Published references
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These publications have a reference to ProboStat™ or other NORECS products
All 1-25 26-50 51-75 76-100 101-125 126-150 151-175 176-200 201-225 226-250 251-275 276-300 301-325 326-350 351-375 376-400 401-425 426-450 451-475 476-500 501-525 526-550 551-575 576-600 601-625 626-650 651-675 676-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 |
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J. Phys.: Energy
Volume: 2
Time of Publication: 2019
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| 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 |
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Solid State Sciences
Volume: 96
Time of Publication: 2019
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| 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 |
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Time of Publication: 2019
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| Remark |
Tesi di Laurea Magistrale Link |
Protonic conductivity and thermal properties of cross-linked PVA/TiO2 nanocomposite polymer membranes
ID=536| Authors |
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Journal of Non-Crystalline Solids
Volume: 522
Time of Publication: 2019
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| 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 |
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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 |
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Russian Journal of Inorganic Chemistry
Volume: 64,
Issue: 6,
Pages: 696–704 Time of Publication: 2019 |
| Abstract | Complex oxides Sr2 − xLaxFeCo0.5Mo0.5O6 − δ, (x = 0.2, 0.4; δ ≈ 0.03–0.15) have been first synthesized by the sol-gel method. Their crystal structures have been refined by the Rietveld method; the refinement showed that the complex oxides have the structure of cubic double perovskite (a ≈ 2aper, space group Fm3̄m) with partial ordering of Fe(Co) and Mo in the B positions. Based on the 57Fe Mössbauer measurements, the average formal oxidation state of iron has been found to decrease from +3.20 (x = 0.0) to +3.04 (x = 0.4). Our study of the behavior of perovskites in a reducing Ar/H2 atmosphere (8%) revealed a decrease in the reduction resistance with decreasing La content (x = 0.4 → 0). The combination of the properties studied, namely chemical stability with respect to the reaction with Ce1 − xGdxO2 − x/2 and Zr1 − xYxO2 − x/2, high-temperature thermal expansion, and electrical conductivity in air and Ar/H2, shows that Sr1.6La0.4Fe-Co0.5Mo0.5O6 − δ (δ ≈ 0.03) perovskite is more attractive as an electrode material for medium-temperature symmetric solid oxide fuel cells than Sr2FeCo0.5Mo0.5O6 − δ. |
| Remark | Link |
Influence of Lanthanum Doping on Structural and Electrical/Electrochemical Properties of Double Perovskite Sr2CoMoO6 as Anode Materials for Intermediate-Temperature Solid Oxide Fuel Cells
ID=532| Authors |
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ACS Appl. Mater. Interfaces
Volume: 11,
Issue: 27,
Pages: 24659-24667 Time of Publication: 2019 |
| Abstract | Lanthanum (La3+)-doped double perovskites Sr2CoMoO6 (Sr2–xLaxCoMoO6, 0.00 ≤ x ≤ 0.03) were synthesized via the citrate–nitrate autocombustion route. The Reitveld refinement analysis of X-ray diffraction reveals the tetragonal symmetry as the main phase with space group I4/m and also confirms the presence of some peaks corresponding to extra phase SrMoO4. The SEM micrograph images reflect that grains are in irregular shape and sizes for all samples. Average grain size gradually decreases with the increase of the SrMoO4 phase. The X-ray photoelectron spectroscopy (XPS) analysis confirms the presence of mixed valence states of Mo5+/Mo6+, Co2+/Co3+, and O-lattice/O-chemisorbed/O-physisorbed species. Coefficient of thermal expansion (CTE) analysis shows that the particular composition Sr1.97La0.03CoMoO6 has the lowest CTE value among the compositions studied. The electrical conductivity of Sr2CoMoO6 is enhanced effectively by doping La at Sr sites. The measured area-specific resistance (ASR) for the composition Sr1.97La0.03CoMoO6 (SLCM03) is found to be appreciably low, ∼0.053 Ohm cm–2 at 800 °C. The obtained highest electrical conductivity with the lowest activation energy and low ASR value for the composition Sr1.97La0.03CoMoO6 encompasses it as a promising candidate for anode material in the intermediate-temperature solid oxide fuel cell (IT-SOFC) application. |
