Effect of hierarchically distributed nano-to microscale skutterudite inclusions on the lattice thermal conductivity of TiNiSn-based half-Heusler alloys

Abstract

The goal of this work is an investigation of the reduction in lattice thermal conductivity of a Heusler alloy by introducing inclusions in a host matrix with initially high thermal conductivity. Using panoscopic hierarchical architecture approach and assuming Gamma-distribution for spherical inclusions of different size, a general expression is found for the effective lattice thermal conductivity of a two-phase thermoelectric material in “gray medium” approximation. As an application of this analytical expression, it is shown that the introduction of nano-sized skutterudite inclusions into the half-Heusler matrix can drastically reduce lattice thermal conductivity of the composite structure. Due to this effect, significantly higher ZT values can be achieved in the half-Heusler alloys at 300–700 K.