Temperature and composition insensitivity of thermoelectric properties of high-entropy half-heusler compounds

Composition modification by doping and solid solution is a well-studied strategy in thermoelectric (TE) materials to optimise their properties. Recently, the concept of entropy stabilization has offered the possibility of forming random solid solutions that have properties that go beyond the rule of mixture. In this study, we prepared a series of high-entropy half-Heusler solid solutions (HEHHs) with varying valence electron counts (VEC), (Ti0.33Zr0.33Hf0.33)1-x(V0.33Nb0.33Ta0.33)xCoSb (x = 0.5 to 0.75). Compared to their medium- and low-entropy counterparts, the TE properties of HEHHs are less sensitive to temperature and composition variation (charge carrier concentration efficiency of ∼10%). An ultra-low lattice thermal conductivity for half-Heusler of 1.19 W·m−1·K−1 was achieved.