Enhanced Thermoelectric Performance of Zr1- xTaxNiSn Half-Heusler Alloys by Diagonal-Rule Doping

Xiong Yang; Zhou Jiang; Huijun Kang; Zongning Chen; Enyu Guo; Daquan Liu; Fenfen Yang; Rengeng Li; Xue Jiang; Tongmin Wang

doi:10.1021/acsami.9b21517

Enhanced Thermoelectric Performance of Zr_{1- x}Ta_xNiSn Half-Heusler Alloys by Diagonal-Rule Doping

ACS Appl Mater Interfaces. 2020 Jan 22;12(3):3773-3783. doi: 10.1021/acsami.9b21517. Epub 2020 Jan 8.

Authors

Affiliations

¹ Key Laboratory of Solidification Control and Digital Preparation Technology (Liaoning Province), School of Materials Science and Engineering , Dalian University of Technology , Dalian 116024 , China.
² Key Laboratory of Materials Modification by Laser , Ion and Electron Beams (Dalian University of Technology), Ministry of Education , Dalian 116024 , China.

PMID: 31880427
DOI: 10.1021/acsami.9b21517

Abstract

Although Sb doping is regarded as the most effective method to regulate the carrier concentration within the optimum range for ZrNiSn-based half-Heusler (HH) alloys, the resulting thermal conductivity remains high. Hence, the aim of this study was to investigate the effect of "diagonal-rule" doping; that is, the Zr site was displaced by Ta, which can simultaneously enhance the electrical conductivity and reduce the lattice thermal conductivity. The solid-solubility limit of Ta in the ZrNiSn matrix was determined to be x = 0.04. The highest ZT, 0.72, was achieved at 923 K for Zr_0.98Ta_0.02NiSn. In addition, ZT_avg increased by 10.2% for Zr_0.98Ta_0.02NiSn compared with that for ZrNiSn_0.99Sb_0.01 at 873 K, which was mainly attributed to the reduced lattice thermal conductivity of Zr_0.98Ta_0.02NiSn. These results suggest that Ta doping is more effective than Sb doping in ZrNiSn-based HH alloys. In addition, the microhardness of Zr_1-xTa_xNiSn was substantially improved with increasing Ta content and was also much higher than that of other traditional thermoelectric materials.

Keywords: doping; electrical conductivity; half-Heusler alloys; lattice thermal conductivity; thermoelectric.