Cation transport behavior, diffusion and interface reaction were investigated for La0.8Sr0.2CoO3 (LSC) and La0.8Sr0.2FeO3 (LSF) perovskite cathodes for solid oxide fuel cells (SOFCs). Diffusion couples between two perovskite pellets were annealed around SOFC operating temperatures such as 1071 K, 1175 K, 1279 K and 1379 K. Mass transfer of the iron component from the LSF into the LSC was clearly observed by energy dispersed X-ray analysis (EDX) and secondary ion mass spectrometry (SIMS). At the interface, the precipitation of CoFe2O4 spinel phase was observed on the LSF side. On the LSC side interface, Sr-rich thin layer was observed; iron component difftised through the CoFe2O4 and the Sr-rich thin layer at high temperature. The grain boundary diffusion of iron was faster than bulk diffusion. The intercliffitsion coefficients in bulk are determined by fitting curves of SIMS profiles as follows: Fe in the LSC Dbulk/m(2)s(-1) = 2.2 x 10(-14)exp(-140 kJmol(-1)/RT) (1071K -1379K) Co in the LSF D-bulk /m(2)s(-1) = 3.3 x 10(-16) exp(-90kJmol(-1)/RT) (1071K- 1379K) (C) 2007 Elsevier B.V All rights reserved.