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MOX-Based Resistive Gas Sensors with Different Types of Sensitive Materials (Powders, Pellets, Films), Used in Environmental Chemistry

ID=716
Author Paul Chesler and Cristian Hornoiu
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 Yuki Sakai, Kana Matsuno, Takumi Nishikubo, Masayuki Fukuda, Shogo Wakazaki, Masahito Ikeda, Kazuki Takahashi, Zhao Pan, Lei Hu, and Masaki Azuma
Source
Chem. Mater.
Time of Publication: 2023
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 Youssef Arkame, Achraf Harrati, Yassine Et-Tayea, Ahmed Manni, Fahd Oudrhiri Hassani, Abdeslam El Bouari, Ali Sdiri, Iz-Eddine El Amrani El Hassani, Chaouki Sadik
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 Naouma Bimpiri, Argyro Konstantinidou, Dimitrios Tsiplakides, Stella Balomenou and Kalliopi Maria Papazisi
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 Inger-Emma Nylund, Caren Regine Zeiger, Ding Peng, Per Erik Vullum, Julian Walker, Mari-Ann Einarsrud, and Tor Grande*
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 Muhammad Shahrukh Saleem, Qianli Chen, Nick A. Shepelin, Simone Dolabella, Marta D. Rossell, Xuhai Zhang, Coleman X. Kronawitter, Fabio La Mattina, and Artur Braun
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 Yasushi Sekine
Source
Faraday Discussions
Time of Publication: 2023
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 Marvin Abt, Katharina Kruppa, Mario Wolf, Armin Feldhoff, Ludger Overmeyer
Source
Engineering Reports
Time of Publication: 2022
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 N.V. Lyskov, A.I. Kotova, D.I. Petukhov, S.Ya. Istomin, G.N. Mazo
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 Xinwei Sun, Einar Vøllestad, Per Martin Rørvik, Sebastian Prodinger, Georgios N. Kalantzopoulos, Athanasios Chatzitakis, Truls Norby
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 Kevin G. Both, Vilde M. Reinertsen, Thomas M. Aarholt, Ingvild J.T. Jensen, Dragos Neagu, Øystein Prytz, Truls Norby, Athanasios Chatzitakis
Source
Catalysis Today
Time of Publication: 2023
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 Madalina Nicolescu, Daiana Mitrea, Cristian Hornoiu, Silviu Preda, Hermine Stroescu, Mihai Anastasescu, Jose Maria Calderon-Moreno, Luminita Predoana, Valentin Serban Teodorescu, Valentin-Adrian Maraloiu, Maria Zaharescu and Mariuca Gartner
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 Antonino Curcio, Antonio Gianfranco Sabato, Marc Nuñez Eroles, Juan Carlos Gonzalez-Rosillo, Alex Morata, Albert Tarancón, and Francesco Ciucci
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 Sanaz Zarabi Golkhatmi, Muhammad Imran Asghar, Peter D. Lund
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 Linn Katinka Emhjellen, Xin Liu, Jonathan M. Polfus, Reidar Haugsrud
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 Zuoan Li, Reidar Haugsrud
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 Sjur Storhaug
Source
Time of Publication: 2022
Remark Master Thesis
Link

Electrospun Ca3Co4−xO9+δ nanofibers and nanoribbons: Microstructure and thermoelectric properties

ID=699
Authors Katharina Kruppa, Itzhak I. Maor, Frank Steinbach, Vadim Beilin, Meirav Mann-Lahav, Mario Wolf, Gideon S. Grader, Armin Feldhoff
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 Sea-Fue Wang, Yi-Le Liao, Yung-Fu Hsu, Piotr Jasinski
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 Nikola Kanas, Benjamin A. D. Williamson, Frank Steinbach, Richard Hinterding, Mari-Ann Einarsrud, Sverre M. Selbach, Armin Feldhoff, and Kjell Wiik
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 A.A. Solovyev, A.V. Shipilova, S.V. Rabotkin, E.A. Smolyanskiy, A.N. Shmakov
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 Robles Fernández, Adrián Merino Rubio, Rosa Isabel (dir.) ; Orera Utrilla, Alodia (dir.)
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 Juan de Dios Sirvent, Albert Carmona, Laetitia Rapenne, Francesco Chiabrera, Alex Morata, Mónica Burriel, Federico Baiutti, and Albert Tarancon
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 Cristina Artini, Massimo Viviani, Sabrina Presto, Sara Massardo, Maria Maddalena Carnasciali, Lara Gigli, and Marcella Pani
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 M. M. Abdullaev, N. V. Lyskov, S. Ya. Istomin, E. V. Antipov
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 Sea-Fue Wang, Yi-Le Liao, Yung-Fu Hsu, Piotr Jasinski,
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 M. Tomas, V. Asokan, J. Puranen, J.-E. Svensson, J. Froitzheim
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 Fareenpoornima Rafiq, Parthipan Govindsamy, and Selvakumar Periyasamy
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 Luting Lu, Linhao Li, Xiuzi Che, Gaoyang Zhao
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 N.I. Kadyrova, N.V. Melnikova, A.A. Mirzorakhimov
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 Maria Balaguer, Yoo Jung Sohn, Dietmar Kobertz, Sergey Kasatikov, Andrea Fantin, Michael Muller, Norbert H. Menzler, Olivier Guillon, Mariya E. Ivanova
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 Farha Jabeen, Raza Shahid, M. Shahid Khan, Raghvendra Pandey
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 Nayereh Soltani, Jamil Ur Rahman, Patricia Almeida Carvalho, Calliope Bazioti, Terje Finstad
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 C.G. Mendoza-Serrato, R. Lopez-Juarez, A. Reyes-Montero, J.A. Romero-Serrano, C. Gomez-Yanez, J.A. Fabian-Anguiano, J. Ortiz-Landeros
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 Reshma K. Madathil, Raphael Schuler, Truls Norby
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 Sathya Prakash Singh, Nikola Kanas, Mari-Ann Einarsrud, Kjell Wiik
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 Stephanie E. Wolf, Lucy Dittrich, Markus Nohl, Tobias Duyster, Izaak C. Vinke, Rüdiger-A. Eichel, and L. G. J. (Bert) de Haart
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 Yu.Yu. Dikhtyar, D.A. Spassky, V.A. Morozov, D.V. Deyneko, A.A. Belik, O.V. Baryshnikova, I.V. Nikiforov, B.I. Lazoryak
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 Jon G. Bell, T. Graule, M. Stuer
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
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Mesophase Transitions in [(C2H5)4N][FeBrCl3] and [(CH3)4N][FeBrCl3] Ferroic Plastic Crystals

ID=677
Authors Julian Walker, Kenneth P. Marshall, Jorge Salgado-Beceiro, Benjamin A. D. Williamson, Nora S. Løndal, Socorro Castro-Garcia, Manuel Sánchez Andújar, Sverre M. Selbach, Dmitry Chernyshov, and Mari-Ann Einarsrud
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
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Contact angle screening and asymmetric dual-phase CO2 separation membranes

ID=676
Authors Wen Xing, Anne Store
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
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NaMn0.2Fe0.2Co0.2Ni0.2Ti0.2O2 high-entropy layered oxide – experimental and theoretical evidence of high electrochemical performance in sodium batteries

ID=675
Authors Katarzyna Walczak, Anna Plewa, Corneliu Ghica, Wojciech Zajac, Anita Trenczek-Zajac, Marcin Zajac, Janusz Tobota, Janina Molenda
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
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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 Surbhi Gupta, S.K. Deshpande, V.G. Sathe, V. Siruguri
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
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Tailored and Improved Protonic Conductivity through Ba(ZxCe10−x)0.08Y0.2O3−δ Ceramics Perovskites Type Oxides for Electrochemical Devices

ID=673
Authors Dr. Kwati Leonard, Prof. Yuji Okuyama, Dr. Mariya E. Ivanova, Prof. Wilhelm A. Meulenberg, Prof. Hiroshige Matsumoto
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
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On the mechanism of Mn(II)-doping in Scandia stabilized zirconia electrolytes

ID=672
Authors Einar Vøllestad, Vegar Øygarden, Joachim Seland Graff, Martin Fleissner Sunding, John D. Pietras, Jonathan M. Polfus, Marie-Laure Fontaine
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
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Detailed characterization of oxide-ion and proton transport numbers in Sr–Ti layered perovskites using an improved electromotive force method

ID=670
Authors Yutaro Yagi, Isao Kagomiya & Ken-ichi Kakimoto
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..
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Impedance spectroscopy study of Au electrodes on Gd-doped CeO2 (GDC) – Molten Li2CO3+Na2CO3 (LNC) composite electrolytes

