A new n-type half-Heusler thermoelectric material NbCoSb

Abstract

A B S T R A C TWe surprisingly made a new n-type thermoelectric compound NbCoSb with half-Heusler (HH) structure having valence electron count of 19, different from the traditional 18, which opens up a new route to develop new half-Heusler thermoelectric materials not following the traditional valence electron count of 18. The samples are made by arc melting followed by ball milling and hot pressing. The effect of hot pressing temperature on the thermoelectric properties of NbCoSb samples has been studied. A maximum thermoelectric figure-of-merit (ZT) of $0.4 is achieved at 700 C in NbCoSb sample that is hot pressed at 1000 C. This work add a new member to HH compounds for thermoelectric applications, although the peak ZT of $0.4 is still lower than that of the traditional HHs. Moreover, it is very interesting to see that a traditionally thought of valence electron counts of 18 is not required.

Enhanced thermoelectric properties of n-type NbCoSn half-Heusler by improving phase purity

“…Huang et al reported an even higher carrier concentration of ∼6 × 10 21 cm −3 for NbCoSb. 23 On the other hand, the measured carrier mobility increases significantly from ∼0.2 to ∼11 cm 2 V −1 s −1 with Sb concentration up to 0.05, then it decreases to ∼8.8 cm 2 V −1 s −1 with Sb concentration reaching 0.15 ( Fig. 4(a) right).…”

“…3(g)). It should be mentioned that the decrease in κ L is not due to point defect scattering because the κ L of ternary NbCoSb 23 scattering because of the increased carrier concentration (Fig. 4(a)) or the stronger phonon-phonon interaction with higher concentration of Sb.…”

Phonon transport properties of NbCoSb compound

“…In a result of the geometric optimization, the lattice parameter is found to be 5.9790 Å. The calculated lattice parameter is approximately %1.4 higher than the experimental value (5.897 Å), as expected from PBE [8].…”

“…To the best of our knowledge, there is no detailed study of the NbCoSb compound. The new thermoelectric NbCoSb is recently synthesized using arc melting followed by ball milling and hot pressing by Huang et al [8,9]. Also, they have studied the effect of hot pressing temperature on the thermoelectric properties [8].…”

“…The new thermoelectric NbCoSb is recently synthesized using arc melting followed by ball milling and hot pressing by Huang et al [8,9]. Also, they have studied the effect of hot pressing temperature on the thermoelectric properties [8]. In order to use this and similar compounds in a healthy way in the technology, physical properties should be examined in detail.…”