Oxygen exchange in MIEC perovskite-like oxide La0.6Sr0.4Fe0.965Ta0.035O3-δ: Kinetics and equilibrium parameters

Abstract

Previously, a strategy for doping MIEC perovskites ABO3-δ with highly charged cations B5+ (Nb, Ta) and B6+ (Mo, W) was developed. The doping strategy is based on the idea that strontium ferrite/cobaltite-based perovskites are ferroelastic, whereas highly charged cations are ferroactive species. An increase in the concentration of the dopant leads to a reduction in the size of the domains of the ferroelastic phase down to the nanoscale. This resulted in the smearing of phase transitions with the formation of the highly conductive glassy state. Tantalum-doped lanthanum-strontium-ferrite perovskite (La0.6Sr0.4Fe1-xTaxO3-δ, LSFTx) was prepared via solid-state reaction using chemically pure oxide powders of La2O3, SrCO3, Fe2O3, and Ta2O5, followed by calcination and sintering up to 1350 °C. The structural and surface properties were examined using X-ray diffraction and a scanning electron microscope. The original oxygen partial pressure relaxation (OPPR) method was used to study the kinetic properties of LSFTx. Continuous equilibrium phase diagram “T – pO2 – δ” first obtained by oxygen release technique for composition LSFT3.5. Power law dependencies of the kinetic properties on the oxygen partial pressure are presented.