Solid state synthesis and thermoelectric properties of Mg-Si-Ge system

Thermoelectric materials, Mg₂Si_1-xGe_x (x=0, 0.2, 0.4, 0.6, 0.8, 1), have been prepared by bulk mechanical alloying (BMA) and hot pressing (HP). The electrical conductivity, Seebeck coefficient and thermal conductivity were measured from room temperature up to about 700 K. The electrical conductivity of all the samples increases with increasing temperature, while the Seebeck coefficient and thermal conductivity decrease with increasing temperature. Mg₂Si and Mg₂Si_0.8Ge_0.2 possess negative type of conductivity, while for other compounds it is positive. At the same time, the effect of hot processing condition on thermoelectric properties was also investigated. The maximum figure of merit of Mg₂Si_0.6Ge_0.4 was obtained with the processing parameter of BMA at 600 cycles and hot pressing at 773 K and 1 GPa for 1 h.