Discovery of ZrCoBi based half Heuslers with high thermoelectric conversion efficiency

Hangtian Zhu,Wuyang Ren,Zhifeng Ren,David Broido,Gang Chen,Chunhua Li,Ran He,David J Singh,Jifeng Sun,Zihang Liu,Jun Mao,Zhiming Wang,Andrei Sotnikov,Zhongjia Tang,Qing Zhu,Kornelius Nielsch,Yumei Wang

doi:10.1038/s41467-018-04958-3

Abstract

Thermoelectric materials are capable of converting waste heat into electricity. The dimensionless figure-of-merit (ZT), as the critical measure for the material’s thermoelectric performance, plays a decisive role in the energy conversion efficiency. Half-Heusler materials, as one of the most promising candidates for thermoelectric power generation, have relatively low ZTs compared to other material systems. Here we report the discovery of p-type ZrCoBi-based half-Heuslers with a record-high ZT of ∼1.42 at 973 K and a high thermoelectric conversion efficiency of ∼9% at the temperature difference of ∼500 K. Such an outstanding thermoelectric performance originates from its unique band structure offering a high band degeneracy (Nv) of 10 in conjunction with a low thermal conductivity benefiting from the low mean sound velocity (vm ∼2800 m s−1). Our work demonstrates that ZrCoBi-based half-Heuslers are promising candidates for high-temperature thermoelectric power generation.

Highlights

Thermoelectric materials are capable of converting waste heat into electricity
Our work demonstrates that ZrCoBi-based half-Heuslers are quite promising for high-temperature thermoelectric power generation
The valence bands converge at Γ point and split slightly at L point due to spin-orbit coupling effect as shown in the Supplementary Fig. 1

Summary

Introduction

Thermoelectric materials are capable of converting waste heat into electricity. The dimensionless figure-of-merit (ZT), as the critical measure for the material’s thermoelectric performance, plays a decisive role in the energy conversion efficiency. The power factors can be optimized by tuning the carrier concentration, and further enhancement can be achieved by band engineering[8,9,10], modulation doping[11], introducing the resonant level[12], and tuning the carrier scattering mechanism[13,14,15] Among these approaches, band engineering via increasing the degenerate band valleys (Nv), either by alloying or exploiting the temperature dependence of the electronic bands, has been demonstrated to be effective in enhancing the power factor. Band engineering via increasing the degenerate band valleys (Nv), either by alloying or exploiting the temperature dependence of the electronic bands, has been demonstrated to be effective in enhancing the power factor In this case, a high electrical conductivity can be obtained with the presence of multiple conducting channels enabled by the high number of band valleys. The Seebeck coefficient can still be maintained since the high electrical conductivity do not involve any increase in the carrier concentration

Methods

Results

Conclusion