpy of mobility of protons is 75 ± 3 kJ/mol, while that of oxygen vacancies is 125 ± 7 kJ/mol. The standard enthalpy and entropy of hydration are -100 ± 3 kJ/mol and -157 ± 5 J/mol K, respectively. Langasite based sensors may therefore be affected by dissolution of protons from H2O in the bulk crystal lattice up to temperatures as high as 1000 °C. |
| Keywords | Langasite; Piezoelectric; DFT; Defects; Hydrogen; Conductivity |
Solid-State Synthesis and Properties of Relaxor (1−x)BKT–xBNZ Ceramics
ID=261| Authors |
|
| Source |
J. of American Ceramic Society
Time of Publication: 2014
|
| Abstract | Conventional solid-state synthesis was used to synthesize dense and phase pure ceramics in the (1−x) Bi0.5K0.5TiO3–xBi0.5Na0.5ZrO3 (BKT–BNZ) system. Structural characterization was done using X-ray diffraction at both room temperature and elevated temperatures, identifying a transition from tetragonal xBi0.5Na0.5ZrO3 (xBNZ, x = 0–0.10) to pseudo cubic xBNZ for x = 0.15–0.80. Dielectric properties were investigated with respect to both temperature (RT = 600°C) and frequency (1–106 Hz). Relaxor-like behavior was retained for all the materials investigated, evident by the broadening of the relative dielectric permittivity peaks at transition temperatures as well as frequency dispersion at their maximum. The maximum dielectric constant at elevated temperature was found for 0.15 BNZ. Electric field-induced strain and polarization response were also investigated for several compositions at RT and the largest field-induced strain was observed for the 0.10 BNZ ceramics. The composition range with best performance coincides with the transition from tetragonal to cubic crystal structure. |
| Remark |
DOI: 10.1111/jace.13066 Link |
Ceramic–carbonate dual-phase membrane with improved chemical stability for carbon dioxide separation at high temperature
ID=260| Authors |
|
| Source |
Solid State Ionics
Volume: 263,
Pages: 172–179 Time of Publication: 2014 |
| Abstract | This study examines membrane synthesis, structural stability, permeation properties, and long-term permeation stability of a new dense dual-phase membrane of composition La0.85Ce0.1Ga0.3Fe0.65Al0.05O3 − δ (LCGFA)–carbonate for high temperature CO2 separation. Porous ceramic supports made by sintering pressed powder at a temperature below its densification temperature resulted in a desired support with an open porosity ranging between 40 and 50%. The dual-phase membranes was prepared by direct infiltration of the ceramic supports in molten carbonate at 600 °C, resulting in a four order of magnitude decrease in permeance when compared to the support. LCGFA–carbonate membranes are stable when exposed to gases ranging from gas mixtures containing N2 and various concentrations of CO2 to simulated syngas, and exhibit a stable long term CO2 permeation flux of 0.025 mL·min− 1·cm− 2 for more than 275 h at 900 °C. The CO2 permeation results show exponential dependence to increasing system temperature as well as a linear dependence to logarithmic change in CO2 partial pressure gradients across the membrane in the CO2 pressure range studied. |
| Keywords | Ceramic–carbonate; Carbon dioxide permeation; Dual-phase membrane; Perovskite |
| Remark | Link |
Hydrogen flux in La0.87Sr0.13CrO3–δ
ID=259| Authors |
|
| Source |
Journal of Membrane Science
Volume: 468,
Pages: 317–323 Time of Publication: 2014 |
| Abstract | Acceptor doped LaCrO3 is a promising material for dense, ceramic hydrogen permeable membranes, displaying hydrogen flux in the order of 10−4 ml min−1 cm−1 in a 10% H2+2.5% H2O/dry Ar gradient at 1000 °C. In this work we have characterized the ambipolar proton electron hole conductivity in La0.87Sr0.13CrO3–δ by means of hydrogen flux measurements. Proton transport parameters were extracted, yielding a pre-exponential factor of 3 cm2 K V−1 s−1 and an enthalpy of mobility of 65 kJ mol−1. Hydrogen flux measurements showed that applying a layer of Pt on both feed and sweep side surfaces significantly altered the temperature dependency and increased the hydrogen flux in a 550 μm thick membrane. This indicates that surface kinetics will limit the hydrogen flux in uncoated membranes. From hydrogen surface exchange measurements, a surface exchange coefficient ranging from 10−10 to 10−8 mol cm−2 s−1 at 325–600 °C was obtained. |
| Keywords | Hydrogen permeation; LaCrO3; Proton conductivity; Surface kinetics |
| Remark | Link |
Carbon dioxide permeation properties and stability of samarium-doped-ceria carbonate dual-phase membranes
ID=258| Authors |
|
| Source |
Journal of Membrane Science Volume: 467, Pages: 244–252 Time of Publication: 2014 |
| Abstract | This study examines high temperature carbon dioxide permeation properties and long-term permeation stability of samarium doped ceria (SDC)-carbonate dual-phase membranes. Hermetic SDC-carbonate membranes were prepared by infiltrating porous SDC ceramic support with Li/K/Na molten carbonate. Carbon permeation experiments on the SDC-carbonate membranes were conducted with either atmospheric or high pressure feed of CO2:N2 mixture or simulated syngas with composition of 50% CO, 35% CO2, 10% H2, and 5% N2. The SDC-carbonate membranes exhibit CO2 permeation flux in the range of 0.2–0.8 mL(STP) cm−2 min−1 in 700–950 °C with measured CO2 to N2 separation factor above 1000. The CO2 permeation flux shows power function dependence with CO2 partial pressure and exponential dependence with temperature. The activation energy for CO2 permeation is 63 kJ mol−1, similar to that for oxygen ionic conduction in SDC. Essentially the same CO2 permeation characteristics are observed for the membranes with CO2:N2 and simulated syngas feeds. The membranes exhibit stable long-term permeation flux in 700–900 °C with either CO2:N2 or simulated gas feed at atmospheric pressure or high pressure (5 atm) for various periods of testing time (as long as 35 days). The membranes, with remarkable permeation stability in the presence of H2, show only slight decomposition of the ceramic phase after long-term exposure to feed gas mixtures at high temperature. |
| Keywords | Ceramic-carbonate; Samarium doped ceria; Carbon dioxide permeation; Fluorite; Membrane stability |
| Remark | Link |
Hydrogen permeation characteristics of La27Mo1.5W3.5O55.5
ID=257| Authors |
|
| Source |
Journal of Membrane Science
Volume: 461,
Pages: 81–88 Time of Publication: 2014 |
| Abstract | Hydrogen permeation in 30% Mo-substituted lanthanum tungsten oxide membranes, La27Mo1.5W3.5O55.5 (LWMo), has been measured as a function of temperature, hydrogen partial pressure gradient, and water vapor pressure in the sweep gas. Transport of hydrogen by means of ambipolar proton–electron conductivity and – with wet sweep gas – water splitting contributes to the measured hydrogen content in the permeate. At 700 °C under dry sweep conditions, the H2 permeability in LWMo was 6×10−46×10−4 mL min−1 cm-1, which is significantly higher than that for state-of-the-art SrCeO3-based membranes. Proton conductivity was identified as rate limiting for ambipolar bulk transport across the membrane. On these bases it is evident that Mo-substitution is a successful doping strategy to increase the n-type conductivity and H2 permeability compared to nominally unsubstituted lanthanum tungsten oxide. A steady-state model based on the Wagner transport theory with partial conductivities as input parameters predicted H2 permeabilities in good agreement with the measured data. LWMo is a highly competitive mixed proton–electron conducting oxide for hydrogen transport membrane applications provided that long term stability can be ensured. |
| Remark |
http://dx.doi.org/10.1016/j.memsci.2014.03.011 Link |
Mesoporous NiO-Samaria Doped Ceria for Low-Temperature Solid Oxide Fuel Cells
ID=256| Authors |
|
| Source |
Journal of Nanoscience and Nanotechnology
Volume: 14,
Issue: 8,
Pages: 6399-6403(5) Time of Publication: 2014 |
| Abstract | In order to prepare anode material for low-temperature solid oxide fuel cells (SOFCs), the mesoporous NiO-SDC was synthesized using a cationic surfactant (cetyltrimethyl-ammonium bromide; CTAB) for obtaining wide triple-phase boundary (TPB). In addition, Ni-SDC anode-supported SOFC single cells with YSZ electrolyte and LSM cathode were fabricated and the performance of single cells was evaluated at 600 °C. The microstructure of NiO-SDC was characterized by XRD, EDX, SEM, and BET, and the results showed that the mesoporous NiO-SDC with 10 nm pores could be obtained. It was found that the surface area and the electrical performance were strongly influenced by the Ni content in Ni-SDC cermets. After calcined at 600 °C, the surface area of NiO-SDC was between 90–117 m2/g at 35–45 Ni wt%, which was sufficiently high for providing large TPB in SOFC anode. The optimum Ni content for cell performance was around 45 wt% and the corresponding MPD was 0.36 W/cm2. Indeed, the mesoporous NiO-SDC cermet may be of interest for use as an anode for low-temperature SOFCs. |
| Remark |
DOI: http://dx.doi.org/10.1166/jnn.2014.8452 Link |
Oxide ion transport in (Nd2−xZrx)Zr2O7+δ electrolytes by an interstitial mechanism
ID=255| Authors |
|
| Source |
Journal of Alloys and Compounds
Volume: 603,
Issue: 5,
Pages: 274–281 Time of Publication: 2014 |
| Abstract | We have studied the structure and transport properties of ten (Nd2−xZrx)Zr2O7+x/2 (x = 0–1.27) solid solutions, which lie in the ZrO2–Nd2Zr2O7 isomorphous miscibility range. Major attention has been focused on the pyrochlore-like (Nd2−xZrx)Zr2O7+x/2 solid solutions with x = 0–0.78, which are thought to be potential interstitial oxide ion conductors. The X-ray and neutron diffraction results demonstrate that the (Nd2−xZrx)Zr2O7+x/2 (x = 0–1.27) solid solutions undergo an order–disorder (pyrochlore–defect fluorite) structural phase transition. The (Nd2−xZrx)Zr2O7+x/2 (x = 0.2–0.78) have the bulk conductivity, ∼(1.2–4) × 10–3 S/cm at 750 °C, which is two orders of magnitude higher than that of the ordered pyrochlore Nd2Zr2O7. An attempt has been made to determine the interstitial oxygen content of (Nd2−xZrx)Zr2O7+x/2 (x = 0.2; 0.67) in a reducing atmosphere using thermogravimetry and mass spectrometry. It has been shown that no reduction occurs in the NdZrO system, where neodymium has only one oxidation state, 3+. |
| Keywords | Fuel cells; Ionic conduction; Electrochemical impedance spectroscopy; Neutron diffraction; X-ray diffraction; SEM |
| Remark |
http://dx.doi.org/10.1016/j.jallcom.2014.03.068 Link |
Application of PVD methods to solid oxide fuel cells
ID=254| Authors |
|
| Source |
Applied Surface Science
Time of Publication: 2014
|
| Abstract | In this paper, attention is paid to the application of such a method of vacuum physical vapor deposition (PVD) as magnetron sputtering for fabrication of a solid oxide fuel cell (SOFC) materials and structures. It is shown that the YSZ (yttria-stabilized zirconia) electrolyte and Ni–YSZ anode layers with required thickness, structure and composition can be effectively formed by PVD methods. The influence of parameters of pulsed power magnetron discharge on the deposition rate and the microstructure of the obtained YSZ electrolyte films were investigated. It is shown that the deposition rate of the oxide layers by magnetron sputtering can be significantly increased by using asymmetric bipolar power magnetrons, which creates serious prerequisites for applying this method on the industrial scale. Porous Ni–YSZ anode films were obtained by reactive co-sputtering of Ni and Zr–Y targets and subsequent reduction in the H2 atmosphere at a temperature of 800 °C. The Ni–YSZ films comprised small grains and pores of tens of nanometers. |
| Keywords | Solid oxide fuel cell; Metal support; Magnetron sputtering; Thin film; YSZ electrolyte; NiO/YSZ anode |
| Remark |
http://dx.doi.org/10.1016/j.apsusc.2014.03.163 Link |
Proton conduction in oxygen deficient Ba3In1.4Y0.3M0.3ZrO8 (M = Ga3+ or Gd3+) perovskites
ID=253| Authors |
|
| Source |
Journal of Alloys and Compounds
Volume: 605,
Pages: 56-62 Time of Publication: 2014 |
| Abstract | B -site disordered, oxygen deficient Ba3In1.4Y0.3M 0.3ZrO8 (M = Gd3+ or Ga3+) perovskites of space group View the MathML sourcePm3‾m, were prepared by a solid-state reactive sintering method. Thermogravimetric analysis of the as-prepared samples revealed 79.3% and 55.5% protonation of the available oxygen vacancies by OH groups in the Gd3+ and Ga3+ containing samples, respectively. Conductivity was found to be in the range of 0.3–1.1 × 10−3 S cm−1 (M = Gd3+) and 1.1–4.6 × 10−4 S cm−1 (M = Ga3+) for the temperature interval 300–600 °C in wet Argon. Ba3In1.4Y0.3Ga0.3ZrO8 shows an approximate one order of magnitude increase in conductivity at T > 600 °C under dry oxygen indicating a significant p-type contribution whereas Ba3In1.4Y0.3Gd0.3ZrO8 reveals a smaller enhancement. Ba3In1.4Y0.3Ga0.3ZrO8 displays considerable mixed proton–electronic conduction in the interval 400–800 °C under wet oxidising conditions suggesting possibility of Ga-containing compositions as a cathode materials in a proton conducting fuel cell. |
| Keywords | Proton conducting electrolyte; Oxygen deficient perovskite; Mixed conductor; Cathode material; Impedance spectroscopy |
Role of point defects in bipolar fatigue behavior of Bi(Mg1/2Ti1/2)O3 modified (Bi1/2K1/2)TiO3-(Bi1/2Na1/2)TiO3 relaxor ceramics
ID=252| Authors |
|
| Source |
J. Applied Physics
Volume: 115,
Pages: 154104 Time of Publication: 2014 |
| Abstract | Lead-free Bi(Mg1/2Ti1/2)O3-(Bi1/2K1/2)TiO3-(Bi1/2 Na 1/2)TiO3 (BMT-BKT-BNT) ceramics have been shown to exhibit large electromechanical strains under high electric fields along with negligible fatigue under strong electric fields. To investigate the role of point defects on the fatigue characteristics, the composition 5BMT-40BKT-55BNT was doped to incorporate acceptor and donor defects on the A and B sites by adjusting the Bi/Na and Ti/Mg stoichiometries. All samples had pseudo-cubic symmetries based on x-ray diffraction, typical of relaxors. Dielectric measurements showed that the high and low temperature phase transitions were largely unaffected by doping. Acceptor doping resulted in the observation of a typical ferroelectric-like polarization with a remnant polarization and strain hysteresis loops with significant negative strain. Donor-doped compositions exhibited characteristics that were indicative of an ergodic relaxor phase. Fatigue measurements were carried out on all of the compositions. While the A-site acceptor-doped composition showed a small degradation in maximum strain after 106 cycles, the other compositions were essentially fatigue free. Impedance measurements were used to identify the important conduction mechanisms in these compositions. As expected, the presence of defects did not strongly influence the fatigue behavior in donor-doped compositions owing to the nature of their reversible field-induced phase transformation. Even for the acceptor-doped compositions, which had stable domains in the absence of an electric field at room temperature, there was negligible degradation in the maximum strain due to fatigue. This suggests that either the defects introduced through stoichiometric variations do not play a prominent role in fatigue in these systems or it is compensated by factors like decrease in coercive field, an increase in ergodicity, symmetry change, or other factors. |
| Remark |
http://dx.doi.org/10.1063/1.487167 Link |
Structure and transport properties in un-doped and acceptor-doped gadolinium tungstates
ID=251| Authors |
|
| Source |
Solid State Ionics
Volume: 261,
Pages: 87-94 Time of Publication: 2014 |
| Abstract | Nominal Gd6WO12, Gd5.94Ca0.06WO12 − δ, Gd5.7Ca0.3WO12 − δ and Gd5.7WO12 − δ were synthesized by solid state reaction and wet chemistry methods. The structure and morphology of the materials were analyzed by XRD, SEM and TEM and the electrical conductivity was measured as a function of temperature in reducing and oxidizing atmospheres under wet and dry conditions. The total conductivity is essentially independent of composition above 700 °C. Below 700 °C, the conductivity of Ca-doped samples is higher than that of Gd6WO12 and Gd5.7WO12 − δ and increases with increasing doping concentration. The conductivity below 700 °C is also higher under wet compared to dry conditions and, moreover, the H–D isotope effect on the conductivity is significant. Based on this, and on conductivity characterization as a function of pO2pO2 and pH2OpH2O, it was concluded that the materials are mixed ionic and electronic conductors where electrons and holes dominate at high temperatures and intermediate temperatures under sufficiently reducing and oxidizing conditions, respectively. Protons are the predominating ionic charge carriers below approximately 700 °C. The hydrogen flux through Gd5.7Ca0.3WO12 − δ was measured as a function of temperature under wet and dry sweep gas conditions, as well as with varying pH2pH2 on the feed side, confirming the picture outlined by the conductivity measurements. A defect chemical model has been derived to which the conductivity data were fitted yielding thermodynamic and transport parameters describing the functional characteristics of the materials. |
| Keywords | Proton; Structure; Gd6WO12; Ambipolar conductivity; Hydrogen flux |
| Remark | Link |
Solid Oxide-Molten Carbonate Nano-composite Fuel Cells: Particle Size Effect
ID=250| Authors |
|
| Source |
Journal of Power Sources
Time of Publication: 2014
|
| Abstract | Varying the amount of specific interface area in the CeO2-Na2CO3 nano-composite fuel cell electrolyte helped reveal the role of interfaces in ionic conductivity. We mixed ceria particles with micrometer or nanometer size distributions to obtain a specific surface area (SSA) in the composite from 47 m2/g to 203 m2/g. Micro-structural investigations of the nano-composite showed that the Na2CO3 phase serves as the glue in the microstructure, while thermal analysis revealed a glass transition-like behavior at 350 °C. High SSA enhanced the ionic conductivity significantly at temperatures below 400 °C. Moreover, the activation energy for the Arrhenius conductivity (σT) of the composites was lower than that of the Na2CO3 phase. This difference in the activation energies is consistent with the calculated dissociation energy of the carbonate phase. The strong dependence of conductivity on the SSA, along with differences in the activation energies, suggests that the oxide surface acted as a dissociation agent for the carbonate phase. A model for the solid composite electrolyte is proposed: in the nano-composite electrolyte, the oxide surface helps Na2CO3 dissociate, so that the "liberated" ions can move more easily in the interaction region around the oxide particles, thus giving rise to high ionic conductivities. |
| Keywords | composite electrolyte; ionic conductivity; impedance spectroscopy; SOFC; interphase; activation energy |
| Remark |
in press, http://dx.doi.org/10.1016/j.jpowsour.2014.05.010 Link |
Hydrogen permeation characteristics of La27Mo1.5W3.5O55.5
ID=249| Authors |
|
| Source |
Journal of Membrane Science
Time of Publication: 2014
|
| Abstract | Hydrogen permeation in 30 % Mo-substituted lanthanum tungsten oxide membranes, La27Mo1.5W3.5O55.5 (LWMo), has been measured as a function of temperature, hydrogen partial pressure gradient, and water vapour pressure in the sweep gas. Transport of hydrogen by means of ambipolar proton-electron conductivity and – with wet sweep gas – water splitting contribute to the measured hydrogen content in the permeate. At 700 °C under dry sweep conditions, the H2 permeability in LWMo was 6×10−46×10−4 mL min−1 cm-1, which is significantly higher than for state-of-the-art SrCeO3-based membranes. Proton conductivity was identified as rate limiting for ambipolar bulk transport across the membrane. On these bases it is evident that Mo-substitution is a successful doping strategy to increase the n-type conductivity and H2 permeability compared to nominally unsubstituted lanthanum tungsten oxide. A steady-state model based on Wagner transport theory with partial conductivities as input parameters predicted H2 permeabilities in good agreement with the measured data. LWMo is a highly competitive mixed proton-electron conducting oxide for hydrogen transport membrane applications provided that long term stability can be ensured. |
| Remark |
Available online 14 March 2014 Link |
Performance Variability and Degradation in Porous La1-xSrxCoO3-δ Electrodes
ID=248| Authors |
|
| Source |
J. of the Electrochemical Society
Volume: 161,
Issue: 4,
Pages: F561-F568 Time of Publication: 2014 |
| Abstract | Porous La1-xSrxCoO3-δ (LSC) electrodes with Sr composition x = 0.2 (LSC-82) and x = 0.4 (LSC-64) were prepared by screenprinting LSC powders onto rare-earth doped ceria electrolytes, followed by sintering at 950 ∼ 1100°C, and characterization using scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) surface-area analysis, 3-D morphological imaging based on focused ion beam scanning electron microscopy (FIB-SEM), and energy dispersion X-ray spectroscopy (EDX/EDS). The batch-to-batch variability and degradation (over 1000 ∼ 2000 hours) of the electrochemical performance of these cells were studied using electrochemical impedance spectroscopy (EIS) and measurements of nonlinear electrochemical impedance (NLEIS). These measurements reveal a strong correlation between the characteristic frequency (ωc) and characteristic resistance (Rc) of the electrodes, which, when analyzed in light of microstructural data, indicates that performance variability and degradation are caused primarily by variations in the surface rate coefficient k(T) for O2 exchange. |
| Remark |
doi: 10.1149/2.101404jes Link |
Doped Germanate-Based Apatites as Electrolyte for Use in Solid Oxide Fuel Cells
ID=247| Authors |
|
| Source |
Fuel Cells
Time of Publication: 2014
|
| Abstract | Apatite ceramics, known for their good electrical conductivities, have garnered substantial attention as an alternative electrolyte for solid oxide fuel cells (SOFCs). However, studies focusing on the electrochemical performances of SOFCs with apatities as electrolytes remain rare, partly due to their high sintering temperature. In this study, the effects of Mg2+, Al3+, Ga3+, and Sn4+ dopants on the characteristics of La9.5Ge6O26 ± δ are examined and their potential for use as SOFC electrolytes evaluated. The results indicate that La9.5Ge5.5Al0.5O26 is stabilized into a hexagonal structure, while the La9.5Ge5.5Sn0.5O26.25, La9.5Ge5.5Ga0.5O26, and La9.5Ge5.5Mg0.5O25.75 ceramics reveal triclinic cells accompanied with the second phase La2Sn2O7 or La2GeO5. The study further demonstrates that a high sintering temperature is needed for both the La9.5Ge5.5Mg0.5O25.75 and the La9.5Ge5.5Sn0.5O26.25 ceramics, and the worst electrical conductivity among the examined systems appears in the La9.5Ge5.5Ga0.5O26 ceramic. The La9.5Ge5.5Al0.5O26 ceramic is accordingly selected for cell evaluation due to its ability to reach densification at 1,350 °C, its good electrical conductivity of 0.026 S cm–1 at 800 °C, and its acceptable thermal expansion coefficient of 10.1 × 10–6 K–1. The maximum power densities of the NiO-SDC/La9.5Ge5.5Al0.5O26/LSCF-SDC single cell are found to be respectively 0.22, 0.16, 0.11, and 0.07 W cm–2 at 950, 900, 850, and 800 °C. |
| Keywords | Apatites; Cell Performance; Electrolyte; Impedance; Solid Oxide Fuel Cell |
| Remark |
Article first published online: 19 FEB 2014 DOI: 10.1002/fuce.201300093 Link |
Effect of Nb substitution for Ti on the electrical properties of Yb2Ti2O7-based oxygen ion conductors
ID=246| Authors |
|
| Source |
Solid State Ionics
Time of Publication: 2014
|
| Abstract | We have studied the effect of niobium doping on the electrical conductivity of Yb2Ti2O7-based oxygen ion conductors. Yb2[Ti1 − xNbx]2O7 (x = 0.01, 0.04, 0.1) and (Yb0.8Tb0.1Ca0.1)2[Ti1 − xNbx]2O6.9 (x = 0; 0.05; 0.1) pyrochlore solid solutions were synthesized through coprecipitation followed by firing at 1550 °C for 4 h. The materials were examined by XPS, XRD, scanning electron microscopy and impedance spectroscopy. Yb2(Ti0.99Nb0.01)2O7 was shown to have the highest oxygen ion conductivity in air (2.3 × 10− 3 S/cm at 750 °C), which is however markedly lower than that of undoped Yb2Ti2O7. In the (Yb0.8Tb0.1Ca0.1)2[Ti1 − xNbx]2O6.9 (x = 0; 0.05; 0.1) system, the highest conductivity is offered by (Yb0.8Tb0.1Ca0.1)2[Ti0.95Nb0.05]2O6.9 (σ = 4.44 × 10− 3 S/cm at 650 °C). Additional oxygen vacancies created by Ca doping in pyrochlore structure reduce the detrimental effect of Nb4 + doping on the oxide ion transport up to 5% Nb. The conductivity of the Yb2(Ti0.99Nb0.01)2O7 and (Yb0.8Tb0.1Ca0.1)2[Ti0.95Nb0.05]2O6.9 solid solutions was measured both in air and under reducing conditions (5% H2 in N2 and CO2 atmospheres). A comparative study of both these compositions under 5% H2 in N2 atmosphere showed that the transport mechanism was not affected by complex doping of the lanthanide and titanium sublattices in the Yb2Ti2O7-based materials and was related to oxygen vacancies. Conductivity measurements in CO2 were done to ensure correct evaluation of the ionic conductivity of (Yb0.8Tb0.1Ca0.1)2[Ti0.95Nb0.05]2O6.9, because in air it seems to be a mixed p-type and ionic conductor. |
| Keywords | Oxide ion conductivity; Pyrochlore; Acceptor doping; Donor doping; Impedance spectroscopy |
| Remark |
Available online 1 February 2014; http://dx.doi.org/10.1016/j.ssi.2014.01.019 Link |
Zr-doped samarium molybdates — potential mixed electron–proton conductors
ID=245| Authors |
|
| Source |
Solid State Ionics
Time of Publication: 2014
|
| Abstract | Two Zr-doped samarium molybdates View the MathML sourceSm6−x7Zrx7Mo17O127+x24−δ corresponding to x = 0.6 and 1 (SZMO) have been synthesized at 1600 °C for 3 h using mechanically activated mixtures of starting oxides. Fluorite-like Sm0.771Zr0.086Mo0.143O1.739 − δ (06SZMO) and Sm0.714Zr0.143Mo0.143O1.756 − δ (10SZMO) have similar total conductivity of about 4 × 10− 4 S/cm at 800 °C in air. Below 600 °C, the total conductivity of 06SZMO in air exceeds that of 10SZMO. An increase in bulk and grain boundary conductivity of 06SZMO observed at low temperate under wet conditions suggests there may be a proton contribution to the total conductivity. Under reducing conditions (5% H2–Ar) 06SZMO becomes essentially an electronic conductor. Its conductivity reaches 0.25 S/cm at 800 °C and the activation energy decreases to 0.3 eV. |
| Keywords | Rare-earth; Sm molybdate; Fluorite; Oxide ion conductivity; Proton conductivity; Electron conductivity; Impedance spectroscopy |
| Remark |
Available online 6 February 2014; http://dx.doi.org/10.1016/j.ssi.2014.01.031 Link |
Interstitial oxide ion conduction in (Sm2 − xZrx)Zr2O7 + δ
ID=244| Authors |
|
| Source |
Solid State Ionics
Time of Publication: 2014
|
| Abstract | The crystal structure and transport properties of (Sm2 − xZrx)Zr2O7 + x/2 (x = 0; 0.2; 0.32; 0.39; 0.48; 0.67; 0.78; 0.96; 1.14; 1.27) solid solutions have been investigated by X-ray techniques and impedance spectroscopy, respectively. The excess oxygen content of the composition with x = 0.2 has been determined by thermal analysis and mass spectrometry in a reducing atmosphere. The SmZrO system includes a two-phase (fluorite + pyrochlore) region for the (Sm2 − xZrx)Zr2O7 + x/2 (0.48 ≤ x < 0.96) solid solutions. The interstitial oxide ion conductivity of the (Sm2 − xZrx)Zr2O7 + x/2 (0.2 ≤ x < 0.48), 3 × 10− 3 S/cm at 750 °C, is comparable to the vacancy-mediated conductivity of undoped Sm2Zr2O7. The bulk conductivity of the interstitial oxide ion conductors (Sm2 − xZrx)Zr2O7 + x/2 (0.2 ≤ x < 0.48) was shown to vary little in a wide range of Sm2O3 concentrations in contrast to the vacancy mediated oxide ion conductors Sm2(Zr2 − xSmx)O7 − δ (0 ≤ x < 0.29). |
| Remark |
Available online 2 February 2014; http://dx.doi.org/10.1016/j.ssi.2014.01.028 Link |
Atmosphere controlled conductivity and Maxwell-Wagner relaxation in Bi0.5K0.5TiO3—BiFeO3 ceramics
ID=243| Authors |
|
| Source |
Journal of Applied Physics
Volume: 115,
Issue: 4,
Pages: 044104 - 044104-6 Time of Publication: 2014 |
| Abstract | Here, we report on a giant dielectric relaxation in (1 − x)Bi0.5K0.5TiO3—xBiFeO3 ceramics below ∼300 °C, which becomes more pronounced with increasing BiFeO3 content. The relaxation was shown to be of Maxwell-Wagner type and associated with charge depletion at the electroded interfaces. It was also shown that the relaxation could be controlled or, eventually, removed by heat treatment in controlled partial pressure of oxygen. This was rationalized by the relationship between the electrical conductivity and variation in the oxidation state of Fe, which is strongly coupled to the partial pressure of oxygen. The results are discussed with emphasis on oxygen diffusion and point defect equilibria involving oxygen vacancies and iron in divalent and tetravalent state. Finally, the barrier-free dielectric properties of the (1 − x)Bi0.5K0.5TiO3—xBiFeO3 ceramics are reported. |
| Remark | Link |
Atmosphere controlled conductivity and Maxwell-Wagner relaxation in Bi0.5K0.5TiO3—BiFeO3 ceramics
ID=242| Authors |
|
| Source |
J. Appl. Phys.
Volume: 115,
Pages: 044104 Time of Publication: 2014 |
| Abstract | Here, we report on a giant dielectric relaxation in (1 − x)Bi0.5K0.5TiO3 — xBiFeO3 ceramics below ∼300 °C, which becomes more pronounced with increasing BiFeO3 content. The relaxation was shown to be of Maxwell-Wagner type and associated with charge depletion at the electroded interfaces. It was also shown that the relaxation could be controlled or, eventually, removed by heat treatment in controlled partial pressure of oxygen. This was rationalized by the relationship between the electrical conductivity and variation in the oxidation state of Fe, which is strongly coupled to the partial pressure of oxygen. The results are discussed with emphasis on oxygen diffusion and point defect equilibria involving oxygen vacancies and iron in divalent and tetravalent state. Finally, the barrier-free dielectric properties of the (1 − x)Bi0.5K0.5TiO3 — xBiFeO3 ceramics are reported. |
| Remark | Link |
Characterisation of structure and conductivity of BaTi0.5Sc0.5O3 − δ
ID=241| Authors |
|
| Source |
Solid State Ionics
Volume: 225,
Pages: 140–146 Time of Publication: 2014 |
| Abstract | BaTi0.5Sc0.5O3 − δ was prepared via solid state reaction route and final sintering at 1550 °C. High resolution X-ray powder diffraction on the as-prepared material reveals a cubic perovskite structure with a unit cell parameter, a = 4.1343(1) Å. Thermogravimetric analysis revealed the presence of significant levels of protons in the as-prepared material and 74% of the theoretically achievable protonation through filling of oxide ion vacancies was attained on exposure to a humid environment at 185 °C. Infrared spectroscopy revealed a broad Osingle bondH stretching band confirming the presence of OHO• defects. Electrical conductivity was measured with variable frequency AC impedance methods in oxygen, argon, and hydrogen under dry, hydrated (H2O) and heavy water (D2O) conditions. In the temperature range of 150–550 °C in a wet gas atmosphere the conductivity is significantly higher than that observed for dry conditions, indicating that protons are the dominant charge carriers. Conductivity is also found to be higher in dry oxygen in comparison with dry argon over the whole temperature range of 150–1000 °C, characteristic of contribution from p-type charge carriers under oxidising atmospheres. At 550 °C the proton conductivity was estimated to be 2.89 × 10− 4 S cm− 1 in wet Ar. Fitting of conductivity data provides a hydration enthalpy change (ΔHhydr0) of − 100 ± 5 kJ/mol and hydration entropy change (ΔShydr0) of − 160 ± 10 J/mol K. |
| Keywords | Barium titanate; BaTiO3; Perovskite; Proton conductivity; X-ray diffraction; Hydration |
| Remark | Link |
Stability of La-Sr-Co-Fe Oxide-Carbonate Dual-Phase Membranes for Carbon Dioxide Separation at High Temperatures
ID=240| Authors |
|
| Source |
Ind. Eng. Chem. Res.