ID=669
Authors Vijayan Sobhana Dilimon, Ragnar Strandbakke, Truls Norby
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
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Lanthanum strontium cobaltite as interconnect in oxide thermoelectric generators

ID=668
Authors Reshma K.Madathil, TrulsNorby
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
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Oxide Ion and Proton Conductivity in a Family of Highly Oxygen-Deficient Perovskite Derivatives

ID=667
Authors Chloe A. Fuller, Douglas A. Blom, Thomas Vogt, Ivana Radosavljevic Evans, and John S. O. Evans
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
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Advanced metal oxide infiltrated electrodes for boosting the performance of solid oxide cells

ID=666
Authors Alodia Orera, Alejandro Betato, Jorge Silva-Trevino, Angel Larrea and Miguel A. Laguna-Bercero
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 Richard Hinterding, Desiree Rieks, Patrick A. Kissling, Lukas Steinbach, Nadja C. Bigall & Armin Feldhoff
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.
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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 Sea-Fue Wang, Hsi-Chuan Lu, Yung-Fu Hsu, Piotr Jasinski
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.
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Synthesis, structure and ionic conductivity of nanocrystalline Ce1−xLaxO2−δ as an electrolyte for intermediate temperature solid oxide fuel cells

ID=663
Authors Naeemakhtar Momin, J. Manjanna, Lawrence D’Souza, S.T. Aruna, S.Senthil Kumar
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.
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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 Yongliang Zhang, Kevin Huang
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.
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Improved thermoelectric properties in ceramic composites based on Ca3Co4O9 and Na2Ca2Nb4O13

ID=661
Authors R. Hinterding, M. Wolf, M. Jakob, O. Oeckler, A. Feldhoff
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
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Glass-ceramic composites as insulation material for thermoelectric oxide multilayer generators

ID=660
Authors Sophie Bresch, Björn Mieller, Paul Mrkwitschka, Ralf Moos, Torsten Rabe
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 Meshari Alotaibi, Linhao Li and Anthony R Wes
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.
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Electrochemical Performance of SrWO4 Electrolyte for SOFC

ID=658
Authors Ahmed Afif, Nikdalila Radenahmad, Juliana Zaini, Abdalla Mohamed Abdalla, Seikh Mohammad Habibur Rahman, Quentin Hoon Nam Cheok, Abul Kalam Azad
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.
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Electrical properties and charge compensation mechanisms of Cr-doped rutile, TiO2

ID=657
Authors Yun Dang, Xin Li Phuah, Han Wang, Bo Yang, Haiyan Wang and Anthony R. West
Source
Phys. Chem. Chem. Phys.
Volume: 23, Pages: 22133-22146
Time of Publication: 2021
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Protonic Transport Properties of Perovskite Heterostructures A Thin Film Study

ID=656
Author Erik E. P. Alsgaard
Source
Time of Publication: 2021
Remark Master Thesis Materials Science for Energy and Nanotechnology
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Expanded Chemistry and Proton Conductivity in Vanadium-Substituted Variants of γ-Ba4Nb2O9

ID=655
Authors Alex J. Brown, Bettina Schwaighofer, Maxim Avdeev, Bernt Johannessen, Ivana Radosavljevic Evans, and Chris D. Ling
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 Linn Katinka Emhjellen, Ragnar Strandbakke and Reidar Haugsrud
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 Michael S. Bowen
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 A.A. Solovyev, K.A. Kuterbekov, S.A. Nurkenov, A.S. Nygymanova, A.V. Shipilova, E.A. Smolyanskiy, S.V. Rabotkin., I.V. Ionov
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 Lucy Dittrich, Tobias Duyster, Severin Foit, I. C. Vinke, Rüdiger-A. Eichel and L. G. J. (Bert) De Haart
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 Haoyu Zheng, Feng Han, Noriko Sata, Matthias Riegraf, Amir Masoud Dayaghi, Truls Norby and Rémi Costa
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 Stephanie Elisabeth Wolf, Lucy Dittrich, Markus Nohl, Severin Foit, Izaak Vinke, L. G. J. De Haart and Rudiger-A Eiche
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 Haoyu Zheng, Feng Han, Noriko Sata, Matthias Riegraf, Amir Masoud Dayaghi, Truls Norby and Rémi Costa
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 J.A. Fabián-Anguiano, M.J. Ramírez-Moreno, H. Balmori-Ramírez, J.A. Romero-Serrano, I.C. Romero-Ibarra, Xiaoli Ma, J. Ortiz-Landeros
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 Mantas Sriubas, Darius Virbukas, Nursultan Kainbayev, Kristina Bockute and Giedrius Laukaitis
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 Linhao Li, Teresa Roncal-Herrero, John Harrington, Steven J. Milne, Andy P. Brown, Julian S. Deana, Derek C. Sinclair
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 Sun Liping, Li Na, Li Qiang, Huo Lihua, Zhao Hui
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 A.V. Shlyakhtina, N.V. Lyskov, A.N. Shchegolikhin, I.V. Kolbanev, S.A. Chernyak, E. Yu. Konysheva
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 L. Ouachouo, L. Bih, E. Haily, M. Jerroudi, I. Saadoune
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 E. Haily, L. Biha, M. Jerroudi, A. El bouari
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 Yutaro Yagi, Isao Kagomiya, Ken-ichi Kakimoto
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 Kazuhiro Mori, Atsushi Mineshige, Takuro Emoto, Maiko Sugiura, Takashi Saito, Kaoru Namba, Toshiya Otomo, Takeshi Abe, and Toshiharu Fukunaga
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 Priyadarshini Balasubramaniana, Manjusha Battabyal, Arumugam Chandra Bose, Raghavan Gopalan
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 Yudai Hisai, Quanbao Ma, Thomas Qureishy, Takeshi Watanabe,Takuma Higo, Truls Norby and Yasushi Sekine
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 Kaiqi Xu, Athanasios Chatzitakis, Paul Hof fBacke, Qiushi Ruan, Junwang Tang, Frode Rise, Magnar Bjøras,Truls Norby
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 F. Baiutti, F. Chiabrera, M. Acosta, D. Diercks, D. Parfitt, J. Santiso, X. Wang, A. Cavallaro, A. Morata, H. Wang, A. Chroneos, J. MacManus-Driscoll & A. Tarancon
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 Pesce Arianna, Hornes Aitora, Nunez Marca, Morata Alexa, Torrell Marca and Tarancon Alber
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 K.Cwieka, A. Lysik, T. Wejrzanowski, T. Norby, W. Xing
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 Kacper Cichy and Konrad Swierczek
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 Mario Karl Micu-Budisteanu
Source
Time of Publication: 2021
Remark Master Thesis
Link

Fabrication of a Silicide Thermoelectric Module Employing Fractional Factorial Design Principles

