This paper describes the structure and electrochemical properties of solid oxide fuel cell cathodes prepared by infiltration of La0.6Sr0.4Co0.2Fe0.8O3-(delta) (LSCF) into porous Gd-Doped Ceria (GDC). The CDC scaffolds were prepared by partial sintering of GDC compacts on dense CDC electrolytes. LSCF was introduced into these structures by multiple infiltrations of aqueous nitrate solutions followed by firing. The cathode polarization resistance, measured using electrochemical impedance spectroscopy on symmetrical cells, showed a pronounced minimum as a function of CDC firing temperature at 1100-1200 degrees C, where the microstructure was well-necked but porous with similar to 300-nm-sized particles. Increasing the infiltrated LSCF loading decreased the polarization resistance up to the highest loading tested, 12.5 vol.%. Decreasing the LSCF firing temperature decreased the polarization resistance due to a decrease in the LSCF feature size from similar to 1 mu m at 1200 degrees C to similar to 50 nm at 800 degrees C. Thus, the infiltration method allowed separate control over the nnicrostructures of the CDC and LSCF phases. The lowest polarization resistance measured at 600 degrees C was 0.24 Omega cm(2). (C) 2008 Elsevier B.V. All rights reserved.