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Solid oxide fuel cell (SOFC) technology offers tremendous potential for highly efficient and clean power generation. However, its commercialization has lagged owing to the lack of long-term stability. Among the various sources of performance degradation, the interdiffusion between the cathode and electrolyte has been identified as a predominant factor. Herein, we demonstrate a highly reliable diffusion-blocking layer that completely suppresses detrimental chemical interactions at elevated temperatures. This diffusion-blocking layer is constructed via a bilayer approach, in which the top and bottom layers perform individual functions to precisely control the bulk and interfacial properties. Harnessing two types of specially designed nanoparticles for each part enables the realization of the desired film structure. Consequently, the formation of insulating phases and decomposition of the cathode are effectively prevented, resulting in a remarkable improvement in performance and stability. The scalability and feasibility of mass production are verified via the fabrication of large cells (10 cm × 10 cm) and a multi-cell stack. The stack in which the bilayer technique is implemented exhibits an extremely low degradation rate of 0.23% kh−1, which fulfills the strict lifetime requirement for market penetration. This work highlights a scalable, cost-effective, and reproducible method for the production of highly durable multilayer energy devices, including SOFCs. [ABSTRACT FROM AUTHOR]

Studying the possibility of a p-type conduction mechanism in the Ag-doped ZnO can clarify persisting ambiguities in the related materials and devices. Here, utilizing the first principles study by hybrid functional calculations, we conclude that the potential acceptor defects AgZn and VZn are rare in the low Fermi level conditions required for p-type conduction and, hence, can hardly contribute to the hole generation in ZnO regardless of the assumed O-rich condition. Our results also reveal the exothermicity of the reaction between VO and AgZn to form the complex defect VO–2AgZn which is shown to be a less effective donor than VO. The conversion of the VO to a less electronically effective complex defect is proposed as the mechanism responsible for the conductivity instabilities in the silver doped zinc oxide. [ABSTRACT FROM AUTHOR]

Abstract: The time‐resolved oxygen exchange rate of strontium titanate (SrTiO3) single crystals is studied by means of oxygen solid electrolyte coulometry (OSEC) and compared to model calculations. Experiments are performed on pure, ion implanted (Ni, Ag, O and N ions) and partially covered crystals with silver layer. In this work, a theoretical model is used, which is based on defect chemistry under equilibrium conditions. It is applied as a fit in order to determine the effective rate constants and activation energy of the oxygen exchange reaction on the crystal surface. OSEC is used for the first time to characterize kinetic parameters of oxygen exchange on single crystalline surfaces. Transmission electron microscopy and sputter X‐ray photoelectron spectroscopy are performed to determine structural and chemical changes after ion implantation. [ABSTRACT FROM AUTHOR]

The electron structure features in the high‐temperature cubic perovskite‐like ferrite La1−xSrxFeO3−δ are studied depending on concentration of disordered cation and anion defects by use of the Coherent Potential Approximatiom (CPA) taking into account the strong electronic correlations (U) in Fe d‐shell. The variations of electronic‐energy and magnetic characteristics are described at 0 ≤ δ ≤ 0.25 and 0 ≤ x ≤ 0.50. The spin state of iron atoms in stoichiometric δ = 0 compositions is shown to change near x = 0.4, which gives an explanation to the observed experimental data. [ABSTRACT FROM AUTHOR]

In this study, a new method is developed for the fabrication of nanofibrous LaCoO3 (LCO) perovskites as cathodes (oxygen electrodes) for solid oxide fuel cells (SOFCs). The proposed method involves chemically assisted electrodeposition (CAED) of mixed metal hydroxide onto a carbon nanotube (CNT) template, followed by a low-temperature heat-treatment process. The CNT template is first fabricated on porous zirconia-based ion-conducting scaffolds (ICS) by catalytic chemical vapor deposition (CCVD) of C2H4. Perovskite-type LCO is then fabricated on the CNT template by CAED process of mixed La–Co hydroxide combined with thermal conversion of hydroxide to perovskite oxide. The method proposed here allows for the fabrication of LCO perovskites with a unique nanofibrous structure at reduced temperatures (∼900 °C), while avoiding the formation of pyrochlore phases (e.g., La2Zr2O7), which are typically observed during conventional high-temperature sintering processes of LaCoO3 with zirconia-based electrolytes. The new method also provides the precise control needed to achieve desired oxide loadings without the need for repeated deposition-annealing processes. The anode-supported SOFCs with nanofibrous LCO cathodes on zirconia and ceria scaffolds show high and stable electrochemical performance of 0.95 and 1.27 W cm−2, respectively, at 800 °C. In addition to the absence of insulating pyrochlore phases, the unique nanostructure of the LCO cathode is believed to play a beneficial role in improving the electrochemical properties by providing a large number of active reaction sites and by facilitating mass transport through the porous nanofibrous structure. [ABSTRACT FROM AUTHOR]

Abstract: Critical to the development of improved solid oxide fuel cell (SOFC) technology are novel compounds with high oxygen reduction reaction (ORR) catalytic activity and robust stability under cathode operating conditions. Approximately 2145 distinct perovskite compositions are screened for potential use as high activity, stable SOFC cathodes, and it is verified that the screening methodology qualitatively reproduces the experimental activity, stability, and conduction properties of well‐studied cathode materials. The calculated oxygen p‐band center is used as a first principle‐based descriptor of the surface exchange coefficient (k*), which in turn correlates with cathode ORR activity. Convex hull analysis is used under operating conditions in the presence of oxygen, hydrogen, and water vapor to determine thermodynamic stability. This search has yielded 52 potential cathode materials with good predicted stability in typical SOFC operating conditions and predicted k* on par with leading ORR perovskite catalysts. The established trends in predicted k* and stability are used to suggest methods of improving the performance of known promising compounds. The material design strategies and new materials discovered in the computational search help enable the development of high activity, stable compounds for use in future solid oxide fuel cells and related applications. [ABSTRACT FROM AUTHOR]

