Fabrication of Sr-Doped LaFeO[sub 3] YSZ Composite Cathodes

Composites of yttria-stabilized zirconia (YSZ) with Sr-doped LaFeO 3 (LSF) were studied for application as high-performance cathodes for solid oxide fuel cells (SOFCs). The composites were formed by aqueous impregnation of porous YSZ with La, Sr, and Fe salts, followed by calcination at various temperatures. X-ray diffraction measurements showed that the LSF perovskite phase had formed by 1023 K and that solid-state reaction with the YSZ did not occur below approximately 1223 K. The electronic conductivity of the 40 wt % LSF-YSZ composite was maximized by calcination at 1123 K. SOFCs prepared with a 40 wt % LSF-YSZ cathode showed improved performance over SOFCs prepared with conventional LSM-YSZ cathodes at 973 K, although the performance of cells made with cathodes having lower LSF content did not perform as well. Based on measurements with a reference electrode on an electrolyte-supported cell. the impedance of the 40 wt % LSF-YSZ cathode is approximately 0.1 ohm cm 2 in air at 973 K. Finally a cathode-supported cell was fabricated from a 40 wt % LSF-YSZ cathode and shown to perform well in H 2 .