| Remark | Link |
Scheelite type Sr1−xBaxWO4 (x = 0.1, 0.2, 0.3) for possible application in Solid Oxide Fuel Cell electrolytes
ID=531| Authors |
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Scientific Reports
Volume: 9
Time of Publication: 2019
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| Abstract | Polycrystalline scheelite type Sr1−xBaxWO4 (x = 0.1, 0.2 & 0.3) materials were synthesized by the solid state sintering method and studied with respect to phase stability and ionic conductivity under condition of technological relevance for SOFC applications. All compounds crystallized in the single phase of tetragonal scheelite structure with the space group of I41/a. Room temperature X-ray diffraction and subsequent Rietveld analysis confirms its symmetry, space group and structural parameters. SEM illustrates the highly dense compounds. Significant mass change was observed to prove the proton uptake at higher temperature by TG-DSC. All compound shows lower conductivity compared to the traditional BCZY perovskite structured materials. SBW with x = 0.3 exhibit the highest ionic conductivity among all compounds under wet argon condition which is 1.9 × 10−6 S cm−1 at 1000 °C. Since this scheelite type compounds show significant conductivity, the new series of SBW could serve in IT-SOFC as proton conducting electrolyte. |
| Remark |
Article number: 9173 (2019) Link |
Surface Reconstruction under the Exposure of Electric Fields Enhances the Reactivity of Donor-Doped SrTiO3
ID=530| Authors |
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J. Phys. Chem. C
Volume: 123,
Issue: 27,
Pages: 16883-16892 Time of Publication: 2019 |
| Abstract | In the present work, we show how exposure to electric fields during a high-temperature treatment can be used to manipulate surface properties of donor-doped ceramics and thus improve their reactivity. La0.1Sr0.9TiO3 (LSTO) nanoparticles, prepared by hydrothermal synthesis, were consolidated under air with and without external electric fields. Although neither approaches caused grain growth upon consolidation, the treatment under the influence of the electric field (i.e., flash sintering) remarkably enhanced the segregation of Sr on the material’s surface. In addition, a high concentration of O– defects both in bulk as well as on the material surface was demonstrated by spectroscopic methods. This enhanced defect concentration along with the nanoscopic grain size of the field-consolidated materials is probably one of the triggering factors of their improved charge carrier mobility, as observed by impedance spectroscopy. The effect of such a perturbed defect structure on the reactivity of the materials was evaluated by the total oxidation of methane. For materials treated under the influence of electric fields, the catalytic reaction rate improved by a factor of 3 with respect to that of conventionally treated LSTO, along with a remarkable decrease of the activation energy. Thus, electric-field-assisted processes, usually known for their energy-saving character, can also be deemed as an attractive, forward-looking strategy for improving functional properties of ceramics. |
| Remark | Link |
Metal oxides for thermoelectrics
ID=529| Author |
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Time of Publication: 2019
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| Remark |
Dissertation Link |
Mixed proton and electron conducting double perovskite anodes for stable and efficient tubular proton ceramic electrolysers
ID=528| Authors |
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Nature Materials
Volume: 18,
Pages: 752–759 Time of Publication: 2019 |
