The effect of phonon-phonon interaction in Ta based Heusler alloys for accurate phonon transport properties

Background

Lattice thermal conductivity is critical property that influences the efficiency of thermoelectric materials. Understanding the underlying mechanisms including phonon scattering processes and temperature dependence, help to precisely compute lattice thermal conductivity, which is critical for optimizing thermoelectric materials. Neglecting these factors might underestimated the thermal conductivity and inaccurately predicted the material's efficiency.

Methods

This study investigates the interplay between lattice structure, phonon dynamics, and thermal transport in Ta-based Heusler alloys using density functional theory within the Vienna Ab initio Simulation Package. The Boltzmann transport equation was employed to calculate lattice thermal conductivity and other thermoelectric parameters, with results compared to classical Slack equation, which inadequately addresses phonon-phonon interactions.

Significant Findings

The studied alloys are stable in cubic structure, characterized by negative formation energy and hull distance. The band gaps were found to be 0.48 eV for TaMnTe and 1.0 eV for TaCoPb. Significant differences in lattice thermal conductivity were observed, with errors of around 10 % and 13 % for TaMnTe and TaCoPb, respectively. The maximum figure of merit values for p-type TaMnTe and TaCoPb were 0.63 and 0.56 at 1000 K, indicating their potential as promising candidates for waste heat recovery at high temperatures due to their favorable thermal properties.