Structure, electrical and thermal properties of (Ba _0.5Sr _0.5) _{1 - X}Gd _xCo _0.8Fe _0.2O _3-δ perovskite as a solid-oxide fuel cell cathode

In order to develop cathode materials for intermediate temperature solid oxide fuel cell (IT-SOFC), (Ba _0.5Sr _0.5) _{1 - x}Gd _xCo _0.8Fe _0.2O _{3 - δ} (BSGCF: x = 0, 0.02, 0.05, 0.08, and 0.1) oxides were synthesized by sol-gel method. The effects of Gd-doping on the phase structure, thermal expansion coefficient (TEC), thermogravimetric (TG) and the electrical conductivity were investigated. All samples have cubic structure and the lattice shrinks with the increasing content of Gd ^{3 +}. The TEC values of BSGCF are in the range of 20.7-22.4 × 10 ^{- 6} K ^{- 1} from 50 to 900 °C and the abnormal expansion phenomenon at the temperature range of 300-550 °C is observed in all these samples, which is related with the loss of lattice oxygen as proved by the TG result. The conductivity of BSGCF10 is three times as large as BSCF at 500 °C. While abnormal phenomenon of BSGCF for the x = 0.05 is explained through the critical radius calculation.