ID=629
Authors Joachim S. Graff, Raphael Schuler, Xin Song, Gustavo Castillo-Hernandez, Gunstein Skomedal, Erik Enebakk, Daniel Nilsen Wright, Marit Stange, Johannes de Boor, Ole Martin Løvvik & Matthias Schrade
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 R. Hinterding, Z. Zhao, M. Wolf, M. Jakob, O. Oeckler, A. Feldhoff
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 Izabella Dascalu, Jose Maria Calderon-Moreno, Petre Osiceanu, Veronica Bratan, Cristian Hornoiu, Simona Somacescu
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 A. V. Shipilova, A. A. Solov’ev, E. A. Smolyanskii, S. V. Rabotkin & I. V. Ionov
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 M. Jerroudi, L. Biha, E. Haily, I. Saadoune
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 Christopher Panaritis
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 Raphael Schuler, Reshma K. Madathil, and Truls Norby
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 Yu.Yu. Dikhtyar, D.V. Deyneko, K.N. Boldyrev, O.V. Baryshnikova, А.А. Belik, V.А. Morozov, B.I. Lazoryak
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 C. Bergesa, A. Wain, R. Andújar, J. A. Naranjo, A. Gallego, E. Nieto, G. Herranz, R. Campana
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 O. P. Shchetnikov, N. V. Melnikova, A. N. Babushkin & V. M. Kiseev
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 N.A. Tikhonov, M.G. Tokmachev, T. Bakhia & R.Kh. Khamizov
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 Maciej Mozdzierz, Juliusz Dabrowa, Anna Stepien, Marek Zajusz, Miroslaw Stygar, Wojciech Zajac, Marek Danielewski, Konrad Swierczek
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 A. A. Solovyev, A. V. Shipilova, I. V. Ionov, E. A. Smolyanskiy, A. V. Nikonov & N. B. Pavzderin
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 Raphael Schuler, Federico Bianchini, Truls Norby, and Helmer Fjellvåg
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 Haily, E.; Bih, L.; El Bouari, A.; Lahmar, A.; El Marssi, M.; Manoun, B.
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 Anna Niemczyka, Anna Stepien, Kacper Cichy, Juliusz Dabrowa, Zijia Zhang, Barthomiej Gedziorowski, Kun Zheng, Hailei Zhao, Konrad Swierczek
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 Federico Baiutti, Francesco Chiabrera, Matias Acosta, David Diercks, David Parfitt, Jose Santiso, Xuejing Wang, Alex Morata, Andrea Cavallaro, Haiyan Wang, Alexander Chroneos, Judith MacManus-Driscoll, Albert Tarancon
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 Damjan Vengust, Bostjan Jancar, Tilen Sever, Andreja Šestan, Vid Bobnar, Zdravko Kutnjak, Nina Daneu, Danilo Suvorov, Matjaz Spreitzer
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 Nikola Kanas, Rasmus Bjørk, Kristin Høydalsvik Wells, Raphael Schuler, Mari-Ann Einarsrud, Nini Pryds, and Kjell Wiik
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 R. K. Lenka, P.K.Patro, Vivek Patel, L. Muhmood, T. Mahata
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 Aritza Wain-Martin, Roberto Campana, Aroa Morán-Ruiz, Aitor Larrañaga, María Isabel Arriortua
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 Amir Masoud Dayaghi, Reidar Haugsrud, Marit Stange, Yngve Larring, Ragnar Strandbakke, Truls Norby
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 Monica Susana Campos Covarrubias, Mantas Sriubas, Kristina Bockute, Piotr Winiarz, Tadeusz Miruszewski, Wojciech Skubida, Daniel Jaworski, MichaÅ Bartmanski, Marek Szkodo, Maria Gazda and Giedrius Laukaitis
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 L. Bernadet, M. Morales, X. G. Capdevila, F. Ramos, M. C. Monterde, J. A. Calero, A. Morata, M. Torrell and A. Tarancón
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.
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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 Kacper Cichy, Konrad Åšwierczek, Katarzyna Jarosz, Alicja Klimkowicz, Mateusz Marzec, Marta Gajewska, Bogdan Dabrowski
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.
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Tuning the RWGS Reaction via EPOC and In Situ Electro-oxidation of Cobalt Nanoparticles

ID=604
Authors Dimitrios Zagoraios Dimitrios Zagoraios Department of Chemical Engineering, University oDimitrios Zagoraios, Sotirios Tsatsos, Stella Kennou, Constantinos G. Vayenas, Georgios Kyriakou, and Alexandros Katsaounis
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 Fan Yang, Julian S. Dean, Qiaodan Hu, Patrick Wu, Emilio Pradal-Velázquez, Linhao Li and Derek C. Sinclair
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.
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Thermally stable, low resistance Mg2Si0.4Sn0.6/Cu thermoelectric contacts using SS 304 interlayer by one step sintering

ID=602
Authors B.Jayachandran, B. Prasanth, R. Gopalana, T.Dasgupt°, D. Sivaprahasam
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 Temesgen D.Desissa
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 Kwati Leonard, Wendelin Deibert, Mariya E. Ivanova, Wilhelm A. Meulenberg, Tatsumi Ishihara and Hiroshige Matsumoto
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).
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Cation-driven electrical conductivity in Ta-doped orthorhombic zirconia ceramics

ID=599
Authors Bibi Malmal Moshtaghioun, Miguel A. Laguna-Bercero, Jose I. Peña, Diego Gómez-García, Arturo Domínguez-Rodríguez
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 Severin Foit, Lucy Dittrich, Tobias Duyster, Izaak Vinke, Rüdiger-A. Eichel and L.G.J. (Bert) de Haart
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 E. Hailya, L. Bih, A. El Bouari, A. Lahmar, M. El Marssi & B. Manoun
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.
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Strategies to Mitigate the Degradation of Stainless-SteelInterconnects Used in Solid Oxide Fuel Cells

ID=596
Author Claudia Gоbel
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 D.U. Seifert, L. Li, K-Y. Lee, M.J. Hoffmann, D.C. Sinclair ,M. Hinterstein
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 Tomasz Polczyk, Wojciech Zajac, Magdalena Ziabka, and Konrad Swierczek
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 Yutaro Yagi, Isao Kagomiya, Ken-ichi Kakimoto
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.
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Dynamics of Hydroxyl Anions Promotes Lithium Ion Conduction in Antiperovskite Li2OHCl

ID=592
Authors Fei Wang, Hayden A. Evans, Kwangnam Kim, Liang Yin, Yiliang Li, Ping-Chun Tsai, Jue Liu, Saul H. Lapidus, Craig M. Brown, Donald J. Siegel, and Yet-Ming Chiang
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 Ryan R. McQuade, Pavel Mardilovich, Nitish Kumar & David P. Cann
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.
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Stabilized Charge, Spin, and Orbital Ordering by the 6s2 Lone Pair in Bi0.5Pb0.5MnO3

ID=590
Authors Shogo Wakazaki, Takumi Nishikubo, Yuki Sakai, Kei Shigematsu, Hena Das, Depei Zhang, Qiang Zhang, Masaaki Matsuda, and Masaki Azuma
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 Yang Hu, Ville Miikkulainen, Kenichiro Mizohata, Truls Norby, Ola Nilsen, Helmer Fjellvåg
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 Nathaniel Trobough
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 Kazuhiro Mori, Yoshiyuki Morita, Takashi Saito, Takashi Kamiyama, Toshiya Otomo, Takeshi Abe, and Toshiharu Fukunaga
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 Т.I. Chupakhina, N.V. Melnikova, N.I. Kadyrova, Yu.A. Deeva, А.A. Mirzorakhimov, T.P. Gavrilova, I.F. Gilmutdinov, R.M. Eremina
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 Kazuhiro Mori, Yoshiyuki Morita, Takashi Saito, Takashi Kamiyama, Toshiya Otomo, Takeshi Abe, and Toshiharu Fukunaga
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 Paramananda Jena, Dinesh Kumar, Pankaj Kumar Patro, Raja Kishora Lenka, Akhilesh Kumar Singh
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 F. Hadji, F. Bouremmad, S. ShawutiM. A. Gulgun
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 Anna Niemczyk, Kun Zheng, Kacper Cichy, Katarzyna Berent, Kathrin Küster, Ulrich Starke, Bisham Poudel, Bogdan Dabrowski, Konrad Åšwierczek
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.
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Electrical properties of gadolinia-doped ceria for electrodes for magnetohydrodynamic energy systems

ID=581
Authors Michael S. Bowen, Michael Johnson, Ryan McQuade, Bryce Wright, Kyei-Sing Kwong, Peter Y. Hsieh, David P. Cann & C. Rigel Woodside
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.
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Domain wall conductivity as the origin of enhanced domain wall dynamics in polycrystalline BiFeO3

ID=580
Authors Maja Makarovic, Mustafa ÇaÄri Bayir, Hana Ursic, Andraz Bradesko, and Tadej Rojac
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 M. Jerroudi, L. Bih, S. Yousfi, L. Bejjit, M. Haddad, B. Manoun & P. Lazor
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.
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In-situ Ni exsolution from NiTiO3 as potential anode for solid oxide fuel cells

ID=578
Authors Lucía M.Toscani, Florencia Volpe Giangiordano, Nora Nichio, Francisco Pompeo, Susana A. Larrondo
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 Maki Torimoto, Shuhei Ogo, Yudai Hisai, Naoya Nakano, Ayako Takahashi, Quanbao Ma, Jeong Gil Seo, Hideaki Tsuneki, Truls Norby and Yasushi Sekine
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 Raphael Schuler, Truls Norby, Helmer Fjellvåg
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 M.MakarovicabcN.KanascA.ZorkodeK.ZibernaaH.UrsicabD.R.Smabraten, S. M. Selbachc, T. Rojac
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 Tarjei Bondevik, Jonathan M. Polfus, Truls Norby
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 Xinyu Li, Federico Bianchini, Julia Wind, Christine Pettersen, David S. Wragg, Ponniah Vajeeston, and Helmer Fjellvåg
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 O. V. Baryshnikova, D. V. Deineko, M. A. Potaenko, Yu. Yu. Dikhtyar, S. Yu. Stefanovich, V. A. Morozov & B. I. Lazoryak
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 Dimitrios Zagoraiosa, Christopher Panaritis, Aikaterina Krassakopoulou, Elena A. Baranova, Alexandros Katsaounis, Constantinos G. Vayenas
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 Mario Wolf, Marvin Abt, Gerd Hoffmann, Ludger Overmeyer, Armin Feldhoff
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 Hayato Ishizaki, Yuki Sakai, Takumi Nishikubo, Zhao Pan, Kengo Oka, Hajime Yamamoto, and Masaki Azuma
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 Zivak, Milica
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 P. S. Cardenas-Terrazas, M. T. Ayala-Ayala, J. Muñoz-Saldaña, A. F. Fuentes, D. A. Leal-Chavez, J. E. Ledezma-Sillas, C. Carreño-Gallardo & J. M. Herrera-Ramirez
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 BartÅomiej GÄ™dziorowski, Kacper Cichy, Anna Niemczyk, Anna Olszewska, Zijia Zhang, Szymon KopeÄ, Kun Zheng, Mateusz Marzec, Marta Gajewska, Zhihong Du, Hailei Zhao, Konrad Åšwierczek
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 Kaiqi Xu
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 Chloe A. Fuller, Quentin Berrod, Bernhard Frick, Mark R. Johnson, Maxim Avdeev, John S. O. Evans, and Ivana Radosavljevic Evans
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 Lucile Bernadet, Carlos Moncasi, Marc Torrell, Albert Tarancón
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 Sebastian Andre Steiner
Source
Time of Publication: 2019
Remark Dissertation
Link