| Abstract | Hydrogen production from water electrolysis is a key enabling energy storage technology for the large-scale deployment of intermittent renewable energy sources. Proton ceramic electrolysers (PCEs) can produce dry pressurized hydrogen directly from steam, avoiding major parts of cost-driving downstream separation and compression. However, the development of PCEs has suffered from limited electrical efficiency due to electronic leakage and poor electrode kinetics. Here, we present the first fully operational BaZrO3-based tubular PCE, with 10 cm2 active area and a hydrogen production rate above 15 Nml min−1. The novel steam anode Ba1−xGd0.8La0.2+xCo2O6−δ exhibits mixed p-type electronic and protonic conduction and low activation energy for water splitting, enabling total polarization resistances below 1 Ω cm2 at 600 °C and Faradaic efficiencies close to 100% at high steam pressures. These tubular PCEs are mechanically robust, tolerate high pressures, allow improved process integration and offer scale-up modularity. |
| Remark | Link |
Long-term stability of iron-doped calcium titanate CaTi0.9Fe0.1O3−δ oxygen transport membranes under non-reactive and reactive atmospheres
ID=527| Authors |
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Journal of Membrane Science
Volume: 583,
Pages: 171-179 Time of Publication: 2019 |
| Abstract | Oxygen transport membranes (OTM) are widely considered as a possible solution to limit the carbon footprint, but are notoriously afflicted by performance issues due to chemical instability observed during long-term operation. This paper reports on the stability of an OTM made of CaTi0.9Fe0.1O3−δ (CTF), and addresses its applicability. The redox stability of CTF was investigated using thermal gravimetry up to 1000 °C under air and H2, coupled with XRD and Mössbauer analyses. The redox potential of iron was measured using an electrochemical potential relaxation as a function of temperature. The baseline oxygen semi-permeability flux of dense CTF membranes was measured in inert atmospheres (air/argon or air/helium), and the long-term stability established for up to 1600 h under simulated operation atmospheres containing CO, CO2, H2 and CH4. CTF shows a remarkable performance stability and post mortem XRD, SEM-EDS and Raman analyses show no evidence of decomposition or reaction byproducts. |
| Remark |
https://doi.org/10.1016/j.memsci.2019.04.049 Link |
Inkjet Printing Functionalization of SOFC LSCF Cathodes
ID=526| Authors |
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Nanomaterials
Time of Publication: 2019
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| Abstract | An important segment of the future renewable energy economy is the implementation of novel energy generation systems. Such electrochemical systems are solid oxide fuel cells, which have the advantage of direct conversion of the chemical energy stored in the fuel to electrical energy with high effciency. Improving the performance and lowering the cost of solid oxide fuel cells (SOFCs) are strongly dependent on finding commercially viable methods for nano-functionalization of their electrodes via infiltration. Inkjet printing technology was proven to be a feasible method providing scalability and high-resolution ink delivery. LaxSr1-xCoyFe1-yO3 cathodes were modified using inkjet printing for infiltration with two different materials: Gd-doped ceria (CGO) commonly used as ion-conductor and La0.6Sr0.4CoO3 (LCO) commonly used as a mixed ionic electronic conductor. As-modified surface structures promoted the extension of the three-phase boundary (TPB) and enhanced the mechanisms of the oxygen reduction reaction. Electrochemical impedance measurements revealed significantly lowered polarization resistances (between 2.7 and 3.7 times) and maximum power output enhancement of 24% for CGO infiltrated electrodes and 40% for LCO infiltrated electrodes. |
| Remark | Link |
AlTiN based thin films for degradation protection of tetrahedrite thermoelectric material
ID=525| Authors |
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Journal of Alloys and Compounds
Volume: 792,
Pages: 953-959 Time of Publication: 2019 |
| Abstract | Efficient protection against degradation process of tetrahedrite-based thermoelectric materials was obtained employing AlTiN based thin films. The coatings were deposited via reactive direct current physical vapour deposition magnetron sputtering. The composition, thermal and electrical behaviour of thin films were investigated by X-ray diffraction, energy dispersive spectroscopy associated to field emission scanning electron microscopy, thermogravimetric analyses and electrical conductivity measurements. The barrier features for oxygen protection during thermal treatment in air at 500 °C were qualitatively evaluated, studying the coating behaviour over the higher operating temperature of tetrahedrite based thermoelectric devices. |