A new TbNbO4 single-crystal with a monoclinic structure has been grown successfully using the Czochralski method for the first time. The material belongs to the space group C2/c, with unit-cell parameters of a = 7.173(3) Å, b = 11.186(5) Å, c = 5.156(2) Å and β = 131.082(3)°. The thermal properties of the as-grown TbNbO4 crystal, including specific heat, thermal expansion coefficient, thermal diffusion coefficient, and thermal conductivity, were measured systematically. The TbNbO4 crystal exhibits strong anisotropic thermal expansion; a negative thermal expansion along the c direction is presented, and a zero thermal expansion coefficient in some directions can be obtained. The emission and absorption spectra were also measured. The strongest emission peak in the green spectral domain of TbNbO4 corresponding to the 5D4→7F5 transition of Tb3+ is located at 549 nm. In the range of 350–1500 nm, the as-grown TbNbO4 crystal has low absorption. X-ray photoelectron spectroscopy (XPS) was used to study the valence of the elements in the TbNbO4 crystal; the result shows that there are two different valence states of Tb in the as-grown crystal. [ABSTRACT FROM AUTHOR]

Cubic perovskite-type Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) is one of the mixed ionic-electronic conductors with the highest oxygen permeability known to date. It serves as a parent material for the development of functional derivatives for electrochemical applications including oxygen separation membranes, solid electrolyte cell electrodes and electrocatalysts for the oxygen evolution reaction. The present study is focused on the determination of the precise stability boundaries of cubic perovskite BSCF employing a coulometric titration technique in combination with thermogravimetric analysis, X-ray and neutron diffraction, and molecular dynamics simulations. Both the low-p(O2) and high-p(O2) stability boundaries at 700–950 °C were found to correspond to a fixed value of oxygen content in the perovskite lattice of 3 −δ = ∼2.13 and ∼2.515, respectively. The stability limits in this temperature range are expressed by the following equations: high-p(O2) boundary: log p(O2) (atm) (±0.1) = −10 150/T (K) + 8.055; low-p(O2) boundary: log p(O2) (atm) (±0.03) = −20 750/T (K) + 4.681. The p(O2)–T phase diagram of the BSCF system under oxidizing conditions is addressed in a wider temperature range and is shown to include a region of precipitation of a “low-temperature” phase occurring at 400–500 °C. The fraction of the low-temperature precipitate, which co-exists with the cubic perovskite phase and is stable up to 790–820 °C, increases upon increasing p(O2) in the range 0.21–1.0 atm. [ABSTRACT FROM AUTHOR]

In order to enhance low field magnetoresistance (LFMR) of bulk manganite materials, two series of composites, La[sub 0.7]Sr[sub 0.3]MnO[sub 3]/SrTiO[sub 3] and La[sub 0.7]Sr[sub 0.3]MnO[sub 3]/SrZrO[sub 3], have been prepared by thermal processing of mixed powders. For both series annealing of pelletized mixtures over certain critical temperature leads to the substantial enhancement of LFMR for compositions close to theoretical percolation threshold. At higher processing temperatures enhanced MR values are observed for composites with higher La[sub 0.7]Sr[sub 0.3]MnO[sub 3] content, while compositions with a lower amount of manganite become insulating. The magnitude of enhanced MR remains almost the same within the same series, but the value of enhancement is substantially different for composites, containing SrTiO[sub 3] and SrZrO[sub 3] (1.5% and 2.5% at H = 100 Oe, respectively). Similar dependencies are observed for coercive field values. Observed shift of the enhancement boundary during thermal processing and significant dependence of SrZrO[sub 3] lattice parameters versus components ratio and composite processing temperatures (1100-1200°C) show at substantial chemical interaction in these composites. [ABSTRACT FROM AUTHOR]

Diffusivity on the A- and B-site of polycrystalline perovskite CaMnO3−δ with Ca deficiency and spinel CaMn2O4 (marokite) as a secondary phase was studied using chemical tracers and secondary ion mass spectrometry (SIMS) complemented by electron probe microanalysis (EPMA). Thin films containing Sr and Co chemical tracers were deposited on the polished surface of the polycrystalline composite sample followed by annealing at 800–1200 °C for 96 h. Diffusion profiles for each tracer were determined with SIMS, followed by calculation of diffusion coefficients by fitting to appropriate models. The Sr tracer showed mainly lattice diffusion, with an activation energy of 210 ± 30 kJ mol−1, whereas the Co tracer showed a combination of lattice and enhanced grain-boundary diffusion, with activation energies of 270 ± 30 kJ mol−1 and 380 ± 40 kJ mol−1, respectively. The diffusivities may be used to predict interdiffusion and lifetime of junctions between n-type CaMnO3−δ or CaMnO3−δ/CaMn2O4 composites and metallization interlayers or p-type leg materials in oxide thermoelectrics. In particular, the relatively high effective diffusivity of Co in polycrystalline CaMnO3−δ may play a role in the reported fast formation of the secondary phase (Ca3Co2−yMnyO6) between p-type Ca3Co3.92O9+δ and n-type CaMnO3−δ in a direct p–n thermoelectric junction. [ABSTRACT FROM AUTHOR]