Mixed-conducting ceramic-carbonate dual-phase membranes: Gas permeation and counter-permeation

ID=561
Authors Han-Chun Wu, Gabriel Nile, Jerry Y.S. Lin
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 Yasushi Sekine and Ryo Manabe
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 Anna Olszewska, Konrad Swierczek and Anna Niemczyk
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 Yu.A. Deeva, T.I. Chupakhina, N.V. Melnikova, A.A. Mirzorakhimov
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 Sarah Petit, Cyril Thomas, Yannick Millot, Jean‐Marc Krafft, Christel Laberty‐Robert, Guylène Costentin
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 Yudai Hisai, Kota Murakami, Yukiko Kamite, Quanbao Ma, Einar Vøllestad, Ryo Manabe, Taku Matsuda, Shuhei Ogo, Truls Norby and Yasushi Sekine
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 R. Ortega-Lugo, J.A. Fabián-Anguiano, O. Ovalle-Encinia, C. Gomez-Janez, B.H. Zeifert, J. Ortiz-Landeros
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 Wojciech Skubida, Kun Zheng, Konrad Swierczek, Mateusz Michna, Lukasz Kondracki
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 Alessandro Donazzi, Giulio Cordaro, Andrea Baricci, Zhao-Bin Ding, Matteo Maestri
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 Kaiqi Xu, Athanasios Chatzitakis, Sanne Risbakk, Mingyi Yang, Paul Hoff Backe, Mathieu Grandcolas, Magnar Bjøråsb, Truls Norby
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 Ming Li, Hongjun Niu, John Druce, Helena Téllez, Tatsumi Ishihara, John A. Kilner, Hripsime Gasparyan, Michael J. Pitcher, Wen Xu, J. Felix Shin, Luke M. Daniels, Leanne A. H. Jones, Vin R. Dhanak, Dingyue Hu, Marco Zanella, John B. Claridge, and Matth
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 Anton L. Buzlukov, Irina Yu. Arapova, Yana V. Baklanova, Nadezhda I. Medvedeva, Tatiana A. Denisova, Aleksandra A. Savina, Bogdan I. Lazoryak, Elena G. Khaikina and Michel Bardet
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 Claudia Goebel, Robert Berger, Carlos Bernuy-Lopez, Jörgen Westlinder, Jan-Erik Svensson, Jan Froitzheim
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 Anurak Prasatkhetragarn, Jaru Jutimoosik, Pongsakorn Jantaratana, Pinit Kidkhunthod, Rattikorn Yimnirun, James Ren
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 Priyadarshini Balasubramanian, Manjusha Battabyal, Dhruba Das, Arumugam Chandra Bose and Raghavan Gopalan
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 Katarzyna Walczak, Bartłomiej Gędziorowski, Andrzej Kulka, Wojciech Zając, Magdalena Ziąbka, Rafał Idczak, Vinh Hung Tran and Janina Molenda
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 M. I. Asghar, X.Yao, S. Jouttijärvi, E. Hochreiner, R. Virta, P. D. Lund
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 Anna Olszewska, Yang Zhang, Zhihong Du, Mateusz Marzec, Konrad Świerczek, Hailei Zhao, Bogdan Dabrowski
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 J. A. Fabián-Anguiano, C. G. Mendoza-Serrato, C. Gómez-Yáñez, B. Zeifert, Xiaoli Ma, J. Ortiz-Landeros
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 Zuoan Li, Jonathan M. Polfus, Wen Xing, Christelle Denonville, Marie-Laure Fontaine and Rune Bredesen
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 Sathya Prakash Singh, Nikola Kanas, Temesgen D.Desissa, Mats Johnsson, Mari-Ann Einarsrud, Truls Norby, Kjell Wiik
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 Albert Gili , Benjamin Bischo, Ulla Simon, Franziska Schmidt, Delf Kober, Oliver Görke, Maged F. Bekheet and Aleksander Gurlo
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 Laura Rioja-Monllor, Carlos Bernuy-Lopez, Marie-Laure Fontaine,Tor Grande and Mari-Ann Einarsrud
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 N. Srinivasan, G.V.M. Kiruthika
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 Andrea Turchi
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 G.M. Aparicio, R.A. Vargas, P.R. Bueno
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 Shunsuke Akasaka, Encho Boku, Yurina Amamoto, Hiroyuki Yuji, Isaku Kanno
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 M. M. Abdullaev, S.Ya. Istomin, A.V. Sobolev, I.A. Presnyakov, E.V. Antipov
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 Pravin Kumar, Paramananda Jena, P. K. Patro, R. K. Lenka, A. S. K. Sinha, Prabhakar Singh, Rajendra Kumar Singh
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 Ahmed Afif, Juliana Zaini, Seikh Mohammad Habibur Rahman, Sten Eriksson, Md Aminul Islam & Abul Kalam Azad
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 Buğra Kayaalp, Kurt Klauke, Mattia Biesuz, Alessandro Iannaci, Vincenzo M. Sglavo, Massimiliano D’Arienzo, Heshmat Noei, Siwon Lee, WooChul Jung, Simone Mascotto
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 Johannes Gutenberg
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 Einar Vøllestad, Ragnar Strandbakke, Mateusz Tarach, David Catalán-Martínez, Marie-Laure Fontaine, Dustin Beeaff, Daniel R. Clark, Jose M. Serra & Truls Norby
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 C. Salles, M.-C. Steil, J. Fouletier, M. Duttine, A. Wattiaux, D. Marinha
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 Eleonora Venezia, Massimo Viviani, Sabrina Presto, Vasant Kumar and Rumen I. Tomov
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 S. Battiston, F. Montagner, S. Fiameni, A. Famengo, S. Boldrini, A. Ferrario, C. Fanciulli, F. Agresti, M. Fabrizio
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 Nikolai G. Dorbakov, Vladimir V. Titkov, Sergey Y. Stefanovich, Oksana V. Baryshnikova, Vladimir A. Morozov, Alexei A. Belik, Bogdan I. Lazoryak
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 Anna V. Shlyakhtina, Nikolay V. Lyskov, Maxim Avdeev, Vladimir G. Goffman, Nikolay V. Gorshkov, Alexander V. Knotko, Igor V. Kolbanev, Olga K. Karyagina, Konstantin I. Maslakov, Lidia G. Shcherbakova, Ekaterina M. Sadovskaya, Vladislav A. Sadykov, Nikita
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 Laura Rioja-Monllor, Carlos Bernuy-Lopez, Marie-Laure Fontaine, Tor Grandea and Mari-Ann Einarsrud
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 J. A. Cebollero, M. A. Laguna-Bercero, R. Lahoz, J. Silva, R. Moreno, A. Larrea
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 Sebastian Steiner, In‐Tae Seo, Pengrong Ren, Ming Li, David J. Keeble, Till Frömling
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 Aritza Wain-Martin, Aroa Morán-Ruiz, Miguel Angel Laguna-Bercero, Roberto Campana, Aitor Larrañaga, Peter Raimond Slater, María Isabel Arriortua
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 Evgeniya S. Zhukovskaya, Dina V. Deyneko, Oksana V. Baryshnikova, Alexei A. Belik, Ivan I. Leonidov, Alexey V. Ishchenko, Sergey Y. Stefanovich, Vladimir A. Morozov, Bogdan I. Lazoryak
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 Rokas Sažinas,Martin F. Sunding, Annett Thøgersen, Isao Sakaguchi, Truls Norby, Tor Grande and Jonathan M. Polfus
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 C.E. Botez, I. Martinez, A. Price, H. Martinez, J.H. Leal
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 Keerthana Muthamilselvam, M Mayarani, G Mohan Muralikrishna, Manjusha Battabyal, and Raghavan Gopalan
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 Buğra Kayaalp, Siwon Lee, Kurt Klauke, Jongsu Seo, Luca Nodaric, Andreas Kornowski, WooChul Jung, Simone Mascotto
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 Anna Olszewska, Konrad Świerczek, Wojciech Skubida, Zhihong Du, Hailei Zhao, Bogdan Dabrowski
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 Francesco Chiabrera, Iñigo Garbayo, Dolors Pla, Mónica Burriel, Fabrice Wilhelm, Andrei Rogalev, Marc Núñez, Alex Morata, and Albert Tarancón
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 A.A. Solovyeva, A.M. Lebedynskiy, A.V. Shipilova, I.V. Ionov, E.A. Smolyanskiy, A.L. Lauk, G.E. Remnev
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 Francesco Chiabrera, Iñigo Garbayo, Lluis López‐Conesa, Gemma Martín, Alicia Ruiz‐Caridad, Michael Walls, Luisa Ruiz‐González, Apostolos Kordatos, Marc Núñez, Alex Morata, Sonia Estradé, Alexander Chroneos, Francesca Peiró, Albert Taranc
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 Wen Xing, Zuoan Li, Thijs Peters, Marie-Laure Fontaine, Michael McCann, Anna Evans, Truls Norby, Rune Bredesen
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 Mantas Sriubas, Kristina Bockute, Nursultan Kainbayev and Giedrius Laukaitis
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 Vasiliy N. Yudin, Evgeniya S. Zolotova, Sergey F. Solodovnikov, Zoya A. Solodovnikova, Iliya V. Korolkov, Sergey Yu. Stefanovich, Boris M. Kuchumov
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 Alex Morata, Mercè Pacios, Gerard Gadea, Cristina Flox, Doris Cadavid, Andreu Cabot & Albert Tarancón
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 Michael Bittner, Nikola Kanas, Richard Hinterdinga, Frank Steinbach, Jan Räthel, Matthias Schrade, Kjell Wiik, Mari-Ann Einarsrud, Armin Feldhoff
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 Michael Bittner, Nikola Kanas, Richard Hinterding, Frank Steinbach, Dennis Groeneveld, Piotr Wemhoff, Kjell Wiik, Mari-Ann Einarsrud, Armin Feldhoff
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 Liping Sun, Huan Li, Jiaqi Zhao, Guiling Wang, Lihua Huo, Hui Zhao
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 Adrián López-Vergara, José M. Porras-Vázquez*, Einar Vøllestad, Jesús Canales-Vazquez, Enrique R. Losilla, David Marrero-López
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 Ramya Hariharan, Prakash Gopalan
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 Dimitrios P. Grigoriou
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 Dimitrios P. Grigoriou
Source
Time of Publication: 2018
Remark Link

