ZnSb Polymorphs with Improved Thermoelectric Properties

ZnxSb1-x, systems are one of the most promising materials for thermoelectric applications due to their low cost, low toxicity, and high thermoelectric figure of merit. We report the discovery and characterization of novel ZnSb polymorphs with improved thermoelectric properties from a systematic ab initio structural search. The putative ground state at low temperature is a structure with Pbca symmetry. Corresponding electron and phonon transport properties are computed, where the lattice thermal conductivity was accurately obtained through third-order interatomic force constants. At 500 K, both the reduced figure of merit S-2/L as well as the lattice thermal conductivity are superior to any previously reported numbers on ZnSb polymorphs, rendering the Pbca phase a promising candidate for an exceptionally good thermoelectric material.