Half‐Heusler Thermoelectric Module with High Conversion Efficiency and High Power Density

Abstract Half‐Heusler (HH) compounds have shown great potential in waste heat recovery. Among them, p‐type NbFeSb and n‐type ZrNiSn based alloys have exhibited the best thermoelectric (TE) performance. However, TE devices based on NbFeSb‐based HH compounds are rarely studied. In this work, bulk volumes of p‐type (Nb 0.8 Ta 0.2 ) 0.8 Ti 0.2 FeSb and n‐type Hf 0.5 Zr 0.5 NiSn 0.98 Sb 0.02 compounds are successfully prepared with good phase purity, compositional homogeneity, and matchable TE performance. The peak zT s are higher than 1.0 at 973 K for Hf 0.5 Zr 0.5 NiSn 0.98 Sb 0.02 and at 1200 K for (Nb 0.8 Ta 0.2 ) 0.8 Ti 0.2 FeSb. Based on an optimal design by a full‐parameters 3D finite element model, a single stage TE module with 8 n‐p HH couples is assembled. A high conversion efficiency of 8.3% and high power density of 2.11 W cm −2 are obtained when hot and cold side temperatures are 997 and 342 K, respectively. Compared to the previous TE module assembled by the same materials, the conversion efficiency is enhanced by 33%, while the power density is almost the same. Given the excellent mechanical robustness and thermal stability, matchable thermal expansion coefficient and TE properties of NbFeSb and ZrNiSn based HH alloys, this work demonstrates their great promise for power generation with both high conversion efficiency and high power density.