Sm0.5Sr0.5MnO3 as a potential cathode material for intermediate temperature solid oxide fuel cells

Perovskite Sm0.5Sr0.5MnO3 (SSM55) material is prepared via the sol-gel method, and its crystal structure, chemical stability, thermal expansion coefficient (TEC), and electrical conductivity are characterized. The electrochemical performance of a SSM55 cathode on 8 mol % Y2O3 stabilized ZrO2 (8YSZ) electrolyte is evaluated by electrochemical impedance spectroscopy in the temperature range between 650 and 800 °C, and compared to a La0.8Sr0.2MnO3 (LSM82) cathode. The SSM55 is thermally stable at temperatures up to 1400 °C with a TEC of 10.7 × 10−6 K−1 in the temperature range between 20 and 800 °C, and its electrical conductivity varies from 64 to 138 S cm−1 between 300 and 800 °C. The polarization resistance of SSM55 cathode on 8YSZ electrolyte is determined as 64.98, 39.44, 8.67 and 1.92 Ω cm2 at 650, 700, 750 and 800 °C respectively, which is significantly lower than that of a LSM82 cathode at temperatures above 700 °C. To further increase the electrochemical performance of the cathode, SSM55-8YSZ composite cathode was obtained with a polarization resistance of 1.08 and 0.45 Ω cm2 at 750 and 800 °C, respectively. These values are considerably lower than that of a LSM82-8YSZ cathode, suggesting that the SSM55 is a promising cathode material for intermediate temperature solid oxide fuel cells operated at 750 °C and above.