Characterization of layered perovskite oxides NdBa1−xSrxCo2O5+δ (x = 0 and 0.5) as cathode materials for IT-SOFC

The crystal structure, thermal expansion, and electrochemical properties of the layered perovskite series NdBa1−xSrxCo2O5+δ (x = 0 and 0.5) were investigated to study the effects of substituting Sr for Ba on a layered perovskite oxide. A tetragonal layered perovskite structure was observed in NdBaCo2O5+δ (NBCO), and a tetragonal structure was also observed in NdBa0.5Sr0.5Co2O5+δ (NBSCO) when Sr was substituted into NBCO. The thermal expansion coefficients (TECs) of NBSCO and NBCO were both bigger than 22 × 10−6 K−1 at 530 °C. However, the TEC values for 50 wt% of NBSCO and 50 wt% of Ce0.9Gd0.1O2−δ (CGO91) (NBSCO:50) were 13.2 × 10−6 K−1 at 600 °C and 13.7 × 10−6 K−1 at 700 °C; for 50 wt% of NBCO and 50 wt% of CGO91 (NBCO:50) they were 12.4 × 10−6 K−1 at 600 °C and 12.5 × 10−6 K−1 at 700 °C. The cathode polarizations (Rp) of NBSCO and NBCO on a CGO91 electrolyte were observed to be 0.25 and 0.11 Ωcm2, respectively, at 700 °C. The Rps of composite cathodes in NBSCO:50 and NBCO:50 were 0.061 and 0.038 Ωcm2, respectively, at 700 °C.