Orbital-selective band engineering realizes high zT in p-type Ru2Ti1−xHfxSi full-Heusler thermoelectrics

Abstract

Abstract Heusler compounds have emerged as important thermoelectric materials due to their combination of promising electronic transport properties, mechanical robustness and chemical stability – key aspects for practical device integration. While a wide range of XYZ-type half-Heusler compounds have been studied for high-temperature applications, X 2 YZ-type full-Heuslers, often characterized by narrower band gaps, may offer potential advantages at different temperature regimes but remain less explored. In this work, the discovery of p -type Ru 2 Ti 1−x Hf x Si full-Heusler thermoelectrics, exhibiting a high figure of merit zT = 0.7 over a broad range of temperatures 700–1000 K, is reported. These results not only represent the largest values known to date among full-Heusler materials but confirm earlier theoretical predictions that p -type Ru 2 TiSi systems would be superior to their n -type counterparts. Moreover, using a two-band model, electronic structure changes induced by the Hf substitution at the Ti site are unveiled and strategies to further improve zT up to zT > 1 are outlined. These findings highlight the untapped potential of new semiconducting full-Heusler phases and the crucial need for continued exploration of this rich materials class for thermoelectric applications.