Time of Publication: 2014
|
| Abstract | Dual-phase membranes consisting of a mixed ionic and an electronic conducting ceramic phase and an ionically conductive molten carbonate phase have the ability to selectively separate CO2 at high temperature with or without the presence of O2. This study examines the stability of a dual-phase ceramic-carbonate membrane consisting of La0.6Sr0.4Co0.8Fe0.2O3-δ (LSCF) and an eutectic molten carbonate phase composed of Li2CO3, Na2CO3, and K2CO3. LSCF-carbonate membranes exposed to a CO2/He gradient at temperatures between 800-900oC result in a drastic decrease in CO2 permeation before reaching steady-state after more than 60 hours of exposure to the permeating gases due to surface reaction between CO2 and the LSCF ceramic phase of the membrane, resulting in decomposition of the membrane surface. The introduction of O2 in the feed gas, however, helps maintain the LSCF ceramic phase structure and results in stable CO2 permeation flux at much higher value due to a change in transport mechanism in the membrane. The results suggest finding oxygen ionic or mixed-conducting ceramic material stable in CO2 for the dual-phase membrane is critical to ensure stability of the membrane for CO2 permeation. |
| Remark |
DOI: 10.1021/ie4033523 Link |
Synthesis and characterization of the micro-mesoporous anode materials and testing of the medium temperature solid oxide fuel cell single cells
ID=239| Author |
|
| Source |
Time of Publication: 2013
|
| Remark |
Dissertation Link |
Polymorphism and properties of Bi2WO6 doped with pentavalent antimony
ID=238| Authors |
|
| Source |
Journal of Alloys and Compounds
Time of Publication: 2014
|
| Abstract | Antimony-containing solid solutions isostructural with bismuth tungstate, Bi2WO6, have been prepared in air as polycrystalline samples by solid-state reactions and as single crystals by unseeded flux growth. The antimony in the solid solutions is in a pentavalent state and substitutes for tungsten in the structure of Bi2WO6. The Bi2W1–xSbxO6–y solid solutions have been shown to exist in the composition range 0 ⩽ x ⩽ 0.05. We have examined the effect of Sb5+ doping on the polymorphism and properties of Bi2WO6. In contrast to undoped Bi2WO6, antimony-substituted bismuth tungstate does not completely transform into its high-temperature, monoclinic phase at 960 °C and remains two-phase up to temperatures approaching its melting point. Antimony substitution for tungsten has a weak effect on the temperatures of the ferroelectric phase transitions. Heterovalent substitution of Sb5+ for W6+ is accompanied by the formation of extra oxygen vacancies and an increase in the electrical conductivity of the solid solutions by one to two orders of magnitude relative to undoped Bi2WO6. |
| Keywords | Aurivillius phases; Bi2WO6; Ceramics; Phase transitions; Electrophysical properties; Differential scanning calorimetry |
| Remark |
Available online 3 January 2014 Link |
Effect of Ni Concentration on Phase Stability, Microstructure and Electrical Properties of BaCe0.8Y0.2O3-δ - Ni Cermet SOFC Anode and its application in proton conducting ITSOFC
ID=237| Authors |
|
| Source |
Electrochimica Acta
Time of Publication: 2013
|
| Abstract | In this work we have studied the effect of Ni concentration on phase stability, microstructure and electrical properties of BaCe0.8Y0.2O3-δ (BCY)-Ni cermet SOFC anode. It has been seen that Ni forms composite with BCY without forming any solid solution in both oxidized and reduced state. Also, microstructural analysis reveals the effect of Ni on porosity and triple phase boundaries necessary for electrochemical reactions during cell operation. Electrical conductivity values obtained from dc four probe technique in H2 atmosphere increase with an increase in Ni content. Composites with low vol% of Ni contents i.e. 19% (Ni19) and 26% (Ni26) show predominantly semiconductor-like behaviour whereas higher vol% viz. 35% (Ni35), 45% (Ni45) and 56% (Ni56) composites show electronic conductivity behaviour. This confirms that electronic conduction occurs through metallic Ni phase. Also, anode supported single cell for proton conducting SOFC has been fabricated using Ni35 composition and its current-potential characteristics measured at different temperatures. |
| Keywords | Cermet; X-ray diffraction; Electrical conductivity; Four probe; Single Cell |
| Remark |
Available online 25 December 2013 Link |
Cathode compatibility, operation, and stability of LaNbO4-based proton conducting fuel cells
ID=236| Authors |
|
| Source |
Solid State Ionics
Time of Publication: 2013
|
| Abstract | Cathodes compatible with Ca-doped LaNbO4 (LCNO) and the operation of a complete proton conducting fuel cell based on this electrolyte are presented. The best performing cathode was a 50 vol.% La0.8Sr0.2MnO3 (LSM)–50 vol.% LCNO composite, with an overall area specific resistance (ASR) of ~ 10 Ω cm2 at 800 °C in wet air. Pt and La0.8Sr0.2(Cr0.5Mn0.5)O3-based cathodes exhibit higher ASRs. The performance of a complete Ni–LCNO//LCNO//LSM–LCNO fuel cell shows a high open circuit voltage but with relatively low performance, in agreement with the modest proton conductivity of LaNbO4-based materials and cathode performances. The cell exhibits stable operation with CO2 containing atmosphere on the cathode side, confirming the chemical robustness of LaNbO4-based electrolytes. |
| Keywords | Proton conducting fuel cells; Manufacturing; Impedance spectroscopy; LaNbO4; Characterization; Cathode performance |
| Remark |
Available online 22 December 2013; Link |
Determination of Oxygen Diffusion Coefficients in La1-xSrxFe1-yGayO3-δ Perovskites Using Oxygen Semi-Permeation and Conductivity Relaxation Methods
ID=235| Authors |
|
| Source |
Journal of the Electrochemical Society
Volume: 161,
Issue: 3,
Pages: F153-F160 Time of Publication: 2014 |
| Abstract | This paper reports new evidence that oxygen surface exchange and bulk diffusion in a mixed conductor can be simultaneously determined via the oxygen semi-permeation method. Herein, we report the use of an original apparatus for oxygen activity measurements at both membrane surfaces to evaluate the oxygen surface exchange and bulk diffusion coefficients. Oxygen surface exchange and bulk diffusion in the La1-xSrxFe1-yGayO3-δ perovskite series are also determined and compared with the results from three different methods: isotopic exchange, conductivity relaxation, and oxygen semi-permeation. Although the thermodynamic conditions for these methods are not exactly the same, the values obtained for the oxygen surface exchange and bulk diffusion coefficients are in good agreement. |
| Remark | Link |
Entwicklung protonenleitender Werkstoffe und Membranen auf Basis von Lanthan-Wolframat für die Wasserstoffabtrennung aus Gasgemischen
ID=234| Author |
|
| Source |
Book of its own
Time of Publication: 2013
|
| Remark | Link |
Porous La 0.6 Sr 0.4 CoO 3-δ thin film cathodes for large area micro solid oxide fuel cell MEMS power generators
ID=233| Authors |
|
| Source |
Journal of Power Sources
Time of Publication: 2013
|
| Abstract | Porous La0.6Sr0.4CoO3-δ thin films were fabricated by pulsed laser deposition for being used as a cathode for micro solid oxide fuel cell applications as MEMS power generators. Symmetrical La0.6Sr0.4CoO3-δ/yttria-stabilized zirconia/La0.6Sr0.4CoO3-δ free-standing membranes were fabricated using silicon as a substrate. A novel large-area membrane design based on grids of doped-silicon slabs. Thermo-mechanical stability of the tri-layer membranes was ensured in the intermediate range of temperatures up to 700°C. In-plane conductivity of ca. 300 S/cm was measured for the cathode within the whole range of application temperatures. Finally, area specific resistance values below 0.3 Ω·cm2 were measured for the cathode/electrolyte bi-layer at 700°C in the exact final micro solid oxide fuel cell device configuration, thus presenting La0.6Sr0.4CoO3-δ as a good alternative for fabricating reliable micro solid oxide fuel cells for intermediate temperature applications. |
| Keywords | Micro Solid Oxide Fuel Cell, thin film cathode, self-supported electrolyte |
| Remark |
DOI: 10.1016/j.jpowsour.2013.10.038 |
Nanocrystalline Sm0.5Sr0.5CoO3−δ synthesized using a chelating route for use in IT-SOFC cathodes: microstructure, surface chemistry and electrical conductivity
ID=228| Authors |
|
| Source |
Journal of Solid State Chemistry
Time of Publication: 2013
|
| Abstract | Nanocrystalline Sm0.5Sr0.5CoO3−δ powders were synthesized by a chelating route using different polyfunctional HxAPC acids (APC=aminopolycarboxylate; x= 3, 4, 5). Different homologous aminopolycarboxylic acids, namely nitrilotriacetic (H3nta), ethylenediaminetetraacetic (H4edta), 1,2-cyclohexanediaminetetracetic (H4cdta) and diethylenetriaminepentaacetic (H5dtpa) acid, were used as chelating agents to combine Sm, Sr, Co elements into a perovskite structure. The effects of the chelating agents on the crystalline structure, porosity, surface chemistry and electrical properties were investigated. The electrical properties of the perovskite-type materials emphasized that their conductivities in the temperature range of interest (600–800 °C) depend on the nature of the precursors as well as on the presence of a residual Co oxide phase as shown by XRD and XPS analysis. The surface chemistry and the surface stoichiometries were determined by XPS revealing a complex chemical behavior of Sr that exhibits a peculiar „surface phase” and „bulk phase” chemistry within the detected volume (<10 nm). |
| Keywords | Cathode; Perovkites; Electrical Conductivity; XPS; IT-SOFC |
| Remark |
Available online 5 November 2013 Link |
Effects of temperature, triazole and hot-pressing on the performance of TiO2 photoanode in a solid-state photoelectrochemical cell
ID=226| Authors |
|
| Source |
Electrochimica Acta
Time of Publication: 2013
|
| Abstract | The photocurrent of hydrogen generating solid-state photoelectrochemical cell utilising a polybenzimidazole proton-conducting membrane and gaseous anode reactants has been enhanced by operation at higher temperatures. With a bias of 0 V for example, photocurrent increased from 15 to 30 μA/cm2 on moving from 25 °C to 45 °C. The increase in photocurrent, which was limited by the dehydration of the cell, was shown to have contribution from improved electrode kinetics. Modification of TiO2 surface with triazole, a conjugated heterocyclic compound, led to significant increase in photocurrent - up to 4 fold increase at 0 V and 25 °C. This was attributed to improved separation of photogenerated charge carriers, as confirmed by correspondingly increased carrier lifetimes from 50 ns to 90 ns for triazole-modified TiO2. Assembly of the photoelectrochemical cell by hot-pressing induced a ̴ 0.3 eV red shift in optical absorption edge of TiO2, in agreement with a shift of its valence band maximum to higher binding energy. |
| Keywords | Solid-state; photoelectrochemical; XPS; carrier lifetime; triazole |
| Remark |
Available online 28 October 2013 Link |
Synthesis and Investigation of Porous Ni–Al Substrates for SolidOxide Fuel Cells
ID=225| Authors |
|
| Source |
Materials of power engineering and radiationresistant materials
Time of Publication: 2013-10
|
| Abstract | Selfpropagating hightemperature synthesis (SHS) is applied for the production of porous supporting Ni–Al bases of solidoxide fuel cells. The effect of synthesis onditions and the composition of source powders on the phase composition, microstructure, gas permeability, corrosion resistance, and other proper ties of obtained Ni–Al samples is investigated. The possibility is shown for the formation of solidoxide fuel cells (SOFCs) on the surface of porous Ni–Al plates. The cells have the structure Ni–ZrO3:Y2O3 anode/ZrO3:Y2O3 electrolyte/La0.8Mn0.2SrO3 cathode and provide a specific power of 400 mW/cm2 at a temperature of 800°C. |
| Keywords | selfpropagating hightemperature synthesis, Ni–Al, solidoxide fuel cells, ZrO3:Y2O3 electrolyte, magnetron sputtering. |
| Remark | Link |
Galliosilicate glasses for viscous sealants in solid oxide fuel cell stacks: Part III: Behavior in air and humidified hydrogen
ID=224| Authors |
|
| Source |
International Journal of Hydrogen Energy
Time of Publication: 2013
|
| Abstract | Optimized boro-galliosilicate glasses were selected to evaluate their viscous sealing performance in both air and humidified hydrogen atmospheres. Selected low-alkali and alkali-free glasses show excellent performance, with viscous behavior maintained for more than 1000 h in wet hydrogen. Candidate sealants were thermally treated at 850 and 750 °C for up to 1000 h in contact with alumina coated 441 stainless steel (Al-SS) and 8 mol% yttria-stabilized zirconia (8YSZ). Each sealant crystallizes appreciably by 1000 h, and their coefficients of thermal expansion range from 10.2 to 11.7 × 10−6 K−1, 100–400 °C. The remnant amorphous phases in most of the partially crystallized sealants show softening points near or below the target operating temperatures, thus enabling viscous sealing. Humidified hydrogen in general increases the rate of crystallization but does not change the crystalline phases formed or interactions with 8YSZ. For the low-alkali GaBA series, wet H2 enhances the interfacial interaction between potassium in the glass phase and the protective alumina coating on the stainless steel. |
| Keywords | Solid oxide fuel cell; Sealing glass; Galliosilicate; Thermal expansion; Hydrogen |
| Remark |
Available online 25 October 2013 Link |
Porous La0.6Sr0.4CoO3-δ thin film cathodes for large area micro solid oxide fuel cell MEMS power generators
ID=223| Authors |
|
| Source |
Journal of Power Sources
Time of Publication: 2013
|
| Abstract | Porous La0.6Sr0.4CoO3-δ thin films were fabricated by pulsed laser deposition for being used as a cathode for micro solid oxide fuel cell applications as MEMS power generators. Symmetrical La0.6Sr0.4CoO3-δ/yttria-stabilized zirconia/La0.6Sr0.4CoO3-δ free-standing membranes were fabricated using silicon as a substrate. A novel large-area membrane design based on grids of doped-silicon slabs. Thermo-mechanical stability of the tri-layer membranes was ensured in the intermediate range of temperatures up to 700°C. In-plane conductivity of ca. 300 S/cm was measured for the cathode within the whole range of application temperatures. Finally, area specific resistance values below 0.3 Ω·cm2 were measured for the cathode/electrolyte bi-layer at 700°C in the exact final micro solid oxide fuel cell device configuration, thus presenting La0.6Sr0.4CoO3-δ as a good alternative for fabricating reliable micro solid oxide fuel cells for intermediate temperature applications. |
| Remark |
Available online 18 October 2013 Link |
Nano Coated Interconnects for SOFC (NaCoSOFC)
ID=222| Authors |
|
| Source |
ECS Transactions
Volume: 57,
Issue: 1,
Pages: 2187-2193 Time of Publication: 2013 |
| Abstract | The NaCoSOFC project is focused on the development of nano coatings for SOFC interconnects. The project is sponsored by the Nordic Top Level Research Initiative and has four project partners: Sandvik Materials Technology which is producing coated interconnects, Chalmers University of Technology and the University of Oslo that characterize samples with respect to e.g. corrosion, Cr evaporation and ASR as well as Topsoe Fuel Cell that is testing the developed interconnects in its stacks. The developed coatings are based on a combination of Co with RE elements and exhibit high corrosion resistance, 10 fold decrease in Cr evaporation and ASR values that are approximately 50% of the uncoated material. |
| Remark | Link |
Nano Coated Interconnects for SOFC (NaCoSOFC)
ID=221| Source |
Time of Publication: 2013
|
Application of FIB-TOF-SIMS and FIB-SEM-EDX Methods for the Analysis of Element Mobility in Solid Oxide Fuel Cells
ID=220| Authors |
|
| Source |
ECS Transactions
Volume: 57,
Issue: 1,
Pages: 581-587 Time of Publication: 2013 |
| Abstract | The solid oxide fuel cell single cells with porous Pr0.6Sr0.4CoO3-δ and La0.6Sr0.4CoO3-δ (PSCO, LSCO respectively) cathodes on compact Ce0.9Gd0.1O2-δ|Zr0.85Y0.15O2-δ or Ce0.9Gd0.1O2-δ|Zr0.85Sc0.15O2-δ bi-layered electrolytes deposited onto Ni-Zr0.85Y0.15O2-δ (Ni-ZYO) or Ni- Ce0.9Gd0.1O2-δ (Ni-CGO) supporting anode were prepared for ion (element) mobility studies. Focused ion beam - time of flight - secondary ion mass spectrometry (FIB-TOF-SIMS) method in addition to FIB-SEM, SEM-EDX and XRD methods has been used for analysis of mass-transfer (interlayer diffusion) of cathode electrode elements, demonstrating that during PSCO and LSCO sintering at 1100°C on to CGO|ZYO or CGO|ZScO bilayered electrolyte, noticeable mass-transfer of Sr2+ cations through the partially microporous CGO has been verified using FIB-TOF-SIMS and SEM-EDX methods. The single cells have been additionally studied using cyclic voltammetry, electrochemical impedance and chronoamperometry methods and high power densities have been demonstrated. |
| Remark | Link |
Chromium Poisoning of La2NiO4+δ Cathodes
ID=219| Authors |
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| Source |
ECS Transactions
Volume: 57,
Issue: 1,
Pages: 605-613 Time of Publication: 2013 |
| Abstract | It has been reported that Sr-containing materials (such as LSCF) are susceptible to Cr-poisoning by the formation of SrCrO4 and therefore there is interest in Sr-free cathodes such as La2NiO4+δ (LNO). In this study, La2NiO4+δ electrodes were deposited symmetrically onto Ce0.9Gd0.1O1.95 electrolytes by screen printing. The LNO electrodes were solution impregnated with targeted amounts of chromium and then characterised by impedance spectroscopy (520- 800°C). XRD of LNO/Cr2O3 powder mixtures annealed at 900°C showed that there is a reaction between them. Nevertheless, the impedance results indicate that LNO is less prone to chromium deactivation than LSCF. |
| Remark | Link |
Effect of Steam-to-Carbon Ratio on Degradation of Ni-YSZ Anode Supported Cells
ID=218| Authors |
|
| Source |
ECS Transaction
Volume: 57,
Issue: 1,
Pages: 1517-1525 Time of Publication: 2013 |
| Abstract | Internal steam reforming (IR) of methane was investigated on Ni-YSZ anode supported cells, looking in particular at the effect of the steam to carbon (S/C) ratio on the degradation rate. The cells were fed with different H2O/CH4 mixtures during 100 hours sequences, alternating with sequences of dry H2 feeding. V-I characterization was performed before and after each sequence, and EIS measurements were performed regularly. A marked degradation was observed during the IR sequences while it was negligible under dry H2 feed. The observed degradation, attributed to carbon deposition on the anode active sites, was partially reversible for S/C >1.5, whereas it became irreversible at lower S/C. |
| Remark | Link |
Synthesis, properties and phase transitions of pyrochlore- and fluorite-like Ln2RMO7 (Ln=Sm, Ho; R=Lu, Sc; M= Nb, Ta)
ID=217| Authors |
|
| Source |
Materials Research Bulletin
Time of Publication: 2013
|
| Abstract | We have studied the new compounds with fluorite-like (Ho2RNbO7 (R = Lu, Sc)) and pyrochlore-like (Sm2ScTaO7) structure as potential oxide ion conductors. The phase formation process (from 1200 to 1600 °C) and physical properties (electrical, thermo mechanical, and magnetic) for these compounds were investigated. Among the niobate materials the highest bulk conductivity is offered by the fluorite-like Ho2ScNbO7 synthesized at 1600 °C: 3.8 × 10−5 S/cm at 750 °C, whereas in Sm system the highest bulk conductivity, 7.3 × 10−6 S/cm at 750 °C, is offered by the pyrochlore Sm2ScTaO7 synthesized at 1400 °C. In Sm2ScTaO7 pyrochlore we have observed the first-order phase transformation at ∼650–700 °C is related to rearrangement process in the oxygen sublattice of the pyrochlore structure containing B-site cations in different valence state and actually is absent in the defect fluorites. The two holmium niobates show Curie–Weiss paramagnetic behavior, with the prevalence of antiferromagnetic coupling. The magnetic susceptibility of Sm2ScTaO7 is a weak function of temperature, corresponding to Van Vleck paramagnetism. |
| Keywords | Pyrochlore; Fluorite; Phase transition; Ionic conductivity; Thermo mechanical analysis; Dielectric permittivity; Loss tangent; Magnetic susceptibility |
| Remark |
Available online 11 October 2013 Link |
Proton Conductivity in Solid Solution 0.7(CaWO4)–0.3(La0.99Ca0.01NbO4) and Ca(1−x)LaxW(1−y)TayO4
ID=216| Authors |
|
| Source |
Journal of the American Ceramic Society
Time of Publication: 2013
|
| Abstract | The conductivity of nominal CaWO4, CaW0.99Ta0.01O4–δ, 0.7(CaWO4)–0.3(La0.99Ca0.01NbO4–δ), and Ca0.9La0.1WO4+δ has been studied by means of a.c. impedance measurements. Proton conductivity was observed for CaW0.99Ta0.01O4–δ, which displayed exothermic hydration with enthalpy and entropy of –82 kJ/mol and –120 J/molK, respectively. The proton mobility in CaW0.99Ta0.01O4–δ was low, with enthalpy and preexponential factor of mobility of 82 kJ/mol and 0.7 cm2K/Vs. The high enthalpy of mobility is interpreted to reflect association between the acceptor dopant and protonic defects, whereas the low preexponential factor of mobility may reflect a lower proton concentration than assumed. Rietveld refinement indicated low solubilities of La on Ca-site and Ta on W-site. Proton conductivity was also observed in undoped CaWO4, however, not in Ca0.9La0.1WO4+δ. The conductivity of 0.7(CaWO4)–0.3(La0.99Ca0.01NbO4–δ) behaved much like that of undoped LaNbO4, likely due to a very low acceptor dopant concentration. |
| Remark |
Article first published online: 1 OCT 2013. DOI: 10.1111/jace.12587 Link |
The Investigation of E-beam Deposited Titanium Dioxide and Calcium Titanate Thin Films
ID=215| Authors |
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| Source |
MATERIALS SCIENCE (MED´IAGOTYRA)
Volume: 19,
Issue: 3,
Pages: 245-249 Time of Publication: 2013 |
| Abstract | Thin titanium dioxide and calcium titanate films were deposited using electron beam evaporation technique. The substrate temperature during the deposition was changed from room temperature to 600 °C to test its influence on TiO2 film formation and optical properties. The properties of CaTiO3 were investigated also. For the evaluation of the structural properties the formed thin ceramic films were studied by X-ray diffraction (XRD), energy dispersive spectrometry (EDS), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Optical properties of thin TiO2 ceramics were investigated using optical spectroscope and the experimental data were collected in the ultraviolet-visible and near-infrared ranges with a step width of 1 nm. Electrical properties were investigated by impedance spectroscopy.It was found that substrate temperature has influence on the formed thin films density. The density increased when the substrate temperature increased. Substrate temperature had influence on the crystallographic, structural and optical properties also. |
| Keywords | electron beam evaporation; titanium oxide; calcium titanate; optical properties |
| Remark |
DOI: http://dx.doi.org/10.5755/j01.ms.19.3.1805 Link |
Synthesis and Characterization of Nonsubstituted and Substituted Proton-Conducting La6–xWO12–y
ID=214| Authors |
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| Source |
Inorganic Chemistry
Publisher: ACS Publications,
Time of Publication: 2013
|
| Abstract | Mixed proton–electron conductors (MPEC) can be used as gas separation membranes to extract hydrogen from a gas stream, for example, in a power plant. From the different MPEC, the ceramic material lanthanum tungstate presents an important mixed protonic–electronic conductivity. Lanthanum tungstate La6–xWO12–y (with y = 1.5x + δ and x = 0.5–0.8) compounds were prepared with La/W ratios between 4.8 and 6.0 and sintered at temperatures between 1300 and 1500 °C in order to study the dependence of the single-phase formation region on the La/W ratio and temperature. Furthermore, compounds substituted in the La or W position were prepared. Ce, Nd, Tb, and Y were used for partial substitution at the La site, while Ir, Re, and Mo were applied for W substitution. All substituents were applied in different concentrations. The electrical conductivity of nonsubstituted La6–xWO12–y and for all substituted La6–xWO12–y compounds was measured in the temperature range of 400–900 °C in wet (2.5% H2O) and dry mixtures of 4% H2 in Ar. The greatest improvement in the electrical characteristics was found in the case of 20 mol % substitution with both Re and Mo. After treatment in 100% H2 at 800 °C, the compounds remained unchanged as confirmed with XRD, Raman, and SEM. |
| Keywords | ProGasMix |
| Remark |
lanthanum tungstate La6–xWO12–y Link |
Synthesis and Characterization of Nonsubstituted and Substituted Proton-Conducting La6–xWO12–y
ID=213| Authors |
|
| Source |
Inorg. Chem.
