The stability of La0.6Sr0.4Co0.2Fe0.8O3-delta impregnated Y2O3 stabilized ZrO2 (LSCF-YSZ) cathodes was investigated under the condition of open circuit or current polarization at 750 degrees C in air. The electrochemical measurement and the microstructure characteristic show that the flattening of LSCF particles has great contribution to the increase of resistance of LSCF-YSZ cathodes after 500 h heat treatment at 750 degrees C. Microstructure coarsening and the damage of well-connected porous structure are main reasons of the performance degradation for LSCF-YSZ cathodes testing at 200 mA cm(-2) and 750 degrees C in air. Higher current density of 500 mA cm(-2) applying on cathodes accelerates degradation processes. X-ray photoelectron spectroscopy (XPS) shows that Sr concentration on the cathode surface decreases after current polarization, which plays a main role in performance activation processes observed at the beginning stage. The enhancement of cobalt activity in LSCF lattice by current polarization increases the conductivity and decreases the stability of LSCF-YSZ cathodes. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.