SmBa_1-xCa_xCo₂O_5+d Layered Perovskite Cathodes for Intermediate Temperature-operating Solid Oxide Fuel Cells

In SmBa_1-xCa_xCo₂O_5+d (x = 0.01, 0.03, 0.1, and 0.2, SBCCO) oxide systems calcined at 1100°C for 8 h, the XRD patterns of the SBCCO single phase were maintained in the cases of SmBa_0.97Ca_0.03Co₂O_5+d (SBCCO-0.97) and SmBa_0.99Ca_0.01Co₂O_5+d (SBCCO-0.99) compositions. In SmBa_0.8Ca_0.2Co₂O_5+d (SBCCO-0.8) and SmBa_0.9Ca_0.1Co₂O_5+d (SBCCO-0.9), CaCoSmO₄ existed with the pattern SBCCO. SBCCO structures were identified as orthorhombic crystal structures because they showed splitting of the X-ray diffraction (XRD) peaks at 23.4°, 47.9°, and 59.1°.Typical metallic conduction behaviors were found in all measured compositions except SBCCO-0.8, which showed a metal-insulator transition (MIT) behavior. Compared to other SmBa_1-xCa_xCo₂O_5+d compositions, SBCCO-0.8 showed the highest electrical conductivity of 460 S/cm at 500°C. In particular, SBCCO-0.9 was found to have an excellent ASR characteristic of about 0.077 Ωcm² at 700°C. The activation energy of SBCCO-0.9 was the lowest among SBCCO oxide systems with a value of 0.77 eV.