Investigation on Preparation and Electrical Properties of Novel Perovskite Cathode Materials Doped with Multi-Elements for IT-SOFC

Abstract

To develop novel cathode materials with high electrical performances for intermediate temperature solid oxide fuel cells (IT-SOFCs) and optimize the preparation process, perovskite-type oxides Pr1-x-ySrxCayCo1-zFezO3-δ (x=0.1, 0.2; y=0.1, 0.2; z=0.2, 0.3, 0.4; denoted as PSCCF-81182, PSCCF-72173 and PSCCF-62264) were prepared by solid state reaction. The formation process, phase structure and microstructure of the prepared samples were measured using TG-DTA, FT/IR, XRD and SEM techniques. The mixed conductivity of the samples was measured using DC four-terminal method in the range of 150-950 °C. Chemical state of the elements was measured by XPS experiments. The results show that the prepared samples PSCCF-81182, PSCCF-72173 and PSCCF-62264 exhibit a single phase with cubic perovskite structure after sintered at 1200 °C for 6 h. The mixed conductivity of the samples increases with temperature up to a maximum value, and then decreases. At lower temperature, the conductivity follows small polaron hopping mechanism. The negative temperature dependence occurring at higher temperature is due to the creation of oxygen vacancies for charge balance. At intermediate temperature (600-800 °C), the mixed conductivity values of the prepared samples are all much higher than 100 S•cm-1，and can meet the demand of cathode materials for IT-SOFC. XPS tests show that Co and Fe elements in PSCCF-72173 are all of + 3 and + 4 valence. Absorbed oxygen can also be found from the XPS patterns, which is related to the concentration of oxygen vacancies in the perovskite-type oxides.