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Efficient use of barium-containing electrocatalysts for NO x decomposition in electrochemical solid oxide cells requires good chemical compatibility of these materials with the electrolyte in a temperature range 300–600 °C and imply the use of porous electrolytes allowing significant gas flows across the cell. BaZr 0.85 Y 0.15 O 3 electrolyte has good chemical compatibility with Ba-containing materials and potentially appropriate level of ionic conductivity. This work is focused on guidelines for processing BaZr 0.85 Y 0.15 O 3 ceramics with cellular porosity (i.e., with spherical pores and with developed gas interconnections), using emulsification of paraffin in water-based ceramic suspension. Porosity of sintered at 1500 °C ceramics is practically open and varies in the range of 70–84%, with average pore sizes in the range ~3–30 µm. The type of pore size distribution is close to log-normal. Microstructure, average cell size and level of gas permeability mainly depends on surfactant content, while total porosity is mostly determined by paraffin content. [ABSTRACT FROM AUTHOR]

Magnesium-substituted europium vanadate ceramics, Mg x EuVO 4 ± δ ( x = 0–0.5), were prepared by solid state method and characterized by XRD, SEM/EDS, dilatometry, UV–vis spectroscopy, impedance spectroscopy, and measurements of oxygen-ion transference numbers ( t o ¯ ). Magnesium was found to substitute preferentially into vanadium sublattice of zircon-type EuVO 4 with limited solubility of ∼5 at.%. Additions of magnesium increase slightly coefficients of thermal expansion (3.2–6.0 ppm/K at 150–400 °C) and have negligible effect on the optical properties. Undoped EuVO 4 is predominantly an oxygen-ionic conductor with t o ¯ = 0.96–0.99 at 700–900 °C under oxidizing conditions. Acceptor-type substitution suppresses total conductivity and oxygen-ionic transport. The variations of electrical transport properties are discussed in terms of interstitial oxygen diffusion in the parent EuVO 4 and oxygen vacancy diffusion in Mg-substituted vanadate. Humidified atmosphere has negligible impact on the electrical properties of substituted ceramics but results in increased electrical conductivity of EuVO 4 indicating a protonic contribution to the total electrical transport. [ABSTRACT FROM AUTHOR]

The influence of elevated oxygen pressure (from 1 to 50 bar) on phase separation in Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3−δ (BSCF) cubic perovskite was investigated in the range of 300to 1300 K. X-ray diffraction and thermogravimetric analysis revealed two separation processes occurring in the high temperature (HT), ~1043 K, and low temperature (LT), ~713 K, ranges. Increasing oxygen pressure shifts slightly the LT phase separation to lower temperature, but has a rather minor effect on the volume fraction growth of the secondary phase. Phase transformation in the HT range is a slow process and the degree of decomposition is strongly influenced by the cooling rate from higher temperatures. On the contrary, the LT separation is relatively fast and is essentially independent of the cooling rate. The BSCF ceramics thermally treated at p (O 2 )=50 bar was analyzed by different electron microscopy techniques. The structures of separation products were identified as trigonal Ba 3 Co 10 O 17 -like lamellae and 2H-hexagonal Ba 0.5±x Sr 0.5±x CoO 3−δ perovskite, respectively. [ABSTRACT FROM AUTHOR]

The prospects for processing Ta-substituted titanium dioxide (TiO 2) for thermoelectric applications were explored in this work using the Laser Floating Zone (LFZ) method under different growth atmospheres, specifically air and H 2 /N 2. An intermediate approach, where the samples were initially LFZ-grown in air and subsequently post-annealed in H 2 /N 2 , was also evaluated to gain deeper insights into the effects of the processing conditions. XRD results revealed rutile as the majority phase regardless of the applied conditions. The phase composition was found to be strongly affected by the growth atmosphere, from the formation of TiTa 2 O 7 to Magnéli phase-based impurities when shifting from oxidising to reducing conditions. The formation of Magnéli phases was favoured by lower tantalum content. LFZ processing under a hydrogen-containing atmosphere was found to promote the reduction of titanium cations and inducing oxygen deficiency, as confirmed by thermogravimetric analysis. This reduction significantly enhanced the electrical properties of the samples. The thermoelectric properties were evaluated by measuring the Seebeck coefficient and electrical conductivity at high temperatures. The electrical performance was found to be sensitive to both Ta content and specific microstructural features, including the presence of Magnéli phases. A maximum power factor of 735 μW/(m·K²) was achieved at 1120 K, which is one of the best values reported in the literature for similar materials. [ABSTRACT FROM AUTHOR]

