Nanograined Half-Heusler Semiconductors as Advanced Thermoelectrics: An Ab Initio High-Throughput Statistical Study

Nanostructuring has spurred a revival in the field of direct thermoelectric energy conversion. Nanograined materials can now be synthesized with higher figures of merit (ZT) than the bulk counterparts. This leads to increased conversion efficiencies. Despite considerable effort in optimizing the known and discovering the unknown, technology still relies upon a few limited solutions. Here ab initio modeling of ZT is performed for 75 nanograined compounds-the result of accurate distillation with electronic and thermodynamic filtering techniques from the 79 057 half-Heusler entries available in the AFLOWLIB.org repository. For many of the compounds, the ZTs are markedly above those attainable with nanograined IV and III-V semiconductors. About 15% of them may even outperform ZT approximate to 2 at high temperatures. This analysis elucidates the origin of the advantageous thermoelectric properties found within this broad material class. Machine learning techniques are used to unveil simple rules determining if a nanograined half-Heusler compound is likely to be a good thermoelectric given its chemical composition.