Time of Publication: 2013
|
| Abstract | Mixed proton–electron conductors (MPEC) can be used as gas separation membranes to extract hydrogen from a gas stream, for example, in a power plant. From the different MPEC, the ceramic material lanthanum tungstate presents an important mixed protonic–electronic conductivity. Lanthanum tungstate La6–xWO12–y (with y = 1.5x + δ and x = 0.5–0.8) compounds were prepared with La/W ratios between 4.8 and 6.0 and sintered at temperatures between 1300 and 1500 °C in order to study the dependence of the single-phase formation region on the La/W ratio and temperature. Furthermore, compounds substituted in the La or W position were prepared. Ce, Nd, Tb, and Y were used for partial substitution at the La site, while Ir, Re, and Mo were applied for W substitution. All substituents were applied in different concentrations. The electrical conductivity of nonsubstituted La6–xWO12–y and for all substituted La6–xWO12–y compounds was measured in the temperature range of 400–900 °C in wet (2.5% H2O) and dry mixtures of 4% H2 in Ar. The greatest improvement in the electrical characteristics was found in the case of 20 mol % substitution with both Re and Mo. After treatment in 100% H2 at 800 °C, the compounds remained unchanged as confirmed with XRD, Raman, and SEM. |
| Remark |
DOI: 10.1021/ic401104m; Publication Date (Web): September 3, 2013 Link |
Defects and Transport Properties in TiNb2O7
ID=212| Authors |
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| Source |
Journal of the American Ceramic Society
Time of Publication: 2013
|
| Abstract | The electrical conductivity of TiNb2O7 was characterized as a function of temperature, inline image and inline image. The total conductivity was independent of inline image in the low oxygen partial pressure regime, while a dependency of inline image was observed at higher oxygen partial pressures. The conductivity increased with increasing inline image under oxidizing conditions below 700°C. Mixed electronic and protonic conduction was indicated by H/D isotope exchange and transport number measurements. A defect model based on interstitial type of hydration was established and fitted to the conductivity data allowing for determination of physicochemical parameters of hydration and electron migration. |
| Remark |
Article first published online. DOI: 10.1111/jace.12558 Link |
CO2 removal at high temperature from multi-component gas stream using porous ceramic membranes infiltrated with molten carbonates
ID=211| Authors |
|
| Source |
Energy Procedia
Volume: 37,
Pages: 941–951 Time of Publication: 2013-09 |
| Abstract | This work reports on the investigation of CO2 selective membranes for pre-combustion and post- combustion processes, in which CO2 is extracted from multi-component gas streams at intermediate temperature (400 – 600 °C). The dual-phase membranes developed in this work are designed as a porous oxide ion conducting ceramic matrix, which is infiltrated with a molten carbonate phase. Both ex-situ and in-situ characterization methods were used to study disk shaped and tubular membranes. The gas transport properties of disk-shaped membranes were further investigated under various operating conditions relevant for both post-combustion and pre-combustion applications. |
| Keywords | Membrane; CO2 separation; molten carbonate; dual-phase membrane; ionic conductor |
| Remark | Link |
Preparation and electrical properties of Li–Si–Al–O–N ceramics
ID=209| Authors |
|
| Source |
Journal of Asian Ceramic Societies
Volume: 1,
Pages: 191–196 Time of Publication: 2013 |
| Abstract | Ceramic samples were synthesized by hot pressing mixtures of Li3N, Si3N4, AlN, Al2O3, and Li2CO3withnominal compositions of LiSi2−xAlxOxN3−x(x = 0–0.75) at 20 MPa and 1773–2073 K in a N2atmosphere of0.10 MPa. The samples prepared with nominal compositions, x = 0.25 and 0.50, showed electronic con-ductivities of 2.2 and 4.2 S m−1at room temperature with activation energies of 3.8 and 3.9 kJ mol−1,respectively. Electronic conductive parts were detected in the sample of x = 0.50 by conductive atomicforce microscopy (AFM). In this sample, a glassy thin layer, having a Si/Al atomic ratio of 3.8, was observedbetween the grains of LiSi2−xAlxOxN3−xsolid solution by high-resolution transmission electron microscopy(HRTEM). It was expected that the glassy phase of grain boundaries is an electronic conductive pathwaybesides the conductive parts observed by AFM. |
Effects of Nb5+, Mo6+, and W6+ dopants on the germanate-based apatites as electrolyte for use in solid oxide fuel cells
ID=208| Authors |
|
| Source |
International Journal of Hydrogen Energy
Volume: 38,
Issue: 27,
Pages: 12015–12023 Time of Publication: 2013-09 |
| Abstract | Rare information is available in the literature on the cell performance of the solid oxide fuel cells (SOFCs) using apatites known for their good electrical conductivity as electrolyte materials. In this study, La9.5Ge5.5Nb0.5O26.5, La9.5Ge5.5Mo0.5O26.75, and La9.5Ge5.5W0.5O26.75 ceramics were prepared and characterized. The results indicated that the La9.5Ge5.5Nb0.5O26.5 and La9.5Ge5.5W0.5O26.75 ceramics reported hexagonal phase, while the La9.5Ge5.5Mo0.5O26.75 ceramic demonstrated triclinic symmetry. Among the apatities evaluated, La9.5Ge5.5Nb0.5O26.5 sintered at 1450 °C showed the best conduction with an electrical conductivity value of 0.045 S/cm at 800 °C. Button cells of NiO–SDC/La9.5Ge5.5Nb0.5O26.5/LSCF–SDC were built and revealed good structural integrity. The total ohmic resistance (R0) and interfacial polarization resistance (RP) of the cell read 0.428 and 0.174 Ω cm2 and 0.871 and 1.164 Ω cm2, respectively at 950 and 800 °C. The maximum power densities (MPD) of the single cell at 950 and 800 °C were respectively 0.363 and 0.095 W cm−2. Without optimizing the anode and cathode as well as hermetic sealing of the cell against the gas, the study found the performance of the single cell with the pure La9.5Ge5.5Nb0.5O26.5 as its electrolyte material superior to those of the SOFC cells with a YSZ electrolyte of comparable thickness shown in the literature. |
| Keywords | Solid oxide fuel cell; Apatite; Impedance; Cell performance |
| Remark | Link |
Transformation from insulating p-type to semiconducting n-type conduction in CaCu3Ti4O12-related Na(Cu5/2Ti1/2)Ti4O12 ceramics
ID=207| Authors |
|
| Source |
Journal of Applied Physics
Volume: 114,
Issue: 3,
Pages: 034106 - 034106-8 Time of Publication: 2013-07 |
| Abstract | A double doping mechanism of Na+ + ½ Ti4+ → Ca2+ + ½ Cu2+ on the general formula Ca1-xNax(Cu3-x/2Tix/2)Ti4O12 has been used to prepare a series of isostructural CaCu3Ti4O12 (CCTO)-type perovskites. A complete solid solution exists for 0 ≤ x ≤ 1 and all compositions exhibit incipient ferroelectric behaviour with higher than expected intrinsic relative permittivity. Although CCTO ceramics typically exhibit n-type semiconductivity (room temperature, RT, resistivity of ∼10–100 Ω cm), Na(Cu5/2Ti1/2)Ti4O12 (NCTO) ceramics sintered at 950 °C consist of two insulating bulk phases (RT resistivity > 1 GΩ cm), one p-type and the other n-type. With increasing sintering temperature/period, the p-type phase transforms into the n-type phase. During the transformation, the resistivity and activation energy for electrical conduction (Ea ∼ 1.0 eV) of the p-type phase remain unchanged, whereas the n-type phase becomes increasingly conductive with Ea decreasing from ∼ 0.71 to 0.11 eV with increasing sintering temperature. These changes are attributed to small variations in stoichiometry that occur during high temperature ceramic processing with oxygen-loss playing a crucial role. |
| Remark | Link |
New double molybdate Na9Fe(MoO4)6: Synthesis, structure, properties
ID=206| Authors |
|
| Source |
Journal of Solid State Chemistry
Volume: 205,
Pages: 149–153 Time of Publication: 2013-09 |
| Abstract | A new double molybdate Na9Fe(MoO4)6 was synthesized using solid state reactions and studied with X-ray powder diffraction, second harmonic generation (SHG) technique, differential scanning calorimetry, X-ray fluorescence analysis, Mössbauer and dielectric impedance spectroscopy. Single crystals of Na9Fe(MoO4)6 were obtained and its structure was solved (the space group RView the MathML source3¯, a=14.8264(2), c=19.2402(3) Å, V=3662.79(9) Å3, Z=6, R=0.0132). The structure is related to that of sodium ion conductor II-Na3Fe2(AsO4)3. The basic structure units are polyhedral clusters composed of central FeО6 octahedron sharing edges with three Na(1)О6 octahedra. The clusters share common vertices with bridging МоО4 tetrahedra to form an open 3D framework where the cavities are occupied by Na(2) and Na(3) atoms. The compound melts incongruently at 904.7±0.2 K. Arrhenius type temperature dependence of electric conductivity σ has been registered in solid state (σ=6.8×10−2 S сm−1 at 800 K), thus allowing considering Na9Fe(MoO4)6 as a new sodium ion conductor. |
| Keywords | Sodium–iron molybdate; Crystal structure; Solid-state electrolyte |
| Remark | Link |
Study of bulk and grain-boundary conductivity of Ln2+xHf2−xO7−δ (Ln = Sm-Gd; x = 0, 0.096) pyrochlores
ID=205| Authors |
|
| Source |
Journal of Electroceramics
Volume: 24,
Issue: 4,
Pages: 300-307 Time of Publication: 2010-06 |
| Abstract | The electrical conductivity of new solid electrolytes Eu2.096Hf1.904O6.952 and Gd2Hf2O7 have been compared with those for different pyrochlores including titanates and zirconates Ln2+xМ2−xO7−δ (Ln = Sm-Lu; M = Ti, Zr; x = 0−0.81). Impedance spectroscopy data demonstrate that Eu2.096Hf1.904O6.952 and Gd2Hf2O7 synthesized from mechanically activated oxides have high ionic conductivity, comparable to that of their zirconate analogues. The bulk and grain-boundary components of conductivity in Sm2.096Hf1.904O6.952 (Тsynth = 1600°С), Eu2.096Hf1.904O6.952 and Gd2Hf2O7 (Тsynth = 1670°С) have been determined. The highest bulk conductivity is offered by the disordered pyrochlores prepared at 1600°C and 1670°C: ~1.5 × 10−4 S/cm for Sm2.096Hf1.904O6.952, 5 × 10−3 S/cm for Eu2.096Hf1.904O6.952 and 3 × 10−3 S/cm for Gd2Hf2O7 at 780°С, respectively. The conductivity of the fluorite-like phases at the phase boundaries of the Ln2+xМ2−xO7−δ (Ln = Eu, Gd; M = Zr, Hf; x ~ 0.286) solid solutions, as well as that of the high-temperature fluorite-like phases Ln2+xМ2−xO7−δ (Ln = Eu, Gd; M = Zr, Hf; x = 0−0.286), is lower than the conductivity of the disordered pyrochlores Ln2+xМ2−xO7−δ (Ln = Eu, Gd; M = Zr, Hf; x = 0−0.096). |
| Remark | Link |
Ionic conduction in glasses in the MnNbOF5-BaF2-BiF3 system
ID=204| Authors |
|
| Source |
Russian Journal of Inorganic Chemistry
Volume: 58,
Issue: 4,
Pages: 387-391 Time of Publication: 2013-04 |
| Abstract | The electrical conductivity of oxyfluoride glasses in the MnNbOF5-BaF2-BiF3 system in the temperature range 299–550 K was studied by impedance spectroscopy. It was shown that the conductivity is mainly caused by fluoride ions forming fluorobismuth polyhedra in the glass structure, being as high as 7.46 × 10−3 S/cm (533 K) in the 20MnNbOF5-30BaF2-50BiF3 system reaches, which is at the level of the best values for fluoride glasses. |
| Remark | Link |
Solid-state photoelectrochemical H2 generation with gaseous reactants
ID=203| Authors |
|
| Source |
Electrochimica Acta
Volume: 97,
Pages: 320–325 Time of Publication: 2013-05 |
| Abstract | Photocurrent and H2 production were demonstrated in an all solid-state photoelectrochemical cell employing gaseous methanol and water vapour at the photoanode. Open circuit photovoltage of around -0.4 V and short circuit photocurrent of up to 250 μA/cm2 were obtained. At positive bias, photocurrent generation was limited by the irradiance, i.e., the amount of photogenerated charge carriers at the anode. Time constants and impedance spectra showed an electrochemical capacitance of the cell of about 15 μF/cm2 in the dark, which increased with increasing irradiance. With only water vapour at the anode, the short circuit photocurrent was about 6% of the value with gaseous methanol and water vapour. The photoanode and electrocatalyst on carbon paper support were affixed to the proton conducting membrane using Nafion® as adhesive, an approach that yielded photocurrents up to 15 times better than that of a cell assembled by hot-pressing, in spite of the overall cell resistance of the latter being up to 5 times less than that of the former. This is attributed, at least partially, to reactants being more readily available at the photoanode of the better performing cell. |
| Keywords | Photoelectrochemical; hydrogen; TiO2; solid-state; Nafion® |
| Remark | Link |
Metallic Interconnects for Proton Ceramic Fuel Cells. Oxidation behavior and transport properties under simulated fuel cell conditions
ID=202| Author |
|
| Source |
Time of Publication: 2013-03
|
| Remark |
Dissertation for the degree of Philosophiae Doctor Link |
Synthesis and characterization of perovskite-type SrxY1−xFeO3−δ (0.63≤x<1.0) and Sr0.75Y0.25Fe1−yMyO3−δ (M= Cr, Mn, Ni), (y=0.2, 0.33, 0.5)
ID=201| Authors |
|
| Source |
Journal of Solid State Chemistry
Volume: 200,
Pages: 30-38 Time of Publication: 2013-04 |
| Abstract | Abstract Oxygen-deficient ferrates with the cubic perovskite structure SrxY1−xFeO3−δ were prepared in air (0.71≤x≤0.91) as well as in N2 (x=0.75 and 0.79) at 1573 K. The oxygen content of the compounds prepared in air increases with increasing strontium content from 3-δ=2.79(2) for x=0.75 to 3-δ=2.83(2) for x=0.91. Refinement of the crystal structure of Sr0.75Y0.25FeO2.79 using TOF neutron powder diffraction (NPD) data shows high anisotropic atomic displacement parameter (ADP) for the oxygen atom resulting from a substantial cation and anion disorder. Electron diffraction (ED) and high-resolution electron microscopy (HREM) studies of Sr0.75Y0.25FeO2.79 reveal a modulation along <1 0 0>p with G± ~0.4<1 0 0>p indicating a local ordering of oxygen vacancies. Magnetic susceptibility measurements at 5–390 K show spin-glass behaviour with dominating antiferromagnetic coupling between the magnetic moments of Fe cations. Among the studied compositions, Sr0.75Y0.25FeO2.79 shows the lowest thermal expansion coefficient (TEC) of 10.5 ppm K−1 in air at 298–673 K. At 773–1173 K TEC increases up to 17.2 ppm K−1 due to substantial reduction of oxygen content. The latter also results in a dramatic decrease of the electrical conductivity in air above 673 K. Partial substitution of Fe by Cr, Mn and Ni according to the formula Sr0.75Y0.25Fe1−yMyO3−δ (y=0.2, 0.33, 0.5) leads to cubic perovskites for all substituents with y=0.2. Their TECs are higher in comparison with un-doped Sr0.75Y0.25FeO2.79. Only M=Ni has increased electrical conductivity compared to un-doped Sr0.75Y0.25FeO2.79. |
| Keywords | Perovskites; Neutron diffraction; Electron diffraction; High-temperature conductivity; Thermal expansion; Magnetic susceptibility |
| Remark | Link |
Optimization of synthesis conditions for rare-earth titanate based oxygen ion conductors
ID=200| Authors |
|
| Source |
Solid State Ionics
Volume: 230,
Pages: 52-58 Time of Publication: 2013-01 |
| Abstract | High-density (Yb0.9Ca0.1)2Ti2O6.9, (Yb0.8Ca0.1Tb0.1)2Ti2O7 − δ, and (Dy0.8Ca0.1Tb0.1)2Ti2O7 − δ solid solutions have been prepared through co-precipitation followed by firing for 4 h at 1500 and 1550 °C, and their crystal structure (XRD), microstructure (SEM), and oxygen ion conductivity (impedance spectroscopy) have been studied in relation to the firing temperature and precipitant used. As in the case of (Yb0.9Ca0.1)2Ti2O6.9 and (Yb0.8Ca0.1Tb0.1)2Ti2O7 − δ, the optimal synthesis temperature for (Dy0.8Ca0.1Tb0.1)2Ti2O7 − δ is 1500 °C. The bulk oxygen ion conductivity of the pyrochlore-like solid solutions (Yb0.9Ca0.1)2Ti2O6.9 is a stronger function of synthesis temperature than that of the (Dy0.8Ca0.1Tb0.1)2Ti2O7 − δ and (Yb0.8Ca0.1Tb0.1)2Ti2O7 − δ solid solutions with more complex A sublattice. The rise of the synthesis temperature from 1500 to 1550 °C has detrimental effect on the grain boundary conductivity of the (Yb0.9Ca0.1)2Ti2O6.9 and (Dy0.8Ca0.1Tb0.1)2Ti2O7 − δ ceramics. That effect is connected with a considerable grain-boundary segregation of a calcium-containing phase in the (Yb0.9Ca0.1)2Ti2O6.9 and (Dy0.8Ca0.1Tb0.1)2Ti2O7 − δ. The bulk and grain boundary conductivity of (Dy0.8Ca0.1Tb0.1)2Ti2O7 − δ are independent of the precursor synthesis conditions (homogeneous and non-homogeneous co-precipitation). |
| Keywords | Synthesis; Co-precipitation; Pyrochlore; Doping; Oxide ion conductivity; Impedance spectroscopy |
| Remark | Link |
Multilayered thin films for oxidation protection of Mg2Si thermoelectric material at middle–high temperatures
ID=199| Authors |
|
| Source |
Thin Solid Films
Volume: 526,
Pages: 150–154 Time of Publication: 2012-12 |
| Abstract | Multilayered molybdenum silicide-based thin films were deposited via radio frequency magnetron sputtering in order to obtain efficient barrier against oxidation process which affected Mg2Si thermoelectric materials at middle–high temperatures. X ray diffraction, energy dispersive spectroscopy, secondary ion mass spectroscopy, field emission scanning electron microscopy (FE-SEM) and electrical measurements at high temperature were carried out in order to obtain, respectively, the structural, compositional, morphological and electrical characterization of coatings. Furthermore, the mechanical behavior of the thin film/Mg2Si-pellet system was observed in situ as a function of temperature by FE-SEM employing a heating module. Moreover, the barrier properties for oxygen protection after thermal treatment in air at high temperature were qualitatively evaluated. |
| Keywords | Thin film; Thermoelectric material; Magnesium silicide; Molybdenum silicide; Middle–high temperature |
| Remark | Link |
Thin films of SnO2-CeO2 binary oxides obtained by pulsed laser deposition for sensing application
ID=198| Authors |
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| Source |
Applied Surface Science
Time of Publication: 2012-11
|
| Abstract | Binary tin oxide – cerium oxide thin films with ceria concentrations in the range 10- 30% have been obtained by pulsed laser deposition technique, with or without additional oxygen RF plasma beam assistance. A good preservation of the Ce/Sn atomic concentration and Ce3+ content on the film surface of about 30% was obtained for almost all the investigated conditions of substrate temperature and RF powers. The sharp decrease of the electrical resistance in hydrogen environment at temperatures above 300 °C indicates a direct interaction between hydrogen and metal oxides surfaces leading to OH groups formation, as evidenced by XPS measurements. The highest sensitivity (∼40) was attained for the sample with 10% ceria and RF assistance, while the lowest operating temperature (∼250-320 °C) was encountered for that with 30% ceria deposited in the presence of RF discharge. |
| Keywords | RF assisted pulsed laser deposition; SnO2-CeO2 binary oxides; Ce3+ and Ce4+ concentration; sensitivity in H2 atmosphere |
| Remark |
Available online Link |
Phase formation, electrical properties and morphotropic phase boundary of 0.95Pb(ZrxTi1−x)O3–0.05Pb(Mn1/3Nb2/3)O3 ceramics
ID=197| Authors |
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| Source |
Ceramics International
Volume: 39,
Pages: S91–S95 Time of Publication: 2013-05 |
| Abstract | Ferroelectric ceramics in specific composition of 0.95Pb(ZrxTi1−x)O3–0.05Pb(Mn1/3Nb2/3)O3 or PZT–PMnN (with x=0.46, 0.48, 0.50, 0.52, and 0.54) have been investigated in order to identify the morphotropic phase boundary (MPB) composition. The effects of Zr/Ti ratio on phase formation, dielectric and ferroelectric properties of the specimens have also been investigated and discussed. X-ray diffraction patterns indicate that the MPB of the tetragonal and rhombohedral phase lies in x=0.52. The crystal structure of PZT–PMnN appeared to change gradually from tetragonal to rhombohedral phase with increasing Zr content. The dielectric and ferroelectric properties measurements also show a maximum value (εr, tan δ and Pr) at Zr/Ti=52/48, while the transition temperature decreases with increasing Zr content. |
| Keywords | Dielectric properties; Ferroelectric properties; MPB |
| Remark | Link |
Oxygen ion conductivity of (Yb0.9 − xTbxCa0.1)2Ti2O7 − δ solid solutions
ID=196| Authors |
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| Source |
Inorganic Materials
Volume: 48,
Issue: 11,
Pages: 1126-1130 Time of Publication: 2012-11 |
| Abstract | We have studied terbium substitution for ytterbium in (Yb0.9 − x Tb x Ca0.1)2Ti2O7 − δ (x = 0.1, 0.2, 0.3, 0.4) pyrochlore solid solutions synthesized through coprecipitation followed by firing at 1550°C. The results indicate that only a small amount of terbium (less than 10%) can be incorporated into the pyrochlore structure of (Yb0.9Ca0.1)2Ti2O6.9 because of the large difference in ionic radius between the terbium and ytterbium cations: Δr = r(TbCN 83+) − r(YbCN 83+) = 0.055 Å. The oxygen ion conductivity of the (Yb0.9 − x Tb x Ca0.1)2Ti2O7 − δ solid solutions has been determined by impedance spectroscopy in air in the temperature range 300 to 900°C. At high temperatures (t > 640°C), their bulk conductivity was essentially independent of the Yb/Tb ratio. The observed decrease in density and microstructural changes were insignificant. At relatively low temperatures (t < 640°C), the bulk conductivity decreased slightly, and the decrease depended little on terbium concentration. |
| Remark | Link |
H and Li Related Defects in ZnO and their Effect on Electrical Properties
ID=195| Authors |
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| Source |
J. Phys. Chem. C Volume: 166, Issue: 44, Pages: 23764–23772 Time of Publication: 2012-10 |
| Abstract | Li and H are important electrically active impurities in ZnO and this work presents a detailed experimental and computational study of the behavior of H and Li in ZnO, and their effect on its defect structure. We employ AC conductivity measurements as a function of temperature and partial pressure of O2, H2O and D2O, which is combined with first principles density functional theory (DFT) calculations and thermodynamic modeling (TDM) of finite temperature defect structures in undoped and Li doped ZnO. Undoped ZnO is dominated by protons as hydroxide defects (OH_O^•), oxygen vacancies (v_O^(••)) and electrons under a large variety of atmospheric conditions, and we also predict from DFT and TDM the substitutional hydride ion (H_O^•) to dominate concentration-wise under the most reducing conditions at temperatures above 500 °C. The equilibrium concentrations of defects in ZnO are small, and dopants such as Li strongly affect the electrical properties. Experimentally, Li doped ZnO is found to be n-type under all available atmospheric conditions and temperatures, with a n-type conductivity significantly lower than that of as-grown ZnO. The n-type conductivity also increases with decreasing p_(O_2 ) and with increasing p_(H_2 O). The observed electrical properties of Li doped ZnO are attributed to dominance of the ionic defects Li_Zn^/, OH_O^•, Li_i^•, v_O^(••), and the neutral complexes (Li_Zn OH_O)^× and (Li_Zn Li_i)^×. Although Li doping lowers the Fermi level of as-grown ZnO significantly, low formation energy of the ionic donors, and passivation of Li_Zn^/ in the form of (Li_Zn OH_O)^× and (Li_Zn Li_i)^×, prevents realization of significant/stable p-type activity in Li doped ZnO under equilibrium conditions. |
| Remark | Link |
Crystal structure, hydration and ionic conductivity of the inherently oxygen-deficient La2Ce2O7
ID=194| Authors |
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| Source |
Solid State Ionics
Volume: 228,
Pages: 1–7 Time of Publication: 2012-11 |
| Abstract | The crystal structure, hydration and ionic conductivity of the inherently oxygen deficient La2Ce2O7 system have been investigated. On the basis of Rietveld analysis of neutron diffraction data, the material is found to adopt a cation disordered oxygen-deficient fluorite structure. Impedance spectroscopy, performed in the temperature range 1000–200 °C and as a function of water vapor and oxygen partial pressure, suggests that oxide ion conductivity dominates at high temperatures, while protons are the main charge carrier at temperatures below approximately 450 °C. Proton conductivity was confirmed by isotope shifts under H2O and D2O. The dissolution of water was measured by means of thermogravimetry (TG). A defect chemical model is developed to derive hydration thermodynamic parameters based on TG and conductivity data. The hydration enthalpy was, moreover, determined directly by simultaneous TG and differential scanning calorimetry (TG–DSC). The TG–DSC values were in good agreement with those modeled from conductivity and TG data. |
| Keywords | La2Ce2O7; Proton conductivity; Pyrochlore structure; Fluorite structure; Nonstoichiometric oxides |
| Remark | Link |
Microstructure and electrical properties of zirconia and composite nanostructured ceramics sintered by different methods
ID=192| Authors |
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| Source |
Ceramics International
Volume: 39,
Issue: 3,
Pages: 2535–2543 Time of Publication: 2013-04 |
| Abstract | The aim of this study is the preparation and characterization of dense cubic zirconia ceramics and zirconia nanocomposites (reinforced with 5 wt% alumina). The powders were obtained through sol–gel methods and densified using classical sintering and spark plasma sintering (SPS) methods. The obtained ceramics were characterized through X-ray diffraction, scanning electron microscopy and impedance spectroscopy at room and high temperature. The average grain size of cubic zirconia particles was found to be approximately 8 and 2.5 μm for the classical sintering and 99 nm for SPS. The alumina particles in composites have an average grain size of 0.7 μm for classical sintering and 53 nm for SPS ones. The total conductivity for nanocomposites sintered through both methods was also determined. |
| Remark | Link |
Characteristics of SrCo1 − xSnxO3 − δ cathode materials for use in solid oxide fuel cells
ID=191| Authors |
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| Source |
Solid State Ionics
Volume: 227,
Pages: 10–16 Time of Publication: 2012-10 |
| Abstract | In this study, introduction of tin ions in the SrCoO3 − δ oxide is attempted to modify its electrochemical behavior for serving as a cathode of intermediate-temperature solid oxide fuel cells (IT-SOFCs). Doping of tin ions appears to stabilize the cubic Pm-3m phase of the SrCo1 − ySnyO3 − δ ceramics but generates SrSnO3 precipitates and inhibits the grain growth as y value rises to a level greater than 10%. Obtained at 550 °C, the maximum electrical conductivity of SrCo0.95Sn0.05O3 − δ reads 545 S cm− 1. Single cells with a structure of NiO–Sm0.2Ce0.8O2 − δ (SDC)/SDC/SrCo0.95Sn0.05O3 − δ–SDC are built and characterized. Though SrCo0.95Sn0.05O3 − δ is regarded as an MIEC (mixed ionic/electronic conductivity material), adding SDC to SrCo0.95Sn0.05O3 − δ guarantees good adhesion to and fine electrical contact with the electrolyte layer, thereby contributing to the reduction in R0 and RP values. The single cell with the SrCo0.95Sn0.05O3 − δ–SDC composite cathode at 700 °C registers respectively an R0 value of 0.044 Ω cm2 and an RP value of 0.109 Ω cm2. In the absence of microstructure optimization and hermetic sealing of cells, a high power density of 0.847 W cm− 2 is reached. SrCo1 − ySnyO3 − δ thus emerges to be a promising cathode material for IT-SOFCs applications. |
| Keywords | Solid oxide fuel cell; Cathode; Impedance; Cell performance |
| Remark | Link |
Investigation of La1−xSrxCrO3−∂ (x ~ 0.1) as Membrane for Hydrogen Production
ID=190| Authors |
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| Source |
Membranes
Volume: 2,
Issue: 3,
Pages: 665-686 Time of Publication: 2012-09 |
| Abstract | Various inorganic membranes have demonstrated good capability to separate hydrogen from other gases at elevated temperatures. Hydrogen-permeable, dense, mixed proton-electron conducting ceramic oxides offer superior selectivity and thermal stability, but chemically robust candidates with higher ambipolar protonic and electronic conductivity are needed. In this work, we present for the first time the results of various investigations of La1−xSrxCrO3−∂ membranes for hydrogen production. We aim in particular to elucidate the material’s complex transport properties, involving co-ionic transport of oxide ions and protons, in addition to electron holes. This opens some new possibilities for efficient heat and mass transfer management in the production of hydrogen. Conductivity measurements as a function of pH2 at constant pO2 exhibit changes that reveal a significant hydration and presence of protons. The flux and production of hydrogen have been measured under different chemical gradients. In particular, the effect of water vapor in the feed and permeate gas stream sides was investigated with the aim of quantifying the ratio of hydrogen production by hydrogen flux from feed to permeate and oxygen flux the opposite way (“water splitting”). Deuterium labeling was used to unambiguously prove flux of hydrogen species. |
| Keywords | hydrogen transport membrane; proton permeation; oxygen permeation; water splitting |
| Remark | Link |
CO2 decomposition via oxygen deficient ferrite electrodes using solid oxide electrolyser cell
ID=189| Source |
Time of Publication: 2012-09
|
| Abstract | Oxygen Deficient Ferrites (ODF) electrodes integrated with Yttria Stabilized Zirconia (YSZ) electrolyte, electrochemically decompose carbon dioxide (CO2) into carbon (C)/carbon monoxide (CO) and oxygen (O2) in a continuous process. The ODF electrodes can be kept active by applying a small potential bias across the electrodes. CO2 and water (H2O) can also be electrolyzed simultaneously to produce syngas (H2+CO) and O2 continuously that can be fed back to the oxy-fuel combustion. With this approach, CO2 can be transformed into a valuable fuel source allowing CO2 neutral use of the hydrocarbon fuels. |
| Remark |
United States Patent Application 20120228150 Link |
Transient Oxygen Permeation and Surface Catalytic Properties of Lanthanum Cobaltite Membrane under Oxygen–Methane Gradient
ID=188| Author |
|
| Source |
Ind. Eng. Chem. Res.
