Pressure effects on the electrical transport and anharmonic lattice dynamics of r-GeTe: A first-principles study

doi:10.1016/j.jmat.2021.03.008

Journal of Materiomics

Volume 7, Issue 6, November 2021, Pages 1190-1197

https://doi.org/10.1016/j.jmat.2021.03.008 Get rights and content

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Highlights

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The effects of pressure on the transport properties of GeTe have been studied from DFT calculations.
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A high valley degeneracy and a small band effective mass are found in r-GeTe at 5 GPa.
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Microscopic mechanisms are explored for the enhanced electrical and thermal transport properties of r-GeTe under pressure.

Abstract

Various strategies for thermoelectric material optimization have been widely studied and used for promoting electrical transport and suppressing thermal transport. As a nontraditional method, pressure has shown great potential, as it has been applied to obtain a high thermoelectric figure of merit, but the microscopic mechanisms involved have yet to be fully explored. In this study, we focus on r-GeTe, a low-temperature phase of GeTe, and investigate the pressure effects on the electronic structure, electrical transport properties and anharmonic lattice dynamics based on density functional theory (DFT), the Boltzmann transport equations (BTEs) and perturbation theory. Electronic relaxation times are obtained based on the electron-phonon interaction and the constant relaxation time approximation. The corresponding electrical transport properties are compared with those obtained from previous experiments. Hydrostatic pressure is shown to increase valley degeneracy, decrease the band effective mass and enhance the electrical transport property. At the same time, the increase in the low-frequency phonon lifetime and phonon group velocity leads to an increase in lattice thermal conductivity under pressure. This study provides insight into r-GeTe under hydrostatic pressure and paves the way for a high-pressure strategy to optimize transport properties.

Graphical abstract

Keywords

GeTe

Pressure effect

Electronic structure

Transport properties

Cited by (0)

Juan Cui is a joint Ph.D. candidate at Southern University of Science and Technology and the University of Hong Kong. She received her bachelor degree in materials physics from Nanjing University in 2014 and received her master degree in materials engineering from the University of Alberta in 2017. Her current research focuses on first-principles study on thermoelectric materials.

Yue Chen is an associate professor at the University of Hong Kong, Department of Mechanical Engineering. His research interests are focused on the materials physics for electrical and thermal transports, such as electronic structures and lattice dynamics. His interests stem from the studies of materials science at University of Oxford and Beihang University. He was a postdoctoral fellow at Columbia University and Institute of Metal research, Chinese Academy of Science before joining HKU.

Jiaqing He is a chair professor at Southern University of Science and Technology. He received his joint Ph.D. degree in physics from both Juelich Research Center and Wuhan University in 2004. He was a postdoc at Brookhaven National Laboratory (2004–2008), research associate (2008–2010) and research assistant professor (2010–2012) at Northwestern University, and a professor at Xi’an Jiaotong University (2012–2013). His research interests include transmission electron microscopy, thermoelectric materials, and structure and property relationship.

: Peer review under responsibility of The Chinese Ceramic Society.

¹: These authors contributed equally.