Synthesis and Thermoelectric Properties of Sn_1−xGe_xTe by High Temperature and High Pressure

In many thermoelectric materials, SnTe has the same crystal structure as PbTe, but does not contain heavy metal Pb, which has attracted extensive attention in recent years. At present, the thermoelectric properties of intrinsic SnTe are not particularly excellent. There are some disadvantages: a large number of intrinsic Sn vacancies lead to high carrier concentration, which worsens the electrical transport performance; the energy splitting between the light band and the heavy band in the valence band is large and the band gap is too narrow, which is not conducive to the Seebeck coefficient participating in the electrical transport through the heavy band; the lattice thermal conductivity is large. In this study, SnTe doped with Ge was prepared under high pressure and high temperature conditions. The results show that the band structure and the electrical transport properties of SnTe can be tuned effectively by Ge doping. At the same time, Ge doping can modulate the microstructure of the SnTe, which induced the formation of fine grains and second nanophases then reduced the thermal conductivity. The maximum figure-of-merit is 0.35 at 700 K for Ge_0.2Sn_0.8Te.