High temperature properties of La0.6Sr0.4Co0.8Fe0.2O3−δ phase structure and electrical conductivity

High-temperature phase relation of La0.6Sr0.4Co0.8Fe0.2O3−δ (LSCF) was studied with XRD in controlled atmospheres. The electrical conductivity was measured by the four-probe DC method, at temperatures 973–1173 K, in the PO2 range of 1–10−5 Pa. These properties are discussed in combination with oxygen nonstoichiometry and the diffusion constant of oxide ions. It was found that LSCF has a phase transition from rhombohedral to cubic, occurring at about 773 K. The lattice constant of the high-temperature phase was found to increase with decreasing, PO2 showing the reduction of metallic ions with increased oxygen nonstoichiometry. Although the reduction causes the hole concentration to decrease, hole conduction dominants in the measured PO2 range. The mobility of holes is almost a constant, 1.17 cm2 V−1 s−1, at 973–1173 K. At 1073 K, the ionic conductivity has a maximum value of 0.08 S cm−1 under 103 Pa of, PO2 the value is close to that of Gd-doped ceria at the same temperature.