Strontium-cerium manganite Sr 0.7 Ce 0.3 MnO 3-δ was evaluated as a Co-free candidate material for oxygen electrodes of commercial-grade solid oxide fuel and electrolysis cells (SOFC/SOEC). Sr 0.7 Ce 0.3 MnO 3-δ ceramics was confirmed to show high electrical conductivity (304–309 S/cm at 700–800 °C) and moderate thermal expansion coefficient (12.3 ppm/K at 25–1100 °C) at atmospheric oxygen pressure, and very small changes in oxygen nonstoichiometry on p(O 2)-T cycling under oxidizing conditions below 1000 °C. The studies of oxygen transport properties by electrical conductivity relaxation technique revealed that, compared to (La,Sr)(Co,Fe)O 3-δ perovskites, Sr 0.7 Ce 0.3 MnO 3-δ exhibits an order of magnitude lower oxygen diffusivity, with D chem in the range of (4–10) × 10−6 cm2/s at 875–950 °C, but similar oxygen surface exchange kinetics, with k ex in the range (0.5–5.6) × 10−3 cm/s at these temperatures. The electrochemical performance of fuel electrode-supported solid oxide cells with Sr 0.7 Ce 0.3 MnO 3-δ oxygen electrodes at 700–800 °C was found to be moderate but could be improved by surface activation of Sr 0.7 Ce 0.3 MnO 3-δ electrode layers with praseodymia. The activation of the oxygen electrode resulted in a reduction in total polarization resistance of the cells by 2 and 7 times in SOFC and SOEC modes, respectively, under moderate current densities at 800 °C. The polarization losses in SOFC mode at 700–800 °C were 1.5–2.0 times higher than in the SOEC regime. Further improvements in oxygen electrode performance are necessary to compete with solid electrolyte cells with (La,Sr)CoO 3-δ and (La,Sr)(Co,Fe)O 3-δ electrodes. • Sr 0.7 Ce 0.3 MnO 3-δ (SCM) was evaluated as a Co-free oxygen electrode material for SOFC/SOEC. • Oxygen diffusivity in SCM is lower but surface exchange kinetics is comparable to LSCF. • Surface activation of SCM electrodes by PrO y substantially enhances SOC performance. • Polarization losses in SOFC mode at 700–800 °C are 1.5–2.0 times higher than in SOEC mode. [ABSTRACT FROM AUTHOR]

The present work aims to evaluate relevant effects of the size of substituting rare-earth cation on electrical conductivity and thermal expansion of donor-doped SrTiO 3 as ceramic components of electrochemical solid electrolyte cells. A series of strontium titanate-based ceramics with a moderate doping level and different cation stoichiometry, Sr 0.90 Ln 0.10 TiO 3±δ and Sr 0.85 Ln 0.10 TiO 3±δ (Ln = La–Yb), are prepared under identical conditions with the final reductive treatment in 10%H 2 –N 2 atmosphere at 1500 °C for 10 h. The solubility of rare-earth cations in the strontium sublattice of perovskite-type SrTiO 3 is found to decrease with reducing ionic radius leading to a segregation of secondary pyrochlore-type Ln 2 Ti 2 O 7 phase in the case of smaller rare-earth cations (Ln = Dy–Yb). The results of electrical, dilatometric and thermogravimetric studies suggest that the size of donor Ln3+ cation and cation stoichiometry have no evident impact on the electrical conductivity or thermal expansion behavior as long as the content of Ln3+ is within the solubility limits. All reduced donor-doped titanate ceramics (except Yb-doped) show a similar level of electrical conductivity, 100–155 S cm−1 at 800 °C, determined by the content of Ln3+ in the strontium sublattice, and moderate thermal expansion coefficients, 11.9–12.1 ppm K−1 at 25–1100 °C, compatible with that of conventional solid electrolytes. Image 1 • Reduced Sr 0.90 Ln 0.10 TiO 3±δ and Sr 0.85 Ln 0.10 TiO 3±δ were prepared identically. • Ln3+ size has no evident impact on electrical conductivity and thermal expansion. • Electrical conductivity is determined by the content of Ln3+ in the Sr sublattice. • Reduced titanates exhibit a similar conductivity of 100–155 S cm−1 at 800 °C. • Thermal expansion coefficients are 11.9–12.1 ppm K−1 at 25–1100 °C. [ABSTRACT FROM AUTHOR]

