Solid-State Synthesis and Thermoelectric Properties of Al-Doped Mg2Si

Abstract

The electronic transport and thermoelectric properties of Al-doped Mg2Si (Mg2Si:Alm, m = 0, 0.005, 0.01, 0.02, 0.03) compounds prepared by solid-state synthesis were examined. Mg2Si was synthesized by solid-state reaction (SSR) at 773 K for 6 h, and Al-doped Mg2Si powders were obtained by mechanical alloying (MA) for 24 h. Mg2Si:Alm were fully consolidated by hot pressing (HP) at 1073 K for 1 h, and all samples showed n-type conduction, indicating that the electrical conduction is due mainly to electrons. The electrical conductivity increased significantly with increasing Al doping content, and the absolute value of the Seebeck coefficient decreased due to the significant increase in electron concentration from 1016 cm−3 to 1019 cm−3 by Al doping. The thermal conductivity was increased slightly by Al doping, but was not changed significantly by the Al doping content due to the much larger contribution of lattice thermal conductivity over electronic thermal conductivity. Mg2Si:Al0.02 showed a maximum thermoelectric figure of merit of 0.47 at 823 K.