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Quasi-2D Carrier Transport in KMgBi for Promising Thermoelectric Performance
Journal
ACS Applied Energy Materials
Date Issued
2022-07-25
Author(s)
Vikram,
Sahni, Bhawna
Jain, Ankit
Alam, Aftab
Abstract
KMgBi is an interesting system with several unconventional electronic transport properties. Despite numerous studies exploring its topological trivial/nontrivial nature, it has never been studied from a thermoelectric (TE) perspective. Its band structure shows appropriate degenerate flat bands near the valence band edge that are useful for high thermopower. We also show that KMgBi acquires a high degree of anharmonicity that leads to low lattice thermal conductivity. This yields a high TE figure of merit, ZT ∼2.21 (p-type) at ∼600 K temperature. A careful analysis of electron and phonon dispersion establishes an interesting quasi-2D nature of KMgBi. Utilizing the flat degenerate valence band and strong spin-orbit coupling, we discuss how to further enhance the TE performance of KMgBi via alloy engineering. Substituting Li at K and As at Bi sites increases the band gap with little effect on the band curvature, further improving the TE performance. With 50% As alloying, we expect ∼10-11% enhancement in the ZT.
Volume
5
Subjects