The present work explores mechanosynthesis of lanthanum aluminate-based perovskite ceramics and corresponding effects on ionic-electronic transport properties. La 1- x Ca x AlO 3-δ (x = 0.05–0.20) nanopowders were prepared via one-step high-energy mechanochemical processing. Sintering at 1450 °C yielded dense ceramics with submicron grains. As-prepared powders and sintered ceramics were characterized by XRPD, XPS and SEM. Electrochemical studies showed that partial oxygen-ionic conductivity in prepared La 1- x Ca x AlO 3-δ increases with calcium content up to 10 at.% in the lanthanum sublattice and then levels off at ∼6 × 10−3 S/cm at 900 °C. La 1- x Ca x AlO 3-δ ceramics are mixed conductors under oxidizing conditions and ionic conductors with negligible contribution of electronic transport in reducing atmospheres. Oxygen-ionic contribution to the total conductivity is 20–68% at 900 °C in air and increases with Ca content, with temperature and with reducing p(O 2). Impedance spectroscopy results showed however that electrical properties of mechanosynthesized La 1- x Ca x AlO 3-δ ceramics below ∼800 °C are determined by prevailing grain boundary contribution to the total resistivity. [ABSTRACT FROM AUTHOR]

Abstract The proton conductivity and solid solubility limits of acceptor strontium doped vanadium stabilised lanthanum niobate (Sr y La 1−y Nb 1-x V x O 4-δ , x = 0.25, 0.30 and y = 0 to 0.10) were explored as potential proton conducting ceramic electrolytes. All samples were synthesized via a solid-state method. The phase purity, microstructure and thermal expansion behaviour of the materials were studied using powder X-ray diffraction, scanning electron microscopy and dilatometry, respectively. A maximum solid solution limit of 5% Sr in the A-site of Sr y La 1−y Nb 1-x V x O 4-δ samples is observed for a vanadium content of x = 0.25, while further increases in the Sr or vanadium contents lead to the presence of Sr 3 (VO 4) 2 as a secondary phase. This acceptor dopant content of 5%Sr in the current scheelite material exceeds that possible in the parent vanadium-free fergusonite Sr y La 1−y NbO 4-δ material by a factor of 5. All Sr doped scheelite materials show linear thermal expansion behaviour, successfully avoiding the scheelite to fergusonite structural phase change during thermal cycling. The average grain size is shown to be increased by increasing vanadium content. In humid conditions, all phase pure samples show predominantly proton conductivity at lower temperatures, while p-type conductivity is noted at higher temperatures under dry oxidising conditions. In the low temperature range, the Sr 0.05 La 0.95 Nb 0.75 V 0.25 O 4-δ sample, containing the largest acceptor dopant concentration, exhibits slightly higher bulk and specific grain boundary conductivities in comparison to other phase pure compositions. Highlights • Proton conductivity Sr 1-y La y Nb 1-x V x O 4-δ , x = 0.25, 0.30 and y = 0 to 0.10 assessed. • At low T, bulk + specific grain boundary conductivities increased by Sr-doping. • Solid solubility limits clarified. • Sr content scheelite Sr 0.05 La 0.95 Nb 0.85 V 0.25 O 4-δ > parent fergusonite by factor of 5. • Scheelite/fergusonite structural phase change avoided by vanadium substitution. [ABSTRACT FROM AUTHOR]

