Cathode materials Sr1-x Ho x CoO3-δ (SHC, x aparts per thousandcurrency sign 0.3) for IT-SOFC

Cathode materials consisting of Sr1-x Ho (x) CoO3-delta (SHC, x a parts per thousand currency sign 0.3) were synthesized by solid-state reaction for intermediate temperature solid oxide fuel cell (IT-SOFC). The crystal structures, total electrical conductivity, thermogravimetric analysis (TGA), thermal expansion coefficient (TEC), area-specific resistance (ASR), and cell performance were investigated. X-ray powder diffraction (XRD) shows the presence of two structural phases in the series belonging to Pm-3m for Sr0.9Ho0.1CoO3-delta and I4/mmm for Sr0.8Ho0.2CoO3-delta and Sr0.7Ho0.3CoO3-delta . Electrical conductivity measurements show that the conductivity is all higher than 182 S cm(-1) from 170 to 800 A degrees C. TGA and thermal expansion measurement shows that oxygen vacancies and TEC decrease with increasing x at high temperature. The TECs are influenced by the concentration of oxygen vacancies and the transition of the Co(III) ions from a low-spin to a high-spin state. AC impedance measurements in symmetrical cells with La0.8Sr0.2Ga0.83Mg0.17O2.815 (LSGM) as an electrolyte show that the ASR and activation energy increase with increasing x. Sr0.9Ho0.1CoO3-delta exhibits the best cathode characteristics with a maximum power density of 839 mW/cm(2).