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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
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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.
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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
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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.
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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.
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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
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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.
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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.
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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.
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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.
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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
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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
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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.
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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
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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.
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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.
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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.
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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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