Structural and defect chemistry guidelines for Sr(V,Nb)O-3-based SOFC anode materials
authors Macias, J; Yaremchenko, AA; Fagg, DP; Frade, JR
nationality International
journal PHYSICAL CHEMISTRY CHEMICAL PHYSICS
keywords LANTHANUM STRONTIUM VANADATE; OXIDE FUEL-CELLS; ELECTRICAL-CONDUCTIVITY; SRVO3; PERFORMANCE; EXPANSION; ELECTROLYSIS; STABILITY; CERAMICS; SYNGAS
abstract Structural and defect chemistry guidelines were used for Nb-substituted SrVO3-delta materials, designed to meet SOFC anode requirements, with emphasis on redox tolerance, thermochemical compatibility with other SOFC materials, electrical conductivity and adjustable changes in oxygen stoichiometry for their prospective impact on electrocatalytic performance. SrV1-xNbxO3-delta (x = 0-0.30) ceramics were prepared by solid-state synthesis and sintered at 1773 K in a reducing atmosphere. XRD and SEM/EDS showed that under these conditions a single-phase cubic perovskite structure appears up to x approximate to 0.25. Electrical conductivity is metallic-like and nearly p(O-2)-independent. Although substitution by niobium decreases the conductivity, which still exceeds 100 S cm(-1) for x <= 0.20 at temperatures below 1273 K, it also expands the stability domain of the cubic perovskite phase and suppresses partly high thermochemical expansion characteristic of parent SrVO3-delta. The upper p(O-2) limit of phase stability was found to shift from similar to 2 x 10(-15) atm for the undoped material to similar to 2 x 10(-12) atm for x = 0.30, whereas the average thermal expansion coefficient at 773-1223 K decreased from 22.7 x 10(-6) to 13.3 x 10(-6) K-1. SrV1-xNbxO3-delta perovskites undergo oxidative decomposition in air, which causes dimensional and microstructural changes. However, sluggish kinetics of oxidation under inert gas conditions results in nearly reversible behavior in relatively short-term redox cycles between reducing and inert atmospheres. Subtle structural changes and a close correlation with point defect chemistry clarify these sluggish changes and provide guidelines to retain the metastability.
publisher ROYAL SOC CHEMISTRY
issn 1463-9076
year published 2015
volume 17
issue 16
beginning page 10749
ending page 10758
digital object identifier (doi) 10.1039/c5cp00069f
web of science category Chemistry, Physical; Physics, Atomic, Molecular & Chemical
subject category Chemistry; Physics
unique article identifier WOS:000352707200047
link http://pubs.rsc.org/en/Content/ArticleLanding/2015/CP/C5CP00069F#!divAbstract

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