Sr-substituted SmBa_0.75Ca_0.25CoFeO_5+δ as a cathode for intermediate-temperature solid oxide fuel cells

Layered perovskite oxides have received enormous attention as promising cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). In this work, the SmBa_0.75-xSr_xCa_0.25CoFeO_5+δ (x = 0 and 0.25) samples are synthesized by solid-state reaction method. The effect of Sr doping on the crystal structure, chemical compatibility with the electrolyte, thermal expansion behavior, electrical conductivity, and electrochemical performance have been investigated. The substitution of Sr for Ba improves the electrical conductivity in comparison with the undoped sample. At 800 °C, the area specific resistance (ASR) value is decreased by 24% and the maximum powder density of the anode-supported single cell is increased by 30%. In contrast, at 600 °C, the ASR value is decreased by 41% and the maximum powder density is increased by 102%. The results indicate that the Sr-doping for this system has greater impact on electrochemical performance at lower temperature.