Volume: 51,
Issue: 39,
Pages: 12917–12925 Time of Publication: 2012-09 |
| Abstract | Oxygen permeation through mixed-conducting ceramic membranes in an air/methane gradient is important for their applications in membrane reactors for air separation and partial oxidation of hydrocarbons. This study examines transient characteristics of oxygen permeation and surface catalytic properties of La0.6Sr0.4Co0.8Fe0.2O3-δ (LSCF) membranes in an oxygen/methane gradient for an extended period of time. Upon exposure to an oxygen/methane gradient, the oxygen permeation flux of the membrane increases to a maximum at around 55 h, then decreases and reaches a steady-state value at around 200 h. The maximum and steady-state flux is approximately 60% and 30% higher than the initial flux of the fresh membrane, respectively. The surface catalytic properties of the membrane exposed to methane also change with the exposure time in a similar fashion. However, the apparent activation energy for oxygen permeation for the membranes at various stages of the transient study is nearly constant while the effects of temperature, feed pressure, and sweep flow rate on catalytic properties are also similar for the fresh and aged membranes. The surface of a LSCF membrane reacts with methane resulting in a formation of a thin porous layer which changes the surface catalytic properties. The membrane surface becomes more active for reaction with increased selectivity for carbon monoxide formation upon exposure to methane. This lowers oxygen partial pressure in the permeate side and increases the driving force for oxygen permeation and, therefore, increases oxygen permeation flux. Under the studied experimental conditions the membrane can reach steady-state for continuous operation. |
| Remark | Link |
Fabrication, sealing and high pressure testing of tubular La2NiO4+δ membranes for air separation
ID=187| Authors |
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| Source |
Energy Procedia
Volume: 23,
Pages: 187–196 Time of Publication: 2012-09 |
| Abstract | Recent results achieved on fabrication of La2NiO4+δ membranes, sealing technology and performance in pressurized conditions are presented. Porous tubular membrane supports of up to 1 m length are prepared by ceramic extrusion. Asymmetric La2NiO4+δ membranes are prepared by coating dense selective layers of 10-15 μm thickness onto the porous supports. Glass ceramic seals in the system Na2O-CaO-Al2O3-SiO2 are currently being evaluated for joining the membranes with high temperature steel alloys coated with a corrosion resistance protective layer. By adjusting the composition of the glass system the thermal expansion coefficient is tailored to match that of the membrane and steel material. Good seal adherences towards these materials are obtained. Long term oxygen flux measurements (>4000 hours continuous operation) performed on symmetric (dense) La2NiO4+δ membranes are conducted under various conditions (atmosphere, temperature, pressure). The oxygen flux dependency on the oxygen partial pressure (pO2) is investigated by increasing the feed pressure and oxygen content. An asymptotic flux behavior is observed with increasing pO2. It is seen a significant increase in the flux (by a factor of 6) when increasing the feed pO2 from 0.8 to 2.4 bars while a less significant pO2 dependency is observed with further increase. |
| Keywords | Oxygen transport membranes; fabrication; sealing; pressurized testing |
| Remark | Link |
Effects of the microwave heating on the properties of gadolinium-doped cerium oxide prepared by polyol method
ID=186| Authors |
|
| Source |
Journal of the European Ceramic Society
Volume: 33,
Issue: 1,
Pages: 67–77 Time of Publication: 2013 |
| Abstract | Gadolinium doped ceria (GDC) has received a lot of attention as possible electrolyte material for Intermediate-Temperature (500–800 °C) Solid Oxide Fuel Cells (IT-SOFC). Microwave heating has been recently considered in combination with precipitation for the production of oxide or non-oxide nano-powders. In this study, crystalline CeO2 powders doped with different amount of gadolinium were successfully prepared by microwave-assisted polyol method under mild conditions and in one single step. The microwave heating was found to strongly influence the morphological properties of the powder especially for low gadolinium content. IR and thermal analyses helped to identify the major reaction path for the formation of the as-observed complex morphologies. Regardless to the morphology, the powders showed good densification behavior and expected electrochemical properties; Ce0.9Gd0.1O1.95 exhibited the highest conductivity. |
| Keywords | Doped ceria; Microwave processing; Ionic conductivity; Fuel cells; Polyol method |
| Remark | Link |
Investigating Reliability on Fuel Cell Model Identification. Part II: An Estimation Method for Stochastic Parameters
ID=185| Authors |
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| Source |
Fuel Cells
Time of Publication: 2012-08
|
| Abstract | An alternative way to process data from polarization measurements for fuel cell model validation is proposed. The method is based on re- and subsampling of I–V data, with which repetitive estimations are obtained for the model parameters. This way statistics such as standard deviations and correlations between the parameters may be experimentally derived. Histograms may also be produced, approximating the probability distributions that they follow. Two experimental case studies are discussed. In the first case, observations are made on the behavior of the parameter values for two mathematical models. As the number of data points (measurement points) employed in the estimation of the parameters increases, parameters with high variances converge to specific values. On the contrary, parameters with small variances diverge linearly. The parameters' histograms do not usually follow normal distributions rather they show a connection between the number of peaks in the graphs and correlations of the parameters. The second case study is an application on a fast degraded SOFC button cell, where the values and the histograms of the parameters are compared before and after degradation. |
| Keywords | Data Fitting; Design of Experiments; Diagnostics; Fast Degradation; Identification; Parameter Estimation; Polarization Curves; Robust Regression; Solid Oxide Fuel cells; Stein's Paradox |
| Remark |
DOI: 10.1002/fuce.201200031 Link |
Extending the family of oxygen ion conductors isostructural with La2Mo2O9
ID=184| Authors |
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| Source |
Journal of Solid State Chemistry
Volume: 196,
Pages: 45–51 Time of Publication: 2012-12 |
| Abstract | X-ray diffraction characterization of materials prepared by solid-state reactions in the ternary systems La2Mo2O9–Nd2W2O9–“Nd2Mo2O9” and La2Mo2O9–Pr2W2O9–Pr2Mo2O9 has shown that, in these systems, compounds isostructural with the oxygen ion conductor La2Mo2O9 exist in wide single-phase regions. Partial tungsten substitution for molybdenum may yield stable Ln2Mo2−2xW2xO9 compounds with the La2Mo2O9 structure, where Ln is a rare-earth element different from lanthanum and praseodymium, e.g., neodymium. Tungsten also stabilizes Pr2Mo2O9, which otherwise decomposes above 700 °C. A series of continuous solid solution was found in the La2Mo2O9–Pr2Mo2O9 system. Polymorphism of compounds existing in the above ternary systems was studied by differential scanning calorimetry. The conductivity of most of the compounds studied approaches that of lanthanum molybdate. |
| Remark | Link |
BaTiO3–Bi(Zn1/2Ti1/2)O3–BiScO3 Ceramics for High-Temperature Capacitor Applications
ID=183| Authors |
|
| Source |
Journal of the American Ceramic Society
Volume: 95,
Issue: 11,
Pages: 3554–3561 Time of Publication: 2012-09 |
| Abstract | Ceramics based on solid solutions of xBaTiO3–(100−x)(0.5Bi(Zn1/2Ti1/2)O3–0.5BiScO3), where x = 50, 55, and 60 were prepared by solid-state reaction which resulted in a single perovskite phase with pseudocubic symmetry. Dielectric property measurements revealed a high relative permittivity (>1000), which could be modified with the addition of Bi(Zn1/2Ti1/2)O3 (BZT) and BiScO3 (BS) to engineer a temperature-stable dielectric response with a temperature coefficient of permittivity (TCε) as low as −182 ppm/°C. By incorporating 2 mol% Ba vacancies into the stoichiometry, the resistivity increased significantly, especially at high temperatures (>200°C). Vogel–Fulcher analysis of the permittivity data showed that the materials exhibited freezing of polar nanoregions over the range of 100–150 K. An analysis of optical absorption near the band edge for the Ba-deficient compositions suggested that the enhanced resistivity values were linked to a decrease in the concentration of defect states. An activation energy of ~1.4 eV was obtained from DC resistivity measurements suggesting that an intrinsic conduction mechanism played a major role in the high temperature conductivity. Finally, multilayer capacitors based on these compositions were fabricated, which exhibited dielectric properties comparable to the bulk material. Based on these results, this family of materials has great promise for high-temperature capacitor applications. |
| Remark | Link |
Sr1−xPrxCo0.95Sn0.05O3−δ ceramic as a cathode material for intermediate-temperature solid oxide fuel cells
ID=182| Authors |
|
| Source |
International Journal of Hydrogen Energy
Volume: 37,
Issue: 17,
Pages: 12548–12556 Time of Publication: 2012-10 |
| Abstract | In this study, the physical properties of the Sr1−xPrxCo0.95Sn0.05O3−δ ceramics were measured and their potential for use as a cathode material of intermediate-temperature solid oxide fuel cells (IT-SOFCs) was evaluated. A cubic phase was retained in all of the Sr1−xPrxCo0.95Sn0.05O3−δ ceramics. Analysis of the temperature-dependent conductivity found the SrCo0.95Sn0.05O3−δ and Sr0.9Pr0.1Co0.95Sn0.05O3−δ ceramics exhibiting semiconductor-like behavior below 550 °C and metal-like behavior above the same temperature. The Sr0.8Pr0.2Co0.95Sn0.05O3−δ and Sr0.7Pr0.3Co0.95Sn0.05O3−δ ceramics, however, reported a metal-like conductivity in the whole temperature range. The electrical conductivities of the Sr0.8Pr0.2Co0.95Sn0.05O3−δ ceramic at 500 °C and 700 °C read respectively 1250 S/cm and 680 S/cm, both of which were superior than those in most of the common perovskites. Single cells with a structure of NiO–Sm0.2Ce0.8O2−δ (SDC)/SDC/Sr0.8Pr0.2Co0.95Sn0.05O3−δ-SDC were built and characterized. Addition of SDC in Sr0.8Pr0.2Co0.95Sn0.05O3−δ emerged to be a crucial factor reducing the ohmic resistance (R0) and polarization resistance (RP) of the cell by facilitating a better adhesion to and electrical contact with the electrolyte layer. The R0 and RP of the cell read respectively 0.068 Ω cm2 and 0.0571 Ω cm2 at 700 °C and 0.298 Ω cm2 and 1.310 Ω cm2 at 550 °C. With no microstructure optimization and hermetic sealing of the cells, maximum power density (MPD) and open circuit voltage (OCV) reached respectively 0.872 W/cm2 and 0.77 V at 700 °C and 0.482 W/cm2 and 0.86 V at 550 °C. It is evident that Sr1−xPrxCo0.95Sn0.05O3−δ is a promising cathode material for IT-SOFCs. |
| Keywords | Solid oxide fuel cell; Cathode; Impedance; Cell performance |
| Remark | Link |
Nitrogen and hydrogen defect equilibria in Ca12Al14O33: a combined experimental and computational study
ID=181| Authors |
|
| Source |
Journal of Materials Chemistry
Volume: 22,
Pages: 15828-15835 Time of Publication: 2012-07 |
| Abstract | The defect structure of mayenite is investigated by Density Functional Theory (DFT) defect calculations; in situ electrical conductivity measurements in NH3 atmosphere at high temperature; and X-ray photoelectron spectroscopy (XPS) and gas phase mass spectrometry (GP-MS) of NH3 treated specimens. The computational results suggest that nitrogen is primarily incorporated substitutionally on oxygen sites as NH−2 and N3−. The concentration of nitrogen was estimated to be within the same order of magnitude by XPS, GP-MS and DFT, yielding a stoichiometry close to Ca12Al14O31.5N0.5:(NH2)0.5O0.5 which corresponds well with that obtained by Boysen et al. from similarly treated samples. Out diffusion of nitrogen was found to occur around 700 °C in Ar by XPS, GP-MS and conductivity measurements, also in accordance with Boysen et al. The conductivity measurements showed that NH3 treatment had a significant effect on the defect structure of the material which became evident only after replacing the NH3 atmosphere with Ar: the conductivity increased abruptly due to a temporary non-equilibrium reduction of the material as nitrogen diffuses out while the lack of a sufficiently large source of oxygen in the surrounding atmosphere prevents the specimen from re-oxidizing. Further, based on the computational results and the pH2 dependency on conductivity after NH3 treatment, we propose dissolution of hydride ions from H2 in the reduced and highly conductive post-NH3 state. |
| Remark | Link |
Relaxor to Ferroelectric Transitions in (Bi1/2Na1/2)TiO3–Bi(Zn1/2Ti1/2)O3Solid Solutions
ID=180| Authors |
|
| Source |
Journal of the American Ceramic Society
Volume: 95,
Issue: 11,
Pages: 3509–3513 Time of Publication: 2012-11 |
| Abstract | Recently, (Bi1/2Na1/2)TiO3 solid solutions have been found to exhibit excellent dielectric and piezoelectric properties. In this study, the dielectric and ferroelectric properties of (1–x)(Bi1/2Na1/2)TiO3–xBi(Zn1/2Ti1/2)O3 (BNT–BZT) solid solutions were investigated. Up to a solubility limit of 8% BZT, distortions to the parent cubic perovskite phase were observed in the diffraction data through splitting of the (001), (011), and (111) reflections. At low concentrations of BZT, the material behaved very much like a conventional ferroelectric, with well-saturated loops with high remanent polarization (Pr ~ 35 μC/cm2). As the BZT content increased, the dielectric behavior displayed characteristics of relaxor behavior. Polarization hysteresis data at elevated temperatures and a thermal hysteresis in the dielectric maximum were evidence for a relaxor to ferroelectric transition. |
| Remark | Link |
Fabrication, structural and electrical characterization of Lanthanum Tungstate films by Pulsed Laser Deposition
ID=179| Authors |
|
| Source |
Thin Solid Films
Volume: 520,
Issue: 21,
Pages: 6531–6534 Time of Publication: 2012-08 |
| Abstract | Films of lanthanum tungstate, 3 μm in thickness, were fabricated by means of Pulsed Laser Deposition on a Pd foil. The films were characterized by X-ray diffraction, scanning electron microscopy, X-ray Photoelectron Spectroscopy and their electrical conductivity was measured at temperatures between 400 and 800 °C in different gas atmospheres. The films’ structure and electrical characteristics are close to what is reported in the literature for corresponding polycrystalline material. The films exhibit fairly high proton conductivity at elevated temperatures, which make them interesting for components in hydrogen-related technologies. Changes in microstructure and the crystallographic orientation observed at higher temperatures were accompanied by changes in the conductivity characteristics. |
| Keywords | Proton conducting oxide; ceramics; Hydrogen transport membrane; Films by Pulsed Laser Deposition; ionic conductor; lanthanum tungstate; La6WO12 |
| Remark | Link |
Nd-doped Ba(Ce,Zr)O3 − δ proton conductors for application in conversion of CO2 into liquid fuels
ID=178| Authors |
|
| Source |
Solid State Ionics
Volume: 225,
Pages: 297–303 Time of Publication: 2012-10 |
| Abstract | The paper presents crystal structure, transport properties, chemical stability in CO2 atmosphere and thin film membrane preparation for materials from the Ba(Ce1 − xZrx)0.9Nd0.1O2.95 (x = 0, 0.25, 0.5, 0.75, 1) group of perovskite-type structure oxides. Transformation of crystal structure from orthorhombic Pnma to orthorhombic Imma and cubic with increasing xZr was observed along with linear decrease of pseudo-cubic unit cell volume and free lattice volume. Electrical conductivity of bulk and grain boundary was determined in dry air, as well as in air humidified with H2O or D2O. The highest proton conductivity was observed for material with xZr = 0.25. Further increase of Zr content led to decrease of conductivity as high as 2 orders of magnitude. This effect was coupled with bell-shape dependence of activation energy and pre-exponential term. Such behavior was explained as superimposed effects of high proton mobility for zirconium-rich materials due to cubic symmetry and cerium-rich materials due to softness of oxygen–oxygen separation distance, along with high proton concentration for cerium-rich perovskites. The deteriorating effect of grain boundaries on total electrical conductivity was far more pronounced for Zr-rich materials than in the case of Ce-rich ones. Declining grain boundary conductivity was attributed to both increase of number of grain boundaries and decrease of inherent grain boundary conductivity for Zr-rich samples. The highest chemical stability in CO2 atmosphere was achieved for high-Zr content materials, on the contrary, for BaCe0.9Nd0.1O2.95 in CO2 atmosphere, the decomposition onset temperature was below 500 °C. 2 μm thin film membrane of Ba(Ce0.75Zr0.25)0.9Nd0.1O2.95 was successfully prepared on c-plane sapphire and fused silica substrates. Film's crystal structure matched that of the bulk material. The electrical conductivity of thermally treated film obtained on c-plane sapphire in wet air was 3.7 × 10− 4 S cm− 1 at 600 °C. |
| Keywords | Proton conductors; BaCeO3–BaZrO3 solid solutions; Isotope effect; Grain boundary effect; Thin films |
| Remark | Link |
High Curie temperature ternary piezoelectric ceramics
ID=177| Authors |
|
| Source |
Time of Publication: 2012-06
|
| Abstract | A preferred piezoelectric ceramic material is a BiFeO3—PbZrO3—PbTiO3 ternary solid solution wherein proportions of the constituent perovskite metal oxides are selected so that the material exhibits relatively high Curie temperatures above 380° C. and useful piezoelectric properties. |
| Remark |
United States Patent Application 20120145943 Link |
Hydrogen permeation, transport properties and microstructure of Ca-doped LaNbO4 and LaNb3O9 composites
ID=176| Authors |
|
| Source |
Journal of Membrane Science
Volume: 415-416,
Pages: 878–885 Time of Publication: 2012-10 |
| Abstract | Two composites consisting of the proton conducting Ca-doped LaNbO4 and electron conducting LaNb3O9 with respectively 90 and 70 vol% LaNbO4 were prepared by spark plasma sintering. The amount of hydrogen produced at the sweep side was measured as a function of temperature and pH2 gradient under wet and dry sweep gas conditions. The hydrogen flux increases with increasing temperature and feed-sidepH2. The flux is significantly higher for the 70 vol% LaNbO4 composite than the 90 vol% LaNbO4 composite. Ambipolar conductivities calculated from the flux data showed the same pH2 dependence for both composites. The electrical conductivity of the 70 vol% LaNbO4 composite was characterized as a function of temperature under wet hydrogen. The microstructure and phase distribution of the two composites are analyzed and their transport properties with different flux limiting processes are discussed. An increased hydrogen production with wet compared to dry sweep gas is concluded to reflect water splitting due to transport of oxygen from the permeate to the feed side. |
| Keywords | Hydrogen flux; Proton conductivity; Ceramic-ceramic composite; LaNbO4; LaNb3O9; Ambipolar conductivity; Water splitting |
| Remark | Link |
A novel coulometric titration setup—Principals, design and leakage minimization
ID=175| Authors |
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| Source |
Thermochimica Acta
Time of Publication: 2012-05
|
| Abstract | This article presents a new coulometric titration setup and describes the principles of operation, the main precautions to be taken into account to reduce the systematic errors, and evaluates the working range and the accuracy of the measurements. The major source of error, the oxygen leakage, is studied in detail and modeled based on leakage of oxygen through the YSZ solid electrolyte. Decreasing the difference in chemical potential of oxygen between inside and outside of the cell is studied as an applied measure to decrease the oxygen leakage. Flushing the pumping solid electrolyte by N2 shows a reasonable improvement. Eventually, oxygen non-stoichiometry of SrFeO3−δ is measured at 1273 K in the oxygen partial pressure range of 0.6 < −log(pO2/atm) < 12. The resulting values are in good agreement with the literature. |
| Keywords | Coulometric titration; Oxygen non-stoichiometry; Oxygen leakage |
High Power Plasma Sprayed Intermediate Temperature Solid Oxide Fuel Cells with Sm0.5Sr0.5CoO3-δ Cathode
ID=174| Authors |
|
| Source |
Procedia Engineering
Volume: 36,
Pages: 81–87 Time of Publication: 2012-05 |
| Abstract | The cells with porous Ni/Fe(∼10 wt%) metal plate as a supporting substrate, double layers of La0.75Sr0.25Cr0.5Mn0.5 O3-δ (LSCM) and nanostructured Ce0.55La0.45O2-δ/Ni (LDC/Ni) as an anode, LDC as an anode interlayer, La0.8Sr0.2Ga0.8Mg0.2O3-δ (LSGM) as an electrolyte, LSGM/Sm0.5Sr0.5CoO3-δ (SSC) as a cathode interlayer and SSC as a cathode current collector, were prepared by atmospheric plasma spraying (APS) coating processes followed by a heating treatment. The current-voltage-power and AC impedance measurement results show that the prepared cell heat-treated at 850 °C for 3 hours in air with a dead load of 1000 g cm-2 has an attracting performance. The measured maximum output power densities of this cell have reached 0.777, 0.742, 0.659, 0.542, 0.393, and 0.250 W cm-2 at 800, 750, 700, 650, 600, and 550 °C respectively. The measured ohmic and polarization resistances are 0.241, 0.254, 0.282, 0.328, 0.42, 0.62 and 0.055, 0.064, 0.083, 0.128, 0.23, 0.471 Ω cm2 at 800, 750, 700, 650, 600, and 550 °C respectively. After correction of the resistance inside the ProboStat system, the predicted actual maximum power densities that a cell can deliver are 1.95, 1.613, 1.186, 0.823, 0.512, and 0.293 W cm-2 at 800, 750, 700, 650, 600, and 550 °C respectively. |
| Keywords | Atmospheric plasma spray; solid oxide fuel cells; metal-supported; nanostructured; Sm0.5Sr0.5CoO3-δ |
| Remark | Link |
Electromechanical strain in Bi(Zn1/2Ti1/2)O3–(Bi1/2Na1/2)TiO3–(Bi1/2K1/2)TiO3 solid solutions
ID=173| Authors |
|
| Source |
Journal of Applied Physics
Volume: 111,
Issue: 9
Time of Publication: 2012-05
|
| Abstract | Solid solutions ceramics of the Bi(Zn0.5Ti0.5)O3–(Bi0.5K0.5)TiO3–(Bi0.5Na0.5)TiO3 ternary system for <20 mol. % BZT were created and confirmed to be single phase using x-ray diffraction. The dielectric dispersion showed decreasing Tmax of the dielectric spectrum with a broadening of the transition with increasing BZT content. At 2.5BZT–40BKT–57.5BNT, a secondary transition commonly observed for morphotropic phase boundary (MPB) BNT–BKT was observed. The ferroelectric behavior of the system was characterized by a transition where the polarization hysteresis showed a severe pinching effect on remanent polarization (20.8 μC/cm2 at 2.5% BZT) as BZT contents was increased (Pr = 2.3 μC/cm2 at 20% BZT). Similarly, as the temperature increased to 175 °C, the remanent polarization of the 2.5% BZT composition significantly reduced to 2.1 μC/cm2. The onset of this transition corresponds to the lower temperature frequency dispersion observed in the dielectric spectrum. The strain hysteresis experienced analogous transition to the polarization, with a change in shape from typical ferroelectric butterfly to a complete loss of negative strain as BZT concentration increased. Maximum strain values of 0.33% were observed at 5-40-55 accompanied by a large d33* = 547pm/V. |
| Remark |
Published online 10 May 2012 Link |
Process and Apparatus of CO2 Energy Source Adopted in Solid Oxide Fuel Cell - CO2 Energy Conversion Cycle
ID=172| Authors |
|
| Source |
Time of Publication: 2012-05
|
| Abstract | A process and apparatus of “Solid Oxide Fuel Cell (SOFC)-CO2 Energy Conversion Cycle (referred to as SOFC-CO2-ECC)” are invented to adopt CO2 as energy sources from waste/stock gas or convert and fix it in the useful compounds. CO2 is converted into CO and O2 via simultaneously catalytic and electrochemical reactions in SOFC for power generation and CO2 cracking. Furthermore, CO is used either as the fuel in SOFC for power generation or starting materials in the chemical reactors to produce CO-derivatives of energy source materials and useful chemical compounds. Hence, SOFC-CO2-ECC is an active or scientific carbon cycle with zero emission of CO2. Thus, the efficacy of environmental protection via solving the problem of CO2 greenhouse effect is achieved, so as to grasp of the “Right of Carbon Emission Trading” issues. |
| Remark |
United States Patent Application 20120115067 Link |
Effect of doped ceria interlayer on cathode performance of the electrochemical cell using proton conducting oxide
ID=171| Authors |
|
| Source |
Electrochimica Acta
Volume: 75,
Pages: 179–184 Time of Publication: 2012-07 |
| Abstract | Introduction of doped ceria interlayer to cathode/electrolyte interface of the electrochemical cell with proton conducting electrolyte was investigated using thin Ce0.8Yb0.2O2−δ (YbDC) interlayer of about 500 nm thickness. YbDC interlayer conducted a large amount of protons as much as 170 mA cm−2. It was also found that cathode overpotential of the YbDC interlayer cells consistently showed a plateau at about 400 mV, at which that of the non-interlayer cells did not show, suggesting a possibility that cathode reaction is changed by introducing the doped ceria interlayer. This result also indicates that the interlayer showed high activity for cathode reaction when enough cathodic bias was applied. Especially, the interlayer showed high activity for the improvement of poor cathode reaction between SrZr0.9Y0.1O3−α (SZY-91) electrolyte and platinum cathode. |
| Keywords | Proton conduction; Doped ceria; Cathode interlayer; Electrochemical steam electrolysis |
| Remark |
Available online 4 May 2012 Link |
Polymorphism and Oxide Ion Migration Pathways in Fluorite-Type Bismuth Vanadate, Bi46V8O89
ID=170| Authors |
|
| Source |
Chem. Mater.
Volume: 24,
Issue: 11,
Pages: 2162–2167 Time of Publication: 2012-05 |
| Abstract | We report the synthesis, structural characterization, and ionic conductivity measurements for a new polymorph of bismuth vanadate Bi46V8O89, and an ab initio molecular dynamics study of this oxide ion conductor. Structure determination was carried out using synchrotron powder X-ray and neutron diffraction data; it was found that β-Bi46V8O89 crystallizes in space group C2/m and that the key differences between this and the previously reported α-form are the distribution of Bi and V cations and the arrangement of the VO4 coordination polyhedra in structure. β-Bi46V8O89 exhibits good oxide ion conductivity, with σ = 0.01–0.1 S/cm between 600 and 850 °C, which is about an order of magnitude higher than yttria stabilized zirconia. The ab initio molecular dynamics simulations suggest that the ion migration pathways include vacancy diffusion through the Bi–O sublattice, as well as the O2– exchanges between the Bi–O and the V–O sublattices, facilitated by the variability of the vanadium coordination environment and the rotational freedom of the VOx coordination polyhedra. |
| Keywords | Oxide ion conductors; bismuth vanadates; X-ray and neutron diffraction; AIMD simulations |
| Remark |
Publication Date (Web): May 3, 2012 Link |
SrCo1−xSbxO3−δ cathode materials prepared by Pechini method for solid oxide fuel cell applications
ID=169| Authors |
|
| Source |
Ceramics International
Volume: 38,
Issue: 7,
Pages: 5941–5947 Time of Publication: 2012-09 |
| Abstract | In this study, SrCo1−ySbyO3−δ powders were prepared by a modified Pechini method. According to the study results, the cubic Pm3m phase of the SrCo1−ySbyO3−δ ceramics was obtained as 10% of cobalt ions were substituted by antimony ions. Doping of Sb3+ ions appeared both to stabilize the Pm3m phase of the SrCo1−ySbyO3−δ ceramics and to enhance densification and retard grain growth. The coefficient of thermal expansion of the SrCo1−xSbxO3−δ ceramics increased with the content of the antimony ions, ranging from 10.17 to 15.37 ppm/°C at temperatures lower than the inflection point (ranging from 450 °C to 550 °C) and from 22.16 to 29.29 ppm/°C at higher temperatures. For the SrCo0.98Sb0.02O3−δ ceramic, electrical conductivity reached a maximum of 507 S/cm at 450 °C. The ohmic and polarization resistances of the single cell with the pure SrCo0.98Sb0.02O3−δ cathode at 700 °C read respectively 0.298 Ω cm2 and 0.560 Ω cm2. The single cell with the SrCo0.98Sb0.02O3−δ-SDC composite cathode appeared to reduce the impedances with the R0 and RP at 700 °C reading respectively 0.109 Ω cm2 and 0.127 Ω cm2. Without microstructure optimization and measured at 700 °C, the single cells with the pure SrCo0.98Sb0.02O3−δ cathode and the SrCo0.98Sb0.02O3−δ-SDC composite cathode, demonstrated maximum power densities of 0.100 W/cm2 and 0.487 W/cm2. Apparently, SrCo1−ySbyO3−δ is a potential cathode for use in IT-SOFCs. |
| Keywords | Solid oxide fuel cell; Cathode; Impedance; Cell performance |
| Remark |
Available online 19 April 2012 Link |
Synthesis, Sintering, Transport Properties, and Surface Exchange of La2Ni0.9Cu0.1O4+δ
ID=168| Authors |
|
| Source |
Journal of the American Ceramic Society
Volume: 95,
Issue: 6,
Pages: 2065–2073 Time of Publication: 2012-06 |
| Abstract | Dense La2Ni0.9Cu0.1O4+δ ceramics were sintered from powders synthesized through a wet-chemical citrate nitrate route with optimized ratios of citrate to nitrate. Less citrate decreases the required sintering temperature and improves the oxygen permeativity. The oxygen permeation was measured as a function of oxygen activity gradient, membrane thickness (0.4–2.6 mm) and temperature (800°C–950°C). The oxygen self diffusion coefficient DO and the surface exchange coefficient k show Arrhenius-type behaviors with activation energies of ~50 and ~100 kJ/mol, respectively. The oxygen chemical diffusion coefficient Dchem and surface exchange coefficient kchem, measured by conductivity relaxation, exhibit Arrhenius-type behaviors with activation energies of 62 and 104 kJ/mol, respectively. Dchem and kchem are related to DO and k through the thermodynamic factor ωO. |
| Remark | Link |
LaCoO3 ceramics obtained from reactive powders
ID=167| Authors |
|
| Source |
Ceramics International
Volume: 38,
Issue: 7,
Pages: 5433–5443 Time of Publication: 2012-09 |
| Abstract | The aim of the present study was to establishing the correlation between the structure and properties of the LaCoO3 powders obtained by aqueous sol–gel method with citric acid and their sintering behavior in order to obtain fully densified ceramics with perovskite structure. Two types of cobalt and lanthanum reagents were used in synthesis, namely nitrates and acetates. The sintering was realized at temperatures ranging between 800 and 1200 °C for 2 h. The sintered samples were investigated by classical ceramic methods (shrinkage, density, porosity) and by structural and morphological investigations: XRD, SEM, AFM and XPS. The electrical properties of the samples were determined by impedance spectroscopy. The ceramics obtained with powders starting with acetates have presented a lower sintering ability as compared with the samples obtained from powders starting with nitrates. LaCoO3 ceramics with best properties was obtained from powders starting with nitrates sintered at 1100 °C. |
| Remark |
Available online 11 April 2012 Link |
