Cathodic Activity and Interfacial Stability of Y0.8Ca0.2Co1–xFexO3/YSZ Electrodes for Solid Oxide Fuel Cells

The Fe-doped cobaltates, Y0.8Ca0.2Co1–xFexO3– (x = 0.1–0.7), were prepared and their high-temperature phase stability and cathodic activity were investigated. The perovskite/yttria-stabilized zirconia (YSZ) electrodes were fabricated via a silk printing technique. It was found that the undoped cobaltate (x = 0) is so thermally unstable that the preparation of pure perovskite phase was unsuccessful. The partial Fe-doping to Co (x = 0.1–0.7), however, gave us highly crystalline perovskite powders of an orthorhombic lattice. Among those samples of x = 0.1–0.7, the Y0.8Ca0.2Co0.7Fe0.3O3– showed the best cathodic activity which is superior to La0.9Sr0.1MnO3. The thermal expansion coefficient of this material (10.5 × 10–6 cm/cm-K at 25–1000°C) was very close to that of 8 mol % YSZ (10.8 × 10–6 cm/cm-K). As a result of interfacial reaction between Y0.8Ca0.2Co0.7Fe0.3O3– and YSZ electrolyte, a spinel-type oxide was produced. But the interfacial product formation proceeded mainly during the electrode adhesion period (1200°C) whereas its growth during the cell operation (900–1000°C) was negligible.This work was supported by Ssangyong Cement Industry and Korea Science and Engineering Foundation (966-0304-005-2)