Sutdy of Perovskite Oxides as the Cathode for Solid Oxide Fuel Cell (SOFC)

Abstract

The perovskite type manganite systems, Ln_1-xA_xMO₃ (Ln=rare earth, A=Sr, Ca) were studied as the electrode materials for solid oxide fuel cells (SOFC). The highest cathodic activity was obtained for the La_1-xSr_xCoO₃ electrode. The reactivity tests of La_1-xA_xMO₃ with yttria-stabilized zirconia (YSZ) showed that the formation of the pyrochlore Ln₂Zr₂O₇ decreases the electrode activity. However, this was suppressed for the perovskites having smaller lanthanoids than La, for example, for the Gd_1-xA_xMnO₃ and GdCoO₃ systems. No reaction product appeared between the Gd_1-xA_xMnO₃ perovskite and YSZ even at a high annealing temperature of 1400°C. GdCoO₃ did not react with YSZ even at 1000°C. The adjustment of the thermal expansion rate to YSZ needed the formation of solid solution such as Ln_1-xSr_xMn_1-yO₃, some of which showed the high cathodic activity and good compatibility.