Abstract: Iron-based oxides are considered as promising consumable anode materials for high temperature pyroelectrolysis. Phase relationships, redox stability and electrical conductivity of Fe3−x Al x O4 spinels were studied at 300–1773K and p(O2) from 10−5 to 0.21atm. Thermogravimetry/XRD analysis revealed metastability of the sintered ceramics at 300–1300K. Low tolerance against oxidation leads to dimensional changes of ceramics upon thermal cycling. Activation energies of the total conductivity corresponded to the range of 16–26kJ/mol at 1450–1773K in Ar atmosphere. At 1573–1773K and p(O2) ranging from 10−5 to 0.03atm, the total conductivity of Fe3−x Al x O4 is nearly independent of the oxygen partial pressure. The conductivity values of Fe3−x Al x O4 (0.1≤ x ≤0.4) at 1773K and p(O2) ∼10−5 to 10−4 atm were found to be only 1.1–1.5 times lower than for Fe3O4, showing high potential of moderate aluminium additions as a strategy for improvement of refractoriness for magnetite without significant deterioration of electronic transport. [Copyright &y& Elsevier]

Ruddlesden-Popper La 2- x Gd x NiO 4+δ (x = 0–0.4) nickelates were synthesized by glycerol-nitrate combustion technique and explored as potential oxygen electrode materials for solid oxide fuel/electrolysis cells. Similar to the parent La 2 NiO 4+δ , the metastability of RP-type n = 1 structure limits the applicability of La 2- x Gd x NiO 4+δ to temperatures below 900 °C. These solid solutions are mixed conductors with predominantly p -type electronic conductivity that exceeds 50 S/cm at 500–800 °C in air. Substitution by gadolinium does not change the overstoichiometric oxygen content in air but has a negative impact on the mobility of interstitial oxygen, most likely, due to steric effects associated with the lattice shrinkage on doping. The electrochemical activity of bilayer electrodes comprising functional La 2- x Gd x NiO 4+δ and current collecting LaNi 0.6 Fe 0.4 O 3-δ + 3 wt% CuO layers in contact with Ce 0.8 Gd 0.2 O 1.9 electrolyte was studied in air at 550–850 °C. Analysis of electrochemical impedance spectroscopy data employing the ALS (Adler-Lane-Steele) model revealed the limiting role of oxygen-ionic conductivity of functional La 2- x Gd x NiO 4+δ materials in overall electrode performance. • La 2- x Gd x NiO 4+δ (x = 0–0.4) were synthesized by the glycerol-nitrate combustion method. • Gd substitutions do not change oxygen nonstoichiometry in air. • p -type electronic conductivity is above 50 S/cm in air at 500–800 °C. • Crystal lattice shrinkage on substitution has a negative effect on oxygen-ion mobility. • Electrochemical activity of La 2- x Gd x NiO 4+δ electrodes correlates with ionic conductivity. [ABSTRACT FROM AUTHOR]

Abstract Nano-sized composite La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF)-Ce 0.8 Sm 0.2 O 1.9 (SDC) powder was synthesised by one-step microwave self-assisted combustion synthesis and characterized by X-ray diffraction and transmission electron microscopy. Electrochemical performance of composite LSCF-SDC cathode in contact with Ce 0.8 Gd 0.2 O 1.9 (GDC) solid electrolyte under steady state polarisation was studied employing electrochemical impedance spectroscopy in 3-electrode cell configuration. The evolution of elementary steps of oxygen reduction reaction was analysed under cathodic polarisation in potentiostatic mode (up to −0.8 V) in the temperature range 650–750 °C. The composite LSCF-SDC cathode prepared by one-step microwave combustion route demonstrated a lower overall polarisation resistance when compared to literature reports of similar cathodes produced by other synthesis routes. [ABSTRACT FROM AUTHOR]

