Ca and Fe co-doped SmBaCo₂O_{5 + δ}layered perovskite as an efficient cathode for intermediate-temperature solid oxide fuel cells

A-site Ca and B-site Fe co-doped SmBa_{1 − x}Ca_xCo_{2 − y}Fe_yO_{5 + δ}(x = 0, y = 0; x = 0.25, y = 0; x = 0.25, y = 1.0) layered perovskites are prepared and evaluated as the cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The synergistic effects of co-doping on the crystal structure, chemical compatibility with the electrolyte, thermal expansion behavior, electrical conductivity, and electrochemical performance are investigated. Ca and Fe co-doping lowers the thermal expansion coefficient of SmBaCo₂O_{5 + δ}. The area specific resistance of the Ca and Fe co-doped sample (SmBa_0.75Ca_0.25CoFeO_{5 + δ}-GDC) is decreased by 49.3%, compared with that of the undoped sample at 800 °C, based on a GDC electrolyte. Furthermore, the maximum power density of a GDC electrolyte-supported single cell with a SmBa_0.75Ca_0.25CoFeO_{5 + δ}-GDC cathode is increased by 50.7% at 800 °C. The results indicate that the Ca and Fe co-doping layered perovskite SmBa_0.75Ca_0.25CoFeO_{5 + δ}is an excellent cathode material for IT-SOFC applications.