Effect of Impurity Doping on Thermoelectric Properties of Melt-Grown Mg<sub>2</sub>Sn Crystals

Abstract

We investigated the thermoelectric properties of melt-grown Mg2Sn crystals doped with various impurities such as Al, Bi, Sb, P, In, Ag, Au, W, and Mo; a large difference in the carrier concentration was observed for each impurity. The Bi- and Sb-doped Mg2Sn crystals showed n-type conductivity and had enough electron concentrations in the order of 1019 cm-3 by doping, and the maximum figure of merit (ZT) of 0.35 was observed in the crystal doped with 1.5 at% of Bi at 550 K. The Ag-, P-, In-, Au-, W-, and Mo-doped materials exhibited p-type conductivity. The Ag-doped samples had sufficient hole concentrations of more than 1019 cm-3, and the ZT reached 0.25 in the sample doped with 1.0 at% of Ag at 450 K. The P- and Sb-doped Mg2Sn crystals became dark gray powder within 1–2 weeks, but the crystals doped with the other impurities did not. This result suggested that the oxidation resistance of Mg2Sn crystals varied greatly depending on the type of dopant impurity.