Preparation and characterization of composite membranes based on sulfonated PEEK and AlPO4 for PEMFCs
ID=166| Authors |
|
| Source |
Solid State Ionics
Volume: 219,
Pages: 83–89 Time of Publication: 2012-05 |
| Abstract | Sulfonated poly(ether ether ketone) (PEEK) and their composites are considered one of the most promising alternatives for Nafion, the industry benchmark for electrolytic membranes in proton exchange membrane (PEM) fuel cells. In the present study, PEEK was non-homogeneously sulfonated using concentrated H2SO4 at different temperatures (room temperature, 60 °C, and 80 °C) and time durations (5, 7, 48, and 72 h). Composite membranes of SPEEK with different weight ratios of AlPO4 synthesized by sol–gel were also prepared. Depending on the degree of sulfonation (DS), the Ion Exchange Capacity (IEC) of the membranes varied from 1.06 to 2.9 meq g− 1. XRD results show the increasing amorphous nature of the membranes with increase in IEC and DS value. The water uptake of the membranes also increased with DS. Simultaneous TGA–FTIR measurement of the composite membranes showed better thermal stability compared to pure SPEEK membranes. The water uptake and proton conductivity of the composite SPEEK membranes were found to be lower than that of pure SPEEK membranes, while the composite membranes exhibited a better swelling behavior and mechanical stability than the pure SPEEK samples. |
| Keywords | Proton exchange membrane (PEM); Composite membranes; Sulfonated poly(etheretherketone) (SPEEK); Proton conductivity; Ion exchange capacity (IEC); Sol–gel |
| Remark | Link |
Synthesis and electrical properties of a new fluorite-like anionic conductor in the Nd2O3–MoO3 system (43–47 mol% Nd2O3)
ID=165| Authors |
|
| Source |
Solid State Ionics
Volume: 225,
Pages: 654–657 Time of Publication: 2012-10 |
| Abstract | This work addresses phase relations in the Nd2O3–MoO3 system (25–50 mol% Nd2O3) and properties of a fluorite-like compound existing in this system in the composition range of 43–47 mol% Nd2O3. We describe for the first time the crystal growth of this compound. The composition of the crystals is Nd10Mo6O33 (Nd2O3:MoO3 = 5:6, 45.5 mol% Nd2O3), which falls within the above composition range. Dielectric spectroscopy data for polycrystalline Nd14Mo8O45 (within the homogeneity range of the fluorite-like compound) suggest a phase transition at 650–700 °C. The exact mechanism of the transition remains to be clarified. Nd14Mo8O45 has rather high bulk conductivity, approaching 10− 2 S/cm at 800 °C. The low activation energy and key structural features of the compound in question indicate that it is an anionic conductor. |
| Keywords | Fluorite-like compounds; Rare-earth molybdates; Single crystals; Relaxation; Anionic conductor |
| Remark |
Available online 22 March 2012 Link |
Temperature dependent thermoelectric material power factor measurement system
ID=164| Authors |
|
| Source |
Review of scientific instruments
Volume: 81,
Issue: 075107
Publisher: American Institute of Physics,
Time of Publication: 2010-06
|
| Abstract | Thermoelectric materials can be used for cooling/heating applications, or converting waste heat into electricity. Novel thermoelectric materials have been discovered in recent years. Characterization of an electrical conductivity and thermopower of a sample from room temperature to ≥ 900 K is often necessary for thermoelectric materials. This paper describes a system built for measurement of the power factor of thermoelectric materials from 300 to 1273 K. Characterization results of the system are also presented. |
High temperature electronic properties of BaTiO3 – Bi(Zn1/2Ti1/2)O3 – BiInO3 for capacitor applications
ID=163| Author |
|
| Source |
Journal of Electroceramics
Volume: 28,
Issue: 2-3,
Pages: 165-171 Time of Publication: 2012-03 |
| Abstract | Solid solutions xBaTiO3 – (1-x)(0.5Bi(Zn1/2Ti1/2)O3 – 0.5BiInO3), where x = 0.95–0.60, were prepared by conventional mixed oxide method. The single phase perovskite structure was obtained for the composition with x ≥ 0.75. Phase transformation from tetragonal to pseudocubic was observed from x-ray diffraction patterns when x decreased from 0.95 to 0.75. In tetragonal phase region, x ≥ 0.90, the increase of Bi(Zn1/2Ti1/2)O3 – BiInO3 content decreased the tetragonality and the temperature at which the relative permittivity is maximum (Tmax). The increase in lattice parameter and Tmax were observed in the pseudocubic phase region, x < 0.90. Additionally, a highly broad and diffuse phase transition was observed from the dielectric data in the pseudocubic phase region. The introduction of Ba vacancies in compositions with x = 0.80 and 0.75 also improved dielectric loss at high temperatures. The incorporation of BiInO3 into the BaTiO3 – Bi(Zn1/2Ti1/2)O3 compound was also found to improve the temperature coefficient of the relative permittivity, with values as low as approximately −1,000 ppm/K. Overall, ternary perovskite solid solutions based on adding Bi(Zn1/2Ti1/2)O3 – BiInO3 to BaTiO3 shows excellent potential for high temperature capacitor applications |
| Keywords | High temperature capacitor – Bi-based perovskite – BiInO3 – Bi(Zn1/2Ti1/2)O3 – BaTiO3 – Insulation resistance |
| Remark | Link |
Stability of (Ln0.8Ca0.1Ln′0.1)2Ti2O7−δ (Ln=Dy, Yb; Ln′=Ce, Tb) and (Tb0.9Ca0.1)2Ti2O7−δ pyrochlores under redox conditions
ID=162| Authors |
|
| Source |
Solid State Ionics
Volume: 225,
Pages: 457–463 Time of Publication: 2012-10 |
| Abstract | The stability of (Ln0.8Ca0.1Ln′0.1)2Ti2O7−δ (Ln=Dy, Yb; Ln′=Ce, Tb) pyrochlores under different redox conditions (air, dry and wet H2) has been studied. The bulk conductivity of the terbium-containing materials is slightly higher under reducing conditions (5% H2 + 95% Ar) than in air, reaching ~ 6 × 10− 2 and 2.5 × 10− 2 S/cm at 800 °C for (Yb0.8Ca0.1Tb0.1)2Ti2O7−δ and (Dy0.8Ca0.1Tb0.1)2Ti2O7−δ, respectively. In air–hydrogen–air cycles, the bulk conductivity returns to its original level in air: ~ 2 × 10− 2 and 1 × 10− 2 S/cm at 800 °C in (Yb0.8Ca0.1Tb0.1)2Ti2O7−δ and (Dy0.8Ca0.1Tb0.1)2Ti2O7−δ, respectively. Exposure of (Dy0.8Ca0.1Tb0.1)2Ti2O7−δ to a flowing mixture of 5% H2 and 95% Ar for 100 h slightly reduces its conductivity: from 0.029 to 0.023 S/cm at 900 °C. The cerium-containing materials (Yb0.8Ca0.1Ce0.1)2Ti2O7−δ and (Dy0.8Ca0.1Ce0.1)2Ti2O7−δ were found to be unstable under reducing conditions. The bulk conductivity of (Yb0.8Ca0.1Ce0.1)2Ti2O7−δ is practically independent on the atmosphere while the grain boundary conductivity increased from 5.6 × 10− 8 in air to ~ 1 × 10− 5 S/cm at 425 °C on reducing the sample in 5%H2–Ar gas mixture. However, after two redox cycles air–5%H2–Ar–air the sintered pellet of (Yb0.8Ca0.1Ce0.1)2Ti2O7−δ fractured whereas (Dy0.8Ca0.1Ce0.1)2Ti2O7−δ degraded immediately under reducing conditions. It was observed that the size mismatch between Ln and Ln´ cations strongly affects the bulk to grain boundary conductivity ratio in (Ln0.8Ca0.1Ln′0.1)2Ti2O7−δ (Ln=Dy, Yb; Ln′=Ce, Tb) pyrochlores. |
| Keywords | Pyrochlore; Donor doping; High-temperature conductivity; Ionic conductivity; Solid electrolyte; Electronic conductivity |
| Remark |
Available online 8 March 2012; http://dx.doi.org/10.1016/j.ssi.2012.02.009 Link |
Spark Plasma Sintering and Hot Pressing of Hetero-Doped LaNbO4
ID=161| Authors |
|
| Source |
Journal of the American Ceramic Society
Volume: 95,
Issue: 5,
Pages: 1563–1571 Time of Publication: 2012-05 |
| Abstract | LaNbO4/La3NbO7 and LaNbO4/LaNb3O9 cer-cer composites were prepared by impregnating Ca-doped LaNbO4 powder, synthesized by spray pyrolysis, with La- or Nb-precursor solutions. The sintering of the calcined powders was investigated by dilatometry, and dense composites were prepared by conventional sintering, hot pressing, and spark plasma sintering. The particle size of the starting powders was about 50 nm, and the average grain size of the dense materials ranged from 100 nm and upwards, depending on the sintering temperature, sintering procedure, and the phase composition. The unit cell parameters of LaNbO4 showed a finite size effect and approached the cell parameters of tetragonal LaNbO4 with decreasing crystallite size, both for the single-phase material and the composites. The minority phase (La3NbO7 or LaNb3O9) were observed as isolated grains and accumulated at triple points and not along the grain boundaries, pointing to a large dihedral angle between the phases. The calcium-solubility in the minority phases was larger than in LaNbO4, which corresponds well with previous reports. The electrical conductivity of the hetero-doped materials was similar to, or lower than, that for Ca-doped LaNbO4. |
| Remark | Link |
Sandvik Sanergy HT – A potential interconnect material for LaNbO4-based proton ceramic fuel cells
ID=160| Authors |
|
| Source |
Journal of Power Sources
Volume: 206,
Pages: 70–76 Time of Publication: 2012-05 |
| Abstract | High temperature properties of Sandvik Sanergy HT have been studied to evaluate the alloy's suitability as an interconnect material for LaNbO4 based proton ceramic fuel cells (PCFCs). The thermal expansion behavior of the alloy deviates from LaNbO4 at higher temperatures which may be unfavorable, however the average values for the two materials over the whole temperature region are rather similar. The oxidation kinetics was parabolic and the rate constants were low at temperatures below 1000 °C. Accelerated oxidation was encountered after 300 h at 1000 °C revealing that the material may undergo severe degradation at sufficiently high temperatures. A complex oxide scale containing an inner layer of chromium oxide and an outer layer of various spinel phases containing chromium, manganese and iron was formed at all temperatures. As a consequence of high oxidation resistance and an oxide with relatively high electronic conductivity, the area specific resistance (ASR) of Sandvik Sanergy HT measured at 700 °C proved to be low. |
| Keywords | Proton ceramic fuel cell; Interconnect; Sandvik Sanergy HT; Oxidation kinetics; Thermal expansion; Area specific resistance |
| Remark | Link |
A novel perovskite-based proton conductor for solid oxide fuel cells
ID=159| Authors |
|
| Source |
Scripta Materialia
Volume: 66,
Issue: 9,
Pages: 658–661 Time of Publication: 2012-05 |
| Abstract | A perovskite-based electrolyte, Ca-substituted YAlO3, has been synthesized by the citrate gel process. The conductivity of Y0.9Ca0.1AlO3-δ has been studied by AC impedance spectroscopy in controlled atmospheres in the temperature range 300–800 °C. The material has been found to be a mixed conductor with dominant p-type electronic conduction at elevated temperatures and a combined protonic conduction below 600 °C in wet conditions. The H/D isotope effect on conductivity confirms the presence of protonic conductivity between 400 and 600 °C. |
| Keywords | Proton conduction; Electrical properties; Solid electrolyte; Perovskite oxide; Fuel cell materials |
| Remark | Link |
50 mol% indium substituted BaTiO3: Characterization of structure and conductivity
ID=158| Authors |
|
| Source |
International Journal of Hydrogen Energy
Volume: 37,
Issue: 9,
Pages: 7975–7982 Time of Publication: 2012-05 |
| Abstract | BaTi0.5In0.5O3−δ was prepared by solid state reaction at 1400 °C. Rietveld analysis of high resolution X-ray powder diffraction data indicated phase pure as-prepared material that adopts a cubic perovskite structure with a = 4.1536(1) Å. Thermogravimetric analysis revealed the presence of significant levels of protons in the as-prepared material and 57% of the theoretically achievable protonation was attained on exposure to a humid environment at 185 °C. After hydration the cell parameter increased to 4.1623(1) Å. Electrical conductivity was measured both with fixed and variable frequency ac impedance methods as a function of temperature, oxygen-, water vapour- and heavy water vapour partial pressures. In the temperature range 400–800 °C a slight increase in the total conductivity with increasing oxygen partial pressure is encountered, characteristic of a contribution from p-type charge carriers. The effect of the water vapour pressure on conductivity below 600 °C is much more prominent indicative of dominant proton conduction. At 300 °C the total conductivity in wet O2 was estimated to be 9.30 × 10−5 S/cm. At T > 800 °C the material is a pure oxide ion conductor. |
| Keywords | Barium titanate; Perovskite; Brownmillerite; Proton conductivity; X-ray diffraction; Impedance spectroscopy |
| Remark | Link |
Ion mobility, phase transitions, and conductivity of crystal phases in KF-CsF-SbF3-H2O system according to data of NMR and impedance spectroscopy
ID=157| Authors |
|
| Source |
Russian Journal of Electrochemistry
Volume: 48,
Issue: 1,
Pages: 104-110 Time of Publication: 2012-01 |
| Abstract | The methods of NMR, thermogravimetric analysis, and impedance spectroscopy were used to study ion mobility, phase transitions, and ion conductivity in crystal phases in the KF-CsF-SbF3-H2O system. Analysis of 19F NMR spectra allowed tracing the dynamics of ion movement in the fluoride sublattice under temperature variations, determining their types and temperature ranges, in which they are implemented. The observed phase transitions in potassium-cesium fluoroantimonates(III) are phase transitions to the superionic state. It is found that the predominant form of ion movement in the high-temperature modifications formed as a result of phase transitions becomes diffusion of fluoride ions. According to the results of electrophysical studies the K1−xCsx SbF4 (x ≤ 0.2) high-temperature phases are superionic. Their conductivity reaches the values of ∼10−2 to 10−3 S/cm at 463–483 K. The high-temperature phases are stabilized under cooling, which results in a significant increase in conductivity at the room temperature. |
| Keywords | potassium-cesium tetrafluoroantimonates(III) – ion mobility – phase transitions – conductivity – NMR spectra |
| Remark |
DOI: 10.1134/S1023193512010090 Link |
Defect structure and its nomenclature for mixed conducting lanthanum tungstates La28–xW4+xO54+3x/2
ID=156| Authors |
|
| Source |
International Journal of Hydrogen Energy
Volume: 37,
Issue: 9,
Pages: 8051–8055 Time of Publication: 2012-05 |
| Abstract | Based on results from experimental and theoretical studies of the crystal structure of lanthanumtungstateView the MathML source, we present a defect model comprising an inherently disordered and partially occupied oxide ion sublattice, which rationalizes hydration and ionic conduction of the materials in the undoped state. Applying the model to experimental conductivity data enables extraction of defect thermodynamics and transport parameters of protons, oxide ions and electronic defects. The standard enthalpy and entropy changes of the hydration of inherent oxygen vacancies are estimated to be −83 kJ/mol and −125 J/mol K (per mole of H2O), respectively. |
| Keywords | Lanthanum tungstate; Defect structure; Inherent disorder; Partial occupancy; Mixed conductor |
| Remark | Link |
The role of B-site cations on proton conductivity in double perovskite oxides La2MgTiO6 and La2MgZrO6
ID=155| Authors |
|
| Source |
International Journal of Hydrogen Energy
Volume: 37,
Issue: 9,
Pages: 7983–7994 Time of Publication: 2012-05 |
| Abstract | Acceptor-doped La2MgTiO6 (LMTO) and La2MgZrO6 (LMZO) have been investigated to contribute to clarify the role of the B-site cations in A2B′B″O6 double perovskite oxides on formation and mobility of protons. Thermogravimetry and a.c. conductivity measurements in the temperature range 1000-300 °C, as well as DFT-calculations of LMTO, have been the basis for evaluating hydration thermodynamics and transport parameters of the materials. Both compounds show exothermic hydration of oxygen vacancies, but low concentrations of protons. The proton transport is limited by relatively high activation energies of mobility; 0.84 eV and 0.78 eV for LMTO and LMZO, respectively. This is suggested to reflect association to effectively negative charged defects formed by site exchange among the B-site cations. Consequently, the maximum proton conductivity of LMTO and LMZO is in the order of 10−5 S/cm. |
| Keywords | Double perovskite; La2MgTiO6; La2MgZrO6; Proton mobility; Hydration thermodynamics |
| Remark | Link |
Influence of Microwave-Assisted Pechini Method on La0.80Sr0.20Ga0.83Mg0.17O3–δ Ionic Conductivity
ID=154| Authors |
|
| Source |
Fuel Cells
Volume: 12,
Issue: 1,
Pages: 54–60 Time of Publication: 2012-02 |
| Abstract | With the aim of investigating the microwave influence on the electrolyte material properties, La0.80Sr0.20Ga0.83Mg0.17O2.815 was prepared by both a conventional and a microwave-assisted sol–gel Pechini method. With respect to the conventional Pechini method (hereafter SGP), the microwave assisted process (hereafter MWA-SGP) guaranteed a faster procedure, reducing the time needed to remove the excess solvents to complete the polyesterification reaction from some days to a few hours. In fact, when a MWA-SGP method was used, powders having higher phase purity were obtained. The sintering process at 1,450 °C of the powders prepared by both methods yielded pellets with similar density values (≥92% of theoretical). Nevertheless, only by microwave-assisted process single-phase products were obtained and no secondary phases such as tetragonal LaSrGaO4 and LaSrGa3O7 were detected. These by-products have been demonstrated to be detrimental for conductivity. Indeed, pellets obtained by MWA-SGP method showed oxygen ionic conductivity values higher (about 30–40%) than those checked for SGP samples, thus demonstrating the important role of the microwave process on reducing time and costs and on improving the electrolyte properties. |
| Keywords | Ionic Conductivity;IT-SOFC;Microwave Processing;(Sr, Mg)-Doped LaGaO3;Sol–Gel |
| Remark | Link |
Impact of Parylene-A Encapsulation on ZnO Nanobridge Sensors and Sensitivity Enhancement via Continuous Ultraviolet Illumination
ID=153| Authors |
|
| Source |
Journal of Electronic Materials
Volume: 41,
Issue: 5,
Pages: 873-880 Time of Publication: 2012-05 |
| Abstract | The impact of parylene-A encapsulation and the effect of continuous ultraviolet (UV) exposure on ZnO nanobridge sensor response are investigated. ZnO nanowire (NW) devices are fabricated using a novel method that involves selective growth of ZnO nanobridges between lithographically defined pads of carbonized photoresist (C-PR). We find that a thin coating of parylene-A effectively attenuates the response of NW devices to O2, H2O vapor, and UV illumination. The accessibility of the amine group on parylene-A for chemical functionalization is verified by transforming the amine groups on the surface of the parylene-A coating into aromatic imine groups, followed by UV–Vis absorption. Our results suggest that, in addition to modulating environmental sensitivity and providing protection of the ZnO NWs for liquid- and vapor-phase sensing, the parylene-A encapsulation may also serve as an activation layer for further specific functionalization targeting selective sensing. We also found that the sensitivity and response time of ZnO nanobridge devices to O2 are dramatically improved by continuously exposing the nanobridge devices to UV illumination. Finally, we show that the C-PR directed growth method can also be used to isolate free-standing NW carpet. |
| Keywords | ZnO – nanowire – parylene – CVD – nanobridge – sensor – functionalization – directed integration |
| Remark | Link |
On the hydration of grain boundaries and bulk of proton conducting BaZr0.7Pr0.2Y0.1O3-δ
ID=152| Authors |
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| Source |
International Journal of Hydrogen Energy
Volume: 37,
Issue: 9,
Pages: 7970–7974 Time of Publication: 2011-12 |
| Abstract | We report here for the first time bulk and grain boundary conductivities from impedance spectra of a ceramic proton conductor (BaZr0.7Pr0.2Y0.1O3-δ) taken during hydration and H/D isotope exchange transients (at 400 °C). The results suggest that water moves quickly along grain boundary cores, and then interact from there with the space charge layers and, in turn, grain interiors. Hydration and H/D isotope exchange have simple monotonic effects on the bulk conductivity in line with what is expected from it being dominated by protons. The transients for grain boundary conductivity exhibit however hysteresis: During hydration, the core charge and grain boundary resistance appear to go through transient minima related to non-equilibrium distributions of defects between the core and grain interior – notably because protons diffuse faster than oxygen vacancies between the grain boundary and grain interior. At equilibrium, hydration increases the core charge and the depletion of positive charge carriers in the space charge layers. During H/D isotope exchange relatively fast hysteretic transients indicate that the space charge layers experience changes in charge carrier (D+ vs. H+) mobility as well as in D2O vs. H2O hydration thermodynamics. |
| Keywords | BaZrO3, Pr-substituted, acceptor-doped; BaZr0.7Pr0.2Y0.1O3-δ; Proton conductivity; Grain boundaries, space charge layer; Hydration; Impedance spectroscopy |
| Remark | Link |
Synthesis, structural and electrical properties of double perovskite Sr2NiMoO6 ceramics
ID=151| Authors |
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| Source |
Applied Physics A: Materials Science & Processing
Volume: 107,
Issue: 1,
Pages: 117-121 Time of Publication: 2012-01 |
| Abstract | The double perovskite Sr2NiMoO6 powders and ceramics were prepared by two different (conventional and precursor) solid-state reaction methods. The phase structure was characterized by XRD and TEM techniques. It has been indicated that single-phase perovskite powders were obtained when calcined in air at 1300°C. However, nano-particles of the size 30–60 nm have been found in powders prepared with the precursor method, while those from the conventional route exhibit large irregular shaped particles with aggregation. The dielectric properties (ε r and tanδ) were also examined in the sintered ceramics. The results showed the transition point at 280°C for conventional route, while no clear phase change was observed in ceramics from the precursor route. These observations clearly indicate that the different starting processes affected the phase formation behavior and the electrical properties of Sr2NiMoO6 ceramics. |
| Remark | Link |
Dielectric Relaxation in BaTiO3–Bi(Zn1/2Ti1/2)O3 Ceramics
ID=150| Authors |
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| Source |
Journal of the American Ceramic Society
Volume: 95,
Issue: 5,
Pages: 1604–1612 Time of Publication: 2012-05 |
| Abstract | A dramatic improvement in the dielectric and electrical properties has been observed in ceramics of 0.8BaTiO3–0.2Bi(Zn1/2Ti1/2)O3 through the introduction of Ba vacancies. It possesses a high relative permittivity (εr > 1150) along with a low dielectric loss (tan δ < 0.05) that is maintained up to temperatures as high as 460°C. It is also characterized by a high resistivity of 70 GΩ-cm, which remains constant up to 270°C. Analysis of complex impedance (Z*) and complex electric modulus (M*) data, measured over the frequency range of 1–106 Hz, revealed a number of important findings. At high temperatures (T > 255°C), a complex plane analysis of Z″ versus Z′ and the frequency dependence of Z″ suggests an electrically inhomogeneous microstructure for the stoichiometric composition. The stoichiometric composition exhibited activation energies of ~1 eV which suggests an extrinsic conduction mechanism. However, the introduction of Ba vacancies resulted in electrically homogeneous microstructure. An overlap of the Z″ and M″ peaks in the frequency domain and much larger activation energies were observed, on the order of half of the band gap, suggesting an intrinsic conduction mechanism. A more detailed analysis of the data reveals insights into the physical mechanisms underpinning the dielectric and ac conductivity. |
| Remark | Link |
Fabrication and electrochemical properties of cathode-supported solid oxide fuel cells via slurry spin coating
ID=148| Authors |
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| Source |
Electrochimica Acta
Volume: 63,
Pages: 277–286 Time of Publication: 2012-02 |
| Abstract | A cathode-supported SOFC consisting of LSM (La0.8Sr0.2MnO3-δ) cathode supporter, LSM-Sm0.2Ce0.8O2-δ (SDC) cathode functional layer (CFL), yttria stabilized zirconia (YSZ)/SDC bi-layered electrolyte and Ni-YSZ anode layer was fabricated by a slurry spin coating technique. The influence of the porosity in both the CFL and cathode supporter on the electrochemical properties of the cells has been investigated. It was found that properly controlling the porosity in the CFL would improve the performance of the cells using O2 in the cathode side (O2-cells), with a maximum power density (MPD) value achieving as high as 0.58 W•cm−2 at 850 °C. However, this improvement is not so evident for the cells using air in the cathode side (air-cells). When increasing the porosity in the cathode-supporter, a significant increase of the power density for the air cells due to the decreasing Rconc,c(concentration polarization to the cell resistance) can be ascertained. In terms of our analysis on various electrochemical parameters, the Ract (activation polarization to the cell resistance) is assumed to be mainly responsible for the impedance arcs measured under the OCV condition, with a negligible Rconc,cvalue being able to be detected in our impedances. In this case, a significant decreasing size of the impedance arcs due to the increasing porosity in the cathode supporter would correspond to a decrease of the Ract values, which was proved to be induced by the decreasingRconc,c. |
| Keywords | Slurry spin coating; Cathode-supported SOFC; Concentration polarization; Activation polarization; Power density |
| Remark | Link |
The effect of cation non-stoichiometry in LaNbO4 materials
ID=145| Authors |
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| Source |
International Journal of Hydrogen Energy
Volume: 37,
Issue: 9,
Pages: 8017–8026 Time of Publication: 2012-05 |
| Abstract | The effect of cation non-stoichiometry in LaNbO4 was investigated by impregnating nano-crystalline LaNbO4 with small amounts of La3+, Nb5+ and Ca2+ oxide precursors. The sintering properties of the modified LaNbO4 powders were investigated by dilatometry, and the microstructure and phase composition were studied by electron microscopy and X-ray diffraction. The electrical properties of the materials were studied by 4-point DC-conductivity and 2-point 4-wire AC-conductivity at elevated temperatures in controlled atmosphere. Minor variations in the cation stoichiometry were shown to have a pronounced effect on both the sintering properties as well as the electrical conductivity. Addition of CaO, which introduced secondary phases above 0.25 mol% CaO, increased the sintering temperature and improved the conductivity of the materials. La2O3- and Nb2O5-excess materials did not show large variation in the electrical conductivity relative to pure LaNbO4, while the sintering properties were strongly affected by the nominal La/Nb ratio in LaNbO4. The present findings demonstrate the sensitivity of cation non-stoichiometry in materials with limited solid solubility. |
| Keywords | LaNbO4; Proton conductivity; Phase purity; Solid solubility |
| Remark | Link |
Effects of surface coatings on the determination of Dchem and kchem in La2NiO4+δ by conductivity relaxation
ID=144| Authors |
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| Source |
Solid State Ionics
Volume: 206,
Pages: 67-71 Time of Publication: 2012-01 |
| Abstract | In this work, we utilize surface modification to accurately determine oxygen diffusivity and surface exchange in La2NiO4 + δ by transient conductivity. To achieve ‘instantaneous’ gas exchange in the reaction cell, a total pressure change was adopted instead of exchange of gas mixtures at 1 atm. Conductivity relaxation measurements were performed in the temperature range of 600–900 °C and at oxygen partial pressures of 0.2, 1.0 and 1.9 atm. Due to the large uncertainties associated with deriving oxygen chemical diffusion and surface coefficients simultaneously, we limited the relaxation to pure bulk diffusion control by coating nano-grained La2NiO4 + δ particles on the sample surface. After determining Dchem, kchem was derived by fitting the relaxation data of the uncoated sample. The transient experiments via both oxidation (a step change of pO2 from 0.2 to 1.0 atm) and reduction (1.9 to 1.0 atm) give consistent results of Dchem and kchem showing Arrhenius-type behaviour with activation energies of ~ 90 kJ/mol and ~ 150 kJ/mol, respectively. |
| Keywords | Conductivity relaxation; Surface modification; Surface exchange; Oxygen diffusion; La2NiO4 + δ |
| Remark | Link |
Hydration and proton conductivity in LaAsO4
ID=143| Authors |
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| Source |
Journal of Materials Chemistry
Volume: 22,
Issue: 4,
Pages: 1652-1661 Time of Publication: 2012-04 |
| Abstract | Incorporation and transport of protonic defects have been studied in nominally undoped and 1 and 3 mol% Sr-doped LaAsO4 prepared by a co-precipitation route. AC impedance of the materials was measured as a function of temperature (1150 to 400 °C), pO2 (1 to 1 × 10−5 atm) and pH2O (0.025 to 3 × 10−5 atm). The bulk conductivities generally decrease with decreasing temperature and moreover with decreasing pH2O within the whole temperature range. At the highest temperatures, a small decrease in the conductivity with decreasing pO2 was also observed. The defect structure of Sr-doped LaAsO4 appears to be dominated by oxygen vacancies in the form of pyroarsenate ions, As2O4−7, in dry atmospheres at high temperatures and by protonic defects in the form of hydrogen arsenate ions, HAsO2−4, in wet atmospheres. A significant isotope effect shows that protons contribute to the total conductivity at all temperatures under wet conditions and predominate at temperatures below [similar]850 °C. The remaining contributions are attributed to oxide ions and electron holes. The extracted hydration thermodynamics are comparable to those determined for other LnXO4 (X = P, V, Nb, Ta) compounds, and the enthalpy of mobility of protons (86 ± 5 and 88 ± 5 kJ mol−1 for the 1 and 3 mol% doped samples, respectively) follows an apparent trend for the isostructural LaXO4 (X = P, As, V) series with the enthalpy of mobility of protons decreasing with increasing radius of the X-site cation. However, the partial proton conductivities of Sr-doped LaAsO4 are lower than those determined for acceptor doped LaPO4 and LaVO4 for which the possible reasons are discussed. |
| Remark | Link |
Evaluation of the electrode/electrolyte contact quality in solid oxide fuel cells
ID=142| Authors |
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| Source |
Electrochimica Acta
Volume: 60,
Pages: 224–229 Time of Publication: 2012-01 |
| Abstract | Symmetrical cells have been prepared by depositing suspensions with different active powder concentrations (50% and 60% by weight respectively) of lanthanum strontium cobalt iron oxide (La0.6Sr0.4Co0.2Fe0.8O3-δ) on identical yttria stabilized zirconia pellets (LSCF/YSZ/LSCF). Their impedance characteristics are compared to that of a symmetrical cell with platinum electrodes deposited on a similar zirconia pellet (Pt/YSZ/Pt). The LSCF cells show different values of the electrolyte resistance. Referring to the electrolyte resistance obtained with the Pt cell and assuming that this value corresponds to almost perfect electrode/electrolyte contacts, it is possible to estimate the Effective Conducting Area (ECA) of the electrodes. The use of the ECA parameter allows a better comparison of the electrode polarizations. |
