Synthesis and Thermoelectric Properties of n-Type Mg2Si

Abstract

Group BV(Bi, Sb)- and BVI(Te, Se)-doped Mg2Si compounds were synthesized by solid state reaction and mechanical alloying. 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 powder was synthesized successfully by solid state reaction at 773 K for 6 h and doped by mechanical alloying for 24 h. Powder was fully consolidated by hot pressing at 1073 K for 1 h. All doped Mg2Si compounds showed n-type conduction, indicating that the electrical conduction is due mainly to electrons. The electrical conductivity increased greatly by doping due to an increase in the carrier concentration. However, the thermal conductivity did not change significantly by doping, which was due to the much larger contribution of the lattice thermal conductivity over the electronic thermal conductivity. Group BV (Bi, Sb) elements were much more effective at enhancing the thermoelectric properties of Mg2Si than group BVI(Te, Se) elements.