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

Perovskite oxides in the system Pr1-xSrxCo0.2Fe0.8O3-delta (0 less than or equal to x less than or equal to 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 less than or equal to x less than or equal to 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 Pr0.8Sr0.2Co0.2Fe0.8O3-delta showed the best performance, since its TEC and conductivity values at 700 degreesC (14X10(-6) cm (cm degreesC)(-1) and 159 S cm(-1), respectively), meet the requirements for application in SOFC cathodes. (C) 2000 Elsevier Science B.V. All rights reserved.