Electrochemical property of solid solutions formed in (La,Sr)(Co,Fe)O3 − δ cathode/doped-CeO2 interlayer/Y2O3–ZrO2 electrolyte system during operation of solid oxide fuel cells

Abstract

The application of solid oxide fuel cells consisting of (La,Sr)(Co,Fe)O3−δ (LSCF) cathode/doped ceria interlayer/zirconia-based electrolyte has been widely examined for the residential cogeneration system. It is well recognized that the microstructural change of cell components proceeds with time, leading to the performance deterioration. Various factors were proposed for this degradation behavior, e.g. the formation of highly-resistive SrZrO3 phase and the agglomeration of LSCF cathode. However, the quantitative influence of the ceria-zirconia solid solutions on the performance has not been studied, with applying the results of dissection analysis of the cells operated; the ceria-zirconia solid solutions are formed at the doped ceria interlayer/zirconia-based electrolyte interface. In this study, the ionic conductivity of these solid solutions formed in the LSCF/Sm2O3–CeO2/Y2O3–ZrO2 system was investigated in detail. The dissolution of Sm3+ into the Y2O3–ZrO2 phase resulted in the significant reduction in ionic conductivity. Furthermore, the influence of dopant species in the doped ceria interlayer, Sm3+ and Gd3+, on the ionic conductivity of solid solutions was studied.