Study on the surface segregation of mixed ionic-electronic conductor lanthanum-based perovskite oxide La_1−xSr_xCo_1−yFe_yO_3−δ materials

High-temperature solid oxide fuel cells (HT-SOFCs) generally operate at 800°C to 1000°C and intermediate temperature SOFCs (IT-SOFCs) at 600°C to 800°C. Reducing the SOFCs operational from high to ITs results in many issues mainly at the cathode site. One of the shortcomings that have been addressed is high polarization losses associated with oxygen reduction reaction (ORR) and degradation of La_1−xSr_xCo_1−yFe_yO_3−δ (LSCF) cathode materials. Strontium (Sr) has been discovered to segregate and inhibit the surface-active site for the ORR under specified conditions (temperature, relative humidity, and suppressing activity). It enriched the surface, formed Sr-rich secondary phases, and eventually changes the composition and the structure of the perovskite surfaces. Therefore, this review aims to summarize the occurrences of Sr segregation at the LSCF cathode surfaces as a function of operating conditions and their effects on the material performance. In addition, the characterization techniques utilized to investigate the Sr segregation, and strategies for Sr segregation mitigation are also discussed.