Enhanced thermoelectric performance of Hafnium free n-type ZrNiSn half-Heusler alloys by isoelectronic Si substitution. (May 2022)

• Record Type: Journal Article
• Authors: Zhang, Q.; Xie, P.; Liu, C.; Li, S.; Lei, X.; Huang, L.; Yuan, G.; Cai, F.
• Is Part Of: Materials today physics. Volume 24(2022)
• Publication Date: 2022-05
• Subjects: ZrNiSn -- Half-heusler -- Thermoelectric performance -- Debye-callaway model; Materials science -- Periodicals; Physics -- Periodicals; Electronic journals; 530.41
• DOI: 10.1016/j.mtphys.2022.100648
• Languages: English
• ISSNs: 2542-5293

Abstract

Abstract: In this work, cheap element Si is added into Hafnium-free ZrNiSn half-Heusler (HH) compound to reduce its lattice thermal conductivity. We report a comprehensive analysis of the isoelectronic Si substitution on the electrical and thermal conductivity for ZrNiSn half-Heusler alloys. The first-principles calculations show that Si doping has a negligible effect on the electronic structure of ZrNiSn1-x Six HH materials. The band gap of 0.48 eV for ZrNiSn sample is compared to that of 0.49 eV for Zr27 Ni27 Sn26 Si. The transmission electron microscopy (TEM) images display the nano structure in the ZrNiSn0.98 Si0.02 sample, which strongly affects the lattice thermal conductivity. The contribution of point defect scattering by Si substitution on the lattice thermal conductivity is quantitatively analyzed by using Debye-Callaway model, suggesting that the strain fluctuation is the main factor to reduce lattice thermal conductivity. Finally, the maximum zT value reaches 0.78 at 873 K for the ZrNiSn0.98 Si0.02 sample. Graphical abstract: Image 1 Highlights: A high zT value of 0.78 is achieved in Hafnium free n-type ZrNiSn half-Heusler alloys by isoelectronic Si substitution. The decreased lattice thermal conductivity results in a higher maximum potential zT. The strain fluctuation is one of effective methods to reduce lattice thermal conductivity.