Investigation of layered perovskite NdBa0.5Sr0.25Ca0.25Co2O5+δ as cathode for solid oxide fuel cells

Layered perovskite oxides with and without Ca-doped NdBa0.5Sr0.25Ca0.25Co2O5+δ (NBSCaCO) and NdBa0.5Sr0.5Co2O5+δ (NBSCO) are studied to investigate the effects of Ca doping on the crystal structure, thermal behavior, electrical and electrochemical properties. Both NBSCO and NBSCaCO are tetragonal structure with P4/mmm space group. The average thermal expansion coefficient (TEC) value is reduced from 23.3 × 10−6 K−1 to 19.8 × 10−6 K−1 during 30-800 °C. The electrical conductivities are increased by Ca doping. Both electrical conductivities of NBSCO and NBSCaCO are higher than 600 S·cm−1 over 30-800 °C. Substitution of Sr with Ca can effectively improve the electrochemical properties of NBSCaCO. From 650 °C to 800 °C, the area specific resistance (ASR) of NBSCaCO are decreased from 0.62 to 0.062 Ω cm2 and the corresponding output power density are increased from 258 to 812 mW cm−2. On the basis of these results, Ca doped layered perovskite NBSCaCO can be a good cathode candidate material for SOFC application.