Solid state synthesis of ternary thermoelectric magnesium alloy, Mg 2Si1-xSnx

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 Mg 2Sn 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, Mg2Si1-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. © 2006 The Japan Institute of Metals.