Half-Heusler-like compounds with wide continuous compositions and tunable p- to n-type semiconducting thermoelectrics

Zirui Dong,Ying Jiang,Jiye Zhang,Chenyang Wang,Yuri Grin,Shihua Tan,Zhiyang Yu,Kai Guo,Wenqing Zhang,Yubo Zhang,Jun Luo

doi:10.1038/s41467-021-27795-3

Abstract

Half-Heusler and full-Heusler compounds were considered as independent phases with a natural composition gap. Here we report the discovery of TiRu1+xSb (x = 0.15 ~ 1.0) solid solution with wide homogeneity range and tunable p- to n-type semiconducting thermoelectrics, which bridges the composition gap between half- and full-Heusler phases. At the high-Ru end, strange glass-like thermal transport behavior with unusually low lattice thermal conductivity (~1.65 Wm−1K−1 at 340 K) is observed for TiRu1.8Sb, being the lowest among reported half-Heusler phases. In the composition range of 0.15 < x < 0.50, TiRu1+xSb shows abnormal semiconducting behaviors because tunning Ru composition results in band structure change and carrier-type variation simultaneously, which seemingly correlates with the localized d electrons. This work reveals the possibility of designing fascinating half-Heusler-like materials by manipulating the tetrahedral site occupancy, and also demonstrates the potential of tuning crystal and electronic structures simultaneously to realize intriguing physical properties.

Highlights

Half-Heusler and full-Heusler compounds were considered as independent phases with a natural composition gap
In both chemistry and materials science communities, the HH and FH compounds have been considered as independent phases with a natural HH-FH composition gap for nearly 100 years
We report on the discovery of the TiRu1+xSb solid solution falling in the HH-FH composition gap and at the same time with tunable p- to n-type semiconducting thermoelectrics

Summary

Introduction

Half-Heusler and full-Heusler compounds were considered as independent phases with a natural composition gap. The results of XRD and TEM analysis clearly prove that the HH-FH composition gap can be bridged by filling the vacant tetrahedral interstitial sites with appropriate atoms, with the Rubased TiRu1+xSb solid solution as a representative and unambiguous example. The unusually low lattice thermal conductivities of TiRu1+xSb samples can be ascribed to the increased structural disorder due to the partial filling of Ru in two sites, which is reflected by their low sound velocities (Fig. 3d) and large crystal anharmonicities (see Supplementary Section 2 and Table S3).

Results

Conclusion