The electrochemical properties of porous composite cathode consisting of Sm0.5Sr0.5CoO3 (SSC) and 8 mol% Y2O3 doped zirconia (YSZ) have been investigated in Ni/YSZ anode-supported single cells at 600 C under oxygen with/without ozone conditions. The Microscopic features and X-ray powder diffraction patterns of the cathode don't show obvious change before and after the measurement. However, the power density of the cell increases in ozone-contained ambient, which is approximately 140% higher than that in ozone-free ambient in most. The effect of the ozone on the performance of cathode is also examined by impedance spectra and Raman spectra. The results of the impedance spectra indicate that polarization resistance decreases in the ozone-contained ambient compared with that in ozone-free ambient. And the Raman spectra suggest that the physicochemical properties of SSC/YSZ porous cathode are also modified. (C) 2014 Published by Elsevier B.V.