| Remark |
https://doi.org/10.1016/j.jallcom.2019.04.116 Link |
Barium-induced effects on structure and properties of β-Ca3(PO4)2-type Ca9Bi(VO4)7
ID=524| Authors |
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Journal of Alloys and Compounds Volume: 793, Pages: 56-64 Time of Publication: 2019 |
| Abstract | Ca9–xBaxBi(VO4)7 (0 ≤ x ≤ 1.5) solid solutions with the β-Ca3(PO4)2-type structure were prepared by a solid-state method. Powder X-ray diffraction study of 0 ≤ x ≤ 0.7 showed that Bi3+ and Ba2+ cations were completely incorporated into the β-TCP-type host framework up to x = 0.7. Ca9-xBaxBi(VO4)7 (x = 0.25, 0.5) structures were refined by the Rietveld method using powder synchrotron X-ray diffraction data. DSC, SHG and dielectric properties measurements of Ca9-xBaxBi(VO4) (x = 0, 0.25, 0.5) revealed two reversible first-order phase transitions (PT1 and PT2). Increase of Ba2+ content in Ca9-xBaxBi(VO4)7 leads to lowering PT1 and PT2 phase transitions temperatures due to the increase of cell volume and the structure looseness. Nonlinear optical activity of Ca9–xBaxBi(VO4)7 reaches its maximum response at x = 0.5. The amount of (M1–(M3)–M2) dipoles in Ca9–xBaxBi(VO4)7 (0 < x ≤ 0.7) structures increases with increasing Ba2+ content from 0.25 to 0.5 and decreases with changing x from 0.5 to 0.7. |
| Remark |
https://doi.org/10.1016/j.jallcom.2019.03.365 Link |
Comparative Study of Electrical Conduction and Oxygen Diffusion in the Rhombohedral and Bixbyite Ln6MoO12 (Ln = Er, Tm, Yb) Polymorphs
ID=523| Authors |
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Inorg. Chem.
Volume: 58,
Issue: 7,
Pages: 4275-4288 Time of Publication: 2019 |
| Abstract | Electrical conduction and oxygen diffusion mobility in the bixbyite (Ia3̅) and rhombohedral (R3̅) polymorphs of the Ln6MoO12−Δ (Ln = Er, Tm, Yb; Δ = δ, δ1, δ2; δ1 > δ2) heavy lanthanide molybdates, belonging to new, previously unexplored classes of potential mixed (ionic–electronic) conductors, have been studied in the range of 200–900 °C. The oxygen self-diffusion coefficient in bixbyite (Ia3̅) Yb6MoO12−δ phase estimated by the temperature-programmed heteroexchange with C18O2 was shown to be much higher than that for rhombohedral (R3̅) RI (with large oxygen deficiency) and (R3̅) RII (with small oxygen deficiency) Ln6MoO12−Δ (Ln = Tm, Yb; Δ = δ1; δ1 > δ2) oxides. According to the activation energy for total conduction in ambient air, 0.99, 0.93, and 1.01 eV in Er6MoO12−δ, Tm6MoO12−δ, and Yb6MoO12−δ bixbyites, respectively, oxygen ion conductivity prevails in the range ∼200–500 °C. Oxygen mobility data for the rhombohedral Ln6MoO12−Δ (Ln = Er, Tm, Yb; Δ = δ1, δ2) phases RI and RII indicate that the oxygen in these phases exhibits mobility at much higher temperatures, such as those above 600–700 °C. Accordingly, below 600–700 °C they have predominantly electronic conductivity. As shown by total conductivity study of Ln6MoO12−δ (Ln = Er, Tm, Yb) bixbyites (Ia3̅) and rhombohedral phases Ln6MoO12−Δ (Ln = Er, Tm, Yb; Δ = δ1, δ2) (R3̅) in dry and wet air, the proton conductivity contribution exists only in Ln6MoO12−δ (Ln = Er, Tm, Yb) bixbyites up to 450–600 °C and decreases with a decreasing of the lanthanide ionic radius. The obtained data on the mobility of oxygen and the presence of proton contribution in bixbyites in the 300–600 °C temperature range make it possible to confirm unequivocally that Ln6MoO12−δ (Ln = Er, Tm, Yb) bixbyites are mixed electron–proton conductors at these temperatures. |
| Remark | Link |
Processing of high performance composite cathodes for protonic ceramic fuel cells by exsolution
ID=522| Authors |
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J. Mater. Chem. A
Volume: 7,
Pages: 8609-8619 Time of Publication: 2019 |
