Ultra-low lattice thermal conductivity of MgPb$_2$Te -- A first principles study

TL;DR

This study uses first principles calculations to reveal that MgPb$_2$Te has an ultra-low thermal conductivity, making it a promising candidate for thermoelectric applications by efficiently converting waste heat into electricity.

Contribution

The paper reports the first calculation of ultra-low thermal conductivity in MgPb$_2$Te and analyzes the underlying phonon mechanisms contributing to this property.

Findings

Thermal conductivity of MgPb$_2$Te is 2.08 and 2.9 W/mK along c-axis and a-axis at room temperature.

Nanostructuring reduces thermal conductivity to below 1 W/mK at 50 nm size.

MgPb$_2$Te shows potential for thermoelectric applications due to its ultra-low thermal conductivity.

Abstract

Thermoelectric technology is an alternate way to efficiently utilize the energy by converting waste heat into electricity. Thermoelectric requires material with low thermal conductivity to improves its thermoelectric performance. In this work, by solving Boltzmann transport equation based on first principles calculations, we report an ultra-low room temperature thermal conductivity of 2.08 Wm$^{-1}$K$^{-1}$ and 2.9 Wm$^{-1}$K$^{-1}$ along c-axis and a-axis respectively for pure MgPb$_2$Te. To explain this ultra-low thermal conductivity, we analyzed the elastic constants, phonon group velocity, phonon-phonon scattering and contribution from transverse acoustic, longitudinal acoustic and optical phonon branches. We also report the thermal conductivity of MgPb$_2$Te nanostructures. At 50 nm, the room temperature thermal conductivity of MgPb$_2$Te is 0.957 Wm$^{-1}$K$^{-1}$ and 1.459 Wm$^{-1}$K$^{-1}$ along c-axis and a-axis respectively. Ultra-low thermal conductivity unraveled in this work shows MgPb$_2$Te would a promising material for thermoelectric applications.