The uv-coverage of the current VLBI network between Australia northern Asia will be significantly enhanced with an existence of a middle baseline VLBI station located in Malaysia. This paper investigated the connecting route of the first half of the Asia-Oceania VLBI network i.e. from Malaysia to China. The investigation of transmission network characteristics between Malaysia and China was carried out in order to perform a real-time and reliable data transfer within the e-VLBI network for future eVLBI observations. MyREN (Malaysia) and CSTNET (China) high-speed research networks were utilized for this proposed e-VLBI connection. Preliminary network test was performed by ping, traceroute, and iperf prior to data transfer tests, which were evaluated with three types of protocols namely FTP, Tsunami-UDT and UDT. The results showed that, on average, there were eighteen hops between Malaysia and China networks with 98 ms round trip time (RTT) delay. Overall UDP protocol has a better throughput compared to TCP protocol. UDP can reach a maximum rate of 90 Mbps with 0% packet loss. In this feasibility test, the VLBI test data was successfully transferred between Malaysia and China by utilizing the three types of data transfer protocols. [ABSTRACT FROM AUTHOR]

Both aliovalent doping and the charge state of multivalent lattice ions determine the oxygen non-stoichiometry (δ) of mixed ionic and electronic conductors (MIECs). Unfortunately, it has been challenging for both modeling and experiments to determine the multivalent ion charge states in MIECs. Here, the Fe charge state distribution was determined for various compositions and phases of the MIEC La1−xSrxFeO3−δ (LSF) using the spin-polarized density functional theory (DFT)-predicted magnetic moments on Fe. It was found that electron occupancy and crystal-field-splitting-induced differences between the Fe 3d-orbitals of the square pyramidally coordinated, oxygen-vacancy-adjacent Fe atoms and the octahedrally-coordinated, oxygen-vacancy-distant-Fe atoms determined whether the excess electrons produced during oxygen vacancy formation remained localized at the first nearest neighbor Fe atoms (resulting in small oxygen vacancy polarons, as in LaFeO3) or were distributed to the second-nearest-neighbor Fe atoms (resulting in large oxygen vacancy polarons, as in SrFeO3). The progressively larger polaron size and anisotropic shape changes with increasing Sr resulted in increasing oxygen vacancy interactions, as indicated by an increase in the oxygen vacancy formation energy above a critical δ threshold. This was consistent with experimental results showing that Sr-rich LSF and highly oxygen deficient compositions are prone to oxygen-vacancy-ordering-induced phase transformations, while Sr-poor and oxygen-rich LSF compositions are not. Since oxygen vacancy induced phase transformations cause a decrease in the mobile oxygen vacancy site fraction (X), both δ and X were predicted as a function of temperature and oxygen partial pressure, for multiple LSF compositions and phases using a combined thermodynamics and DFT approach. [ABSTRACT FROM AUTHOR]

The chemical surface reaction rate constant controlling the change of oxidation state of undoped ceria, kChem, was measured at 1400 °C in the range of (∼0 ≤ (pH2O/atm) ≤ 0.163(9)) and (10−3.85≤ (pO2/atm) ≤ 10−2.86) via the electrical conductivity relaxation method. In humidified atmospheres, kChem is fully described as the sum of kChem,O2 and kChem,H2O, which are, respectively, the rate constants for oxidation by O2 and by H2O alone. Using measurements under appropriately controlled gas conditions, the total rate constant is found to follow the correlation kChem/cm s−1 = 10−(1.35±0.07)× (pO2/atm)0.72±0.02 + 10−(3.85±0.03)× (pH2O/atm)0.36±0.03 where the pO2 and pH2O values of relevance are explicitly those of the final gas condition. The results suggest that at such high temperatures, the concentrations of surface adsorbed species are too low to influence the independent reaction pathways. [ABSTRACT FROM AUTHOR]

Primary Sjögren's syndrome is an autoimmune disease characterized by dry eye and dry mouth. We systematically reviewed all the randomized controlled clinical trials published in the last 15 years that included ocular outcomes. We found 22 trials involving 9 topical, 10 oral, 2 intravenous and 1 subcutaneous modalities of treatment. Fluoromethalone eye drops over 8 weeks were more effective than topical cyclosporine in the treatment of dry eye symptoms and signs; similarly, indomethacin eye drops over 1 month were more efficacious than diclofenac eye drops. Oral pilocarpine 5 mg twice daily over 3 months was superior to use of lubricants or punctal plugs for treating dry eye, but 5% of participants had gastrointestinal adverse effects from pilocarpine, though none discontinued treatment. In contrast, etanercept, a TNF-alpha blocking antibody, administered as subcutaneous injections twice weekly, did not improve dry eye significantly compared to placebo injections. In conclusion, topical corticosteroids have been shown to be effective in dry eye associated with Sjögren's syndrome. As some topical non-steroidal anti-inflammatory drugs may be more effective than others, these should be further evaluated. Systemic secretagogues like pilocarpine have a role in Sjögren's syndrome but the adverse effects may limit their clinical use. It is disappointing that systemic cytokine therapy did not produce encouraging ocular outcomes but participants should have assessment of cytokine levels in such trials, as those with higher baseline cytokine levels may respond better. [ABSTRACT FROM AUTHOR]