Dy doped SrTiO3: A promising anodic material in solid oxide fuel cells

ID=496
Authors Saurabh Singh, Prabhakar Singh, Massimo Viviani, Sabrina Presto
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 Kwati Leonard, Yuji Okuyama, Yasuhiro Takamura, Young-Sung Lee, Kuninori Miyazaki, Mariya E. Ivanova, Wilhelm A. Meulenberg and Hiroshige Matsumoto
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 Christos A. Tzitzeklis, Jyoti K. Gupta, Matthew S. Dyer, Troy D. Manning, Michael J. Pitcher, Hongjun J. Niu, Stanislav Savvin, Jonathan Alaria, George R. Darling, John B. Claridge, and Matthew J. Rosseinsky
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 Vikrant Trivedi, Manjusha Battabyal, Priyadarshini Balasubramanian, G. Mohan Muralikrishna, Pawan Kumar Jain and Raghavan Gopalan
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 Christos A. Tzitzeklis, Jyoti K. Gupta, Matthew S. Dyer, Troy D. Manning, Michael J. Pitcher, Hongjun J. Niu, Stanislav Savvin, Jonathan Alaria, George R. Darling, John B. Claridge, and Matthew J. Rosseinsky
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 Ashutosh Kumar, Karuna Kumari, B Jayachandran, D Sivaprahasam and Ajay D Thakur
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 Muhammad Imran Asghar, Sami Jouttijärvi, Riina Jokiranta, Anna-Maija Valtavirta, Peter D. Lund
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 Gunnar Svensson, Louise Samain, Jordi Jacas Biendicho, Abdelfattah Mahmoud, Raphaël P. Hermann, Sergey Ya. Istomin and Jekabs Grins
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 Nikola Kanas, Michael Bittner, Temesgen Debelo Desissa, Sathya Prakash Singh, Truls Norby, Armin Feldhoff, Tor Grande, Kjell Wiik, and Mari-Ann Einarsrud
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 David Young, Ariel Jackson, David Fork, Seid Sadat, Daniel Rettenwander, Jesse D. Benck, Yet - Ming Chiang
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 Ragnhild Hancke, Thorbjørn V. Larsen, Wen Xing, Zuoan Li, Marie-Laure Fontaine, Truls Norby
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 Min Chen, Yang Hu, Dongchu Chen, Huawen Hu, Qing Xu
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 Anna Niemczyk, Anna Olszewska, Zhihong Du, Zijia Zhang, Konrad Świerczeka, Hailei Zhao
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 Izabella Dascalu, Simona Somacescu, Cristian Hornoiu, Jose M. Calderon-Moreno, Nicolae Stanica, Hermine Stroescu, Mihai Anastasescu, Mariuca Gartner
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 Jia, Zhenyuan; Wang, Peida; Zhong, Yuhan; Mei, Huayue
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 Kapil Sood, Jyoti Kaswan, Surinder P. Singh, Truls Norby, Suddhasatwa Basu
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 Anna Olszewska, Zhihong Du, Konrad Świerczek, Hailei Zhao and Bogdan Dabrowski
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 M.I. Asghar, S. Jouttijärvi, P.D. Lund
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 Miguel Morales, Arianna Pesce, Aneta Slodczyk, Marc Torrell, Paolo Piccardo, Dario Montinaro, Albert Tarancón, and Alex Morata
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 Yi-Xin Liu , Sea-Fue Wang, Yung-Fu Hsu, Wan-Yun Yeh
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 Saim Saher, Jia Song, Vaibhav Vibhu, Clément Nicollet, Aurélien Flura, Jean-Marc Bassat and Henny J. M. Bouwmeester
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 Ashutosh Kumar, Karuna Kumari, B. Jayachandran, D. Sivaprahasam, Ajay D.Thakur
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 Dariusz Burnat, Gunnar Nurk, Lorenz Holzer, Michal Kopecki, Andre Heel
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 J. Keppner, J. Schubert, M. Ziegner, B. Mogwitz, J. Janek and C. Korte
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 Wojciech Skubida, Anna Niemczyk, Kun Zheng, Xin Liu and Konrad Świeczek
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 Izabella Dascalu, Cristian Hornoiu, Jose Maria Calderon-Moreno, Madalin Enache, Daniela Culita, Simona Somacescu
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 Fayaz Hussain, Iasmi Sterianou, Amir Khesro, Derek C. Sinclair, Ian M. Reaney
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 T.I. Chupakhina, N.V. Mel’nikova, E.A. Yakovleva, Yu. A. Nikitina
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 Temesgen D. Desissa, Reidar Haugsrud, Kjell Wiik, Truls Norby
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 A. Kotsirasa, I. Kalaitzidoua, D. Grigorioua, A. Symillidisa, M. Makria, A. Katsaounisa, C.G. Vayenas
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 Kacper Cichy, Wojciech Skubid, Konrad Świerczek
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 A.G. Goos, A.J. Encerrado Manriquez, H. Martinez, A.D. Price, C.E. Botez
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 Lokesh Bele, R.K. Lenka, P.K. Patro, L.M. uhmood, T. Mahata and P.K. Sinha
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 Claudia Goebel, Alexander G. Fefekos, Jan-Erik Svensson, Jan Froitzheim
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 Andrea Cavallaro, Stevin S. Pramana, Enrique Ruiz-Trejo, Peter C. Sherrell, Ecaterina Ware, John A. Kilner and Stephen J. Skinner
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 J.H.Leal, H.Martinez, I.Martinez, A.D.Price, A.G.Goos, C.E.Botez
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 Likun Zhang, Shuli Li, Tian Xia, Liping Sun, Lihua Huo, Hui Zhao
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 A.A .Solovyev, A.M. Lebedynskiy, A.V. Shipilova, I.V.Ionov, E.A. Smolyanskiy, A.L. Lauk, G.E. Remnev
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 Yi-Xin Liu, Sea-Fue Wang, Yung-Fu Hsu, Chi-Hua Wang
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 Sabrina Presto, Pravin Kumar, Salil Varma, Massimo Viviani, Prabhakar Singh
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 A.A. Solovyev, I.V. Ionov, A.V. Shipilova, P.D. Maloney
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 A. V. Shlyakhtina, K. S. Pigalskiy, D. A. Belov, N. V. Lyskov, E. P. Kharitonova, I. V. Kolbanev, A. B. Borunova, O. K. Karyagina, E. M. Sadovskaya, V. A. Sadykov and N. F. Eremeev
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 ABBAS ABDUL KADHIM KLAIF RIKABI, MARIANA BALABAN (CHELU), IULIA HARABOR, PAUL CONSTANTIN ALBU, MIRCEA SEGARCEANU, GHEORGHE NECHIFOR
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 PSf –magnetite membrane > PSf-PANI membrane. In the case of alcohols flow, hydrocarbon chain has influence on flows and this correlates with hydrophily of membranes. Following bovine serum albumin retention tests, PSf-PANI membrane has the best performance (R> 95%), which correlates with the higher permeate flows.
Remark Link

