Anode-supported solid oxide fuel cells were fabricated with La0.6Sr0.4CoO3-lambda-Zr0.84Y0.16O2-delta (LSC-YSZ) composite cathodes by an infiltration method and evaluated at 800 C. Cells with optimized composite cathode layers exhibited power densities of 1.7 W/cm(2) at 0.7 V, peak power densities of 2.1 W/cm(2), and area-specific resistances of 0.11 Omega cm(2) at 800 C. The LSC-YSZ composite cathodes were fabricated by infiltrating a porous YSZ layer with metal salts and then firing at 800 C. This fabrication method produced a unique cathode microstructure with a highly porous and contiguous YSZ network and a finely dispersed LSC phase. The low sintering temperature of the LSC phase in the porous YSZ network prevented the formation of the secondary phases La2Zr2O7 and SrZrO3. A systematic variation of the YSZ and LSC content in the composite indicated that a minimum of 20 vol % of the infiltrated LSC phase was necessary for the cathode to perform effectively. The optimal composition of the composite cathode was found to be similar to 49 vol % YSZ, 30 vol % LSC, and 21 vol % porosity. (c) 2006 The Electrochemical Society.