| Abstract | La0.5Ba0.5CoO3−δ–BaZrO3 (LB–BZ)-based composite materials were prepared by a modified Pechini sol–gel method combined with exsolution. Two different LB–BZ composites were prepared through two alternative thermal treatments of the precursor gel. A metastable single phase with a perovskite crystal structure was first obtained upon annealing the precursor in an inert atmosphere, and it was further transformed into a two-phase composite by in situ exsolution in air. Comparatively, direct calcination of the LB–BZ gel in air resulted in a two-phase composite with different microstructures and compositions of the two phases. The composite cathode formed by exsolution consisted of a matrix of BZ-phase with ∼45 nm grain size embedding ∼20 nm grains of LB-phase, while the composite cathode obtained by direct calcination consisted of a mixture of both phases with 50–60 nm grain size. Electrodes of symmetric half-cells were spray-coated on the BaZr0.9Y0.1O2.95 electrolyte to examine the electrochemical performance by impedance spectroscopy. The lowest area specific resistance (ASR) was obtained for the composite cathode produced by exsolution with an excellent ASR of 1.54 Ω cm2 at 600 °C and 18 Ω cm2 at 400 °C and an activation energy (Ea) of 0.60 eV in 3% moist synthetic air. This work demonstrates the potential of fabricating high performance nanocomposite cathodes with tailored chemical composition by a novel exsolution method. |
| Remark |
DOI: 10.1039/C8TA10950H Link |
Optimization of laser-patterned YSZ-LSM composite cathode-electrolyte interfaces for solid oxide fuel cells
ID=521| Authors |
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| Source |
Journal of the European Ceramic Society
Volume: 39,
Issue: 12,
Pages: 3466-3474 Time of Publication: 2019 |
| Abstract | Patterned cathode/electrolyte interfaces formed by a hexagonal array of ∼22 μm deep wells with 24 μm lattice parameter have been prepared by pulsed laser machining to enlarge the contact surface and, consequently, to reduce the cathode polarization of Solid Oxide Fuel Cells. These new interfaces have been tested in YSZ-LSM/YSZ/YSZ-LSM symmetrical cells, where the cathode is deposited by dip-coating. Appropriate ceramic suspensions have been formulated to penetrate into deep wells without presenting interfacial delamination after sintering. We analyse their applicability by comparing their rheology with the microstructure and electrochemical performance of the cells. The activation component of the polarization resistance is reduced by ∼50% using ethanol-based suspensions with 20 wt% solids loading, although the gas diffusion component increases due to excessive densification. Alternative ceramic suspensions with 17.5 wt% solids loading provide optimum electrode gas diffusion but lower activation components, resulting in an overall decrease of ∼20% in polarization resistance. |
| Remark |
https://doi.org/10.1016/j.jeurceramsoc.2019.02.049 Link |
The effect of Fe‐acceptor doping on the electrical properties of Na1/2Bi1/2TiO3 and 0.94 (Na1/2Bi1/2)TiO3–0.06 BaTiO3
ID=520| Authors |
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| Source |
J. of American Ceramic Society
Volume: 102,
Issue: 9,
Pages: 5295-5304 Time of Publication: 2019 |
| Abstract | Na1/2Bi1/2TiO3 (NBT) based ceramics are amongst the most promising lead‐free ferroelectric materials. It was expected that the defect chemistry and the effect of doping of NBT would be similar to that observed for lead based materials, however, acceptor doping does not lead to ferroelectric hardening. Instead, high oxygen ionic conductivity is induced. Nevertheless, for solid solutions with BaTiO3 (BT), which are more relevant with respect to ferroelectric applications, such a drastic change of electrical properties has not been observed so far. To rationalize the difference in defect chemistry between NBT and its solid solution 94(Na1/2Bi1/2TiO3)–0.06 BaTiO3 (NBT–6BT) compositions with different concentrations of Fe‐dopant were investigated. The study illustrates that the materials exhibit very similar behavior to NBT, and extraordinarily high oxygen ionic conductivity could also be induced in NBT–6BT. The key difference between NBT–6BT and NBT is the range of the dependence of ionic conductivity with dopant concentration. Previous studies of NBT–6BT have not reached sufficiently high dopant concentrations to observe high conductivity. In consequence, the same defect chemical model can be applied to both NBT and its solid solutions. This will help to rationalize the effect of doping on ferroelectric properties of NBT‐ceramics and defect chemistry related degradation and fatigue. |
