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

Preparation, thermal expansion, electrical conductivity and polarization of A2−αA α′BO4-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, A2−αSrαBO4−δ (A = Pr, Sm, B = Fe, Co) could be obtained as a single K2NiF4-structural phase. Thermal expansion coefficients (TECs) of the specimens increase with increasing Sr2+ content, TECs of cobaltites are much higher than that of ferrites. The electrical conductivity of cobaltites is in the order of 102 S cm− 1 near 800 °C, which is acceptable for the cathode of IT-SOFC. Polarization measurements showed that Sm0.5Sr1.5CoO4−δ exhibited the lowest cathodic overpotential at 700–900 °C (72 mV at 500 mA/cm2 at 800 °C), being a high potential candidate of cathode material for IT-SOFCs.