Development of the cathode contact materials (CCMs) for intermediate-temperature solid oxide fuel cells (IT-SOFCs) is a relatively new task promoted by the appearance of full-sized cells, which may operate below 700 °C with sufficient performance, on the market. CCM must ensure a low-resistive interface between interconnect and cathode and is supposed to be sintered at temperatures below 800 °C, as imposed by the specifications of IT-SOFCs and corresponding sealants. The present work is focused on the elaboration of CCMs derived from perovskite-like La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ employing two approaches: introduction of the A-site cation vacancies and partial substitution by copper in B sublattice. Both approaches were found to result in a higher electrical conductivity below 800 °C if compared to the parent material. All studied materials exhibit acceptable coefficients of thermal expansion, 13.5–14.8 ppm K −1 at 25–700 °C. Area-specific resistance (ASR) of CCM/chromium barrier (Mn 1.5 Co 1.5 O 4 )/interconnect (Crofer 22APU) assemblies prepared by the screen-printing was measured in air at 660–750 °C. The studies revealed that morphology of CCM powder should be considered as a key parameter in the formation of interfaces with a low resistivity. The best ASR values, below 4 mΩ cm 2 at 660–700 °C, were obtained for La 0.6 Sr 0.4 Co 0.15 Cu 0.10 Fe 0.75 O 3-δ , La 0.6 Sr 0.4 Co 0.15 Cu 0.05 Fe 0.80 O 3-δ and (La 0.60 Sr 0.40 ) 0.995 Co 0.20 Fe 0.80 O 3-δ as CCMs. [ABSTRACT FROM AUTHOR]

In this study, nanostructured ceria (CeO 2 ) films are deposited on Si(100) and ITO coated glass substrates by pulsed DC magnetron sputtering using a CeO 2 target. The influence on the films of using various gas ambients, such as a high purity Ar and a gas mixture of high purity Ar and O 2 , in the sputtering chamber during deposition are studied. The film compositions are studied using XPS and SIMS. These spectra show a phase transition from cubic CeO 2 to hexagonal Ce 2 O 3 due to the sputtering process. This is related to the transformation of Ce 4+ to Ce 3+ and indicates a chemically reduced state of CeO 2 due to the formation of oxygen vacancies. TGA and electrochemical cyclic voltammetry (CV) studies show that films deposited in an Ar atmosphere have a higher oxygen storage capacity (OSC) compared to films deposited in the presence of O 2 . CV results specifically show a linear variation with scan rate of the anodic peak currents for both films and the double layer capacitance values for films deposited in Ar/O 2 mixed and Ar atmosphere are (1.6 ± 0.2) × 10 −4 F and (4.3 ± 0.5) × 10 −4 F, respectively. Also, TGA data shows that Ar sputtered samples have a tendency to greater oxygen losses upon reduction compared to the films sputtered in an Ar/O 2 mixed atmosphere. [ABSTRACT FROM AUTHOR]

• A facile method to process porous Fe 2-x Mn x O 3 catalysts was developed. • Biomass gasification was studied to find out the applicability of the catalyst. • The catalyst exhibited high activity for biomass-derived tar conversion (83%). • Activity is linked to the variable oxygen stoichiometry of mixed Fe/Mn oxides. • Pos-mortem analysis suggests sulphur tolerance in gasification conditions. In the present study, catalytic gasification of biomass was investigated by incorporation of a supported Fe 2-x Mn x O 3 catalyst into the freeboard zone of a bubbling fluidized bed gasifier. The material was processed by combining incipient wetness impregnation with microwave-assisted firing methods. These catalysts were characterized by elemental, structural and microstructural analyses, and redox testing by thermogravimetry. Catalytic performance was assessed by comparison with blank tests and used to study the influence of the catalyst temperature, equivalence ratio and gas hourly space velocity on tar decomposition. The catalyst revealed higher activity in converting tar compounds with increasing temperature and equivalence ratio, while increasing the gas hourly space velocity showed a negative impact on catalyst performance. Under optimal operating conditions, the catalyst exhibited a significant impact on tar conversion (83 %) and gasification parameters, such as the gas yield (0.81 to 0.93 N m d r y , g a s 3 ∙ k g d r y , f u e l - 1 ), carbon conversion efficiency (55.3 to 65.1 %) and cold gas efficiency (50.7 to 61.6 %). Post-mortem analysis of the tested catalyst provided further information on redox changes and their dependence on temperature, which were co-related with catalytic performance. Elemental mapping showed traces of sulphur, which increased with temperature and did not correlate with the catalytic performance; this was interpreted by thermodynamic modelling, based on the wide redox stability range of divalent manganese oxide and its enhanced tolerance to hydrogen sulphide. [ABSTRACT FROM AUTHOR]