| Keywords | solid oxide fuel cells; porous electrodes; cathode |
| Remark | Link |
Influence of Pr substitution on defects, transport, and grain boundary properties of acceptor-doped BaZrO3
ID=141| Authors |
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| Source |
International Journal of Hydrogen Energy
Volume: 37,
Issue: 9,
Pages: 7962–7969 Time of Publication: 2012-05 |
| Abstract | We report on effects of partially substituting Zr with the multivalent Pr on the conductivity characteristics of acceptor (Gd) doped BaZrO3-based materials. BaZr0.6Pr0.3Gd0.1O3−δ was sintered 96% dense at 1550 °C with grains of 1–4 μm. The electrical conductivity was characterised by impedance spectroscopy and EMF transport number measurements as a function of temperature and the partial pressures of oxygen and water vapour. H2O/D2O exchanges were applied to further verify proton conduction. The material is mainly a mixed proton–electron conductor: the p-type electronic conductivity is ∼0.004 and ∼0.05 S/cm in wet O2 at 500 and 900 °C, respectively, while the protonic conductivity is ∼10−4 S/cm and ∼10−3 S/cm. The material is expectedly a pure proton conductor at sufficiently low temperatures and wet conditions. The specific grain boundary conductivity is essentially equal for the material with or without Pr, but the overall resistance is significantly lower for the former. We propose that replacing Pr on the Zr site reduces the grain boundary contribution due to an increased grain size after otherwise equal sintering conditions. |
| Keywords | BaZrO3; BaPrO3; Defects and transport; Grain boundaries; Grain boundary specific conductivity |
| Remark | Link |
Effects of A and B site acceptor doping on hydration and proton mobility of LaNbO4
ID=140| Authors |
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| Source |
International Journal of Hydrogen Energy
Volume: 37,
Issue: 9,
Pages: 8004–8016 Time of Publication: 2012-05 |
| Abstract | Acceptor doping of the high temperature proton conductor LaNbO4 has been studied by impedance spectroscopy in various atmospheres at 300–1100 °C and by X-ray powder diffraction and scanning electron microscopy. Doping LaNbO4 on both A and B site (with Ca and Ti, respectively) resulted in a two-phase composition of LaNbO4 and LaNb3O9. This composite is interesting as the two phases make it a mixed proton and electron conductor. The electrical characterisation of Ti-doped LaNbO4 revealed mixed electronic (n- and p-type) and ionic conductivity at temperatures above approx. 750 °C, while proton conductivity was dominating below this temperature under wet conditions. Ti-doping resulted in higher activation enthalpy and lower mobility of protons as compared to Ca-doping, attributed to stronger proton–acceptor association in the former case. Thermodynamic constants for hydration of associated protons and proton–acceptor association as well as mobility parameters were fitted to the experimental data and came out as , , , and , and . Neither B site doping nor A and B site co-doping showed indications of increased solubility relative to sole A site doping in LaNbO4. |
| Keywords | LaNbO4; Ti-doped LaNbO4; Defect association; Proton mobility; Proton conductivity; Hydration thermodynamics |
| Remark | Link |
Effects of (LaSr)(CoFeCu)O3-δ Cathodes on the Characteristics of Intermediate Temperature Solid Oxide Fuel Cells
ID=139| Authors |
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| Source |
Journal of Power Sources
Volume: 201,
Pages: 18–25 Time of Publication: 2012-03 |
| Abstract | In this study, Cu2+ ions doped La0.6Sr0.4Co0.2Fe0.8O3−δ cathodes are prepared for use in solid oxide fuel cells (SOFCs). The maximum electrical conductivities of the La0.6Sr0.4Co0.2Fe0.7Cu0.1O3−δ (438 S cm−1) and the La0.6Sr0.4Co0.1Fe0.8Cu0.1O3−δ (340 S cm−1) discs are higher than that of the La0.6Sr0.4Co0.2Fe0.8O3−δ disc (LSCF; 81 S cm−1) sintered at 1100 °C. The substitution of Cu2+ over Fe3+ leads to a higher coefficients of thermal expansion (CTE), while the replacement of Co3+ by Cu2+ results in a lower CTE. Single cells with the La0.6Sr0.4Co0.2Fe0.8O3−δ, La0.6Sr0.4Co0.2Fe0.7Cu0.1O3−δ, and La0.6Sr0.4Co0.1Fe0.8Cu0.1O3−δ cathodes operating at 650 °C and 550 °C show similar ohmic resistance (R0) values while the polarization resistance (RP) values of the cells with the La0.6Sr0.4Co0.2Fe0.7Cu0.1O3−δ and a0.6Sr0.4Co0.1Fe0.8Cu0.1O3−δ cathodes are slightly lower than that of the single cell with the La0.6Sr0.4Co0.2Fe0.8O3−δ cathode, indicating that the Cu2+-doped LSCF cathode exhibits a greater electrochemical catalytic activity for oxygen reduction. Maximum power densities of the cells with the La0.6Sr0.4Co0.2Fe0.8O3−δ, La0.6Sr0.4Co0.2Fe0.7Cu0.1O3−δ, and La0.6Sr0.4Co0.1Fe0.8Cu0.1O3−δ cathodes operating at 700 °C read respectively 1.07, 1.15, and 1.24 W cm−2. It is evident that the doping of Cu2+ ions in LSCF is beneficial to the electrochemical performance of the cells. |
| Keywords | Solid oxide fuel cell; cathode; cathode; impedance; Cell performance |
| Remark | Link |
Synthesis and Enhanced Proton Conduction in a 20 mol% Ytterbium Doped Barium Zirconate Ceramic Using Zn as Sintering Aid
ID=138| Authors |
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| Source |
Applied Mechanics and Materials
Mechanical and Aerospace Engineering Volume: 110-116 Time of Publication: 2011-10 |
| Abstract | 20% Ytterbium (III)-doped perovskite structured barium zirconate, BaZrO3, was prepared by two different synthesis routes: solid state and sol-gel routes. 2 % Zinc (II) was added as an acceptor dopant at the Zr (IV) site according to stoichiometry. It was also added as 2 % excess of the formula. The purpose of this study is to see how zinc (II) acts as a sintering aid in view of synthesis route, densification and conductivity of the material. A dense ceramic (90% of theoretical density) was achieved by the sol-gel method when stoichiometry was adjusted. Phase purity of the samples was checked by X-ray powder diffraction (XRD). Thermogravimetric analysis (TGA) and Impedance spectroscopy (IS) was used to characterize hydration and electrical conductivity respectively.The data shows that the addition of stoichiometric amounts of Zn2+ via sol-gel synthesis route promotes not only densification but also water incorporation and conductivity in comparison with the solid state route, keeping the same final sintering temperature of 1500°C. For example, pre-hydrated BaZr0.78Zn0.02Yb0.2O3-δ, prepared via the sol-gel method shows total conductivity (σtot) value of 3.14*10-5 and 3.8*10-3 Scm-1, whereas for the solid state route, σtot values are 1.74*10-5 and 8.87*10-4 Scm-1 under dry Ar (heating cycle) at 300° C and 600° C, respectively. |
| Keywords | BaZrO3, Impedance Spectroscopy, Proton Conductivity, Sintering Aid, TGA, X-Ray Diffraction (XRD) |
| Editor |
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| Remark |
Online since October, 2011; DOI 10.4028/www.scientific.net/AMM.110-116.1181 Link |
Effect of nano-grain size on the ionic conductivity of spark plasma sintered 8YSZ electrolyte
ID=137| Authors |
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| Source |
International Journal of Hydrogen Energy
Volume: 37,
Issue: 1,
Pages: 511–517 Time of Publication: 2012-01 |
| Abstract | Densification and micro-structural development of ultra fine 8 mol% yttria stabilized zirconia (8YSZ) nano powder were investigated systematically by varying the SPS sintering temperature at constant applied pressure of 50 MPa. A hundred fold decrease in average grain size ranging from 10 μm to 80 nm is observed on decreasing the SPS sintering temperature from 1200 °C to 1050 °C with >99% of theoretical densities. Impedance measurements on the samples indicated an enhancement in the ionic conductivity at 700 °C from 0.004 S/cm to 0.018 S/cm with decrease in grain size from 10 μm to 0.51 μm and a significant increase in conductivity from 0.018 S/cm to 0.068 S/cm on further reduction of grain size to 80 nm. A significant change in the grain-boundary conductivity is noticed on reducing the grain sizes to nano regime. The diverse microstructure with ultra fine grain size resulting from SPS at 1050 °C could contribute to the enhanced ionic conductivity, which is supported by the activation energy data. |
| Keywords | Solid oxide fuel cells; Electrolyte; Microstructure; Spark plasma sintering |
| Remark | Link |
Dielectric relaxation in a thermosetting polyimide modified with a thermoplastic polyimide
ID=136| Authors |
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| Source |
Polymer Science Series A
Volume: 53,
Issue: 10,
Pages: 963-967 Time of Publication: 2011-10 |
| Abstract | Relaxation processes in glass-fiber-reinforced composites with a polymer matrix based on blends of thermosetting and thermoplastic polyimides are studied via dielectric-relaxation spectroscopy. For all investigated blends, two relaxation processes related to the β relaxation of different fragments of the polymer chain are found. Linear flexiblechain polyimide incorporated into the polymer matrix serves as a plasticizer. |
| Remark |
DOI: 10.1134/S0965545X11100014 Link |
Autothermal Reforming of Methane in Proton-Conducting Ceramic Membrane Reactor
ID=135| Authors |
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| Source |
Ind. Eng. Chem. Res. Volume: 50, Issue: 22, Pages: 12426–12432 Time of Publication: 2011-10 |
| Abstract | Endothermic steam reforming of methane for hydrogen production requires heat input with selective oxidation of methane. Dense SrCe0.75Zr0.20Tm0.05O3-δ perovskite membranes were combined with a reforming catalyst to demonstrate the feasibility of a heat-exchange membrane reactor for steam reforming of methane coupled with selective oxidation of permeated hydrogen. The reforming catalyst used was a prereduced nickel based catalyst supported on γ-Al2O3. Hydrogen produced via the steam reforming of methane or water gas shift reaction was able to diffuse through the catalyst bed and transport through the membrane. The permeated hydrogen reacted with oxygen (from air) to produce heat for the steam reforming of methane on the other side of the membrane. The membrane reactor avoids the use of an expensive air separation unit to produce pure oxygen. The influence of experimental conditions, such as temperature, gas hourly space velocity, and the steam to carbon (S/C) ratio, on the membrane reactor was investigated. SrCe0.75Zr0.20Tm0.05O3-δ showed good chemical stability in steam reforming conditions as X-ray diffraction analysis of the membrane surface exposed to steam-reforming conditions for 425 h showed only minor CeO2 formation. The experimental data demonstrate the feasibility of using a proton conducting ceramic membrane in the heat-exchange membrane reactor for steam reforming of methane coupled with selective oxidation. |
| Remark | Link |
Post-heat treatment pressure effect on performances of metal-supported solid oxide fuel cells fabricated by atmospheric plasma spraying
ID=134| Authors |
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| Source |
Journal of Power Sources
Volume: 197,
Pages: 145–153 Time of Publication: 2012-01 |
| Abstract | The nickel metal-supported cells fabricated by atmospheric plasma spraying are post-heat treated in air at 960 °C for 2 h with different pressures. The current–voltage–power and AC impedance measurements show the prepared cell with an applied pressure of 450 g cm−2 in the post-heat treatment has a better electrochemical performance at test temperatures ≥ 650 °C. For test temperatures < 650 °C, the maximum power densities at 450 g cm−2 pressure are about the same as the maximum power densities at 1250 g cm−2 pressure. The SEM micrograph indicates that the cathode including the cathode interlayer and the cathode collector is the most porous region in the cell. AC impedance results show this cathode is the most sensitive part to the applied pressure in the post-heat treatment and the cell with 450 g cm−2 pressure has the smallest low frequency intercept R2 and the polarization resistance Rp at temperatures from 600 to 800 °C. The performance durability test of the cell post-heat treated at 450 g cm−2 pressure shows a degradation rate of 0.0087 mV h−1 or 0.0026 mW h−1 at 300 mA cm−2 constant current density and 750 °C test temperature. |
| Keywords | Atmospheric plasma spray; Solid oxide fuel cells; Metal-supported; Nanostructured |
| Remark | Link |
The morphotropic phase boundary in the (1 − x)PbZrO3–x[0.3Bi(Zn1/2Ti1/2)O3–0.7PbTiO3] perovskite solid solution
ID=133| Authors |
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| Source |
Journal of Materials Science
Volume: 47,
Issue: 4,
Pages: 1774-1779 Time of Publication: 2012-04 |
| Abstract | Ceramics in the (1 − x)PbZrO3–x[0.3Bi(Zn1/2Ti1/2)O3–0.7PbTiO3] solid solution system with 0.48 ≤ x ≤ 0.56 were investigated. A morphotropic phase boundary separating rhombohedral and tetragonal perovskite phases was identified at x = 0.52. This composition displays the maximum remanent polarization P r of 40.7 μC/cm2 and the best piezoelectric coefficient d 33 of 311 pC/N in the pseudo-binary system. However, the Curie temperature T c for this MPB composition is 291 °C, much lower than initially expected. |
| Remark | Link |
Synthesis and electrical properties of lead free (Bi0.5K0.5)TiO3–BaTiO3–Bi(Zn0.5Ti0.5)O3 ceramics
ID=132| Authors |
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| Source |
Ceramics International
Volume: 38,
Issue: 1,
Pages: 827–830 Time of Publication: 2012-01 |
| Abstract | Lead free ferroelectric materials with high Curie temperature in (x)[(Bi0.5K0.5)TiO3]− (1-x)[0.5Bi(Zn0.5Ti0.5)O3 − 0.5BaTiO3] or (x)BKT − (1-x)[BZT − BT] ternary system, where x = 0.4, 0.5, 0.6 and 0.8, were synthesized. The single phase perovskite for all ceramics were formed at 900 °C for 6 h in air. The ceramic compositions with x = 0.5 and 0.6 exhibited the dielectric properties with relaxor-like phase transition behavior, while the ceramic with x = 0.8 showed the dielectric behavior of normal ferroelectric materials. From room temperature P–E measurement, the maximum remnant polarization (Pr of 2.75 μC/cm2) and coercive field (Ec of 12.41 kV/cm) were obtained in the composition with x = 0.6. In addition, the TC, Pr and Ec were found trend to increase with increasing BKT content. |
| Keywords | Ferroelectric; Dielectric; Relaxor-like behavior; High Curie temperature |
| Remark | Link |
Characterization of individual barium titanate nanorods and their assessment as building blocks of new circuit architectures
ID=131| Authors |
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| Source |
Nanotechnology
Volume: 22,
Issue: 38,
Pages: 385501 Time of Publication: 2011-09 |
| Abstract | In this work, we report on the integration of individual BaTiO3 nanorods into simple circuit architectures. Polycrystalline BaTiO3 nanorods were synthesized by electrophoretic deposition (EPD) of barium titanate sol into aluminium oxide (AAO) templates and subsequent annealing. Transmission electron microscopy (TEM) observations revealed the presence of slabs of hexagonal polymorphs intergrown within cubic grains, resulting from the local reducing atmosphere during the thermal treatment. Electrical measurements performed on individual BaTiO3 nanorods revealed resistivity values between 10 and 100 Ω cm, which is in good agreement with typical values reported in the past for oxygen-deficient barium titanate films. Consequently the presence of oxygen vacancies in their structure was indirectly validated. Some of these nanorods were tested as proof-of-concept humidity sensors. They showed reproducible responses towards different moisture concentrations, demonstrating that individual BaTiO3 nanorods may be integrated in complex circuit architectures with functional capacities. |
| Remark |
doi: 10.1088/0957-4484/22/38/385501 Link |
Structure, chemical stability and mixed proton–electron conductivity in BaZr0.9−xPrxGd0.1O3−δ
ID=130| Authors |
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| Source |
Journal of Power Sources
Time of Publication: 2011-08
|
| Abstract | BaZr0.9−xPrxGd0.1O3−δ (x = 0.3 and 0.6) was prepared by combustion synthesis and characterised with respect to conductivity and stability in an attempt to combine the desirable properties of the end members. The polycrystalline materials exhibit a cubic or pseudo-cubic structure as determined by X-ray synchrotron radiation and transmission electron microscopy. The chemical stability of the compositions is strongly dependent on the praseodymium content, the materials with more Pr present lower stability. Electron holes dominate the conductivity under oxidising atmospheres in BaZr0.3Pr0.6Gd0.1O3−δ, while BaZr0.6Pr0.3Gd0.1O3−δ exhibits a mixed electron hole–proton conducting behaviour. Substitution of Zr by Pr in acceptor-doped BaZrO3 decreases the sintering temperature and increases the grain growth rate. |
| Remark |
Article in press, DOI:10.1016/j.jpowsour.2011.06.076 |
Impedance and modulus spectroscopic studies on 40PrTiTaO6 + 60YTiNbO6 ceramic composite
ID=129| Authors |
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| Source |
Journal of Materials Science: Materials in Electronics
Volume: 23,
Issue: 3,
Pages: 653-658 Time of Publication: 2012-03 |
| Abstract | The 40PrTiTaO6 + 60YTiNbO6 ceramic composite is prepared through the solid state ceramic route. The structure is discussed using X-ray diffraction analysis. Surface morphology is examined by Scanning Electron Microscopy (SEM). Impedance and modulus spectroscopic studies are carried out. A decrease in the resistive behavior of the sample assisted by the grain boundary conduction with rise in temperature is found. The experimental results on electrical properties indicate that the material exhibits conduction both due to bulk and grain boundary effect. The microstructure was investigated by SEM micrographs in which grains separated by grain boundaries are visible. There is a probable change in the capacitance values of the material as a function of temperature. The relaxation time is small at higher temperatures than at lower temperatures. The activation energy is found as 1.52 eV, which suggests the possibility of electrical conduction due to the mobility of oxide ions (O2−) or oxide ion vacancies at higher temperature. |
| Remark | Link |
Proton Conductivity in Acceptor-Doped LaVO4
ID=128| Authors |
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| Source |
J. Electrochem. Soc. Volume: 158, Issue: 8, Pages: B857-B865 Time of Publication: 2011-06 |
| Abstract | Electrical characterization of nominally undoped LaVO4, La0.99Ca0.01VO4− and La0.95Ca0.05VO4− was performed in various partial pressures of oxygen, water vapor and hydrogen isotopes, from 300 to 1100°C by impedance spectroscopy, AC conductivity measurements (10 kHz) and EMF-measurements. XRD, SEM and EDS were used for structural, micro structural and compositional analysis. Acceptor doped LaVO4 is a pure ionic conductor in oxidizing atmospheres in the entire measured temperature range; dominated by proton conductivity at low temperatures (T < 450°C) under wet conditions and oxide ion conductivity at high temperatures. A maximum in the partial proton conductivity of ~ 6 × 10−5 S/cm was reached at 900°C (pH2O2.5·10-2 atm). Thermodynamics of hydration and transport parameters for charge carriers in La0.99Ca0.01VO4 were derived from relations between defect chemistry, transport properties and the measured conductivity data and revealed: S=− 130 ± 10 J/mol K, S =− 142 ± 10 J/mol K, H=− 110 ± 10 kJ/mol, µ0,H+ = 50 ± 6 cm2 K/Vs, Hmob,H+ = 75 ± 10 kJ/mol, µ0,v= 120 ± 20 cm2 K/Vs and Hmob,v = 85 ± 10 kJ/mol. The tetrahedron (XO4) volume and migration enthalpy were found to be correlated for the series of monoclinic LaXO4. |
Nanostructuring phenomena in oxygen-conducting complex oxides of heavy REE
ID=127| Authors |
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| Source |
Russian Journal of Electrochemistry
Volume: 47,
Issue: 5,
Pages: 620-627 Time of Publication: 2011-05 |
| Abstract | In complex oxides of REE (Ln4M3O12 (Ln = Tm, Lu; M = Zr, Hf), Ln2TiO5 (Ln = Er-Yb)) and Ho2TiO5, the following phase transitions of the order-disorder type are studied for different cooling rates: rhombohedral δ-phase-defective fluorite in Ln4M3O12 (Ln = Tm, Lu; M = Zr, Hf), pyrochlor-like phasedefective fluoride in Ln2TiO5 (Ln = Er-Yb), and hexagonal β-phase-pyrochlor in Ho2TiO5. The presence of nanostructuring phenomena typical of fluorite-like polymorphous modifications of complex oxides in the Ln2O3-MO2 (Ln = Ho-Lu; M = Ti, Zr, Hf) systems is confirmed. The conductivity of polymorphous modifications of Ln4Zr3O12 (Ln = Tm, Lu;) and Ln2TiO5 (Ln = Ho-Yb) with different thermal prehistory is studied. The comparative studies of the oxygen-ionic conductivity of fluorite- and pyrochlor-like Ln2TiO5 (Ln = Ho-Yb), pyrochlor Ho2TiO5, and β-Ho2TiO5 and also of the conductivity of fluorite-like compounds and δ-Ln4Zr3O12 (Ln = Tm, Lu) are carried out. The oxygen-ionic conductivity of complex oxides in the Ln2O3-MO2 (Ln = Er-Lu; M = Ti, Zr, Hf) system is shown to decrease in the following series: defective pyrochlor-defective fluorite-rhombohedral δ-phase ∼ hexagonal β-phase. |
Partial Oxidation of Methane and Oxygen Permeation in SrCoFeOx Membrane Reactor with Different Catalysts
ID=126| Author |
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| Source |
Ind. Eng. Chem. Res.
Volume: 50,
Issue: 13,
Pages: 7941–7948 Time of Publication: 2011-05 |
| Abstract | Partial oxidation of methane (CH4) and oxygen permeation in a dense SrCoFeOx disk membrane reactor were studied with the reducing side of the membrane packed with different catalysts (catalyst support γ-Al2O3, La0.6Sr0.4Co0.8Fe0.2O3−δ, and 10 wt % Ni/γ-Al2O3) of increasing reaction activities for CH4 oxidation. The influence of temperature, flow rates, and inlet CH4 concentration (diluted with helium) on the performance of the different membrane reactors was investigated. The oxygen permeation flux and CH4 conversion increased in the following order: γ-Al2O3 < La0.6Sr0.4Co0.8Fe0.2O3−δ < 10% Ni/γ-Al2O3. The membrane reactor with the reforming catalyst of 10 wt % Ni/γ-Al2O3 had the highest CH4 conversion (90%), CO selectivity (97%), and oxygen permeation flux (2.40 mL/(cm2 min)) at 900 °C. The improvement of the oxygen permeation through the membranes with different catalysts emphasizes the effect of the CH4 oxidation reaction rate on the reducing side of the membrane on the oxygen permeation flux through the mixed-conducting ceramic membranes. Under identical conditions, the oxygen permeation flux through mixed-conducting ceramic membrane with a reducing gas is a strong function of the catalytic activity for the oxidation of the reducing gas. |
| Remark | Link |
Phase transition and electrical properties of gallium- and indium-doped Bi10Ti3W3O30
ID=125| Authors |
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| Source |
Inorganic Materials
Volume: 47,
Issue: 5,
Pages: 513-520 Time of Publication: 2011-05 |
| Abstract | Polycrystalline samples of gallium- and indium-doped Bi10Ti3W3O30 (mixed-layer Aurivillius phase with the Ti4+ and W6+ distributed at random over the perovskite-like slabs) have been prepared by solid-state reactions, and their polymorphism and electrical properties have been studied. Doping with both In3+ and Ga3+ yields limited solid solutions and shifts the ferroelectric phase transition to lower temperatures. The heterovalent substitutions of In3+ and Ga3+ for Ti4+ and W6+ increase the oxygen vacancy concentration and, accordingly, the conductivity of the material relative to the undoped compound. |
Lamellar Titanates: A Breakthrough in the Search for New Solid Oxide Fuel Cell Anode Materials Operating on Methane
ID=124| Authors |
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| Source |
Advanced Energy Materials
Volume: 1,
Issue: 4,
Pages: 573–576 Time of Publication: 2011-07 |
| Abstract | Decreasing the dimensionality of the LaxSr1–xTiOmath image family structure from 3D to 2D by increasing the La content greatly enhances the electrochemical performance of the material as an SOFC anode. This is attested to by the strong decrease in the polarization resistance values deduced from the complex impedance spectra (Nyquist plot) recorded at 900 °C in H2/H2O(3%) on a symmetrical cell. |
| Keywords | Solid oxide fuel cells; Anode materials; Titanate; Methane |
| Remark | Link |
An ion-plasma technique for formation of anode-supported thin electrolyte films for IT-SOFC applications
ID=123| Authors |
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| Source |
International Journal of Hydrogen Energy
Volume: 36,
Issue: 9,
Pages: 5550-5556 Time of Publication: 2011-05 |
| Abstract | This paper describes a preparation method and structural and electrochemical properties of a thin bilayer anode-electrolyte structure for a solid oxide fuel cell operating at intermediate temperatures (IT-SOFC). Thin anode-supported yttria-stabilized zirconia electrolyte films were prepared by reactive magnetron sputtering of a Zr–Y target in an Ar–O2 atmosphere. Porous anode surfaces of IT-SOFCs were modified by a pulsed low-energy high-current electron beam prior to film deposition; the influence of this pretreatment on the performance of both the deposited films and a single cell was investigated. The optimal conditions of the pulsed electron beam pretreatment were obtained. For the electrolyte thickness about 2.5 μm and the value of gas permeability of the anode/electrolyte structure 1.01 × 10−7 mol m−2 s−1 Pa−1, the maximum power density achieved for a single cell at 800 °C and 650 °C was found to be 620 and 220 mW cm−2 in air, respectively. |
| Keywords | Solid oxide fuel cell; YSZ electrolyte; Magnetron sputtering; Surface modification of material; Pulsed electron beam treatment; Electrical performance |
Microwave-assisted synthesis of gadolinia-doped ceria powders for solid oxide fuel cells
ID=122| Authors |
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| Source |
Ceramics International
Volume: 37,
Issue: 4,
Pages: 1423-1426 Time of Publication: 2011-05 |
| Abstract | Gadolinia doped ceria (GDC) is an attractive electrolyte material for intermediate temperature solid oxide fuel cells (IT-SOFCs) for its high ionic conductivity at low temperature (500–700 °C). A number of different methods are currently used to prepare nano-sized doped-ceria powder. Among the others, precipitation in solution remains the best method to obtain well-dispersed particles of controlled properties. In this work, nanocrystalline Ce1−xGdxO2−δ (GDC) particles were produced by polyol microwave assisted method in very mild conditions (170 °C, 2 h, 1 atm). The as-synthesized powder showed good sinterability and ionic conductivity comparable to the ones of the corresponding nanometric commercial GDC. |
| Keywords | GDC; Microwave heating; Polyol method; IT-SOFC |
Solid oxide fuel cells with Sm0.2Ce0.8O2−δ electrolyte film deposited by novel aerosol deposition method
ID=121| Authors |
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| Source |
Journal of Power Sources
Volume: 196,
Issue: 11,
Pages: 5064-5069 Time of Publication: 2011-06 |
| Abstract | In this study, dense electrolyte ceramic Sm0.2Ce0.8O2−δ (SDC) thin films are successfully deposited on NiO-SDC anode substrate by aerosol deposition (AD) with oxygen as the carrier gas at the substrate temperature ranging from room temperature to 300 °C. To remove the effect of humidity on the starting powders, this study found that, in depositing SDC films, having the starting powders preheat-treated at 200 °C helped generate a smooth and dense layer, though a lower deposition rate was achieved. At a deposition time of 22 min, SDC films with a uniform thickness of 1.5 μm and grain sizes of ≈67 nm are obtained. SOFC single cells are then built by screen printing a LSCF cathode on the anode-supported substrates with SDC electrolyte. The cross-sectional SEM micrographs exhibit highly dense, granular, and crack-free microstructures. The open circuit voltages (OCV) of the single cells decrease with the rise in temperature, dropping from 0.81 V at 500 °C to 0.59 V at 700 °C. Maximum power densities (MPD) decline with decreasing operating temperature from 0.34 to 0.01 W cm−2 due to the increase of the R0 and RP of the single cells. The electrochemical results testify to the fine quality of SDC films as well as illustrate the electrolyte thickness effect and the effect of mixed ionic and electronic conduction of the SDC electrolyte in the reducing atmosphere. |
| Keywords | SDC films, NiO-SDC substrate, aerosol deposition, Very dense SDC films, uniform thickness of 1.5 μm, Single cell with a MPD of 0.34 W cm−2, 700 °C, Solid oxide fuel cell; Ceria; Aerosol deposition; Electrolyte |
Conductivity, transport number measurements and hydration thermodynamics of BaCe0.2Zr0.7Y(0.1 − ξ)NiξO(3 − δ)
ID=120| Authors |
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| Source |
Solid State Ionics
Volume: 185,
Issue: 1,
Pages: 11-17 Time of Publication: 2011-03 |
| Abstract | BaCe0.2Zr0.7Y(0.1 − ξ)NiξO(3 − δ) compounds with ξ = 0.01 and 0.02 have been synthesized by solid state reaction at 1400 °C and sintered at 1450 °C. TEM analyses were performed and showed a segregation of nickel at the grain boundaries for ξ = 0.02. This apparent solubility limit of Ni in the B-site of the perovskite is in agreement with similar data obtained earlier for the two compositions. The first aim of this work was to evaluate the conductivity of BaCe0.2Zr0.7Y(0.1 − ξ)NiξO(3 − δ) at temperature between 500 and 900 °C, using impedance spectroscopy at different oxygen partial pressures and water vapor pressures, as well as the emf technique. The compounds exhibit p-type conduction in oxidizing atmosphere, and ionic conduction elsewhere. The oxide ion contribution of the conductivity is negligible only for temperatures below 600 °C. The determination of hydration enthalpies, our second goal, was achieved by modelling of the conductivity data and by thermogravimetric measurements (TG-DSC). |
Fabrication and Characterization of Anode-Supported BaIn0.3Ti0.7O2.85 Thin Electrolyte for Solid Oxide Fuel Cell
ID=119| Authors |
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| Source |
International Journal of Applied Ceramic Technology
Article first published online: 28 MAR 2011 Time of Publication: 2011-03 |
| Abstract | BaIn0.3Ti0.7O2.85 (BIT07) is a promising electrolyte for solid oxide fuel cells, due to its chemical compatibility with most of the cathode electrode material such as LSM and Ln2NiO4. The present work is aimed on the fabrication of anode-supported half cells with thin BIT07 electrolyte. For this, Ni-8YSZ cermet was chosen due to its excellent mechanical and electrochemical properties, in addition to its low cost. The NiO–8YSZ anode support was prepared by tape casting, and for this, an organic slurry formulation was optimized. The BIT07 electrolyte thin film was deposited through screen printing on the green anode. The formulation of the ink was optimized, and sintering at 1350°C for 3 h led to a dense electrolyte with controlled thickness varying from 2 to 12 μm. Further, the cermet electrode still had a homogeneous microstructure with well-defined anode/electrolyte interface. The electrode ASR was about 0.5 Ω cm2 and was stable over 500 h at 800°C under H2–3% H2O. The fabrications of half cells were successfully scaled up to 100 mm × 100 mm retaining the dimensional control and without any surface defects. |
Curing of a network polyimide modified with a linear component
ID=118| Authors |
