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

The electrical properties of perovskite structured SrFeO3-delta 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 Sr(1-x)A(x)FeO(3-delta) (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 x 10(-3) S cm(-1) (x = 0.25) and 5.31 x 10(-3) S cm(-1) (x = 0.5) was observed at 800 degrees C for Ca and Ba doped samples, respectively, one order higher than the base SrFeO3-delta.Thus, our results emphasise the importance of dopant addition on tailoring the electrode properties for SOFC application.