\textit{Ab initio} study of Bi-based half Heusler alloys as potential thermoelectric prospects

TL;DR

This study uses first principles calculations to identify bismuth-based half-Heusler alloys with enhanced thermoelectric properties, showing promising power factors and low thermal conductivities compared to existing materials.

Contribution

It introduces six new heavy element bismuth-based half-Heusler alloys with improved thermoelectric potential based on ab initio calculations.

Findings

Power factor increased by ~40% over CoTiSb.

Lower thermal conductivity observed in CoTiBi and CoZrBi.

Estimated figure of merit exceeds CoTiSb and rivals FeNbSb.

Abstract

We investigated six heavy element bismuth-based 18-VEC half-Heusler alloys CoTiBi, CoZrBi, CoHfBi, FeVBi, FeNbBi, and FeTaBi by first principles approach, in search of better thermoelectric prospects. The motivation is driven by expected lower thermal conductivity and the recent discovery of CoZrBi-based materials. Significantly, our calculated power factor values of all the systems show an increment of $\sim$40\% in comparison to the reported \textit{p}-type CoTiSb. We propose that doping at Bi-site, on account of electronic features, will be helpful in achieving the proposed power factor values. Interestingly, the thermal conductivity of CoTiBi and CoZrBi was found to be lower and that of CoHfBi was almost parallel, in comparison to the reported CoTiSb. We also provide conservative estimates of the figure of merit, exceeding the reported CoTiSb and comparable to FeNbSb. Overall, our results suggest potential new candidates of bismuth-based ternary compounds for high thermoelectric performance.