Advanced Electrochemical Properties of LnBa_0.5Sr_0.5Co₂O_5+δ (Ln = Pr, Sm, and Gd) as Cathode Materials for IT-SOFC

Excellent area-specific-resistance (ASR) values have been exhibited by cathode materials with a Sr-doped layer perovskite type structure and therefore show themselves to be possible candidates for intermediate-temperature-operating solid oxide fuel cell (IT-SOFC, 600-800 degrees C) applications. SmBa0.5Sr0.5Co2O5+delta (SBSCO) electrode was sintered onto 10 mol % gadolinia-doped ceria (Ce0.9Gd0.1O2, CGO91) at 1000 degrees C to form symmetrical cells and exhibited an ASR value of 0.092 Omega cm(2) at 700 degrees C. The lowest ASR value was observed when the composite cathode of 50 wt % of SBSCO and 50 wt % of CGO91 (SBSCO50) was used in conjunction with an interlayer of CGO91 applied between the electrode and 8 mol % Y2O3 stabilized ZrO2 electrolyte. These were 0.12 Omega cm(2) at 600 degrees C and 0.019 Omega cm(2) at 700 degrees C, respectively. The coefficient of thermal expansion (CTE) of SBSCO was 21.9x10(-6) K-1 at 700 degrees C. However, the CTE of the composite cathode of SBSCO50 was shown to be 13.6x10(-6) K-1 at 700 degrees C, this being more compatable with the other components within the cell.