Cation diffusion in functional oxide materials is of fundamental interest, particularly in relation to interdiffusion of cations in thin film heterostructures and chemical stability of materials in high temperature electrochemical devices. Here we report on 134Ba tracer diffusion in polycrystalline BaMO3 (M = Ti, Zr, Ce) materials. The dense BaMO3 ceramics were prepared by solid state sintering, and thin films of 134BaO were deposited on the polished pellets by drop casting of an aqueous solution containing the Ba-tracer. The samples were subjected to thermal annealing and the resulting isotope distribution profiles were recorded by secondary ion mass spectrometry. The depth profiles exhibited two distinct regions reflecting lattice and grain boundary diffusion. The grain boundary diffusion was found to be 4-5 orders of magnitude faster than the lattice diffusion for all three materials. The temperature dependence of the lattice and grain boundary diffusion coefficients followed an Arrhenius type behaviour, and the activation energy and pre-exponential factor demonstrated a clear correlation with the size of the primitive unit cell of the three perovskites. Diffusion of Ba via Ba-vacancies was proposed as the most likely diffusion mechanism. [ABSTRACT FROM AUTHOR]

Chemical looping combustion is a technology under development that allows power production with inherent separation of CO2 during fuel combustion. Its principle relies on oxygen carrier materials transporting oxygen from air to oxidize the fuel. One challenge is to develop and produce materials with suitable chemical and physical properties, as well as low environmental impact, while minimizing the cost of production. Herein, it is demonstrated that spray granulation, which is a scalable industrial process, is relevant for the manufacture of promising oxygen carrier materials from low-cost, low-environmental-impact minerals and with good mechanical properties: Ca0.98Mn0.875Ti0.125O3 and Ca0.98Mn0.75Fe0.125Ti0.125O3. Iron substitution clearly reduces the sintering time. Increasing the calcination temperature and calcination time enhances the bulk density and resistance against physical attrition. [ABSTRACT FROM AUTHOR]

A conventional water electrolyzer consists of two electrodes, each of which is embedded with a costly and rare electrocatalyst, typically IrO2/C for oxygen evolution reaction (OER) and Pt/C for hydrogen evolution reaction (HER), respectively. HER and OER electrocatalysts usually require very different pH values to keep them stable and active. Thus, the development of earth-abundant nonprecious metal catalysts for both HER and OER is of great importance to practical applications. This work reports the results of integrated water electrolysis using the hybrids of electrospun La0.5(Ba0.4Sr0.4Ca0.2)0.5Co0.8Fe0.2O3- δ (L-0.5) perovskite nanorods attached to reduced graphene oxide (rGO) nanosheets as bifunctional electrodes. Via rationalizing the composition and morphology of L-0.5/rGO nanohybrids, excellent catalytic performance and stability toward OER and HER are achieved in alkaline media. The operating voltage of integrated L-0.5/rGO electrolyzer is tested to be 1.76 V at 50 mA cm-2, which is close to that of the commercially available IrO2/C-Pt/C couple (1.76 V @ 50 mA cm-2). Such a bifunctional electrocatalyst could be extended toward practical electrolysis use with low expanse and high efficiency. More generally, the protocol described here broadens our horizons in terms of the designs and the diverse functionalities of catalysts for use in various applications. [ABSTRACT FROM AUTHOR]

The most common technological route for metallurgical silicon production is to feed quartz and a carbon source ( e.g., coal, coke, or charcoal) into submerged-arc furnaces, which use electrodes as electrical conductors. We develop a mathematical model of a silicon furnace. A continuum approach is taken, and we derive from first principles the equations governing the time evolution of chemical concentrations, gas partial pressures, velocity, and temperature within a one-dimensional vertical section of a furnace. Numerical simulations are obtained for this model and are shown to compare favorably with experimental results obtained using silicon pilot furnaces. A rising interface is shown to exist at the base of the charge, with motion caused by the heating of the pilot furnace. We find that more reactive carbon reduces the silicon monoxide losses, while reducing the carbon content in the raw material mixture causes greater solid and liquid material to build-up in the charge region, indicative of crust formation (which can be detrimental to the silicon production process). We also comment on how the various findings could be relevant for industrial operations. [ABSTRACT FROM AUTHOR]

This article reports densification process, microstructural evolution and nonlinear electrical properties of ErO (0-2.0 mol%) added ZnO-VO-MnO-NbO varistor powder prepared by high energy ball milling followed by conventional (950-1350 °C, 1 h) sintering. Ball milled powder and sintered pellets have been characterized by density measurement, XRD analysis, TEM and SEM examinations coupled with EDS and image analyses for morphological modifications. Addition of ErO is found to retard the ZnO grain growth significantly due to the formation of Er-rich spinel phases in the intergranular layer that reduces the grain boundary migration. Measurements of nonlinear electrical properties of sintered pellets reveal an enhancement in the breakdown field ( E ) and corresponding nonlinear exponent ( α) of Er added varistor samples. A typical varistor sample with 1 mol% ErO sintered at 1200 °C exhibits ultrafine grain structure (grain size: 1.8 µm and sintered density: >96% theoretical density) with excellent nonlinear properties ( E = 6714 V cm and α = 45). [ABSTRACT FROM AUTHOR]

