Thermoelectric properties of antiperovskite calcium oxides Ca₃PbO and Ca₃SnO

We report the thermoelectric properties of polycrystalline samples of Ca₃Pb_1−xBi_xO (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 Ca₃Pb_1−xBi_xO. On the basis of Hall and Sommerfeld coefficients, the Ca₃SnO sample is found to be a p-type metal with a carrier density of ∼10¹⁹cm⁻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.