Structural and electrochemical characterization of BaCe0.7Zr0.2Y0.05Zn0.05O3 as an electrolyte for SOFC-H

ID=453
Authors Ahmed Afif, Nikdalila Radenahmad, Chee Ming Lim, Quintin Cheok, Md. Aminul Islam, Seikh Mohammad Habibur Rahman, Abul Kalam Azad
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 Polfus, J. M., Xing, W., Riktor, M., Sunding, M. F., Dahl, P. I., Hanetho, S. M., Mokkelbost, T., Larring, Y., Fontaine, M.-L. and Bredesen, R.
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 Atul P. Jamale, C. H. Bhosale, L. D. Jadhav
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 Raymond Gorte, John Vohs, Theis L. Skafte, Robert Kee, John Varcoe, Ian Metcalfe, Sune Dalgaard Ebbesen, Guntae Kim, Dehua Dong, San Ping Jiang, Ming Li, Tatsumi Ishihara, John Bøgild Hansen, Beatriz Molero-Sanchez, Steven McIntosh, Helena Téllez, Alex Mo
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 Matthias Schrade, Anna Magrasó, Augustinas Galeckas, Terje J. Finstad, and Truls Norby
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 Jan Gustav Grolig, Patrik Alnegren, Jan Froitzheim, Jan-Erik Svensson
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 Aleksandra A. Savina, Sergey F. Solodovnikov, Dmitry A. Belov, Zoya A. Solodovnikova, Sergey Yu. Stefanovich, Bogdan I. Lazoryak and Elena G. Khaikina
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 Benjamin Geppert, Artur Brittner, Lailah Helmich, Michael Bittner, Armin Feldhoff
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 V. Nalini, T.Norby, A.M. Anuradha
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 Francis G. Kinyanjui, Stefan T. Norberg, Christopher S. Knee, Istaq Ahmed, Stephen Hull, Lucienne Buannic, Ivan Hung, Zhehong Gan, Fr ́ed ́eric Blanc, Clare P. Grey and Sten G. Eriksson
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 Natalia Maria Mazur
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 Brage Braathen Kjeldby
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 Nitish Kumar, Eric A. Patterson, Till Frömling and David P. Cann
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 R. Manabe, S. Okada, R. Inagaki, K. Oshima, S. Ogo & Y. Sekine
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 Adrian Lervik
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 I.Kalaitzidou, M. Makri, D. Theleritis, A. Katsaounis, C.G. Vayenas
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 Nitish Kumar, Eric A. Patterson, Till Frömling, Edward P. Gorzkowski, Peter Eschbach, Ian Love, Michael P. Müller, Roger A. De Souza, Julie Tucker, Steven R. Reese and David P. Cann
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 Alessandro Longo, Leonarda F. Liotta, Dipanjan Banerjee, Valeria La Parola, Fabrizio Puleo, Chiara Cavallari, Christoph J. Sahle, Marco Moretti Sala, and Antonino Martorana
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 Heber Jair Martinez Salinas
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 A. Magrasó, B. Ballesteros, R. Rodríguez-Lamas, M.F. Sunding, J. Santiso
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 Ashutosh Kumar, D. Sivaprahsam, Ajay D. Thakur
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 F.J. Garcia-Garciaa, F. Yubero, A.R. González-Elipe, R.M. Lambert
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 V E Zaikova, N V Melnikova, A V Tebenkov , A A Mirzorakhimov, O P Shchetnikov, A N Babush kin and G V Sukhanova
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 Wen Xing, Marie-Laure Fontaine, Zuoan Li, Jonathan M. Polfus, Yngve Larring, Christelle Denonville, Emmanuel Nonnet, Adam Stevenson, Partow P. Henriksen, Rune Bredesen
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 S.Masciandaro, M. Torrell, P. Leone, A. Tarancón
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 Yi-XinLiu, Sea-Fue Wang,Yung-Fu Hsu, Hung-Wei Kai, Piotr Jasinski
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 Nikola Kanasac Sathy, Prakash Singh, Magnus Rotan, Mohsin Saleemi, Michael Bittner, Armin Feldhoff, Truls Norby, Kjell Wiika, Tor Grande, Mari-Ann Einarsrud
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 Monica Lin, Ashgar Imran, and Peter Lund
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 S.Ya.Istomin, A.V.Morozov, M.M.Abdullayev, M.BatukbJ.Hadermann, S.M.Kazakov, A.V.Sobolev, I.A.Presniakov, E.V.Antipov
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 Aleksandra A. Savina, Vladimir A. Morozov, Anton L. Buzlukov, Irina Yu. Arapova, Sergey Yu. Stefanovich, Yana V. Baklanova, Tatiana A. Denisova, Nadezhda I. Medvedeva, Michel Bardet, Joke Hadermann, Bogdan I. Lazoryak, and
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 AA Elstad
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  10􀀀2 S cm􀀀1 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  10􀀀2 S cm􀀀1 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  10􀀀6 S cm􀀀1 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  10􀀀6 S cm􀀀1 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  10􀀀3 S cm􀀀1 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  10􀀀8 S cm􀀀1 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  10􀀀8 S cm􀀀1 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 Matthias Schrade, Nahum Masó, Antonio Perejón, Luis A. Pérez-Maqueda and Anthony R. West
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 S.Wachowski, M.Polfus, T.Norby
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 Ashutosh Kumar, D. Sivaprahsam, Ajay D. Thakur
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 Jyothi Sharma, R. D. Purohit, Deep Prakash, and P. K. Sinha
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 Priyadarshini Balasubramanian, Manjusha Battabyal, Duraiswamy Sivaprahasam and Raghavan Gopalan
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 M Battabyal, B Priyadarshini, D Sivaprahasam, N S Karthiselva, R Gopalan
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 Subramaniam Harisha, Duraisamy Sivaprahasam, Manjusha Battabyal, Raghavan Gopalan
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 Anastasia Iakovleva
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 Muhammad Imran Asghar, Mikko Heikkilä, Peter D.Lund
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 Julia Wind, Paula Kayser, Zhaoming Zhang, Ivana Radosavljevic Evansc, Chris D.Ling
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 F.J.Garcia-Garcia, A.M. Beltrán, F. Yubero, A.R. González-Elipe, R.M. Lambert
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 Einar Vøllestad, Matthias Schrade, Julie Segalini, Ragnar Strandbakke, and Truls Norby
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 I.V. Ionov, A.A. Solov’ev, A.M. Lebedinskii, A.V. Shipilova, E.A. Smolyanskii, A N. Koval’chuk, A.L. Lauk
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 J.A.Cebollero, R.Lahoz, M.A.Laguna-Bercero, A.Larrea
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 Fan Yang, Patrick Wu and Derek C. Sinclair
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 Ieeba Khan, Muhammad Imran Asghar, Peter D.Lund, Suddhasatwa Basu
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 Linhao Li, Ming Li, Ian M. Reaney and Derek C. Sinclair
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 Chang-Sing Hwang, Te-Jung Hwang, Chun-Huang Tsai, Chun-Liang Chang, Sheng-Fu Yang, Ming-Hsiu Wu, Cheng-Yun Fu
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 Ming Wei Liao, Tai Nan Lin, Wei Xin Kao, Chun Yen Yeh, Yu Ming Chen, Hong Yi Kuo
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 Hannes Falk-Windisch, Julien Claquesin, Jan-Erik Svensson, Jan Froitzheim
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 Michael Bittner, Lailah Helmich, Frederik Nietschke, Benjamin Geppert, Oliver Oeckler, Armin Feldhoff
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 Tz. Kraia, S. Wachowski, E. Vøllestad, R. Strandbakke, M. Konsolakis, T. Norby, G.E. Marnellos
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 G. Cerretti, M. Schrade, X. Song, B. Balke, H. Lu, T. Weidner, I. Lieberwirth, M. Panthöfer, T. Norby and W. Tremel
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 Shalima Shawuti, Musa Mutlu Can, Mehmet Ali Gülgün, Satoru Kaneko, Endo Tamio
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 M. Stange, E. Stefan, C. Denonville, Y. Larring, P.M. Rørvik, R. Haugsrud
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 Kavita Parmar, Santanu Bhattacharjee
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 Yong Cao, Bo Chi, Jian Pu, Li Jian
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 A. A. Solovyev, I. V. Ionov, A. V. Shipilova, A. N. Kovalchuk, M. S. Syrtanov
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 Bogdan I. Lazoryak, Sergey M. Aksenov, Sergey Yu. Stefanovich, Nikolai G. Dorbakov, Dmitriy A. Belov, Oksana V. Baryshnikova, Vladimir A. Morozov, Mikhail S. Manylov and Zhoubin Lin
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 J. Molenda, J. Kupecki, R. Baron, M. Blesznowski, G. Brus, T. Brylewski, M. Bucko, J. Chmielowiec, K. Cwieka, M. Gazda, A. Gil, P. Jasinski, Z. Jaworski, J. Karczewski, M. Kawalec, R. Kluczowski, M. Krauz, F. Krok, B. Lukasik, M. Malys, A. Mazur, A. Miele
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 R. Manabe, S. Okada, R. Inagaki, K. Oshima, S. Ogo & Y. Sekine
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 A.V. Shlyakhtina, S.N. Savvin, N.V. Lyskov, D.A. Belov, A.N. Shchegolikhin, I.V. Kolbanev, O.K. Karyagina, S.A. Chernyak, L.G. Shcherbakova, P. Núñez
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 Vegar Øygarden, Tor Grande
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 Hannes Falk-Windisch, , Julien Claquesin, Mohammad Sattari, Jan-Erik Svensson, Jan Froitzheim
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 J.A. Cebollero, R. Lahoz, M.A. Laguna-Bercero, J.I. Peña, A. Larrea, V.M. Orera
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 N.G. Dorbakov, O.V. Baryshnikova, V.A. Morozov, A.A. Belik, Y. Katsuya, M. Tanaka, S.Yu. Stefanovich, B.I. Lazoryak
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 Darius Virbukas, Giedrius Laukaitis
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 Sandra H. Skjærvø, Espen T. Wefring, Silje K. Nesdal, Nikolai H. Gaukås, Gerhard H. Olsen, Julia Glaum, Thomas Tybell & Sverre M. Selbach
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 Marius Zienius, Kristina Bockute, Darius Virbukas, Giedrius Laukaitis
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 A. Donazzi, M. Maestri, G. Groppi
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 M. Guin, S. Indris, M. Kaus, H. Ehrenberg, F. Tietz, O. Guillon
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 Svetlana V. Fokina, Eugene N. Borisov, Vladimir V. Tomaev, Ilya I. Tumkin, Yuri S. Tveryanovich
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 Connor S. McCue
Source
Time of Publication: 2016
Remark THESIS
Link