The phase relations in the Si-Al-Pr-O-N-C systems, involving SiC-AlN-PrO, AlN-PrO-AlO and SiC-AlN-PrO-AlO systems were determined by XRD phase analyses of the solid-state reacted samples from powder mixtures of SiC, AlN, PrO, as well as AlO. PrAl(Si)ON(C) solid-solution (1:1 ss) between SiC and PrAlON (1:1 compound) was discovered with the limited solubility of 0.6 SiC at 1650 °C. Subsolidus phase diagram of SiC-AlN-PrO system was presented, SiC was compatible with AlN, PrO and 1:1 ss, respectively. Two-aluminates PrAlO (PrAP) and PrAlO [β(Pr), β-AlO type] were formed when AlO impurity was introduced in AlN powder. They establish the equilibrium relationships respectively with SiC, AlN, PrO and PrAlON. Accordingly, the phase relations in the AlN-PrO-AlO ternary system and SiC-AlN-PrO-AlO quaternary system containing four quaternary phases compatible tetrahedrons were presented. [ABSTRACT FROM AUTHOR]

The subsolidus phase relations of the CoO-CuO-SrO system were investigated in air. The samples were equilibrated at 900 °C. The pseudo-ternary section contains three stoichiometric binary oxide phases (SrCuO, SrCuO and SrCuO) and a binary oxide solid solution: SrCoO (0 ≤ x ≤ 0.36). Two binary phases extend into the ternary system forming solid solutions, i.e., SrCuCoO (0 ≤ x ≤ 5) and SrCoCuO (0 ≤ x ≤ 0.36, 0 ≤ y ≤ 1.0). The SrCoO solid solution was found to undergo a phase separation into a mixture of SrCoO and SrCoO upon annealing at 600 °C. This transformation is reversible. [ABSTRACT FROM AUTHOR]

In this study, the perovskite-type oxides Ba0.5Sr0.5Ni0.2Co0.6Fe0.2O3-δ (BSNCF) with different B-site transition metal elements were investigated as a new catalyst for methanol oxidation. They were prepared by the partial substitution of cobalt by nickel in Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) sample. Both materials prepared using a combined citrate/EDTA complexing method and their catalytic activitiesfor methanol oxidation were comparativelystudied using cyclic-voltammetry (CV) and chronoamperometry (CA) in alkaline media at room temperature. Structural, textural, morphological and redox properties of the synthesized solids were investigated by several physicochemical methods such as XRD, FTIR, LRS, SEM-EDX, BET and H2-TPR. The as-prepared materials were obtained with high purity and high crystallinity. The partial substitution of cobalt by nickel in BSCF perovskite changes the structure of the solid which pass from cubic structure to a mixture of cubic and hexagonal forms. This change is accompanied by an increase in BET surface area and a decrease in crystalline size. For the electro-catalysis measurements, results demonstrated that partially substituting of Co by Ni in BSCF structure enhance the electro-catalytical activity towards the oxidation of methanol under alkaline conditions, making it an electro-catalyst candidate for practical utilization in DMFCs. [ABSTRACT FROM AUTHOR]

Two step metal oxide thermochemical redox cycles have seen growing interest in the research community over the last two decades. In particular, they have often been studied as a means of converting heat from concentrated solar power to chemical energy, which can subsequently be used for a number of applications. In this work, we offer critical perspective and valuable insight on these research fields, from authors with a combined experience of 50+ years in metal oxide redox cycles. The current fundamental understanding of thermochemical redox materials, and the implications and limitations this has on the redox thermodynamics are discussed. The underlying fundamentals of the redox materials are then used to give insight into the theoretical limitations imposed on a number of applications including; solar thermochemical fuel production, solar energy storage for off sun power generation, thermochemical air separation, oxygen pumping, and thermochemical heat pumping. A number of recent novel process developments are also presented, which offer valuable motivation and direction for the respective fields. The analysis shows that oxides which undergo a stoichiometric phase change during reduction, such as ZnO or Co3O4, have much larger specific energy storage than materials undergoing partial reduction such as ceria and perovskites. The partial reduction materials generally have faster kinetics and better activity at low temperature, and the selection of materials for the various applications is often a compromise between the importance of high specific energy storage vs. fast kinetics and low temperature operation. [ABSTRACT FROM AUTHOR]

Spark plasma sintering (SPS) technique was used to densify 7 mol% yttria-stabilized zirconia (7YSZ) powder with Gd2O3-particles, at temperatures ranging between 1000 and 1200 °C. Fine dispersion of Gd2O3-particles into a full-densified matrix was achieved. Shrinkage and microstructure, as well as porosity were investigated. The fine Gd2O3-particles distributed into 7YSZ matrix have influence over the sintering consolidation and final microstructure. An increment in the spark plasma sintering temperature around 70 °C is detected when Gd2O3 particles are present. The thermal characterization was performed using the photothermal infrared radiometry technique. Both thermal diffusivity and thermal conductivity display a similar sigmoidal (Boltzmann type) behavior with the Gd2O3 concentration in the samples. [ABSTRACT FROM AUTHOR]

Cation tracer diffusion in polycrystalline cubic BaZrO3 perovskites was studied using the stable isotopes 134Ba and 96Zr in air at 1015–1200 and 1300–1500 °C, respectively. Thin films of 134BaO and 96ZrO2 were deposited on polished BaZrO3 pellets by drop casting of aqueous precursor solutions containing the tracers. Isotope distribution profiles were recorded using secondary ion mass spectrometry. All the depth profiles exhibited two distinct regions, which enabled the assessment of both lattice and grain boundary diffusion using Fick's second law and Whipple–Le Clair's equation. The grain boundary diffusion of both cations was several orders of magnitude higher than the lattice diffusion. The lattice diffusion of Ba2+ was found to be significantly faster than the lattice diffusion of Zr4+, while the activation energies were comparable, respectively 395 ± 44 and 435 ± 67 kJ mol−1. Activation energies for the diffusion of Ba2+ and Zr4+ through a Ba2+ vacancy were calculated by density functional theory using the nudged elastic band method. The calculated and experimental activation energies were in excellent agreement. The cation diffusion data in BaZrO3 are compared to previous data on A and B-site diffusivity in perovskites. Finally, the diffusivity of Zr4+ in compounds with perovskite and fluorite crystal structures is discussed in relation to the chemical stability of BaZrO3-based materials. [ABSTRACT FROM AUTHOR]

