Mechanically alloyed Mg2Si/sub 1-x/Snx solid solutions as thermoelectric materials

Abstract

Mg/sub 2/Si/sub 1-x/Sn/sub x/ solid solutions with (0/spl les/x/spl les/0.4) were prepared by mechanical alloying and subsequent hot-pressing. It was found that the alloying process during milling develops in one of two different directions. The first one leads to the nominal composition with only a small amount of iron impurities resulting from wear of the milling media. In the second route-which only occurs in the presence of Sn-an abrasive phase is formed and the Fe content may increase up to 50 at%. The Fe is bound in FeSi and consequently, the solid solution has a lack of Si. The hot-pressing was performed at a temperature smaller than the peritectic temperature of the quasibinary Mg/sub 2/Si-Mg/sub 2/Sn system. A decomposition of the solid solutions occurs, which suggest changes on the miscibility gap in published phase diagrams. However, some transport measurements on the multiphase materials were performed, which revealed lower mobility values and lattice thermal conductivities compared to values published in the literature for single crystalline materials. The mobility of our materials was found to be independent from composition whereas the thermal conductivity decreases with increasing Sn content.