SmBaCo2O5+d and LnBa0.5Sr0.5Co2O5+δ, Potential Cathode Materials for IT-SOFC

Abstract

The electrical conductivity of SmBaCo2O5+δ (SBCO) showed a Metal-Insulator Transition (MIT) at about 200åC with maximum conductivity of 570 Scm-1 at 200oC and minimum conductivity 170 Scm-1 at 900oC. The area specific resistance (ASR) of composite cathode (50wt% of SBCO and 50wt% of Ce0.9Gd0.1O2, SBCO:50) on a Ce0.9Gd0.1O2 (CGO91) electrolyte was observed to be 0.05Ωcm2 at 700oC. SmBa0.5Sr0.5Co2O5+δ (SBSCO) electrode was sintered onto CGO91 at 1000oC to form symmetrical cells and exhibited an ASR value of 0.092 Ωcm2 at 700oC. The lowest ASR value was observed when the composite cathode of 50wt% of SBSCO and 50wt% of CGO91 (SBSCO:50) was used and these were 0.10 Ωcm2 at 600oC and 0.013 Ωcm2 at 700oC, respectively. The coefficient of thermal expansion (CTE) was 21.9 x 10-6 K-1 at 700oC. However, the CTE of SBSCO:50 was shown to be 13.6 x 10-6 K-1 at 700oC which are similar to the value of CGO91 electrolyte for intermediate temperature-operating solid oxide fuel cell (IT-SOFC) applications.