Long-term performance testes by CRIEPI (Central Research Institute for Electric Power Industry) on six industrial stacks have revealed an interesting correlation between cathode polarization loss and ohmic loss. To make clear the physicochemical meaning of this correlation, detailed analyses were made on the conductivity degradation of YSZ electrolyte in button cells and then on the ohmic losses in the industrial cells in terms of time constants which are determined from speed of the tetragonal transformation through the Y diffusion from the cubic phase to the tetragonal phase. In some cases, shorter time constants (faster degradations) were detected than those expected from the two-time-constant (with and without NiO reduction effects) model, suggesting that additional ohmic losses after subtracting the contribution from the tetragonal transformation must be caused from other sources such as cathode-degradation inducing effects. Main cathode degradations can be ascribed to sulfur poisoning due to contamination in air in the CRIEPI test site. An important feature was extracted as this cathode degradations became more severe when the gadolinium-doped ceria (GDC) interlayers were fabricated into dense film. Plausible mechanisms for cathode degradations were proposed based on the Sr/Co depletion on surface of lanthanum strontium cobalt ferrite (LSFC) in the active area. Peculiar cathode degradations found in stacks are interpreted in term of changes in surface concentration by reactions with sulfur oxide, electrochemical side reactions for water vapor emission or Sr volatilization, and diffusion of Sr/Co from inside LSCF. [ABSTRACT FROM AUTHOR]

Bismuth has been doped into mixed ionic–electronic conducting La1.75Sr0.25NiO4+δ (LSN) with the 2D K2NiF4-type structure to evaluate its influence on various properties of the host material, which include its potential use as a SOFC cathode. X-ray powder diffraction indicates that LSN retains its tetragonal structure after doping with 5 mol% bismuth to form La1.65Bi0.1Sr0.25NiO4+δ (LSN–Bi). Bismuth doping profoundly lowers (by ∼150 °C) the sintering temperature of LSN. Both LSN and LSN–Bi show excellent compatibility with electrolytes yttria-stabilized zirconia (YSZ) and samaria-doped ceria (SDC) in terms of thermal expansion and chemical reactivity (＜900 °C). The electrical conductivity of both materials is metallic like and reaches values of 99.3 S cm−1 and 100.3 S cm−1 at 550 °C for LSN and LSN–Bi, respectively. The data from electrical conductivity relaxation (ECR) measurements demonstrate that the substitution of lanthanum by bismuth enhances the chemical diffusion coefficient (Dchem) and surface exchange coefficient (kchem) by factors of 2–3. The faster kinetics of oxygen transport exhibited by LSN–Bi relative to parent LSN is reflected by a lower polarization resistance of the former when the electrode performance of both materials is compared in symmetric cells. The corresponding values at 700 °C are 4.2 Ω cm2 and 0.61 Ω cm2 for LSN and LSN–Bi, respectively. High peak power densities are achieved (328 mW cm−2 and 131 mW cm−2 at 700 and 600 °C, respectively), when LSN–Bi is incorporated as the cathode in a fuel cell operated with humidified hydrogen as the fuel and air as the cathode gas. The material is considered a promising candidate for further study. [ABSTRACT FROM AUTHOR]

Samarium substituted lanthanum orthoferrite LaSmFeO thin film has been prepared by soft chemical method. A single perovskite phase with orthorhombic crystallographic structure was attained. Magnetic and ferroelectric orderings of the film is observed at room temperature (RT). The magnetization of the sample measured at room temperature increases non-linearly with the increase of magnetic field, which suggests the presence of dipole-dipole/exchange interaction in the sample. The resistivity measured in the temperature range 25-375 °C showed that the film is a semiconducting material with low resistivity. The Cole-Cole model reveals different grain boundaries electrical resistance caused by the equilibrium concentration of oxygen vacancies in orthoferrite and that the addition of samarium results in loss of oxygen during sintering. The ferroelectric behaviour of LaSmFeO at RT is also confirmed by its capacitance-voltage ( C-V) characteristic suggesting a weak ferroelectric behaviour at room temperature. The variation of dielectric constant as a function of frequency predicts the presence of spontaneous polarization in the sample. The semiconductor electrical behavior of the LaSmFeO is mainly composed of tunneling current. [ABSTRACT FROM AUTHOR]

Perovskite oxides have been under intense investigation as promising candidates for devices in the field of energy conversion and storage. Unfortunately, these perovskites are probably subjected to a frequent performance loss caused by phase transition. A phase-stabilization approach via interdiffusional tailoring is identified in perovskite-based composites. As an example, a phase-stabilized perovskite-fluorite composite material with both components possessing cubic symmetry was obtained by an appropriate one-pot strategy. These findings render possible to develop a high-performance and extremely stable dual-phase oxygen-transporting membrane for intermediate-temperature air separation as well as syngas production, which also opens up numerous opportunities to overcome the phase-transition-induced performance degradation in other systems. [ABSTRACT FROM AUTHOR]

