Xuening Jiang

Defect Chemical Models for Temperature Dependence of Oxygen Stoichiometry and Electrical Conductivities of Ba0.5Sr0.5Co0.8Fe0.2O3-δ

Ba0.5Sr0.5Co0.8Fe0.2O3-δ is a well-known cathode material of intermediate-temperature solid oxide fuel cell. To elucidate its electrical and electrochemical properties, three chemical defect models were adopted in this work for fitting the data of oxygen stoichiometry and electrical conductivities as a function of temperature. Reasonable values of concentrations and mobility of charge carriers, and were obtained with the cluster defect model. The p-type electronic conductivities and oxygen ionic conductivities were separated from the total electrical conductivities. The temperature-dependence of oxygen vacancy diffusion coefficient of BSCF were also obtained, and the results were comparable with the data measured experimentally.

Structures and Properties of LaFe0.8Cu0.2O3−δ and BaFe0.8Cu0.2O3−δ as Cobalt-Free Perovskite-Type Cathode Materials for the Oxygen Reduction Reaction

Abstract Perovskite oxides with mixed electronic–ionic conduction are important catalysts for the oxygen reduction reaction in solid oxide fuel cells (SOFCs). Here, two cobalt‐free perovskite oxides, LaFe0.8Cu0.2O3−δ (LFCuO) and BaFe0.8Cu0.2O3−δ (BFCuO), were synthesized and comparatively studied with respect to their phase structures, oxygen contents, chemical defects, thermal expansion coefficient (TEC), as well as electrical and electrochemical properties. Different structures and properties have been found for each oxide, which have been interpreted based on their tolerance factors and chemical defects. LFCuO showed much better overall performance than BFCuO, and it proved to be a promising cobalt‐free cathode material of intermediate‐temperature SOFCs with a low TEC (12.0×10−6 °C−1) that matches well with TECs of the electrolytes, high catalytic activity for the oxygen reduction reaction characterized by low area specific resistances (0.090 Ω cm2 at 800 °C and 0.20 Ω cm2 at 750 °C), and high‐temperature chemical stability with electrolytes.