La0.6Sr0.4Co0.2Fe0.8O3-delta-Ce0.8Sm0.2O2-theta-CuO composite cathodes were studied for the potential application in intermediate temperature solid oxide fuel cells. Ce0.8Sm0.2O2-theta electrolyte with porous Ce0.8Sm0.2O2-theta interlayer was successfully prepared by one-step sintering process. The effect of interlayer between cathode and electrolyte and CuO on the electrochemical performance of the composite cathodes was investigated by AC impedance spectroscopy. The application of interlayer decreased the area specific resistance of La0.6Sr0.4Co0.2Fe0.8O3-delta-Ce0.8Sm0.2O2-theta cathode. The addition of CuO to La0.6Sr0.4Co0.2Fe0.8O3-delta reduced the phase formation temperature of La0.6Sr0.4Co0.2Fe0.8O3-delta by 150 C and the addition of CuO to La0.6Sr0.4Co0.2Fe0.8O3-delta-Ce0.8Sm0.2O2-theta cathode reduced the optimal calcination temperature of the cathode to 800 degrees C. The composite cathode with 2 mol% CuO calcined at 800 degrees C exhibited the lowest area specific resistance of 0.05 Omega cm(2) at 700 degrees C in air, which was reduced by 67% compared with that of La0.6Sr0.4Co0.2Fe0.8O3-delta-Ce0.8Sm0.2O2-theta cathode. The studies of the corresponding single cell performance, thermal expansion and thermal cycling behaviors further indicated that the composite cathode with 2 mol% CuO could be a promising cathode material. (C) 2012 Elsevier Ltd. All rights reserved.