Ba and Gd doping effect in (Ba _xSr _1-x) _0.95Gd _0.05Co _0.8Fe _0.2O _3-δ (x=0.1-0.9) cathode on the phase structure and electrochemical performance

In this study, Ba _xSr _1-xCo _0.8Fe _0.2O _3-δ (BSCF) doped with trace of Gd were studied for phase structures and properties about thermal expansion, electrical conductivity, and electrocatalytic activity. The solution range of barium in Ba _xSr _1-xCo _0.8Fe _0.2O _3-δ can be extended to 0.1≤ x ≤ 0.7 after the introduction of small amount of Gd ³⁺ ions (only for 5%) into the Ba/Sr-site. The calculation results of the crystal structure and the crystal lattice energy show that the ratio of Ba/Sr and doping of Gd ³⁺ lead to increase the lattice parameter and the Co/Fe ionic average valence state in B-site. Moreover, the ratio of Ba/Sr and doping of Gd ³⁺ were found to have significant impacts on the high-temperature physical properties and electrochemical characteristics. All oxides exhibited decreases in the thermal expansion coefficient (TEC) and electrical conductivity with increasing Ba/Sr ratio. Barium insertion was found to change the area-specific resistance (ASR) of porous (not dense) cathodes. An ASR values of 0.048, 0.072, 0.064, 0.121, and 0.059ωcm ² under air condition were observed at 650°C for BSGCF with x=0.1, 0.2, 0.3, 0.5, and 0.7, respectively.