Issue 11, 2024

Strong electron–phonon coupling and high lattice thermal conductivity in half-Heusler thermoelectric materials

Abstract

Traditional half-Heusler thermoelectric materials, identified as 18-electron compounds, are characterized by the high power factor and the high lattice thermal conductivity. Interestingly, the emerging 19-electron half-Heusler compounds were also found to be promising thermoelectric materials, but with a 5–10 times lower lattice thermal conductivity. Since the two kinds of compounds have similar chemical and physical structures, such as TiCoSb and VCoSb, the large difference in lattice thermal conductivity is a puzzling question. Here, we present a theoretical study to clarify the lattice thermal transport in half-Heusler thermoelectric materials. Based on electronic band structure analysis, we show that the two transition-metal elements in half-Heusler compounds form the strong and direct d–d interaction that is responsible for the high lattice thermal conductivity of 18-electron compounds. In 19-electron half-Heusler compounds, however, the extra valence electron enters the d–d antibonding states, which significantly weakens the atomic bond strength, leading to a large decrease in the cohesive energy. The resulting softened acoustic phonons enhance the phonon–phonon scattering, and thus reduce the lattice thermal conductivity significantly. By constructing an artificial 18-e compound V0.5Sc0.5CoSb, it is proved that the one less electron relative to VCoSb increases the lattice thermal conductivity significantly.

Graphical abstract: Strong electron–phonon coupling and high lattice thermal conductivity in half-Heusler thermoelectric materials

Supplementary files

Article information

Article type
Paper
Submitted
19 Dec 2023
Accepted
19 Feb 2024
First published
20 Feb 2024

Phys. Chem. Chem. Phys., 2024,26, 8932-8937

Strong electron–phonon coupling and high lattice thermal conductivity in half-Heusler thermoelectric materials

R. Wang, J. Cai, Q. Zhang, X. Tan, J. Wu, G. Liu and J. Jiang, Phys. Chem. Chem. Phys., 2024, 26, 8932 DOI: 10.1039/D3CP06160D

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