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| Source |
Russian Journal of Applied Chemistry
Volume: 84,
Issue: 2,
Pages: 301-306 Time of Publication: 2011-03 |
| Abstract | The curing and relaxation processes in polymeric composites based on blends of network and linear polyimides applied onto a filler were studied by dielectric spectroscopy. The sensitivity of dielectric spectroscopy to processes occurring in the course of curing was examined. |
Structure, Water Uptake, and Electrical Conductivity of TiP2O7
ID=117| Authors |
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| Source |
Journal of the American Ceramic Society
Volume: 94,
Issue: 5,
Pages: 1514–1522 Time of Publication: 2011-05 |
| Abstract | We report here on the structure of TiP2O7 and electrical properties of nominally acceptor (Sc, Fe)-doped TiP2O7 synthesized by an aqueous phosphoric acid route. Structural characterization, including studies of the high-temperature phase transition in TiP2O7, was carried out by powder X-ray and neutron diffraction. Ceramic disks were sintered by the spark plasma technique and their conductivities were characterized as a function of p(O2) and p(H2O) in the temperature range of 500°–1000°C by means of AC constant frequency measurements and impedance spectroscopy. As reported earlier, the acceptor doping appears not to influence the defect structure of TiP2O7 significantly. Effects of H+/D+ isotope shift were utilized to identify proton conduction. The conductivity was independent of p(O2) at 500°–900°C under oxidizing conditions suggesting predominantly protonic conduction at these temperatures. Under reducing atmosphere n-type conductivity contributed to the total conductivity at the higher temperatures. p(H2O) dependencies of the conductivities are interpreted in terms of a defect-chemical model involving protons and oxygen interstitials as the dominating defects. The uptake of water was studied by thermogravimetry at high p(H2O) and the thermodynamics of the hydration reaction was derived. Finally, parameters for the mobility of protons were extracted by combining the conductivity and thermogravimetry data. |
| Remark | Link |
Microstructural characterization and electrical properties of spray pyrolyzed conventionally sintered or hot-pressed BaZrO3 and BaZr0.9Y0.1O3 − δ
ID=116| Authors |
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| Source |
Solid State Ionics
Volume: 182,
Issue: 1,
Pages: 32-40 Time of Publication: 2011-02 |
| Abstract | A spray pyrolysis route to BaZrO3 (BZ) and BaZr0.9Y0.1O2.95 (BZY) powders was developed starting from nitrate solutions. Homogeneous powders with a grain size of ~ 100 nm were achieved. A calcination of the powder was necessary to remove carbonates formed during the spray pyrolysis. Hot pressing was in comparison with conventional sintering more effective to enhance densification and suppress grain growth, and dense (> 96%) materials with homogeneous microstructure were obtained. The Y-substitution decreased the densification rate. Minor amounts of a secondary phase was observed at the grain boundary triple points of BZY, but the grain boundaries were otherwise found to be coherent and without significant secondary phase accumulation. Impedance spectroscopy vs T, pO2 and pH2O of conventionally sintered BZ and hot-pressed BZY demonstrated that the conductivity of BZ was orders of magnitude lower than compared to BZY. The conductivity of BZ displayed mixed proton and p-type electronic conduction characteristics in the grain interior which was depressed at the grain boundaries. The grain boundaries showed an additional n-type electronic conduction under reducing conditions. The conductivity characteristics were according to core-space charge layer theory. BZ seems to exhibit a larger ratio of p-type electronic to protonic conduction as compared to BZY, contrary to the prediction of simple defect chemistry. |
BiFeO3–PbZrO3–PbTiO3 ternary system for high Curie temperature piezoceramics
ID=115| Authors |
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| Source |
Journal of the European Ceramic Society
Volume: 31,
Issue: 5
Time of Publication: 2011-05
|
| Abstract | BiFeO3–PbZrO3–PbTiO3 ternary solid solution system was investigated for the development of piezoelectric ceramics with high Curie temperatures. The search for the morphotropic phase boundary (MPB) compositions in this ternary system started from mixing two MPB compositions: 0.70BiFeO3–0.30PbTiO3 and 0.52PbZrO3–0.48PbTiO3. The content of PbTiO3 was then further fine tuned in order to reach the appropriate volume fraction between the rhombohedral and tetragonal phases in the sintered ceramics. It was observed that the sintering temperature has a profound impact on the density, grain morphology, dielectric and ferroelectric properties of the ceramics. The composition that displays the best combined structure and properties was identified to be 0.648BiFeO3–0.053PbZrO3–0.299PbTiO3, with a Curie temperature TC of 560 °C, a remanent polarization Pr of 15.0 μC/cm2, and a piezoelectric coefficient d33 of 64 pC/N. |
Synthesis and characterization of Ca-substituted YAlO3 by pechini route for solid oxide fuel cells
ID=114| Authors |
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| Source |
Solid State Sciences
Volume: 13,
Issue: 1,
Pages: 168-174 Time of Publication: 2011-01 |
| Abstract | The high operating temperature requirement of solid oxide fuel cells demands electrolyte materials stable at temperatures around 800 °C. The perovskite material YAlO3, with yttrium ion on the A-site and the aluminium ion on the B-site is being investigated as an electrolyte for solid oxide fuel cells. This work investigates the structure and electrical conductivity of undoped and Ca-doped YAlO3 compositions that has been synthesized by the Pechini route. The samples have been investigated by X-ray diffraction studies. The electrical conductivity studies have been performed using a.c impedance spectroscopy in the range 200–800 °C in air. The doped YAlO3 of composition x = 0.1 exhibits a total conductivity of about 2.2 mS/cm at 800 °C. The microstructural evaluation of the samples has been conducted by scanning electron microscopy coupled with energy dispersive spectrum analysis. |
δ-Phase to defect fluorite (order–disorder) transition in the R2O3–MO2 (R = Sc; Tm; Lu; M = Zr; Hf) systems
ID=112| Authors |
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| Source |
Materials Research Bulletin
Volume: 46,
Issue: 4,
Pages: 512–517 Time of Publication: 2011-04 |
| Abstract | We have studied the δ-phase to defectfluoriteF* (order–disorder) transition in the R4M3O12 (R = Sc, Tm, Lu; M = Zr, Hf) compounds. The temperature of the δ–F* phasetransition in Tm4Zr3O12 is ∼1600 °C. The rate of this transition in R4Zr3O12 (R = Sc, Tm, Lu) decreases markedly with decreasing difference in ionic radius between the R3+ and Zr4+, leading to stabilization of the δ-phasesR4Zr3O12 with R = Sc and Lu at high temperatures (∼1600 °C). During slow cooling (5 °C/h), the high-temperature defectfluoritesF*-R2Hf2O7 (R = Tm, Lu) decompose reversibly to form the δ-phasesR4Hf3O12. Some of the materials studied exhibit microdomains formation effects, typical of the fluorite-related oxide compounds in the R2O3–MO2 (M = Ti, Zr, Hf) systems of the heavy rare earths. The high-temperature defectfluoritesF*-R4M3O12 (R = Tm, Lu; M = Zr, Hf) as a rule contain antiphase microdomains of δ-R4Zr3O12. After slow cooling (5 °C/h), such microdomains are large enough for the δ-phase to be detected by X-ray diffraction. The conductivity data for R4M3O12 (R = Sc, Tm, Lu; M = Zr, Hf) and Ln2Hf2O7 (Ln = Dy, Lu) prepared by different procedures show that the rhombohedral phasesδ-R4M3O12 (R = Sc, Tm, Lu; M = Zr, Hf) are poorer conductors than the defectfluorites, with 740 °C conductivity from 10−6 to 10−5 S/cm. The conductivity drops with decreasing rare-earth ionic radius and, judging from the Ea values obtained (1.04–1.37 eV), is dominated by oxygen ion transport. The highest conductivity, ∼6 × 10−4 S/cm at 740 °C, is offered by the rapidly cooled F*-Dy2Hf2O7. In the fluorite homologous series, oxygen ion conductivity decreases in the orderdefect pyrochlore > defectfluorite > δ-phase. |
| Keywords | Fluorite; δ-Phases R4M3O12; Pyrochlore; Order–disorder transition; Antiphase microdomains; High-temperature conductivity |
| Remark | Link |
Polymorphism and high-temperature conductivity of Ln2M2O7 (Ln = Sm─Lu; M = Ti, Zr, Hf) pyrochlores
ID=111| Authors |
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| Source |
Solid State Ionics
Volume: 192,
Issue: 1,
Pages: 200–204 Time of Publication: 2011-06 |
| Pyrochlore; Fluorite; Order─disorder; Defects; High-temperature conductivity; Ionic conductivity; Solid electrolyte |
Proton conductivity in Sm2Sn2O7 pyrochlores
ID=110| Authors |
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| Source |
Solid State Ionics
Volume: 181,
Issue: 35-36,
Pages: 1577-1585 Time of Publication: 2010-11 |
| Abstract | The electrical conductivity of the pyrochlore systems, Sm2Sn2O7, Sm1.92Ca0.08Sn2O7 − δ and Sm2Sn1.92Y0.08O7 − δ was studied using impedance spectroscopy under wet and dry gas (O2 and Ar) in the temperature range 150–1000 °C. Enhancements of the bulk conductivity of all samples at temperatures up to ~ 550 °C were observed for wet conditions consistent with significant levels of proton conduction. The presence of dissolved protons in the acceptor-doped materials, Sm1.92Ca0.08Sn2O7 − δ and Sm2Sn1.92Y0.08O7 − δ, is supported by infrared spectroscopy and thermogravimetric analysis. Proton conduction was confirmed by isotope effects under heavy water (O2/D2O and Ar/D2O). The A-site substituted sample Sm1.92Ca0.08Sn2O7 − δ yielded the highest levels of proton conduction and displayed mixed ionic and electronic conduction under dry oxidising conditions. Electron hole conduction dominates in dry oxygen for Sm2Sn1.92Y0.08O7 − δ and Sm2Sn2O7. For the A-site doped sample bulk and grain boundary conduction could be separated. The specific grain boundary conduction was calculated using the brick layer model and was found to be two orders of magnitude lower compared to the bulk conductivity. The unexpected increase in conductivity seen for the undoped sample under wet gas is discussed in the context of structural disorder and possible filling of the un-occupied anion site in the pyrochlore structure by OH-groups. |
| Keywords | Sm2Sn2O7; Proton conductor; Pyrochlore; Oxide ion conductivity; p-type conductivity; Infra-red spectroscopy; Thermogravimetric analysis |
Experimental and theoretical studies of hydrogen permeation for doped strontium cerates
ID=109| Authors |
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| Source |
Solid State Ionics
Volume: 181,
Issue: 29-30,
Pages: 1328-1335 Time of Publication: 2010-09 |
| Abstract | Non-galvanic hydrogen permeation properties of SrCe0.95Yb0.05O3 − α (SCYb-5) and SrCe0.95Tm0.05O3 − α (SCTm-5) dense membranes were investigated in a ‘wet’ hydrogen atmosphere where water vapour partial pressures were well defined and monitored for the entire duration of the experiments. The theoretical modelling of hydrogen permeation flux for SCYb-5 and SCTm-5 was also undertaken, and compared with experimental results. The parameter tuning was also performed by fitting the model to the experimental data obtained in this study. The experimental hydrogen permeation flux for SCYb-5 and SCTm-5 dense membranes was 6.8e− 9 mol/cm2/s and 7.1e− 9 mol/cm2/s, respectively, under the upstream hydrogen partial pressure of 0.25 atm (25%H2/Ar) at 900 °C. As expected, the hydrogen permeation flux increases with the increase in the upstream hydrogen partial pressures, reaching the maximum flux of 1.4e− 8 mol/cm2/s and 1.6e− 8 mol/cm2/s, for SCYb-5 and SCTm-5 respectively, under the upstream hydrogen partial pressure of 1 atm (100%H2) at 900 °C. Previous modelling used hydrogen permeation data collected by others in a permeation test conducted in a ‘dry’ hydrogen atmosphere (with unknown water vapour pressures). The modelled hydrogen permeation flux agreed well with the experimental data attained in this study, for both SCYb-5 and SCTm-5 samples. The parameter tuning further improved the model predictions for those samples. It was apparent that the modelled hydrogen flux agreed better with the experimental data obtained in this study (i.e. in a wet hydrogen atmosphere with known water vapour pressures). |
| Keywords | Dense ceramic membranes; Hydrogen permeation; Modelling |
Directed integration of ZnO nanobridge sensors using photolithographically patterned carbonized photoresist
ID=108| Authors |
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| Source |
Nanotechnology
Volume: 21,
Issue: 19
Time of Publication: 2010-05
|
| Abstract | A method for achieving large area integration of nanowires into electrically accessible device structures remains a major challenge. We have achieved directed growth and integration of ZnO nanobridge devices using photolithographically patterned carbonized photoresist and vapor transport. This carbonized photoresist method avoids the use of metal catalysts, seed layers, and pick and place processes. Growth and electrical connection take place simultaneously for many devices. Electrical measurements on carbonized photoresist/ZnO nanobridge/carbonized photoresist structures configured as three-terminal field effect devices indicate bottom gate modulation of the conductivity of the n-type ZnO channel. Nanobridge devices were found to perform well as ultraviolet and gas sensors, and were characterized as regards ultraviolet light pulsing, oxygen concentration, and humidity. The sensitivity of the three-terminal nanobridge sensors to UV light and oxygen was enhanced by application of a negative bottom gate voltage. |
Yttria-stabilized zirconia thin film electrolyte produced by RF sputtering for solid oxide fuel cell applications
ID=107| Authors |
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| Source |
Materials Letters
Volume: 64,
Issue: 22,
Pages: 2450-2453 Time of Publication: 2010-11 |
| Abstract | Thin film (40–600 nm) yttria-stabilized zirconia (YSZ) electrolytes for solid oxide fuel cells (SOFC) were deposited on NiO-YSZ anodes and fused silica substrates by RF sputtering, using low applied power without the use of post deposition annealing heat treatment. YSZ film showed a nanocrystalline structure and consisted of the Zr.85Y.15O1.93 (fcc) phase. The film was dense and the YSZ/anode interface was continuous and crack free. According to preliminary in-plane conductivity measurements (temperature range 550–750 °C) on the YSZ film, the activation energy for ionic conduction was found to be 1.18 ± 0.01 eV. |
| Keywords | Thin films; Ceramics; Microstructure; Nanomaterials |
High-temperature proton conductivity and defect structure of TiP2O7
ID=106| Authors |
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| Source |
Solid State Ionics
Volume: 181,
Issue: 11-12,
Pages: 510-516 Time of Publication: 2010-04 |
| Abstract | Nominally undoped TiP2O7 and TiP2O7 with 2 mol-% substitution of Ti by Al were synthesized from TiO2 (Al2O3) and H3PO4(aq), sintered at 1050 °C, and characterized by XRD, TEM and SEM. The electrical conductivity was investigated at 300–1000 °C as a function of p(O2), p(H2O), and p(D2O). The material's phase transition around 700 °C is clearly visible in the conductivity curves. Al substitution hardly increased the conductivity. The conductivity was higher in H2O- than in D2O-containing and dry atmospheres, indicating the dominance of proton conduction. The conductivity was accordingly mainly independent of p(O2). A slight increase in the conductivity with decreasing p(O2) at the highest temperatures was indicative of a minor contribution of n-type electronic conduction. The p(H2O) and temperature dependencies of the conductivity have been modelled as a sum of proton and electron partial conductivities under a situation with protons charge compensated by oxygen interstitials as dominating defects. |
| Keywords | Titanium pyrophosphate; TiP2O7; Al-substituted TiP2O7; Proton conduction; Defect structure |
Scandium stabilized zirconium thin films formation by e-beam technique
ID=105| Authors |
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| Source |
Solid State Ionics
Volume: 184,
Issue: 1,
Pages: 10–13 Time of Publication: 2011-03 |
| Abstract | Scandiumstabilizedzirconium (10ScSZ) thin ceramic films were deposited by e-beam evaporation of (ZrO2)0.90(Sc2O3)0.10 micro powder (particle size 0.5 ÷ 0.7 μm). The influence of deposition rate on formed thinfilms microstructure and electrical properties was studied. 10ScSZ thinfilms were deposited on two types of different substrates: optical quartz (SiO2) and Alloy-600 (Fe–Ni–Cr) substrates. Deposition rate was changed from 2 to 16 Å/s to test its influence on thinfilmformation and its properties. The microstructure of formed 10ScSZ thin ceramic films was studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Electrical parameters of formed thin ceramics were investigated in the frequency range from 0.1 Hz to 1.0 MHz (in temperature range from 473 to 873 K). The ionic conductivity of the deposited electrolyte 10ScSZ thinfilms was determined by impedance spectroscopy. It was determined that the deposition rate (in range from 2 to 16 Å/s) has influence on crystallite size. It increases by increasing the deposition rate from 18.4 to 26.9 nm. The XRD measurements show that the formed 10ScSZ thinfilms do not repeat the crystallographic phase of the initial evaporated powder material—it is changes from rhombohedra (initial powder) to cubic (the formed thinfilms). |
| Keywords | Scandium stabilized zirconium (ScSZ); Ionic conductivity; Electron beam deposition; Solid oxide fuel cells (SOFC) |
| Remark | Link |
Effect of sintering temperature and sintering additives on ionic conductivity of LiSi2N3
ID=104| Authors |
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| Source |
Journal of the Ceramic Society of Japan
Volume: 118 ,
Issue: 1381 ,
Pages: 837-841 Time of Publication: 2010-09 |
| Abstract | The effect of sintering temperature and sintering additives on the ionic conductivity of LiSi2N3 was studied by performing complex impedance measurements. LiSi2N3 materials were fabricated by the reaction of Li3N, Si3N4, and sintering additives at temperatures of 1873–2073 K. Dense hot-pressed bodies were obtained at 1973–2073 K in the case of undoped LiSi2N3 and at 1873 K in the case of Y2O3, CaF2, and B2O3 addition. The ionic conductivity increased greatly with increasing sintering temperature and exhibited a strong dependence on the type of sintering additive. When the sintering temperature was constant at 1873 K, although the conductivities of Y2O3-doped LiSi2N3 and CaF2-doped LiSi2N3 were lower than that of undoped LiSi2N3, the conductivity of B2O3-doped LiSi2N3 was higher than that of undoped LiSi2N3. The enhanced conductivity of B2O3-doped LiSi2N3 can be attributed to the increase in the density of the sintered material without the formation of a phase of significant resistance at the grain boundaries. |
| Remark | Link |
Defects and transport properties of Sr-doped LaP3O9
ID=103| Authors |
|
| Source |
Solid State Ionics
Volume: 181,
Issue: 27-28,
Pages: 1264-1269 Time of Publication: 2010-09 |
| Abstract | LaP3O9 and 2 mol-% Sr-doped LaP3O9 have been synthesized by the solid-state reaction method and the phase purity was characterized by powder X-ray diffraction and scanning electron microscopy. The AC conductivity of sintered disks was measured with two-point electrode setup in the temperature range 300 − 700 °C under oxidizing and reducing conditions at different oxygen and water vapor (H2O or D2O) partial pressures by means of impedance spectroscopy. The water vapor dependency and isotope effect reveal that protons are the predominant charge carrier. The conductivity was mainly independent of the partial pressure of oxygen at all measured temperatures under both oxidizing and reducing conditions, suggesting only minor electronic conductivity. Hydration thermodynamics and transport parameters for the Sr-doped sample have been determined based on a defect chemical model applied to thermogravimetry and conductivity data. |
| Keywords | Proton conductivity; LaP3O9; Sr-doped LaP3O9; Defect structure; Thermodynamic relations; Transport parameters |
Charge carriers in grain boundaries of 0.5% Sr-doped LaNbO4
ID=102| Authors |
|
| Source |
Solid State Ionics
Volume: 181,
Issue: 3-4,
Pages: 104-109 Time of Publication: 2010-02 |
| Abstract | The grain boundary and grain interior conductivities of La0.995Sr0.005NbO4 − δ have been studied by means of impedance spectroscopy at 400 °C after quenching from different pH2O, pO2 and temperatures. Effects of H/D isotope shifts on the conductivity were, moreover, determined from 400 to 480 °C under isothermal conditions. The microstructure and composition were characterized by scanning electron microscopy and transmission electron microscopy. On basis of the effects of pH2O and H/D isotope exchange on the grain boundary and grain interior conductivities, it is concluded that protons are the major charge carrier and, furthermore, that they are relatively more predominating in the grain boundaries than in the grain interior. Ionic transport in the grain boundaries is discussed in terms of the grain boundary core–space charge layer model. |
| Keywords | LaNbO4; Grain boundaries; Impedance spectroscopy; TEM; Space charge effects |
Electrical Properties and Gas Sensing Characteristics of the Al2O3/4H SiC Interface Studied by Impedance Spectroscopy
ID=101| Authors |
|
| Source |
Materials Science Forum
Silicon Carbide and Related Materials 2009 Volume: 645 - 648, Pages: 531-534 Time of Publication: 2010-04 |
| Abstract | Using impedance spectroscopy (IS) for characterization of the electrical properties and gas sensing characteristics of Al2O3/4H-SiC (MOS) structures, insight on the capacitive and resistive contributions in the interfacial region of the MOS structures is obtained. Applying DC bias voltages between accumulation and depletion (corresponding to the interfacial region) allows investigation of the voltage shift of the capacitance versus voltage (CV) curve at different temperatures and atmospheres. This voltage shift forms the basis to use the MOS structure as a gas sensor. The MOS capacitance, as extracted from IS data, is different from the one obtained using CV measurements, due to the ability of distinguishing the resistive contribution (using IS). Voltage shifts between 1 and 2 V are clearly revealed during exposure to hydrogen and oxygen, and this shift exhibits a long-term stability of operation at temperatures up to 500°C. Hence, Al2O3 exhibits great promise as a gate dielectric in MOS-based gas detecting devices for use at elevated temperatures. |
| Keywords | Impedance Spectroscopy, MOS Capacitor |
Improved Proton Conductivity in Spark-Plasma Sintered Dense Ceramic BaZr0.5In0.5O3−delta
ID=100| Authors |
|
| Source |
Electrochem. Solid-State Lett.
Volume: 13,
Issue: 11,
Pages: B130-B134 Time of Publication: 2010-11 |
| Abstract | Spark-plasma sintering method was used to prepare dense proton conducting perovskite oxide BaZr0.5In0.5O3−delta. Analysis of X-ray powder diffraction data showed that the sample adopt the cubic crystal structure having the space group Pm[overline 3]m. Thermogravimetric analysis of prehydrated samples showed significant mass losses beyond 300°C due to loss of protons as water vapor. Scanning electron microscope images show that the grain size of the spark-plasma sintered dense sample was smaller than that of solid-state sintered porous sample. The highest total proton conductivity (2×10−3 S cm−1 at 450°C) was found for dense spark-plasma sintered sample under wet H2 than the samples prepared by other routes. |
Oxygen bulk diffusion and surface exchange in Sr-substituted La2NiO4 + δ
ID=99| Authors |
|
| Source |
Solid State Ionics
Volume: 184,
Issue: 1,
Pages: 42–46 Time of Publication: 2011-03 |
| Abstract | The oxygen bulk diffusion and surface exchange in Sr-substituted La2NiO4 + δ were investigated separately in this work. The oxygen flux through La2−xSrxNiO4 + δ (x = 0.1 and 0.2) was measured as a function of temperature and the oxygen self diffusion coefficients, DO, were extracted. The results show that the higher the Sr concentration, the lower the oxygen permeation and the higher the activation energy of DO. The surface exchange rate was determined by measuring isotope exchange with a mass spectrometer. The Sr substitution leads to higher surface exchange rate with lower activation energy. The incorporation of ionized atomic oxygen into surface vacancies was suggested to be the rate determining step. |
| Keywords | Oxygen diffusion; Defect chemistry; Surface exchange; Rate determining step (rds); La2NiO4 + δ; La2−xSrxNiO4 + δ |
| Remark | Link |
Development of an In Situ Surface Deformation and Temperature Measurement Technique for a Solid Oxide Fuel Cell Button Cell
ID=98| Authors |
|
| Source |
International Journal of Applied Ceramic Technology
Volume: 7,
Issue: 1, January/February,
Pages: 55-62 Time of Publication: 2010-01 |
| Abstract | A novel experimental technique is developed to measure the in situ surface deformation and temperature of a solid oxide fuel cell (SOFC) anode surface along with the cell electrochemical performance. The experimental setup consists of a NexTech ProboStat™ SOFC button cell test apparatus integrated with a Sagnac interferometric optical method and an infrared sensor for in situ surface deformation and temperature measurements, respectively. The button cell is fed with hydrogen or simulated coal syngas under SOFC operating conditions. The surface deformation is measured over time to estimate the anode structural degradation. The cell surface transient temperature is also monitored with different applied current densities under hydrogen and simulated coal syngas. The experimental results are useful to validate and develop SOFC structural durability and electrochemical models. |
Synthesis; Functionalization; and Environmental Stabilization of ZnO Nanobridge Transducers for Gas and Liquid-phase Sensing
ID=97| Authors |
|
| Source |
Sensors and Actuators B: Chemical
Volume: 155,
Issue: 1,
Pages: 245–252 Time of Publication: 2011-07 |
| Abstract | Three methods of functionalizing ZnO NW surfaces with biotin were demonstrated. Biotinylated ZnO NWs were found to dissolve during exposure to deionized (DI) water, so a chemical vapor deposition (CVD) process was developed for parylene-A, a common moisture barrier with an amine group which allows further functionalization. Parylene-A coated ZnO NWs were found to be resistant to dissolution. Electrical measurements on parylene-A coated nanobridge devices showed normal operation with higher dark current and an attenuated response to UV and O2, indicating the ability to modulate environmental sensitivity. This work demonstrates the novel use of parylene-A coatings as an encapsulation layer as well as a potential starting platform for general functionalization of ZnO NW devices for selective sensing. |
| Keywords | ZnO; Nanowires; Functionalization; Sensors |
| Remark | Link |
Correlation between microstructure and electrical conductivity in composite electrolytes containing Gd-doped ceria and Gd-doped barium cerate
ID=96| Authors |
|
| Source |
Journal of the European Ceramic Society
Volume: 31,
Issue: 4,
Pages: 559–568 Time of Publication: 2011-04 |
| Composite; Ceria; Impedance spectroscopy; Electrical conductivity; Fuel cell | |
| Remark | Link |
The properties of scandium and cerium stabilized zirconium thin films formed by e-beam technique
ID=94| Authors |
|
| Source |
Solid State Ionics
Volume: 188,
Issue: 1,
Pages: 46–49 Time of Publication: 2011-04 |
| Abstract | Scandium and ceriumstabilizedzirconium (10Sc1CeSZ) thin ceramic films were formed evaporating (ZrO2)0.89(CeO2)0.01(Sc2O3)0.10 micro powder using e-beam evaporation technique. The influence of deposition rate on formedthinfilms electrical properties and microstructure was studied. 10Sc1CeSZ thinfilms were deposited on two types of different substrates: optical quartz (SiO2) and Alloy 600 (Fe–Ni–Cr). Deposition rate was changed from 2 to 16 Å/s to understand its influence on thinfilm formation and other properties. The formed 10Sc1CeSZ thinfilms keep the cubic crystal structure as the initial evaporated powder material but change the main crystallographic peak from (111) to (200) for both types of substrate and used deposition rates. It was determined that the crystallites size increases from 19.0 to 24.9 nm and from 15.6 to 19.9 nm on optical quartz and Alloy 600 respectively by increasing the deposition rate (in range from 2 to 16 Å/s). The thinfilm density decreases by increasing the deposition rate. The ionic conductivity of 10Sc1CeSZ thinfilms was determined by impedance spectroscopy in the frequency range from 0.1 Hz to 1.0 MHz in temperature range from 473 K to 873 K. The best ionic conductivity σtot = 4.91 · 10− 2 Sm− 1 at 873 K temperature and the lowest value of activation energy ΔEa = 0.88 eV were found for 10Sc1CeSZ thinfilmsformed at 4 Å/s deposition rate. |
| Keywords | Scandium and cerium stabilized zirconium (10Sc1CeSZ); Electron beam deposition; Solid oxide fuel cells (SOFC); Ionic conductivity |
| Remark | Link |
Ethanol internal steam reforming in intermediate temperature solid oxide fuel cell
ID=93| Authors |
|
| Source |
Journal of Power Sources
Volume: 196,
Issue: 17,
Pages: 7355–7362 Time of Publication: 2011-09 |
| Abstract | This study investigates the performance of a standard Ni–YSZ anode supported cell under ethanolsteamreforming operating conditions. Therefore, the fuelcell was directly operated with a steam/ethanol mixture (3 to 1 molar). Other gas mixtures were also used for comparison to check the conversion of ethanol and of reformate gases (H2, CO) in the fuelcell. The electrochemical properties of the fuelcell fed with four different fuel compositions were characterized between 710 and 860 °C by I–V and EIS measurements at OCV and under polarization. In order to elucidate the limiting processes, impedance spectra obtained with different gas compositions were compared using the derivative of the real part of the impedance with respect of the natural logarithm of the frequency. Results show that internalsteamreforming of ethanol takes place significantly on Ni–YSZ anode only above 760 °C. Comparisons of results obtained with reformate gas showed that the electrochemical cell performance is dominated by the conversion of hydrogen. The conversion of CO also occurs either directly or indirectly through the water–gas shift reaction but has a significant impact on the electrochemical performance only above 760 °C. |
| Keywords | SOFC; Ni–YSZ anode; Ethanol; Internal reforming; Coking; Impedance spectroscopy |
| Remark | Link |
Synthesis and electrical properties of Gd2MO5 (M = Zr, Hf)
ID=92| Authors |
|
| Source |
Neorganicheskie Materialy
Volume: Vol. 46, No. 12,
Pages: pp. 1476–1482 Time of Publication: 2010-08 |
| Abstract | Polycrystalline Gd2ZrO and Gd2HfO5 have been prepared by heat-treating coprecipitated oxide mixtures, and their order-disorder phase transitions have been studied in the range 20–1600°C. The materials have been shown to consist of nanostructured grains with a nanodomain size of ∼40 nm. Their electrical conductivity has been determined by impedance spectroscopy in air between 300 and 1000°C. The 1000°C conductivities of Gd2ZrO5 and Gd2HfO5 are 3.7 × 10−3 and 1.8 × 10−3 S/cm, and the respective effective activation energies are 1.37 and 1.56 eV. |
Proton Conductivity in Mixed B-Site Doped Perovskite Oxide BaZr0.5In0.25Yb0.25O3−delta
