Solid-State Synthesis of Te-Doped Mg2Si

Abstract

Te-doped Mg2Si (Mg2Si:Tem, m = 0, 0.01, 0.02, 0.03, 0.05) alloys were synthesized by a solid-state reaction and mechanical alloying. The electronic transport properties (Hall coefficient, carrier concentration, and mobility) and thermoelectric properties (Seebeck coefficient, electrical conductivity, thermal conductivity, and figure of merit) were examined. Mg2Si was synthesized successfully by a solid-state reaction at 673 K for 6 h, and Te-doped Mg2Si powders were obtained by mechanical alloying for 24 h. The alloys were fully consolidated by hot-pressing at 1073 K for 1 h. All the Mg2Si:Tem samples showed n-type conduction, indicating that the electrical conduction is due mainly to electrons. The electrical conductivity increased and the absolute value of the Seebeck coefficient decreased with increasing Te content, because Te doping increased the electron concentration considerably from 1016 cm−3 to 1018 cm−3. The thermal conductivity did not change significantly on Te doping, due to the much larger contribution of lattice thermal conductivity over the electronic thermal conductivity. Thermal conduction in Te-doped Mg2Si was due primarily to lattice vibrations (phonons). The thermoelectric figure of merit of intrinsic Mg2Si was improved by Te doping.