Solid State Synthesis of Ternary Thermoelectric Magnesium Alloy, Mg₂Si_1−xSn_x

Abstract

Profound understanding and survey of magnesium base intermetallic compounds is hindered by various difficulties in their processing and fabrication. Solid-state synthesis via the bulk mechanical alloying (BMA) is free from contaminations and segregation through high reactivity of elemental constituents against crucibles or vials. Magnesium–tin system is employed to demonstrate the solid-state reactivity to Mg₂Sn from the elemental powder mixture. This process is characterized by the gradual solid-state reaction to Mg₂Sn with processing time. Since the blended mixture of magnesium and tin with the initial molar ratio of Mg66.7%Sn33.3%, is repeatedly strained via BMA in the controlled conditions, the solid-state reaction advances monotonically with refinement of interparticle distance between magnesium and tin. Ternary semi-conductive compounds, Mg₂Si_1−xSn_x for 0≤x≤1, are also synthesized by this process. Thermoelectric properties of this ternary alloy are investigated to discuss the effect of tin content on the band-gap, the thermal conductivity, the Seebeck coefficient and the figure-of-merit. In addition, these data are compared to the previously reported results by using melt and solidified samples in order to describe the common features in the solid-solution type thermoelectric compounds. Furthermore, p–n transition behavior is also reported in this ternary alloy system.