KMgBi: A Highly Efficient Quasi-2D Thermoelectric Material

Half Heusler alloys are known to showcase a variety of interesting properties which make them potential candidates for energy applications. Here, we present a first principles study of KMgBi which is a promising candidate for thermoelectric(TE) applications. This compound has been experimentally synthesized in the past [Zhang, X. et al. Phys. Rev. B 2017, 035209 (95)], but has never been studied from TE perspective. The presence of flat bands near valence band edge and strong spin-orbit coupling provide a fertile ground to explore the potential of this material. The lattice thermal conductivity was calculated using the modified Debye Callaway Model  which came out to be as low as ≤ 1 W m^-1K^-1. The energy and temperature dependent relaxation time was calculated carefully taking into account different scattering mechanisms. The system shows a high TE figure of merit ZT ~ 2.68 (for p-type) at ~ 400K temperature. We have further discussed enhancing the TE performance of KMgBi via alloy engineering. With the proposed alloy engineering, we expect at least a 20% enhancement in the TE figure of merit.