Abstract:
Cobalt monosilicide and its solid solutions are promising thermoelectrics, as they have a high thermoelectric power factor and mechanical strength. To increase the thermoelectric efficiency of these materials, it is necessary to reduce their lattice thermal conductivity. This work examines the possibility of such reduction using the solid solution approach. Using ab initio calculations, phonon spectra, total and projected densities of phonon states of isostructural to CoSi compounds RhSi and RhSn were obtained. All these compounds have B20 structure of FeSi type. Calculations of the temperature dependence of the thermal conductivity of these crystals, as well as CoSi–RhSi and RhSi–RhSn solid solutions, were carried out. Calculations showed that the lattice thermal conductivity at room temperature in RhSi was 4.9 W/(m $\cdot$ K), and in RhSn – 3.6 W/(m $\cdot$ K), which is significantly lower than in pure CoSi (about 10.4 W/(m $\cdot$ K)). Due to additional alloy scattering in CoSi-RhSi solid solutions, thermal conductivity can be reduced by more than 3 times compared to pure CoSi, and in RhSi-RhSn solid solutions by more than 3 times compared to a pure RhSi crystal.
Keywords:lattice thermal conductivity, thermoelectrics, ab initio lattice dynamics.
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