La0.75Sr0.25FeO3-δ polycrystalline samples were prepared by the solid state reaction at different sintering temperatures. An octahedral tilting Pnma↔R...c transition in La0.75Sr0.25FeO3-δ was detected by mechanical spectroscopy, where a dip of reduced modulus was observed and accompanied by a sharp internal friction peak. The modulus softening is due to the strain/order parameters coupling at this improper ferroelastic transition. The tilting transition shifts toward lower temperature with reducing sintering temperature in La0.75Sr0.25FeO3-δ samples, which is due to the detriment of A-site ordering in the ABO3 perovskite. A higher degree of A-site ordering favors more homogenous structural modulation, which stabilizes the low temperature Pnma phase and results in the shift of the transition to higher temperature. Another internal friction peak just below the tilting transition was observed, which is attributed to domain wall motions. A correlation between the mobility of ferroelastic domain walls in Pnma perovskite and the existence of the high temperature R...c phase was suggested. [ABSTRACT FROM AUTHOR]

Perovskite oxides CaMnO3 and Ca0.8Sr0.2MnO3 show continuous non-stoichiometry over a range of temperatures and oxygen partial pressures. In this work a thermobalance equipped with an oxygen pump was used to measure the equilibrium non-stoichiometry of both materials for temperatures in the range 400–1200 °C and oxygen partial pressures in the range 1–10−5 bar. Analysis of the data showed that Ca0.8Sr0.2MnO3 has a lower enthalpy of reduction and thus can be more easily reduced. The strontium added sample was also robust against a phase transition that was seen in CaMnO3 at high temperatures. A statistical thermodynamic model of the system suggests that the defects form clusters of the form UGRAPHIC DISPLAY="INLINE" ID="UGT1" SRC="UGT1"/. The oxidation kinetics were also investigated with Ca0.8Sr0.2MnO3 showing faster kinetics and maintaining activity at lower temperatures. Overall, Ca0.8Sr0.2MnO3 shows very promising properties for redox applications, including gravimetric oxygen storage up to 4% by mass, high stability and rapid reversibility, with re-oxidation in less than 1 min at 400 °C. Finally, the redox chemistry of Ca0.8Sr0.2MnO3 was also investigated using in situ X-ray photoelectron spectroscopy and near-edge X-ray absorption measurements at near ambient pressure in oxygen atmospheres. [ABSTRACT FROM AUTHOR]

We have investigated the effect of La and Fe deficiency on the c-axis lattice parameter and optical absorption in La1−xFe1−yO3−δ films deposited by oxide MBE. La deficient films display minimal changes in optical and structural properties compared with stoichiometric LaFeO3, even with relatively large cation vacancy concentrations (∼22%). Fe deficient films show a linear increase in c-axis parameter with increasing Fe vacancy concentration. The optical absorption coefficient is reduced for Fe deficient films over the spectral range from 1.2 to 5.0 eV. This leads to a relatively simple and effective method to quantify the approximate Fe deficiency in LaFeO3. Minimal changes in optical and structural properties are observed when cation deficient films are exposed to strongly oxidizing (ozone annealing) conditions. This indicates a strong accompaniment of charge balancing oxygen vacancies to maintain a nominal Fe3+ valence state, acting to stabilize the band structure even in the presence of significant cation off-stoichiometry. [ABSTRACT FROM AUTHOR]

Carbothermal reaction between quartz and two different carbons originating from natural gas were investigated in this paper. One of two carbons is the commercial carbon black produced from natural gas in a medium thermal production process. The other carbon is obtained from natural gas cracking at 1273 K (1000 °C) deposited directly on the quartz pellet. At the 1923 K (1650 °C) and CO atmosphere, the impact of carbon content, pellet structure, gas transfer, and heating rate are investigated in a thermo-gravimetric furnace. The reaction process can be divided into two steps: an initial SiC-producing step followed by a SiO-producing step. Higher carbon content and increased gas transfer improves the reaction rate of SiC-producing step, while the thicker carbon coating in carbon-deposited pellet hinders reaction rate. Better gas transfer of sample holder improves reaction rate but causes more SiO loss. Heating rate has almost no influence on reaction. Mass balance analysis shows that mole ratios between SiO, free carbon, and SiC in the SiC-producing step and SiO-producing step in CO and Ar fit the reaction SiO(s) + 3 C(s) = SiC(s) + 2 CO(g). SiC-particle and SiC-coating formation process in mixed pellet and carbon-deposited pellet are proposed. SiC whiskers formed in the voids of these two types of pellets. [ABSTRACT FROM AUTHOR]

Reversible changes of the structural and electronic transport properties of La1/3Sr2/3FeO3-δ/Gd-doped CeO2 heterostructures arising from the manipulation of δ are presented. Thermally induced oxygen loss leads to a c-axis lattice expansion and an increase in resistivity in a La1/3Sr2/3FeO3-δ film capped with Gd-doped CeO2. In a three-terminal device where a gate bias is applied across the Gd-doped CeO2 layer to alter the La1/3Sr2/3FeO3-δ oxygen stoichiometry, the ferrite channel is shown to undergo a change in resistance of an order of magnitude using gate voltages of less than 1 V applied at 500 K. The changes in resistance remain upon cooling to room temperature, in the absence of a gate bias, suggesting solid state ionic gating of perovskite oxides as a promising platform for applications in non-volatile, multistate devices. [ABSTRACT FROM AUTHOR]