| Remark |
https://doi.org/10.1111/jace.16401 Link |
SOFC cathodic layers using wet powder spraying technique with self synthesized nanopowders
ID=519| Authors |
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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 |
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Journal of Alloys and Compounds
Volume: 787,
Pages: 1301-1309 Time of Publication: 2019 |
| Abstract | Solid solution of Ca10.5–1.5xYbx(PO4)7 (0 ≤ x ≤ 1) was synthesized in the β-Са3(РО4)2-type structure by a standard solid-state method. Second-harmonic generation, differential scanning calorimetry, and dielectric measurements showed the presence of a reversible first-order phase transition of ferroelectric type between the room-temperature polar R3c structure to centrosymmetry. The temperature of the phase transition decreases from 1203 K for x = 0 to 788 K for x = 1, while the second-harmonic generation response decreases from 1.4 to 0.17 α-SiO2 powder standard units. The luminescence spectra of Ca10.5–1.5xYbx(PO4)7 point to two structural Yb3+ positions in full agreement with the structural data. The intensity of the luminescence emission line at ∼975 nm due to the 2F5/2 → 2F7/2 transition reaches the maximum at x = 0.667 in Ca10.5–1.5xYbx(PO4)7. The Yb3+ luminescence spectra studied as a function of the chemical composition 0 < x ≤ 1 are compared with the corresponding crystallographic data obtained from the powder diffraction of both X-Ray and synchrotron radiation. Although the overwhelming majority of the Yb3+ cations are located in the pseudosymmetry in M5 position, their smaller number is located in an acentric manner in M1 and M2. A structural mechanism for the transition between the polar (ferroelectric, space group R3c) and centrosymmetric (paraelectric, space group R-3c) phases is proposed. |
| Remark |
https://doi.org/10.1016/j.jallcom.2019.02.103 Link |
Surface reactivity and cation non-stoichiometry in BaZr1−xYxO3−δ (x = 0–0.2) exposed to CO2 at elevated temperature
ID=517| Authors |
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J. Mater. Chem. A
Volume: 7,
Pages: 3848-3856 Time of Publication: 2019 |
| Abstract | The reactivity of BaZr1−xYxO3−δ (x = 0–0.2) ceramics under 1 atm CO2 at 650 °C for up to 1000 h was investigated in order to elucidate possible degradation processes occurring when the material is applied as a proton-conducting electrolyte in electrochemical devices. The annealed ceramics were characterized by a range of techniques (SEM, TEM, GIXRD, XPS and SIMS) with respect to changes in the phase composition and microstructure. Formation of BaCO3 was observed on the surfaces of the annealed samples and the amount increased with time and was higher for the Y-doped compositions. The subsurface regions were found to be deficient in Ba and, in the case of the Y-doped compositions, enriched in Y in two distinct chemical states as identified by XPS. First-principles calculations showed that they were Y residing on the Zr and Ba-sites, respectively, and that local enrichment of Y both in bulk and on the surface attained a structure similar to Y2O3. Overall, it was substantiated that the reaction with CO2 mainly proceeded according to a defect chemical reaction involving transfer of Y to the Ba-site and consumption of BaZrO3 formula units. It was suggested that a similar degradation mechanism may occur in the case of Ba(OH)2 formation under high steam pressure conditions. |
| Remark | Link |
Superprotonic CsH2PO4 in dry air
ID=516| Authors |
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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. |
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Tuning the optical and thermoelectric properties of SrTi0.8−x Sn0.2FexO3
ID=514| Authors |
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Materials Research Express
Volume: 6,
Issue: 4
Time of Publication: 2019
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| 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. |
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