Synthesis of Mg₂Si_1-xSn_x solid solutions as thermoelectric materials by bulk mechanical alloying and hot pressing

Bulk mechanical alloying with combination of hot pressing is proposed to prepare Mg₂Si_1-xSn_x (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0) solid solutions as thermoelectric materials from elemental granules. Hot pressing condition is optimized in order to obtain higher figure of merit. Temperature dependence of the electrical conductivity, the Seebeck coefficient and thermal conductivity were measured from the room temperature up to 700 K. It was found that the thermoelectric properties of Mg₂Si_1-xSn_x were sensitive to the tin concentration. The p-n conversion takes place at the vicinity of x = 0.2, where the Seebeck coefficient drastically changes its sign. A maximum figure of merit of 0.13 was obtained at 653 K in the samples with nominal compositions of Mg₂Si_0.4Sn_0.6 and Mg₂Si.