Crystal structure, thermal expansion and electrical conductivity of perovskite oxides Ba_xSr_1-xCo_0.8Fe_0.2O_{3- δ} (0.3 ≤ x ≤ 0.7)

Ba_xSr_1-xCo_0.8Fe_0.2O_{3- δ} (0.3 ≤ x ≤ 0.7) composite oxides were prepared and characterized. The crystal structure, thermal expansion and electrical conductivity were studied by X-ray diffraction, dilatometer and four-point DC, respectively. For x ≤ 0.6 compositions, cubic perovskite structure was obtained and the lattice constant increased with increasing Ba content. Large amount of lattice oxygen was lost below 550 °C, which had significant effects on thermal and electrical properties. All the dilatometric curves had an inflection at about 350-500 °C, and thermal expansion coefficients were very high between 50 and 1000 °C with the value larger than 20 × 10^-6 °C^-1. The conductivity were larger than 30 S cm^-1 above 500 °C except for x > 0.5 compositions. Furthermore, conductivity relaxation behaviors were also investigated at temperature 400-550 °C. Generally, Ba_0.4Sr_0.6Co_0.8Fe_0'2O_{3- δ} and Ba_0.5Sr_0.5Co_0.8Fe_0.2O_{3- δ} are potential cathode materials.