No abstract

There are few silicides that could be used for thermoelectric energy conversion, following higher silicides of transition metals: CrSi2, MnSi1.75, β-FeSi2, Ru2Si3, ReSi1.75, and solid solutions based on compounds of Mg2X (X = Si, Ge, and Sn). Some of them have very high figures of merit (ZT). It can be shown that, in some silicides, a high ZT is the result of energy spectrum optimization besides the decrease in thermal conductivity. This is very difficult to achieve in some materials, because the density of states is typically dependent only on the band structure of a material, for which there is no means to produce such a change. However, in solid solutions, if they have a special band structure of components, it is possible to alter the band structure to increase ZT.

The complex study of the thermoelectric properties in solid solutions between compounds Mg2X (X=Si, Ge, Sn) was accomplished. Analysis of the features of band structure, thermal conductivity and electrical properties in the wide range of temperature and carrier concentration has shown that the most effective thermoelectric can be achieved in the Mg2Si-Mg2Sn solid solution. Energy spectrum and carrier concentration optimization, and, also, lattice thermal conductivity minimization allowed to establish the most effective compounds for the thermoelectrics of n- and p- type. Thermoelectrics with the maximum dimensionless figure of merit of more than 1.2 and average ZT0.9 (in the temperature range 300-800K) were obtained with developed synthesis and doping techniques. These materials are cheap, wide spread and environment friendly, have non-toxic initial components. It is very favorable for practical application.