High energy lithium ion battery based on multi-electron redox reaction is often accompanied by inherent large volume expansions, sluggish kinetics, and unstable solid electrolyte interphase layer, leading to capacity failure. Here, thermal induced strain relaxation is proposed to realize the solid electrolyte interphase control. It is demonstrated that through thermal treatment, lattice strain is well released and defect density is well reduced, facilitating the charge transfer, improving the interparticle contacts and the contacts at the interface of electrode to withstand the huge volume expansion/contraction during cycling. In this way, the as-prepared α-Fe2O3 electrode at 800 °C with no protective shell shows an outstanding reversible capacity of 1200 mA h g−1 at 100 mA g−1 and an excellent high-rate cyclability with a capacity fading of 0.056% per cycle for 1200 cycles at 5 A g−1. It is expected that such findings facilitate the applications of high capacity anode and cathode material systems that undergo large volume expansion. [ABSTRACT FROM AUTHOR]

In this study, the influence of long-term annealing at intermediate temperatures on oxygen transport of Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) and 3 mol% Zr-doped BSCF (BSCF-Z3) ceramics with different grain sizes was studied by means of in situ electrical conductivity relaxation (ECR) measurements. Ceramics with different grain sizes in the range of 3–80 μm were obtained by varying the temperature and dwell time during sintering. For both compositions, the apparent values of the chemical diffusion coefficient Dchem and surface exchange coefficient kchem extracted from the data of ECR measurements are found to decrease with the time of annealing. The strongly correlated decreases in Dchem and kchem, being greater in magnitude at a lower grain size and temperature, are observed significantly more pronounced for BSCF than for BSCF-Z3. The results from microstructural analysis provide a clear rationale for the observations from ECR. High-resolution transmission electron microscopy (TEM) images recorded before and after annealing under pure oxygen at 700 °C for 13 d show excessive formation of hexagonal and plate-like lamellar precipitates at the grain boundaries and in the interior of grains of BSCF ceramics during the annealing process, whilst secondary phase formation is restricted solely to the grain boundary regions in BSCF-Z3. The possible importance of grain boundaries in determining the oxygen surface exchange kinetics is emphasized. [ABSTRACT FROM AUTHOR]

The temperature dependences of the structures of three polytypes of BaRuO3 have been investigated between room temperature and 1000 °C using high resolution synchrotron X-ray diffraction. The structural studies reveal a systematic decrease of the Ru–Ru distance as the pressure required to prepare the polytype increases. The O–O distance across the shared face increases as the Ru–Ru separation decreases. The 9R and 4H polytypes undergo unexceptional changes with increasing temperature. In 6H-BaRuO3 there is an apparent increase in the Ru–Ru interaction at around 650 °C and a concurrent reduction in the O–O distance, indicating an anomalous strengthening of the Ru–Ru interactions upon heating. [ABSTRACT FROM AUTHOR]

Neutron powder diffraction is a powerful technique for probing oxygen in nonstoichiometric oxides, but often gives lower oxygen occupancy compared to traditional characterization methods. In this work, the oxygen nonstoichiometry of a model oxide system, cubic perovskite-type Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF), was studied by thermogravimetric analysis, coulometric titration and room-temperature neutron diffraction, with the aim to identify the possible cause of such a discrepancy. Comparative analysis of the obtained results and available literature data indicates that the Rietveld refinement of neutron diffraction data yields strongly overestimated δ values, by 0.20–0.31 oxygen atoms per formula unit, compared to other methods. The uncertainty of oxygen content in BSCF from the neutron diffraction data is discussed in terms of strong diffuse scattering leading to undervalued oxygen occupancy in a standard Rietveld refinement. [ABSTRACT FROM AUTHOR]

A herd of seven captive-born Grevy's zebras ( Equus grevyi ) experienced an outbreak of nasal discharge and sneezing. Clinical signs, including lethargy and anorexia, were severe and acute in three animals, including a 16-mo-old male that died within 48 h. Treatment of two severely affected zebras included valacyclovir (40 mg/kg PO), meloxicam (0.6 mg/kg IM/PO), and cefquinome (2.5 mg/kg IM q48h). An adult female improved rapidly, and clinical signs resolved within 48 h of treatment. Administration of valacyclovir pellets was very complicated in a 2-mo-old female, and death occurred within 48 h. Histologic examination of the two individuals that died revealed severe fibrinonecrotic interstitial pneumonia with prominent hyaline membranes and type II pneumocyte hyperplasia. Additionally, the 16-mo-old male presented systemic endothelial activation with vascular thrombosis and necrosis and mild nonsuppurative meningoencephalitis. Herpesviral DNA was detected in the lungs of both individuals by nested polymerase chain reaction. The nucleic acid sequence of the amplicons showed 100% similarity with previously published equid alphaherpesvirus 9 sequences. Three additional animals developed mild nasal discharge only and recovered spontaneously. The zebras shared housing facilities with other species, including white rhinoceros ( Ceratotherium simum ), reticulated giraffe ( Giraffa camelopardalis reticulata ), and several antelope species. None of these animals showed clinical signs. Additionally, nasal swabs and whole blood samples were collected from cohoused white rhinoceroses ( n = 3) and springboks ( Antidorcas marsupialis , n = 3) as well as nasal swabs from cohoused reticulated giraffes ( n = 4). Nucleic acid sequence from equid herpesviruses was not detected in any of these samples. The source of the infection in the zebras remains unclear.