Growth of homogeneous polycrystalline Si1-xGex and Mg2Si1-xGex for thermoelectric application

Homogeneous polycrystalline Si1-xGex were grown using a Si(seed)/Ge/Si(feed) sandwich structure under the low temperature gradient less than 0.4 °C/mm. It was found that the composition of the Si1-xGex was controlled by the growth temperature. The homogeneous Mg2Si1-xGex was synthesized by heat treatment of the homogeneous Si1-xGex powders under Mg vapor. The Mg2Si1-xGex sample with the relative density of 95% was synthesized by spark plasma sintering technique. The resistivity and the Seebeck coefficient of the Si, Ge, Si1-xGex and Mg2Si1-xGex samples were evaluated as a function of temperature. It indicated that Seebeck coefficients of the Si1-xGex and Mg2Si1-xGex samples were higher than those of Si and Ge. Moreover, the Seebeck coefficient of Mg2Si0.7Ge0.3 sample was higher than that of Mg2Si0.5Ge0.5 and Si0.5Ge0.5 samples.