The current work investigates the redox behaviour of peak performing Ni–BaZr 0.85 Y 0.15 O 3−δ (Ni-BZY) cermet anodes for protonic ceramic fuel cells (PCFCs) by electrochemical impedance measurements, scanning electron microscopy (SEM) and X-ray diffraction (XRD). Peak performing PCFC cermet anodes are documented to require much lower porosity levels than those needed in oxide-ion conducting counterparts. The polarisation behaviour of these optimised PCFC anodes is shown to be drastically impaired by redox cycling, with depletions in performance that correspond to around 80% of the original resistance values noted after the first redox cycle. The ohmic resistance (Rohmic) is also shown to be increased due to delamination at the electrode/electrolyte interface, as confirmed by postmortem microstructural analysis. In-situ measurements by environmental scanning electron microscopy (ESEM) reveal that degradation proceeds due to volume expansion of the nickel phase during the re-oxidation stage of redox cycling. The present study reveals degradation to be very fast for peak performing Ni-BZY cermets of low porosity. Hence, methods to improve redox stability can be considered to be essential before such anodes can be implemented in practical devices. [ABSTRACT FROM AUTHOR]

Abstract: The effects of K2O content on sintering and crystallization of glass powder compacts in the Li2O–K2O–Al2O3–SiO2 system were investigated. Glasses featuring SiO2/Li2O molar ratios of 2.69–3.13, far beyond the lithium disilicate (LD-Li2Si2O5) stoichiometry, were produced by conventional melt-quenching technique. The sintering and crystallization behaviour of glass powders was explored using hot stage microscopy (HSM), scanning electron microscopy (SEM), differential thermal (DTA) and X-ray diffraction (XRD) analyses. Increasing K2O content at the expense of SiO2 was shown to lower the temperature of maximum shrinkage, eventually resulting in early densification of the glass-powder compacts. Lithium metasilicate was the main crystalline phase formed upon heat treating the glass powders with higher amounts of K2O. In contrast, lithium disilicate predominantly crystallized from the compositions with lower K2O contents resulting in strong glass–ceramics with high chemical and electrical resistance. The total content of K2O should be kept below 4.63mol% for obtaining LD-based glass–ceramics. [Copyright &y& Elsevier]

Abstract: A series of alkaline-earth aluminosilicate glass-ceramics (GCs) were appraised with respect to their suitability as sealants for solid oxide fuel cells (SOFCs). The parent composition with general formula Ca0.9MgAl0.1La0.1Si1.9O6 was modified with Cr2O3 and BaO. The addition of BaO led to a substantial decrease in the total electrical conductivity of the GCs, thus improving their insulating properties. BaO-containing GCs exhibited higher coefficient of thermal expansion (CTE) in comparison to BaO-free GCs. An extensive segregation of oxides of Ti and Mn, components of the Crofer22 APU interconnect alloy, along with negligible formation of BaCrO4 was observed at the interface between GC/interconnects diffusion couples. Thermal shock resistance and gas-tightness of GC sealants in contact with yttria-stabilized zirconia electrolyte (8YSZ) was evaluated in air and water. Good matching of CTE and strong, but not reactive, adhesion to the solid electrolyte and interconnect, in conjunction with a high level of electrical resistivity, are all advantageous for potential SOFC applications. [Copyright &y& Elsevier]

