A2−αAα′BO4-type oxides as cathode materials for IT-SOFCs (A=Pr, Sm; A′=Sr; B=Fe, Co)

Abstract Preparation, thermal expansion, electrical conductivity and polarization of A 2− α A α ′ B O 4 -type oxides ( A = Pr, Sm, A ′ = Sr, B = Fe, Co) were investigated systematically to evaluate their potential as cathode materials for IT-SOFCs. Within 0.8 ≤ α ≤ 1.5, A 2− α Sr α B O 4− δ ( A = Pr, Sm, B = Fe, Co) could be obtained as a single K 2 NiF 4 -structural phase. Thermal expansion coefficients (TECs) of the specimens increase with increasing Sr 2+ content, TECs of cobaltites are much higher than that of ferrites. The electrical conductivity of cobaltites is in the order of 10 2 S cm − 1 near 800 °C, which is acceptable for the cathode of IT-SOFC. Polarization measurements showed that Sm 0.5 Sr 1.5 CoO 4− δ exhibited the lowest cathodic overpotential at 700–900 °C (72 mV at 500 mA/cm 2 at 800 °C), being a high potential candidate of cathode material for IT-SOFCs.