Crystal structure, thermal expansion and electrical conductivity of perovskite oxides BaxSr1-xCo0.8Fe0.2O3-δ (0.3 ≤ x ≤ 0.7)

BaxSr1-xCo0.8Fe0.2O3-delta (x = 0.3-0.7) composite oxides were prepared and characterised. The crystal structure, thermal expansion and electrical conductivity were studied by XRD, dilatometry and four-point DC, respectively. For x up to 0.6 compositions, cubic perovskite structure was obtained and the lattice constant increased with increasing Ba content. A 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 a value > 20 x 10 exp(-6)/C. The conductivity was > 30 S/cm above 500 C except for x > 0.5 compositions. Conductivity relaxation behaviour was also investigated at 400-550 C. Generally, Ba0.4Sr0.6Co0.8Fe0.2O3-delta and Ba0.5Sr0.5Co0.8Fe0.2O3-delta are potential cathode materials. 24 refs.