Ba1−xCo0.9−yFeyNb0.1O3−δ (x = 0–0.15, y = 0–0.9) as cathode materials for solid oxide fuel cells

Abstract Perovskite oxide Ba 1.0 Co 0.7 Fe 0.2 Nb 0.1 O 3−δ has been reported as oxygen transport membrane and cathode material for solid oxide fuel cells (SOFCs). In this study, the effects of A-site cation deficiency and B-site iron doping concentration on the crystal structure, thermal expansion coefficient (TEC), electrical conductivity and electrochemical performance of Ba 1−x Co 0.9−y Fe y Nb 0.1 O 3−δ ( x  = 0–0.15, y  = 0–0.9) have been systematically evaluated. Ba 1−x Co 0.9−y Fe y Nb 0.1 O 3−δ ( x  = 0–0.10, y  = 0.2 and x  = 0.10, y  = 0.2–0.6) can be indexed to a cubic structure. Increased electrical conductivity and decreased cathode polarization resistance have been achieved by A-site deficiency. No obvious variation can be observed in TEC by A-site deficiency. The electrical conductivity and TEC of Ba 0.9 Co 0.9−y Fe y Nb 0.1 O 3−δ decrease while the cathode polarization resistance increases with the increase in iron doping concentration. The highest conductivity of 13.9 S cm −1 and the lowest cathode polarization resistance of 0.07 Ω cm 2 have been achieved at 700 °C for Ba 0.9 Co 0.7 Fe 0.2 Nb 0.1 O 3−δ . The composition Ba 0.9 Co 0.3 Fe 0.6 Nb 0.1 O 3−δ shows the lowest TEC value of 13.2 × 10 −6  °C −1 at 600 °C and can be a potential cathode material for SOFCs.