Thermoelectric properties of antiperovskite calcium oxides Ca_3PbO and Ca_3SnO

摘要

We report the thermoelectric properties of polycrystalline samples of Ca_3Pb_(1-x)Bi_x (x = 0,0.1, 0.2) and Ca_3SnO, both crystallizing in a cubic antiperovskite-type structure. The Ca_3SnO sample shows metallic resistivity and its thermoelectric power approaches 100μV K~(-1) at room temperature, resulting in the thermoelectric power factor of Ca_3SnO being larger than that of Ca_3Pb_(1-x)Bi_xO. On the basis of Hall and Sommerfeld coefficients, the Ca_3SnO sample is found to be a p-type metal with a carrier density of ～10~(19)cm~(-3), a mobility of ～80cm~2 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 Ca_3SnO, as well as possible emergence of a multivalley electronic structure with a small band gap at low-symmetry points in £-space, suggests that the antiperovskite Ca oxides have strong potential as a thermoelectric material.