Thermoelectric properties of antiperovskite calcium oxides Ca3PbO and Ca3SnO

We report the thermoelectric properties of polycrystalline samples of Ca3Pb1− x Bi x O (x = 0, 0.1, 0.2) and Ca3SnO, both crystallizing in a cubic antiperovskite-type structure. The Ca3SnO sample shows metallic resistivity and its thermoelectric power approaches 100 μV K−1 at room temperature, resulting in the thermoelectric power factor of Ca3SnO being larger than that of Ca3Pb1− x Bi x O. On the basis of Hall and Sommerfeld coefficients, the Ca3SnO sample is found to be a p-type metal with a carrier density of ∼1019 cm−3, a mobility of ∼80 cm2 V−1 s−1, both comparable to those in degenerated semiconductors, and a moderately large hole carrier effective mass. The coexistence of moderately high mobility and large effective mass observed in Ca3SnO, as well as possible emergence of a multivalley electronic structure with a small band gap at low-symmetry points in k-space, suggests that the antiperovskite Ca oxides have strong potential as a thermoelectric material.