A Practical Approach to Evaluate Lattice Thermal Conductivity in Two-Phase Thermoelectric Alloys for Energy Applications

Modelling of the effects of materials’ microstructure on thermal transport is an essential tool for materials design, and is particularly relevant for thermoelectric (TE) materials converting heat into electrical energy. Precipitates dispersed in a TE matrix act as phonon-scattering centers, thereby reducing thermal conductivity. We introduce a practical approach to tailor a definite precipitate size distribution for a given TE matrix, and implement it for PbTe. We evaluate vibrational properties from first principles, and develop an expression for phonon relaxation time that considers both matrix vibrational properties and precipitate size distribution. This provides us with guidelines for optimizing thermal conductivity.