Modulating the structural and electrical properties of SrFeO3–δ by a-site alkali metal ion doping

Abstract

The electrical properties of perovskite structured SrFeO3–δ can be modulated by A site doping. The present work focuses on the influence of concentration and ionic radii of alkali metal cation on the structural and electrical properties of Sr1–xAxFeO3–δ (A = Ca, Ba and x = 0, 0.25, 0.50, 0.75). The x-ray diffraction studies confirm the phase change from cubic to orthorhombic with Ca content while orthorhombic to cubic structural translation was observed with Ba concentration. A lattice contraction and expansion were observed for doping depending on the ionic radii of dopant cation. The x-ray photoelectron spectroscopy results indicate the presence of Fe in mixed valence state of +2, +3, +4 state and adsorbed oxygen content was found to be higher upon Ba doping than that of Ca. A maximum conductivity of 1.82 × 10−3 S cm−1 (x = 0.25) and 5.31 × 10−3 S cm−1 (x = 0.5) was observed at 800 °C for Ca and Ba doped samples, respectively, one order higher than the base SrFeO3–δ .Thus, our results emphasise the importance of dopant addition on tailoring the electrode properties for SOFC application.