Enhanced Electrochemical Properties of Non-stoichiometric Layered Perovskites, SmBaCoO, for IT-SOFC Cathodes.

In this study, electrochemical properties of layered perovskites having non-stoichiometric compositions (SmBaCoO, = 0, 0. 01, 0.02, 0.03, 0.04, 0.05, 0.10, and 0.15) were analyzed for the direct application of cathode materials for Intermediate Temperature-operating Solid Oxide Fuel Cells (IT-SOFC). From the SmBaCoO oxide systems calcined at 1,100°C for 8 h, single phase (SmBaCoO, SBCO_1) was maintained only in the case of the = 0 composition. In the compositions of = 0.05-0.10, BaCoO was mixed with the pattern of SBCO. In addition, in the composition of = 0.15, it was confirmed that BaCoO and CoO phases coexisted with SBCO. In the compositions of SmBaCoO, the overall Area Specific Resistance (ASR) values decreased as the removal amount of Sm increased from = 0-0.10; then, the values increased for compositions from = 0.15. For example, the ASRs of SBCO_1, SmBaCoO (SBCO_0.95), SmBaCoO (SBCO_0.90), and SmBaCoO (SBCO_0.85) measured at 600°C were 0.301, 0.147, 0.119, and 0.179 Ω cm, respectively. In particular, SBCO_0.90 was found to have an excellent ASR property of about 0.035 Ω cm at 700°C. Typical properties of the metal-insulator transition (MIT) electrical conductivity were shown in all measured compositions. The temperature at which MIT occurred increased as the non-stoichiometric composition increased.