Thermoelectric properties of p-type Mg₂Si_0.6Ge _0.4 fabricated by bulk mechanical alloying and hot pressing

Bulk mechanical alloying (BMA) followed by hot pressing (HP) was used to prepare Mg₂Si_0.6Ge_0.4 thermoelectric material with high densification. Starting from the elemental power mixture, the Mg ₂Si_0.6Ge_0.4 solid solution was solid-state synthesized via BMA. In fact, the peaks for the cubic-structured Mg ₂Si_0.6Ge_0.4 solid solution phase were detected after 300 cycles in BMA. The single phase of Mg₂Si _0.6Ge_0.4 was synthesized at 600 cycles in BMA. Mg ₂Si_0.6Ge_0.4 showed p-type semiconduction without doping. Effects of hot pressing conditions on thermoelectric properties were investigated. With increasing hot pressing temperature from 673 to 773 K and pressure from 500 MPa to 1 GPa, the electrical conductivity increased and the Seebeck coefficient decreased. The maximum figure of merit was obtained with the processing parameter of 600 cycles BMA and hot pressing at 773 K, 1 GPa for 1 h.