Electronic transport properties of the perovskite-type oxides La1−xSrxCoO3±δ

La1−xSrxCoO3 is a leading candidate oxide electrode material for replacing standard metal electrodes. Here we investigate the origin of its high electronic conductivity by means of Rietveld analysis, Hall effect measurements, and band-structure calculations. A high electrical conductivity at room temperature, σ = 4.4 × 103 S cm−1 (which is the largest value for oxides that do not contain noble metals), was achieved by the substitution of 40–50 mol% Sr into the La sites, with a high carrier concentration of 4.5 × 1021 cm−3 and a carrier mobility of 5.8 cm2 V−1 s−1. The carrier concentration results from a trade-off between hole generation via Sr substitution and electron generation via oxygen deficiency. The high mobility arises from the small effective mass originating in the transition to a higher spin state.