Abstract: We report on the optimization of La2O3-containing diopside based glass-ceramics (GCs) for sealant applications in solid oxide fuel cells (SOFC). Seven glass compositions were prepared by modifying the parent glass composition, Ca0.8Ba0.1MgAl0.1La0.1Si1.9O6. First five glasses were prepared by the addition of different amounts of B2O3 in a systematic manner (i.e. 2, 5, 10, 15, 20wt.%) to the parent glass composition while the remaining two glasses were derived by substituting SrO for BaO in the glasses containing 2wt.% and 5wt.% B2O3. Structural and thermal behavior of the glasses was investigated by infrared spectroscopy (FTIR), density measurements, dilatometry and differential thermal analysis (DTA). Liquid–liquid amorphous phase separation was observed in B2O3-containing glasses. Sintering and crystallization behavior, microstructure, and properties of the GCs were investigated under different heat treatment conditions (800 and 850°C; 1–300h). The GCs with ≥5wt.% B2O3 showed an abnormal thermal expansion behavior above 600°C. The chemical interaction behavior of the glasses with SOFC electrolyte and metallic interconnects, has been investigated in air atmosphere at SOFC operating temperature. Thermal shock resistance and gas-tightness of GC sealants in contact with 8YSZ was evaluated in air and water. The total electrical resistance of a model cell comprising Crofer 22 APU and 8YSZ plates joined by a GC sealant has been examined by the impedance spectroscopy. Good matching of thermal expansion coefficients (CTE) and strong, but not reactive, adhesion to electrolyte and interconnect, in conjunction with a low level of electrical conductivity, indicate that the investigated GCs are suitable candidates for further experimentation as SOFC sealants. [Copyright &y& Elsevier]

Abstract: We report on the effect of La2O3 and Cr2O3 on the structural, thermal and crystallization behavior of diopside-based glasses and on the processing, microstructure and properties of the sintered glass-ceramics (GCs). The structural features and thermal behavior of the glasses were investigated by Fourier transform infrared spectroscopy, density measurements, dilatometry and differential thermal analysis. The sintering, crystallization, microstructure and properties of the GCs were investigated under different heat treatment conditions (800–1000°C; 1–300h). The good matching of thermal expansion coefficients and the strong, but not reactive, adhesion to yttria-stabilized zirconia and Crofer 22 APU alloy, in conjunction with a low level of electrical conductivity, indicates that the investigated GCs are suitable candidates for further experimentation as solid oxide fuel cell sealants. [Copyright &y& Elsevier]

In the present work, the anionic doping of a Ba-containing Nd 2 NiO 4+δ mixed conductor is proposed as an efficient means of tuning its functional properties for application as an oxygen/steam electrode material in protonic ceramic electrolysis cells (PCECs). Single-phase Nd 1.9 Ba 0. 1 NiO 4+δ F γ (γ = 0, 0.03, 0.05, 0.07 and 0.1) nickelates having a K 2 NiF 4 -type structure were prepared and comprehensively characterised in the range from room temperature to 1000 °C. A combination of complimentary techniques, including 4-probe DC electrical measurements, an electron-blocking method, electrochemical impedance spectroscopy and analysis of equivalent circuit schemes and distribution of relaxation times, was employed to reveal the fundamental correlations between electrical properties, oxygen-ionic transport and electrochemical performance of fluorinated nickelates. The highest ionic conductivity in combination with the lowest electrode polarisation resistance was found for the composition with γ = 0.05. The enhanced transport properties of this material were attributed to mixed anion lattice effect. Electrochemical tests of an electrolysis cell based on a proton-conducting BaCe 0. 5 Zr 0. 3 Y 0. 1 Y 0. 1 O 3–δ electrolyte with a Nd 1.9 Ba 0. 1 NiO 4+δ F 0.05 oxygen electrode demonstrated competitive performance compared to state-of-the-art PCECs, thus supporting the prospective viability of the proposed approach. • Nd 1.9 Ba 0.1 NiO 4+δ F γ (NBNFγ, where γ = 0–0.1) phases were successfully prepared. • Correlations between composition, defect structure and properties were elucidated. • NBNF0.05 shows improved transport properties: highest σ ion and lowest R p. • NBNF0.05 is a promising oxygen electrode candidate for PCFCs & PCECs. Image 1 [ABSTRACT FROM AUTHOR]