Effect of iron substitution content on structure, thermal expansion behavior and electrochemical properties of La0.5Ba0.5Co1−yFeyO3−δ

Cubic perovskite oxides La0.5Ba0.5Co1−yFeyO3−δ (LBCF-y) with Fe content y = 0.1–0.7 were synthesized by sol-gel method and were studied with respect to their oxygen content, defect chemistry, thermal expansion behavior, and electrical and electrochemical properties. LBCF-y had increased oxygen content and cell volumes with higher Fe content. The chemical defects at B-sites of LBCF-y are Fe4+, Co4+ and Co3+ ions for y = 0.1–0.3, and Fe4+, Fe3+ and Co3+ ions for y ≥ 0.5 respectively. Thermal expansion coefficients of LBCF-y oxides firstly increased to a maximum at y = 0.3 then decreased gradually with bigger y. Conductivities of LBCF-y decreased with higher Fe content, and the maximum conductivity was 800 S cm−1 at 500 K for LBCF-0.1 sample. Fe substitutions for Co in LBCF-y cathodes increase the high-frequency resistance associated with oxygen ionic diffusion process while hardly influence the low-frequency gas diffusion process. Very low area-specific resistances, <0.1 Ω cm2 at 923 K, were obtained for LBCF-y (y = 0.1–0.7) oxides, demonstrating their potential applications as cathode materials for intermediate-temperature solid oxide fuel cells.

► La0.5Ba0.5Co1−yFeyO3−δ (LBCF-y) with Fe content y = 0.1–0.7 are pure cubic perovskite oxides. ► LBCF-y had increased oxygen content/cell volume and decreased conductivities with higher Fe content. ► Thermal expansion coefficients of LBCF-y underwent an up–down transition with higher Fe content. ► Area-specific resistances of LBCF-y cathodes increased with higher Fe content. ► Excellent electrochemical performances were obtained for LBCF-y cathodes.