Magnetron-Sputtered YSZ and CGO Electrolytes for SOFC

ID=378
Authors A.A. Solovyev, A.V. Shipilova, I.V. Ionov, A.N. Kovalchuk, S.V. Rabotkin, and V.O. Oskirko
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 C.F. Rusti, V. Badilita, A.M. Sofronia, D. Taloi, E.M. Anghel, F. Maxim, C. Hornoiu, C. Munteanu, R.M. Piticescu, S. Tanasescu
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 Solid State Ionics
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 N. I. Kadyrova, N. V. Mel’nikova, I. S. Ustinova, Yu. G. Zainulin
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 R.K. Lenka, P.K. Patro, Jyothi Sharma, T. Mahata, P.K. Sinha
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 Shalima Shawuti, , Mehmet Ali Gülgün
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 F. Chiabrera, A. Morata, M. Pacios, A. Tarancón
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 A. Yu. Chufarov, N. V. Melnikova, N. V. Zarubina, A. N. Ermakov, E. G. Vovkotrub, L. N. Maskaeva, V. F. Markov, Yu. G. Zainulin
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 A. A. Solov’ev, A. V. Shipilova, A. N. Koval’chuk, I. V. Ionov, S. V. Rabotkin
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 Yury S. Tveryanovich, Andrei V. Bandura, Svetlana V. Fokina, Evgeny N. Borisov, Robert A. Evarestov
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 Paul Chesler, Cristian Hornoiu, Susana Mihaiu, Cornel Munteanu, Mariuca Gartner
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 N. I. Kadyrova, Yu. G. Zaynulin, A. P. Tyutyunnik, N. V. Melnikova, A. A. Mirzorakhimov
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 Nitish Kumar, David P. Cann
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 A. Caldarelli, E. Mercadelli, S. Presto, M. Viviani, A. Sanson
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 I. Dascalu, D. Culita, J.M. Calderon-Moreno, P. Osiceanu, C. Hornoiu, M. Anastasescu, S. Somacescu, M. Gartner
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
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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 M. Guin, F. Tietz, O. Guillon
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 Cao, Y., Duan, N., Jian, L., Evans, A. and Haugsrud, R.
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 F.J. Garcia-Garcia, F. Yubero, J.P. Espinós, A.R. González-Elipe, R.M. Lambert
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 Yang Hu, Amund Ruud, Ville Miikkulainen, Truls Norby, Ola Nilsen and Helmer Fjellvåg
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 Shunsuke Akasaka
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 Kumar, N., Patterson, E. A., Frömling, T. and Cann, D. P.
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 Kaihua Yia,Liping Sun, Qiang Li, Tian Xia, Lihua Huo, Hui Zhao, Jingwei Li, Zhe Lü, Jean-Marc Bassat, Aline Rougier, Sébastien Fourcade, Jean-Claude Grenier
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 Linhao Li, Ming Li, Huairuo Zhang, Ian M. Reaney and Derek C. Sinclair
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 Antônio de Pádua Lima Fernandes, Eric Marsalha Garcia, Rubens Moreira de Almeida, Hosane Aparecida Taroco, Edyth Priscilla Campos Silva, Rosana Zacarias Domingues, Tulio Matencio
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 D. Ciria, M. Ben Hassine, M. Jiménez-Melendo, A. Iakovleva, P. Haghi-Ashtiani, V. Aubin, G. Dezanneau
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 Ting Zhao, Li-Ping Sun, Qiang Li, Li-Hua Huo, Hui Zhao, Jean-Marc Bassat, Aline Rougier, Sébastien Fourcade and Jean-Claude Grenier
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 S.H.Morejudo, R.Zanon, S.escolastico, I. Yuste-Tirados, H. Malerød-Fjeld, P.K. Vestre, W.G.Coors, A.Martinez, T.Norby, J.M.Serra, C.Kjølseth
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 A. A. Solovyev , A. V. Shipilova, I. V. Ionov, A. N. Kovalchuk, S. V. Rabotkin, V. O. Oskirko
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 Sea-Fue Wang, Yung-Fu Hsu, Jing-Han Chang, Soofin Cheng, Hsi-Chuan Lu
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 Laura Almar, Alex Morata, Marc Torrell, Mingyang Gong, Meilin Liu, Teresa Andreu and Albert Tarancón
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 E.P. Kharitonova, V.I. Voronkova, D.A. Belov, E.I. Orlova
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 Ahmed Afif, Nikdalila Radenahmad, Chee Ming Lim, Mohamad Iskandar Petra, Md. Aminul Islam, Seikh Mohammad Habibur Rahman, Sten Eriksson, Abul Kalam Azad
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 V.I. Voronkova, E.P. Kharitonova, E.I. Orlova, A.V. Levchenko, A.M. Antipin, N.I. Sorokina, D.A. Belov
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 Francis Gachau Kinyanjui, Stefan Tommy Norberg, Christopher Knee, Istaq Ahmed, Stephen Hull, Lucienne Buannic, Ivan Hung, Zhehong Gan, Frédéric Blanc, Clare P. Grey and Sten Eriksson
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 Maxime Rioux, Yannick Ledemi, Jeff Viens, Steeve Morency, Seyed Alireza Ghaffari and Younès Messaddeq
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 Valentina Voronkova, Ekaterina Orlova, Sergey Kazakov, Elena Kharitonova and Dmitry Belov
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
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Phase stability and thermoelectric properties of Cu10.5Zn1.5Sb4S13 tetrahedrite