ID=91| Authors |
|
| Source |
J. Electrochem. Soc.
Volume: Volume 157,
Issue: Issue 12,
Pages: B1819-B182 Time of Publication: 2010-12 |
| Abstract | A wet chemical route was used to prepare the oxygen deficient codoped perovskite oxide BaZr0.5In0.25Yb0.25O3−. Analysis of X-ray powder diffraction data showed that the sample belongs to the cubic crystal system with space group Pmm. Dynamic thermogravimetric (TG) analysis confirmed complete filling of oxygen vacancies (V) by protonic defects (OH) during the hydration process. The proton conductivity was investigated by impedance spectroscopy. The bulk and total conductivities of prehydrated BaZr0.5In0.25Yb0.25O3− were found to be 8.5×10−4 and 2.2×10−5 S cm−1, respectively, at 300°C. The total conductivity in the codoped perovskite oxide was higher compared to that of the respective single doped perovskite oxides with the same doping level. The bulk and grain-boundary mobility and diffusion coefficients of protons were calculated at 200°C using impedance and TG data to obtain the conductivity and proton concentration, respectively. The high bulk diffusivity (2.3×10−7 cm2 s−1) was obtained which indicates that the protons are more free to move in the heavily doped matrix compared to the lightly doped systems where trapping of protons occurs. |
| Keywords | barium compounds, proton exchange membrane fuel cells, thermal analysis, vacancies (crystal), X-ray diffraction, zirconium compounds |
| Remark | Link |
Electrical Conductivity of Nanostructured Fluorite-Like Sc2Ti3O12
ID=89| Authors |
|
| Source |
Inorganic Materials
Volume: 45,
Issue: 5,
Pages: 543-549 Time of Publication: 2009 |
| Abstract | Single-crystal and polycrystalline samples of Sc4Ti3O12 have been shown to contain nanodomains (10–50 nm) with different degrees of ordering, coherent with the fluorite-like matrix. The oxygen-ion conductivity of this compound has been determined in the range 300–1000°C in air using impedance spectroscopy. The nanostructured single-crystal and polycrystalline samples are close in the activation energy for bulk conduction at both low and high temperatures: ≃1.26 and 1.29 eV in the range 300–775°C, ≃1.98 and 2.07 eV in the range 775–1000°C. |
Hydrogen sensitivity of doped CuO/ZnO heterocontact sensors
ID=88| Author |
|
| Source |
Sensors and Actuators B: Chemical
Volume: 106,
Issue: 2,
Pages: 837-842 Time of Publication: 2005 |
| Abstract | Heterocontact sensors based on p-type CuO and n-type ZnO ceramics have been shown to exhibit a high sensitivity to reducing gas species and an intrinsic selectivity. In this work, doped heterocontact sensors were prepared via solid state synthesis routes. CuO was doped with various monovalent (Li, Na) and isovalent (Ca, Sr, Ni) dopants at different compositions to form both single phase and two phase samples. Effects of dopants on hydrogen sensitivity through conductivity and heterogeneous microstructure were investigated using dc current–voltage measurements and ac impedance analysis. It was observed that both monovalent and divalent dopants increased the hydrogen sensitivity significantly. The highest sensitivity was observed in a 2.5 mol% Ni-CuO/ZnO heterocontact and low amounts of Li doping were shown to greatly enhance the rectifying characteristics. |
| Keywords | Hydrogen sensor; Heterocontact; CuO; ZnO |
Synthesis, densification and electrical properties of strontium cerate ceramics
ID=87| Authors |
|
| Source |
Journal of the European Ceramic Society
Volume: 27,
Issue: 16,
Pages: 4461-4471 Time of Publication: 2007 |
Stability and conductivity study of the BaCe0.9−xZrxY0.1O2.95 systems
ID=86| Author |
|
| Source |
Solid State Ionics
Volume: 178,
Issue: 3-4,
Pages: 213-220 Time of Publication: 2007 |
Defects and transport properties in Ln6WO12 (Ln = La, Nd, Gd, Er)
ID=85| Author |
|
| Source |
Solid State Ionics
Volume: 178,
Issue: 7-10,
Pages: 555-560 Time of Publication: 2007 |
Phase transitions and ferroelectric properties in BiScO3-Bi(Zn1/2Ti1/2)O3-BaTiO3 solid solutions
ID=84| Authors |
|
| Source |
Journal of Applied Physics
Volume: 102,
Issue: 4,
Pages: 044103 Time of Publication: 2007 |
Shrinkage Effects of the Conduction Zone in the Electrical Properties of Metal Oxide Nanocrystals: The Basis for Room Temperature Conductometric Gas Sensor
ID=83| Authors |
|
| Source |
Journal of Sensors
Volume: 2009,
Pages: 1-7, doi:10.1155/2009/783675 Time of Publication: 2009 |
Preparation, electrical and thermal properties of new exfoliated graphite-based composites
ID=82| Authors |
|
| Source |
Carbon
Volume: 47,
Issue: 1,
Pages: 263-270 Time of Publication: 2009 |
Structure, defect chemistry, and proton conductivity in nominally Sr-doped Ba3La(PO4)3
ID=81| Authors |
|
| Source |
Solid State Ionics
Volume: 180,
Issue: 4-5,
Pages: 338-342 Time of Publication: 2009 |
Local structure and ionic conductivity in the Zr2Y2O7–Y3NbO7 system
ID=80| Authors |
|
| Source |
Journal of Physics: Condensed Matter
Volume: 21,
Issue: 21,
Pages: 215401 Time of Publication: 2009 |
Thin film chemical sensors based on p-CuO/n-ZnO heterocontacts
ID=79| Authors |
|
| Source |
Thin Solid Films
Volume: 517,
Issue: 15,
Pages: 4448-4454 Time of Publication: 2009 |
Phase formation, microstructure, and dielectric properties of (1 − x)PZT–(x)PCN ceramics
ID=78| Authors |
|
| Source |
Materials Letters
Volume: 63,
Issue: 15,
Pages: 1281-1284 Time of Publication: 2009 |
Characterization of porous lanthanum strontium manganite (LSM) and development of yttria stabilized zirconia (YSZ) coating
ID=77| Authors |
|
| Source |
Ceramics International
Volume: 35,
Issue: 6,
Pages: 2493-2497 Time of Publication: 2009 |
Ordering processes in Ln2TiO5 (Ln = Dy–Lu): The role of thermal history
ID=76| Authors |
|
| Source |
Journal of Alloys and Compounds
Volume: 479,
Issue: 1-2,
Pages: 6-10 Time of Publication: 2009 |
Effects of Zr/Ti ratio on dielectric and ferroelectric properties of 0.8Pb(ZrxTi1−x)O3–0.2Pb(Co1/3Nb2/3)O3 ceramics
ID=75| Authors |
|
| Source |
Current Applied Physics
Volume: 9,
Issue: 4,
Pages: 802-806 Time of Publication: 2009 |
Ce0.9Sr0.1VOx (x = 3, 4) as anode materials for H2S-containing CH4 fueled solid oxide fuel cells
ID=74| Authors |
|
| Source |
Journal of Power Sources
Volume: 192,
Issue: 2,
Pages: 247-257 Time of Publication: 2009 |
Acceptor doping of Ln2Ti2O7 (Ln = Dy, Ho, Yb) pyrochlores with divalent cations (Mg, Ca, Sr, Zn)
ID=73| Authors |
|
| Source |
Materials Research Bulletin
Volume: 44,
Issue: 8,
Pages: 1613-1620 Time of Publication: 2009 |
Effect of substitution with Cr3+ and addition of Ni on the physical and electrochemical properties of Ce0.9Sr0.1VO3 as a H2S-active anode for solid oxide fuel cells
ID=72| Authors |
|
| Source |
Journal of Power Sources
Volume: 194,
Issue: 1,
Pages: 252-262 Time of Publication: 2009 |
Dielectric and ferroelectric properties of 0.8PZT–0.2PCN ceramics under sintering conditions variation
ID=71| Authors |
|
| Source |
Current Applied Physics
Volume: 9,
Issue: 5,
Pages: 1165-1169 Time of Publication: 2009 |
Conductivity and water uptake of Sr4(Sr2Nb2)O11·nH2O and Sr4(Sr2Ta2)O11·nH2O
ID=70| Authors |
|
| Source |
Solid State Ionics
Volume: 180,
Issue: 20-22,
Pages: 1151-1156 Time of Publication: 2009 |
Synthesis and characterization of nanocrystalline Ni–YSZ cermet anode for SOFC
ID=69| Author |
|
| Source |
Materials Characterization
Volume: 61,
Issue: 1,
Pages: 54-58 Time of Publication: 2010-01 |
| Abstract | Ni–YSZ cermet anode has been synthesized in one step using a simple and cost effective combustion synthesis process. The processed powder of NiO–YSZ is found to be nanocrystalline with crystallite sizes of 29 and 22 nm for NiO and YSZ respectively by X-ray diffraction and transmission electron microscopy analysis. X-ray diffraction analysis also shows that the precursor salts are converted to highly crystalline phases of NiO and YSZ (8 mol% Y2O3) without any intermediate calcination step and no undesirable phases are present. Comparison with the X-ray diffraction pattern of a commercial YSZ sample shows that the process is also effective in maintaining a close compositional control. The microstructure of the sintered and reduced sample shows a well defined network of pores which is necessary for the effective functioning of the anode. The electrical conductivity as a function of temperature shows metallic behavior. |
| Keywords | Ni–YSZ anode; Combustion synthesis; Nanocrystalline cermet; Microstructure |
A combined conductivity and DFT study of protons in PbZrO3 and alkaline earth zirconate perovskites
ID=68| Authors |
|
| Source |
Solid State Ionics
Volume: 181,
Issue: 3-4,
Pages: 130-137 Time of Publication: 2010 |
| Abstract | The electrical properties of nominally undoped and 4 mol% Y-doped PbZrO3 have been investigated by AC conductivity measurements and impedance spectroscopy under various pH2O and pO2 at high temperatures. The results indicate that the defect structures are dominated by acceptors (Y dopant and/or Pb vacancies formed during synthesis). In dry atmosphere and at high temperatures, the acceptors are compensated by oxygen vacancies. These are hydrated and replaced by protonic defects (hydroxide ions on oxide ion sites) at higher pH2O and lower temperatures. In oxidizing atmospheres, a minority concentration of electron holes dominates the conductivity. At lower temperatures and in wet atmosphere, a significant protonic conductivity contribution is also observed. Based on pO2 and pH2O isotherms, a model for incorporation of protonic defects has been applied, and the standard enthalpy of hydration of oxygen vacancies in undoped PbZrO3 has been determined (− 1.07 ± 0.13 eV). The measured total conductivities are influenced by high grain boundary resistance. Hence, the enthalpy is at the present stage assigned to the polycrystalline ceramic material as such. Rough estimates of bulk proton mobility in Y-doped PbZrO3 yield uH+0 = 17 cm2K/Vs and ΔHm,H+ = 0.93 eV. A complementary DFT study of the hydration thermodynamics of PbZrO3 and the alkaline earth zirconate perovskites AZrO3 (A = Ca, Sr, Ba) is also reported. The experimental and theoretical hydration enthalpies are compared with those of other ABO3 perovskites. Correlations between the hydration thermodynamics and other properties of the materials are discussed. |
| Keywords | PbZrO3; CaZrO3; SrZrO3; BaZrO3; Conductivity; Proton; Proton mobility; DFT; Thermodynamics; Defects; Hydration |
Electrical conductivity and oxygen permeation properties of SrCoFeOx membranes
ID=67| Authors |
|
| Source |
Solid State Ionics
Volume: 180,
Issue: 40,
Pages: 1633-1639 Time of Publication: 2010 |
| Abstract | The total conductivity and oxygen permeation properties of dense SrCoFeOx membranes synthesized from the solid state method were studied in the temperature range of 700–900 °C. The SrCoFeOx membranes consist of an intergrowth (Sr4Fe6 − xCoxO13 ± δ), perovskite (SrFe1 − xCoxO3 − δ), and spinel (Co3 − xFexO4) phase. SrCoFeOx exhibits n-type and p-type conduction at low and high oxygen partial pressures, respectively, and has a total conductivity of 16.5 S/cm at 900 °C in air. The oxygen permeation fluxes for SrCoFeOx and SrFeCo0.5Ox membranes were measured with either an inert or carbon monoxide sweep gas. The oxygen permeation fluxes were higher through SrCoFeOx membranes than SrFeCo0.5Ox membranes and can be attributed to a difference in the amount and makeup of the perovskite phase present in each composition. The oxygen permeation fluxes with a carbon monoxide sweep gas were approximately two orders of magnitude larger than the fluxes measured with an inert sweep gas for both compositions. The large oxygen permeation fluxes observed with a carbon monoxide sweep are due to a higher driving force for oxygen transport and a reaction on the sweep side of the membrane that maintains a low oxygen partial pressure. |
| Keywords | Mixed-conducting oxide membrane; Oxygen permeation; Strontium iron cobalt oxide |
Transport properties and defect analysis of La1.9Sr0.1NiO4 + δ
ID=66| Authors |
|
| Source |
Solid State Ionics
Volume: 180,
Issue: 26-27,
Pages: 1433-1441 Time of Publication: 2009 |
Investigation of proton conductivity in Sm1.92Ca0.08Ti2O7 − δ and Sm2Ti1.92Y0.08O7 − δ pyrochlores
ID=65| Authors |
|
| Source |
Solid State Ionics
Volume: 181,
Issue: 3-4,
Pages: 148-153 Time of Publication: 2010 |
| Abstract | The results of the synthesis and characterisation of pyrochlore systems Sm1.92Ca0.08Ti2O7 − δ and Sm2Ti1.92Y0.08O7 − δ are reported. The electrical conductivity of the materials was studied using impedance spectroscopy under wet and dry oxygen and argon. Enhancements of the bulk conductivity at temperatures up to 500 °C were observed for wet conditions indicative of significant proton conductivity. The presence of dissolved protons in the materials is supported by thermogravimetric analysis and infrared spectroscopy. Proton conduction was confirmed by measurements in O2/D2O and Ar/D2O. The results reveal the importance of the correct choice of dopant site for the pyrochlore structure, with A-site substitution yielding the highest levels of proton, as well as oxide ion, conduction. For both samples bulk, rather than grain boundary, conduction is found to be dominant. |
| Keywords | Sm2Ti2O7; Pyrochlore; Ionic conductivity; Infrared spectroscopy; Impedance spectroscopy |
Space–charge theory applied to the grain boundary impedance of proton conducting BaZr0.9Y0.1O3 − δ
ID=64| Authors |
|
| Source |
Solid State Ionics
Volume: 181,
Issue: 5-7,
Pages: 268-275 Time of Publication: 2010 |
| Abstract | The specific grain interior and grain boundary conductivities, obtained from impedance spectroscopy and the brick layer model, are reported for BaZr0.9Y0.1O3 − δ as a function of pO2 and temperature. pO2-dependencies were indicative of dominating ionic and p-type electronic conduction for the grain interior under reducing and oxidizing conditions, respectively, while the grain boundaries showed an additional n-type electronic contribution under reducing conditions. Transmission electron microscopy revealed enrichment of Y in the grain boundary region. These findings indicate the existence of space–charge layers in the grain boundaries. A grain boundary core–space–charge layer model is therefore applied to interpret the data. Using a Mott–Schottky approximation, a Schottky barrier height of 0.5–0.6 V and an effective grain boundary width of 8–10 nm (= 2× space–charge layer thickness) is obtained at 250 °C in wet oxygen. Finite-element modelling of the complex impedance over a grain boundary with a space–charge layer depletion of protons yields a distorted semicircle as observed in the impedance spectra. |
| Keywords | BaZrO3; BaZr0.9Y0.1O3 − δ; Proton conductivity; Grain boundary resistance; Impedance spectroscopy; Space–charge layer |
Ceria and copper/ceria functional coatings for electrochemical applications: Materials preparation and characterization
ID=63| Authors |
|
| Source |
Journal of Power Sources
Volume: 195,
Issue: 8,
Pages: 2189-2195 Time of Publication: 2010 |
| Abstract | Following preliminary investigations, two electrodeposition techniques (electrophoretic and electrolytic) were selected and adapted for deposition of doped ceria ceramic and copper/doped ceria composite coatings on Ni substrates (foil and foam). The copper/doped ceria composites have potential value as protective functional coatings for current collectors in electrochemical cells including solid oxide fuel sells (SOFC). The doped ceria ceramic coating has potential application as a porous matrix for anodes of SOFCs operating on syngas, sour gas, or hydrocarbons. |
| Keywords | Electrodeposition; Coating; Ceramics; Composite; Fuel cell |
Effects of hydrogen on phase stability of ytterbium doped strontium cerates
ID=62| Authors |
|
| Source |
Materials Letters
Volume: 64,
Issue: 7,
Pages: 833-835 Time of Publication: 2010 |
| Abstract | The effect of hydrogen on the phase stability of both SrCe0.95Yb0.05O3 − α, (SCYb-5) powder and disk samples in both dry and wet hydrogen atmospheres was investigated. It was found that decomposition of the perovskite phase was especially evident in the disk samples treated in a dry hydrogen atmosphere, probably due to reduction of the tetravalent cerium ions to trivalent cerium ions in the sample. It was interesting to find that the extent of the decomposition of the perovskite phase was most influenced by the status (i.e. either disk or powder form) of the SCYb-5 samples, rather than the temperature or the extent of the reducing atmospheres. The findings of this study indicate that relaxation kinetics may play an important role in the phase stability of perovskite materials. |
| Keywords | Ceramics; Perovskites; Phase stability; Hydrogen permeation |
Electrical conductivity of the proton conductor BaZr0.9Y0.1O3-δ obtained by high temperature annealing
ID=60| Authors |
|
| Source |
Solid State Ionics, 178 (25)
Pages: p.1437-1441 Time of Publication: 2007 |
Trapping phosphate anions inside the [Ag4I]3+ framework: Structure, bonding, and properties of Ag4I(PO4)
ID=59| Authors |
|
| Source |
Journal of Solid State Chemistry, 181 (1)
Pages: p.37-44 Time of Publication: 2008 |
GdBaCo2O5+x layered perovskite as an intermediate temperature solid oxide fuel cell cathode
ID=58| Authors |
|
| Source |
as
Pages: p.255-263 Time of Publication: 2007 |
Effects of protons and acceptor substitution on the electrical conductivity of La6WO12
ID=57| Authors |
|
| Source |
Journal of Physics and Chemistry of Solids, 69 (7)
Pages: p.1758-1765 Time of Publication: 2008 |
Heavily doped oxygen-ion conducting Ln2 + xTi2 − xO7 − δ (Ln = Ho–Lu; x = 0.44–0.81) pyrochlores: Crystal structure, microstructure and electrical conductivity
ID=56| Authors |
|
| Source |
Solid State Ionics, 179 (21)
Pages: p.985-990 Time of Publication: 2008 |
Influence of microstructure on electrical properties in BaZr0.5In0.5O3-δ proton conductor
ID=55| Authors |
|
| Source |
Solid State Ionics, 179 (21)
Pages: p.1155-1160 Time of Publication: 2008 |
Effect of minor element addition on the electrical properties of BaZr0.9Y0.1O3
ID=54| Authors |
|
| Source |
Solid State Ionics, 179 (21)
Pages: p.1112-1115 Time of Publication: 2008 |
Varistor property of SnO2.CoO.Ta2O5 ceramic modified by barium and strontium
ID=53| Authors |
|
| Source |
Journal of Alloys and Compounds, 466 (1)
Pages: p.483-487 Time of Publication: 2008 |
Plasma sprayed metal supported YSZ/Ni–LSGM–LSCF ITSOFC with nanostructured anode
ID=52| Authors |
|
| Source |
Journal of Power Sources, 180 (1),
Pages: p.132-142 Time of Publication: 2008 |
Comperative Seebeck Coefficient Measurements on Ceramic and Compacted Powder Column Samples; Case of ZnO
ID=51| Authors |
|
| Source |
Proceeding of the 1st Nordic School and Symposium on Functional Energy Related Materials
NorFERM-2008, 3-7 October 2008, Gol, Norway Volume: R, Pages: 36 Time of Publication: 2008 |
Water vapor detection with individual tin oxide nanowires
ID=49| Author |
|
| Source |
Nanotechnology 18
Volume: 18,
Issue: 424016
Time of Publication: 2007
|
| Remark |
4-point conductivity measurement on nanowire held in ProboStat in atmospheres with controlled humuidity |
Measurement of oxygen exchange kinetics on thin-filmLa0.6Sr0.4CoO3-δ using non-linear electrochemical impedance spectroscopy
ID=48| Authors |
|
| Source |
Electrochem. Solid State Lett.
Volume: 10,
Issue: 5,
Pages: B81-86 Time of Publication: 2007 |
Role of protons in the electrical conductivity of acceptor-doped BaPrO3, BaTbO3, and BaThO3
ID=47| Authors |
|
| Source |
Solid State Ionics
Volume: 178,
Issue: 7-10,
Pages: 461-467 Time of Publication: 2007 |
| Remark |
Disk samples, impedance spectrocopy, transport number measurements |
High-Temperature Proton Conductivity in Acceptor-Substituted Rare-Earth Ortho-Tantalates, LnTaO4
ID=46| Authors |
|
| Source |
J. Am. Ceram. Soc.
Volume: 90,
Issue: 4,
Pages: 1116-1121 Time of Publication: 2007 |
| Remark |
Disk samples, impedance spectrocopy, transport number measurements |
Mixed ionic and electronic conductivity of undoped and acceptor doped Er6WO12
ID=45| Authors |
|
| Source |
J. Electrochem. Soc.
Volume: 154,
Issue: 1,
Pages: B77-81 Time of Publication: 2007 |
| Remark |
Disk samples, impedance spectrocopy, transport number measurements |
Transport of hydrogen species in a single crystal SrTiO3
ID=44| Authors |
|
| Source |
Solid State Ionics
Volume: 177,
Pages: 1469-1476 Time of Publication: 2006 |
| Remark |
Single crystal disk. Impedance spectrocopy, transport number measurements. |
High-temperature proton conductivity in acceptor-doped LaNbO4
ID=43| Authors |
|
| Source |
Solid State Ionics
Volume: 177,
Issue: 13-14,
Pages: 1129-1135 Time of Publication: 2006 |
| Remark |
Disk samples, impedance spectrocopy, transport number measurements |
Ionic and Electronic Conductivity of 5% Ca-Doped GdNbO4
ID=42| Authors |
|
| Source |
J. Electrochem. Soc.
Volume: 153,
Issue: 8,
Pages: J87-90 Time of Publication: 2006 |
| Remark |
Disk samples, impedance spetroscopy |
Pulsed laser deposition of high temperature protonic films
ID=41| Authors |
|
| Source |
Solid State Ionics
Volume: 177,
Issue: 26-32,
Pages: 2333-2337 Time of Publication: 2006 |
Stoichiometric lanthanum chromite based ceramic inreconnects with low sintering temperature
ID=40| Author |
|
| Source |
Solid State Ionics
Volume: 177,
Issue: 7-8,
Pages: 757-764 Time of Publication: 2006 |
Bismuth ruthenate based pyrochlores for IT-SOFC applications
ID=39| Authors |
|
| Source |
Electrochemical and Solid-State Letters
Volume: 9,
Issue: 4,
Pages: A215-219 Time of Publication: 2006 |
Proton conduction in rare earth ortho-niobates and ortho-tantalates
ID=38| Authors |
|
| Source |
Nature Materials
Volume: 5,
Pages: 193-196 Time of Publication: 2006 |
| Remark | Link |
On the steady state oxygen permeation through La2NiO4+d membranes
ID=37| Authors |
|
| Source |
J. Electrochem. Soc.
Volume: 153,
Issue: 2,
Pages: A233-238 Time of Publication: 2006 |
| Remark |
Oxygen permeation through disks sealed with Au gaskets. Analysis by MS. Link |
Proton conductivity of Ca-doped Tb2O3
ID=36| Authors |
|
| Source |
Solid State Ionics
Volume: 176,
Issue: 39-40,
Pages: 2957-2961 Time of Publication: 2005 |
| Remark |
Disk samples: 2-electrode AC conductivity & impedance spectroscopy vs T, transport number measurements of protons by EMF of concentration cells. |
On the mixed ionic-electronic conductivity in Ca-doped La2Ti2O7
ID=35| Authors |
|
| Source |
Proc. 26th Risø Int. Symp. Mat. Sci. Solid State Electrochem, Risø Natl. Lab., Roskilde, Denmark
Pages: 209-214 Time of Publication: 2005 |
| Editors |
|
| Remark |
Disk samples: 2-electrode AC conductivity & impedance spectroscopy vs T, transport number measurements of protons and oxygen ions by EMF of concentration cells. Link |
Sensor Letters 3
ID=34| Source |
Sensor Letters 3
Volume: 3,
Pages: 258-262 Time of Publication: 2005 |
| Remark | Link |
J.Phys. and Chem. Solids
ID=33| Source |
J.Phys. and Chem. Solids
Pages: 7878-7882 Time of Publication: 2005 |
Sensors and Actuators
ID=32| Source |
B 106
Issue: 837-842
Time of Publication: 2005
|
Temperature dependence of oxygen ion transport in Sr+Mg substituted LaGaO3 (LSGM) with varying grain sizes
ID=31| Authors |
|
| Source |
Solid State Ionics
Volume: 174,
Issue: 1-2,
Pages: 233-243 Time of Publication: 2004 |
| Remark |
Disk samples: 2-electrode and 4-point (van der Pauw) AC conductivity & impedance spectroscopy vs T, use of surface guard. |
Transport numbers from hydrogen concentration cells over different oxides under oxidising and reducing conditions
ID=30| Authors |
|
| Source |
Pages: 3147-3151 Time of Publication: 2004 |
| Remark |
Disk samples: 2-electrode AC conductivity, transport numbers of hydrogen ions by EMF of hydrogen concentration cell |
Conductivity dependence on oxygen partial pressure and oxide-ion transport numbers determination for La2Mo2O9
ID=29| Authors |
|
| Source |
Electrochemical and Solid-State Letters
Volume: 10,
Issue: 7,
Pages: A373-375 Time of Publication: 2004 |
| Remark |
Disk samples: 4-point van der Pauw conductivity, 2-electrode impedance spectroscopy, transport numbers of oxygen ions by EMF of oxygen concentration cell |
Impedance spectroscopy and proton transport number measurements on Sr-substituted LaPO4 prepared by combustion synthesis
ID=28| Authors |
|
| Source |
Solid State Ionics
Volume: 162-163,
Pages: 167-173 Time of Publication: 2003 |
| Remark |
Disk samples: 2-electrode AC conductivity, transport numbers of protons by EMF of hydrogen concentration cell |
HT Corrosion of a Cr-5wt%Fe1wt%Y2O3 Alloy and Conductivity of the Oxide Scale
ID=27| Authors |
|
| Source |
J. Electrochem. Soc.
Volume: 150,
Issue: 8,
Pages: B374-379 Time of Publication: 2003 |
| Remark |
Disk samples of alloy, with gold contact outside one oxide layer. |
Proton and apparent hydride ion conductivity in Al-substituted SrTiO3
ID=26| Authors |
|
| Source |
Solid State Ionics
Volume: 154-155,
Pages: 669-677 Time of Publication: 2002 |
| Remark |
Disk samples, 2-electrodes, Au seal, AC conductivity and concentration cell/EMF measurements of transport numbers for hydrogen and oxygen ions |
Water and protons in electrodeposited MnO2 (EMD)
ID=25| Authors |
|
| Source |
Solid State Ionics
Volume: 152-153,
Pages: 695-701 Time of Publication: 2002 |
| Remark |
Disk samples, 2 electrodes, AC conductivity and concentration cell/EMF measurements of transport numbers for protons. RT-100°C. |
Hydrogen ion conduction in iron substituted strontium titanate, in SrTi1-xFexO3-x/2
ID=24| Authors |
|
| Source |
Solid State Ionics
Volume: 143,
Issue: 1,
Pages: 103-116 Time of Publication: 2001 |
| Remark |
Disk samples, 2-electrodes, AC conductivity and concentration cell/EMF measurements of transport numbers for hydrogen and oxygen ions |
"Spinel and perovskite functional layers between Plansee metallic interconnect (Cr-5wt%Fe-1wt%Y2O3) and ceramic (La0.85Sr0.15)0.91MnO3 cathode materials for solid oxide fuel cells"
ID=23| Authors |
|
| Source |
J. Electrochem. Soc.
Volume: 147 ,
Issue: 9,
Pages: 3251-3256 Time of Publication: 2000 |
| Remark |
Disk samples of alloy + LSM layer |
Phase relations, chemical diffusion and electrical conductivity in pure and doped Sr4Fe6O13 mixed conductor materials
ID=22| Authors |
|
| Source |
Solid State Ionics
Volume: 135,
Pages: 687-697 Time of Publication: 200 |
| Remark |
Disk sample, 4-point van der Pauw conductivity measurements |
Thermoelectric power of the mixed ionic-electronic conductor SrTi0.8Fe0.2O3-d in various atmospheres
ID=21| Authors |
|
| Source |
proc. Nordic Energy Research Workshop on "Hydrogen in Electrochemical Energy Conversion", Geilo
Volume: March 1999
Time of Publication: 1999
|
| thermoelectric | |
| Editors |
|
| Remark |
Bar sample, thermoelectric power (Seebeck coefficient) measurements |
La1-xBaxCr1-yTiyO3 with varied oxygen content
ID=20| Authors |
|
| Source |
J. Electrochem. Soc.
Pages: 264-269 Time of Publication: 1998 |
| Remark |
Disk sample, 4-point van der Pauw conductivity measurements using Au contacts |
Electrochemical behaviour of Ni/YSZ electrodes
ID=19| Author |
|
| Source |
Proc. 2nd European SOFC Forum
Volume: May 1996 ,
Pages: 607-616 Time of Publication: 1996 |
| Editor |
|
| Remark |
Disk samples, 3 electrodes (Working, counter, ring reference) |
Hydrogen isotope effects on Ni/YSZ electrodes
ID=18| Authors |
|
| Source |
Proc. 17th Risø Int. Symp. on Materials Science: High Temperature Electrochemistry: Ceramics and Metals
Risø Natl. Lab., Roskilde, Denmark (1996) Pages: 381-386 Time of Publication: 1996 |
| Editors |
|
| Remark |
Disk samples, 3 electrodes (Working, counter, ring reference) |
Ageing of YSZ electrolytes at 800°C
ID=17| Authors |
|
| Source |
Proc. 2nd European SOFC Forum
Volume: May 1996,
Pages: 315-320 Time of Publication: 1996 |
| Editor |
|
| Remark |
Disk samples, 4 stacked and measured simultaneously, with Pt electrodes in-between. |
Proton conduction in Ca- and Sr-substituted LaPO4
ID=16| Authors |
|
| Source |
Solid State Ionics
Volume: 77,
Pages: 240-243 Time of Publication: 1995 |
| Remark |
Bar samples, 4-point AC conductivity measurements |
Proton and deuteron conductivity in CsHSO4 and CsDSO4 by in situ isotopic exchange
ID=15| Authors |
|
| Source |
Solid State Ionics
Volume: 77,
Pages: 105--110 Time of Publication: 1995 |
| Remark |
Disk sample, 4-point van der Pauw measurements |
Oxidation of methane on a SrFeO3/Au//YSZ electrode characterised by mass spectroscopy and 18O2 pulses
ID=14| Authors |
|
| Source |
Chem. Eng. Technol.
Volume: 18,
Pages: 139-147 Time of Publication: 1995 |
| Remark |
Disk samples, sealed onto support, with electrodes for electrochemical pumping. Exctract to MS directly from electrodes by silica tubes. |
Ageing of YSZ electrolytes at 1000°C
ID=13| Authors |
|
| Source |
Proc. 1st European SOFC Forum
Volume: Oct. 1994,
Pages: 671-679 Time of Publication: 1994 |
| Editor |
|
| Remark |
Disk samples, 4 stacked and measured simultaneously over 40 days, with Pt electrodes in-between |
Oxidation of CH4 on La0.7Ca0.3CrO3//YSZ anodes
ID=12| Authors |
|
| Source |
Proc. 1st European SOFC Forum
Volume: Oct. 1994,
Pages: 217-226 Time of Publication: 1994 |
| Editor |
|
| Remark |
Disk samples, sealed by glass onto support, fuel cell and electrochemical pumping modes, MS analysis of gases. |
Protons in LaErO3
ID=11| Author |
|
| Source |
Solid State Ionics
Volume: 70/71,
Pages: 305-310 Time of Publication: 1994 |
| Remark |
Disk samples, 2 electrodes, EMF transport number and AC conductivity measurements |
Electrical conductivity and ionic transport number of YSZ and Cr-doped YSZ single crystals at 200-1000°C
ID=10| Authors |
|
| Source |
Solid State Ionics
Volume: 67,
Pages: 57-64 Time of Publication: 1993 |
| Remark |
Small single crystals, Pt paint electrodes, placed over small hole in support plate to form concentration cell. Role of sample holder parasitic conductance evaluated. |
Reaction resistance in relation to three phase boundary length of Ni/YSZ electrodes
ID=9| Authors |
|
| Source |
Electrochem. Soc. Proc.
Volume: 93-4,
Pages: 473-477 Time of Publication: 1993 |
| Remark |
Disk sample, 3-electrode setup, patterned working electrode |
Protonic conduction in acceptor-doped cubic rare earth sesquioxides
ID=8| Authors |
|
| Source |
J. Am. Ceram. Soc.
Volume: 75 ,
Pages: 1176-1181 Time of Publication: 1992 |
| Remark |
Disk samples, AC conductivity and EMF transport numbers (protons and oxygen ions). Nice schematic of sample arrangement. |
The electrode system O2/Pt//ZrO2:8Y2O3 investigated by impedance spectroscopy
ID=7| Authors |
|
| Source |
Solid State Ionics
Volume: 47,
Pages: 161-167 Time of Publication: 1991 |
| Remark |
Thin electrolyte disk with 3 Pt electrodes. NOTE: probable reference electrode problem with such a thin electrolyte. |
Electronic, Ionic and Protonic Conductivities of a Commercial, Polycrystalline a-Al2O3
ID=6| Authors |
|
| Source |
High Temp.-High Press.
Volume: 20,
Issue: 3,
Pages: 345-360 Time of Publication: 1988 |
| Remark |
Closed alumina support tube used as sample. AC conductivity, impedance spectroscopy, EMF transport number measurements, long-term measurements at 1400°C. |
Proton and Native-Ion Conductivities of Y2O3 at High Temperatures
ID=5| Authors |
|
| Source |
Solid State Ionics
Volume: 20,
Pages: 169-184 Time of Publication: 1986 |
| Remark |
Disk sample: 2-electrode AC conductivity, transport numbers of protons and oxygen ions by EMF of concentration cells |
Electrical Conductivity and Defect Structure of Y2O3 as a Function of Water Vapor Pressure
ID=4| Authors |
|
| Source |
J. Am. Ceram. Soc.
Volume: 67,
Issue: 12,
Pages: 786-792 Time of Publication: 1984 |
| Remark |
5 disk samples stacked and measured simultaneously (2-electrode AC conductivity) |
