Cation transport behavior in SOFC cathode materials of La 0.8Sr 0.2CoO 3 and La 0.8Sr 0.2FeO 3 with perovskite structure

Abstract

Cation transport behavior, diffusion and interface reaction were investigated for La 0.8Sr 0.2CoO 3 (LSC) and La 0.8Sr 0.2FeO 3 (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 CoFe 2O 4 spinel phase was observed on the LSF side. On the LSC side interface, Sr-rich thin layer was observed; iron component diffused through the CoFe 2O 4 and the Sr-rich thin layer at high temperature. The grain boundary diffusion of iron was faster than bulk diffusion. The interdiffusion coefficients in bulk are determined by fitting curves of SIMS profiles as follows: Fe in the LSC D bulk / m 2 s − 1 = 2.2 × 10 − 14 exp ( − 140 kJmol − 1 / RT ) ( 1071 K − 1379 K ) Co in the LSF D bulk / m 2 s − 1 = 3.3 × 10 − 16 exp ( − 90 kJmol − 1 / RT ) ( 1071 K − 1379 K )