ID=342
Authors Subramaniam Harish, Duraisamy Sivaprahasama, Manjusha Battabyal, Raghavan Gopalan
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 Galina D. Tsyrenova, Erzhena Т. Pavlova, Sergey F. Solodovnikov, Nadezhda N. Popova, Tatyana Yu. Kardash, Sergey Yu. Stefanovich, Irina А. Gudkova, Zoya A. Solodovnikova, Bogdan I. Lazoryak
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
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New methods for the preparation and dielectric properties of Lа2 − xSrxNiO4 (х = 1/8) ceramic

ID=340
Authors T.I. Chupakhina, N.I. Kadyrova, N.V. Melnikova, O.I. Gyrdasova, E.A. Yakovleva, Yu.G. Zainulin
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
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Chemical stability and H2 flux degradation of cercer membranes based on lanthanum tungstate and lanthanum chromite

ID=339
Authors Jonathan M. Polfus, , Zuoan Li, Wen Xing, Martin F. Sunding, John C. Walmsley, Marie-Laure Fontaine, Partow P. Henriksen, Rune Bredesen
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
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Nb-doped TiO2 sol–gel films for CO sensing applications

ID=338
Authors M. Duta, L. Predoana, J.M. Calderon-Moreno, S. Preda, M. Anastasescu, A. Marin, I. Dascalu, P. Chesler, C. Hornoiu, M. Zaharescu, P. Osiceanu, M. Gartner
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 Cédric Périllat-Merceroz, Pascal Roussel, Edouard Capoen, Sébastien Rosini, Patrick Gélin, Rose-Noëlle Vannier, Gilles Gauthier
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
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Molybdenum doped Pr0.5Ba0.5MnO3−δ (Mo-PBMO) double perovskite as a potential solid oxide fuel cell anode material

ID=336
Authors Yi-Fei Sun, Ya-Qian Zhang, Bin Hua, Yashar Behnamian, Jian Li, Shao-Hua Cui, Jian-Hui Lid, Jing-Li Luo
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 P.S. Somayajulu, P.S. Ghosh, J. Banerjee, K.L.N.C. Babu, K.M. Danny, B.P. Mandal, T. Mahata, P. Sengupta, S.K. Sali, A. Arya
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
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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 Jan Gustav Grolig, Jan Froitzheim, Jan-Erik Svensson
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 Savitha Thayumanasundaram, Vijay Shankar Rangasamy, Jin Won Seo andJean-Pierre Locquet
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 Elena Rebollo, Cecilia Mortalò, Sonia Escolástico, Stefano Boldrini, Simona Barison, José M. Serra and Monica Fabrizio
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 M Battabyal, B Priyadarshini, D Sivaprahasam, N S Karthiselva and R Gopalan
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 Jonathan M. Polfus, Wen Xing, Goran Pećanac, Anita Fossdal, Sidsel M. Hanetho, Yngve Larring, Jürgen Malzbender, Marie-Laure Fontaine, Rune Bredesen
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 I. Kalaitzidou, M. Makri, D. Theleritis, A. Katsaounis, C.G. Vayenas
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 I. Kalaitzidou, A. Katsaounis, T. Norby, C.G. Vayenas
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 S. Balomenou, K. M. Papazisi, D. Tsiplakides
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 Ioanna Petrakopoulou, Dimitrios Tsiplakides, Stella Balomenou
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 N. Bogolowski, B. Iwanschitz and J.-F. Drillet
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 Sasiporn Prasertpalichat, David P. Cann
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 Jan Gustav Grolig, , Patrik Alnegren, Jan Froitzheim, Jan-Erik Svensson
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
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Atomic structure and ionic conductivity of glassy materials based on silver sulfide

ID=321
Authors N. V. Melnikova, K. V. Kurochka, O. L. Kheifets, N. I. Kadyrova, Ya. Yu. Volkova
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 Tor Svendsen Bjørheim, Vijay Shanmugappirabu, Reidar Haugsrud, Truls E. Norby
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
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Tetragonal tungsten bronzes Nb8−xW9+xO47−δ: optimization strategies and transport properties of a new n-type thermoelectric oxide

ID=319
Authors Christophe P. Heinrich, Matthias Schrade, Giacomo Cerretti, Ingo Lieberwirth, Patrick Leidich, Andreas Schmitz, Harald Fjeld, Eckhard Mueller, Terje G. Finstad, Truls Norby and Wolfgang Tremel
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 Zhan Shi, Tian Xia, Fuchang Meng, Jingping Wang, Shengming Wu, Jie Lian, Hui Zhao, Chunbo Xu
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
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Multilayer ceramic capacitors based on relaxor BaTiO3-Bi(Zn1/2Ti1/2)O3 for temperature stable and high energy density capacitor applications

ID=317
Authors Nitish Kumar, Aleksey Ionin, Troy Ansell, Seongtae Kwon, Wesley Hackenberger and David Cann
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
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Electrical conductivity of Zn-doped high temperature proton conductor LaNbO4

ID=316
Authors Yong Cao, Yuan Tan, Dong Yan, , Bo Chi, Jian Pu, Li Jian
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
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Gd- and Pr-based double perovskite cobaltites as oxygen electrodes for proton ceramic fuel cells and electrolyser cells

ID=315
Authors Ragnar Strandbakke, Vladimir A. Cherepanov, Andrey Yu. Zuev, Dmitry S. Tsvetkov, Christos Argirusis, Georgia Sourkouni, Stephan Prünte, Truls Norby
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
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Praseodymium-deficiency Pr0.94BaCo2O6-δ double perovskite: A promising high performance cathode material for intermediate-temperature solid oxide fuel cells

ID=313
Authors Fuchang Meng, Tian Xia, Jingping Wang, Zhan Shi, Hui Zhao
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
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Reduced long term electrical resistance in Ce/Co-coated ferritic stainless steel for solid oxide fuel cell metallic interconnects

ID=312
Authors Anna Magrasóa, Hannes Falk-Windisch, Jan Froitzheim, Jan-Erik Svensson, Reidar Haugsrud
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
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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 Nitish Kumar* andDavid P. Cann
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
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Triode operation for enhancing the performance of H2S-poisoned SOFCs operated under CH4–H2O mixtures

ID=310
Authors Foteini M. Sapountzi, Michail N. Tsampas, Chunhua Zhao, Antoinette Boreave, Laurence Retailleau, Dario Montinaro, Philippe Vernoux
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
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High-temperature anion and proton conduction in RE3NbO7 (RE = La, Gd, Y, Yb, Lu) compounds

ID=309
Authors A. Chesnauda, M.-D. Braidab, S. Estradéd, F. Peiród, A. Tarancónf, A. Morataf, G. Dezanneau
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
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Proton transport properties of the RE3Ga5MO14 (RE = La, Nd and M = Si, Ti, Sn) langasite family of oxides

ID=308
Authors Tor S. Bjørheim, Reidar Haugsrud
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
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Diffusion of Nd and Mo in lanthanum tungsten oxide

ID=307
Authors Einar Vøllestad, Markus Teusner, Roger A. De Souza, Reidar Haugsrud
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
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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 Louise Samain, Philipp Amshoff, Jordi J. Biendicho, Frank Tietz, Abdelfattah Mahmoud, Raphaël P. Hermann, Sergey Ya. Istomin, Jekabs Grins, Gunnar Svensson
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
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Atmosphere dependence of anode reaction of intermediate temperature steam electrolysis using perovskite type proton conductor

ID=305
Authors Takaaki Sakai, Keita Arakawa, Masako Ogushi, Tatsumi Ishihara, Hiroshige Matsumoto, Yuji Okuyama
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 Marc Torrell, Sergio García-Rodríguez, Alex Morata, Germán Penelas and Alberto Tarancon
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
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Doping strategies for increased oxygen permeability of CaTiO3 based membranes

ID=303
Authors Jonathan M. Polfus, Wen Xing, Martin F. Sunding, Sidsel M. Hanetho, Paul Inge Dahl, Yngve Larring, Marie-Laure Fontaine, Rune Bredesen
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
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Coated stainless steel 441 as interconnect material for solid oxide fuel cells: Evolution of electrical properties

ID=302
Authors Jan Gustav Grolig , Jan Froitzheim, Jan-Erik Svensson
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
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Steam-promoted CO2 flux in dual-phase CO2 separation membranes

ID=301
Authors Wen Xing, Thijs Peters, Marie-Laure Fontaine, Anna Evans, Partow Pakdel Henriksen, Truls Norby, Rune Bredesen
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
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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 E. T. Wefring, M.-A. Einarsrud and T. Grande
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
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Structure and conductivity of acceptor doped La2BaZnO5 and Nd2BaZnO5

ID=299
Authors Md. Khairul Hoque, Reidar Haugsrud, Christopher S. Knee
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