Discovery of YbNiSb-Based Half-Heusler Alloys as Promising Thermoelectric Materials

Abstract

Half-Heusler materials are promising candidates for high-temperature power generation and have relatively high lattice thermal conductivity compared to other thermoelectric material systems. In this work, we report novel p-type YbNiSbbased half-Heusler alloys with a low lattice thermal conductivity (∼3.6 W m −1 K −1 at 340 K) that resulted from their large Gruneisen parameter, low sound speed, and low Debye temperature. All YbNiSb-based alloys exhibit a high carrier mobility of 30−50 cm 2 V −1 s −1 at room temperature because of their relatively small effective mass. Importantly, the structural analysis reveals that Yb-rich Yb 1.3 Ni 0.9 Sb 0.8 exhibits Yb/Ni and Yb/Sb substitution, indicating a wide homogeneity region of the YbNiSb phase experimentally. The adjustable Yb and Ni contents in YbNiSb-based alloys can modify the band structure around the Fermi level and significantly affect electrical transport properties. Additionally, by doping Ta at Yb sites, the carrier concentration and lattice thermal conductivity of these alloys can be manipulated. Consequently, a peak zT value of 0.45 at 823 K was achieved for Yb 0.95 Ta 0.05 NiSb. Our work demonstrates that YbNiSb-based alloys are promising p-type thermoelectric materials and suggests the possibility of exploring novel thermoelectric alloys in rare-earth nickel pnictides via tuning their composition and crystal structure.

Simultaneous optimization of the electrical and thermal transport properties of LuNiSb via aliovalent doping

“…However, owing to the challenge of synthesis and complex intrinsic defects, Re-based HH compounds have been rarely studied experimentally. 21 In 2020, DyNiSb, ErNiSb, TmNiSb, and LuNiSb were successfully prepared by Ciesielski et al ., 22 of which the κ L were reported to be about 2.0–5.0 W m −1 K −1 at 300 K. The κ L of YbNiSb, prepared by Huang et al ., 21 was reported to be about 2.2 W m −1 K −1 at 300 K. Compared to other typical HH compounds ( κ L : 12 W m −1 K −1 for VFeSb, 23 6 W m −1 K −1 for ZrNiSn, 11 18 W m −1 K −1 for ZrCoSb 24 ), the experimentally reported low κ L s in ReNiSb-based HH compounds might be favorable for good TE performance. To verify this, more systematic studies on the optimization of TE performance should be carried out.…”