Preparation and characterization of Pr 1- xSr xMnO 3 ± δ ( x = 0, 0.15, 0.3, 0.4, 0.5) as a potential SOFC cathode material operating at intermediate temperatures (500–700 °C)

Abstract

The crystal structure, thermal expansion and electrical conductivity of Sr-doped praseodymium manganites (Pr 1- x Sr x MnO 3 ± δ where x = 0, 0.15, 0.3, 0.4, 0.5) were studied in air, and their potential use as cathodes in intermediate temperature SOFCs was evaluated. All compositions have an orthorhombic perovskite-type structure (Pbnm space group). The lattice parameters were determined at room temperature by X-ray powder diffraction. The thermal expansion is almost linear for compositions with x≥0.15. The electrical conductivity can be described by the small polaron hopping conductivity model. The conductivity increases with temperature for all compositions. Both the thermal expansion coefficient (TEC) and the electrical conductivity increase with increasing Sr content, while the activation energy decreases. The low values of the calculated activation energies are in agreement with the small polaron hopping mechanism. Among the compositions studied, Pr 0.5Sr 0.5MnO 3±δ, with a TEC value of 12.2 × 10 −6 cm (cm °C) −1 and a conductivity value of 226 S cm −1 at 500 ° C, seems to be the most promising material that can function as cathode in the intermediate temperature SOFC.