Crystal structure, thermal expansion and electrical conductivity of Pr1−xSrxCo0.2Fe0.8O3−δ (0≤x≤0.5)

Abstract Perovskite oxides in the system Pr 1− x Sr x Co 0.2 Fe 0.8 O 3− δ (0≤ x ≤0.5) were prepared and characterized. The crystal structure, thermal expansion and electrical conductivity of these oxides were studied by X-ray diffraction, dilatometry and 4-point DC, respectively. The structure of the oxides in the range 0≤ x ≤0.4 was orthorhombic (Pbnm space group) and became cubic for x =0.5. The lattice parameters were determined. The thermal expansion coefficient (TEC) decreased for x =0.1, and increased for higher x values. The slope of the thermal expansion curves increased and the electrical conductivity decreased at high temperatures, as a result of the loss of lattice oxygen and the formation of oxygen vacancies, a process which is enhanced as the Sr-doping level is increased. The composition Pr 0.8 Sr 0.2 Co 0.2 Fe 0.8 O 3− δ showed the best performance, since its TEC and conductivity values at 700°C (14×10 −6 cm (cm °C) −1 and 159 S cm −1 , respectively), meet the requirements for application in SOFC cathodes.