Influence of alkaline-earth substitution on structure and oxygen transport of perovskite-type oxides La0.6A0.4FeO3-δ (A = Ca, Sr, Ba)

Structure, oxygen-nonstoichiometry and oxygen transport properties of perovskite-type oxides La0.6A0.4FeO3-δ (A = Ca, Sr and Ba, abbreviated as LCF64, LSF64, LBF64, respectively) were investigated. Rietveld analysis of the high-temperature X-ray diffraction (XRD) patterns recorded in air show an orthorhombic-to-rhombohedral transition at 625 °C for LSF64, a rhombohedral-to-cubic transition at 850 °C for LSF64, while LBF64 remains cubic over the entire temperature range (600-1000 °C) covered by the experiments. Results from electrical conductivity relaxation (ECR) measurements in the range of temperature 650-900 °C and pO2 0.045-0.9 bar indicate that the chemical diffusion coefficients (Dchem) for the three compositions are very close (Fig. 1a). For LSF64, good agreement is noted with data reported previously [1,2]. Using data of oxygen non-stoichiometry of the materials measured by thermogravimetry, values for the oxygen self-diffusion coefficient (DS) and the diffusion coefficient (mobility) of oxygen vacancies (DV) were calculated. While DS increases in the sequence Ca < Sr < Ba, the opposite trend is found for DV as shown in Figs. 1b and 1c, respectively. At the conference, results of density functional theory (DFT) calculations are compared with the experimental data.