Unraveling the dominant phonon scattering mechanism in thermoelectric compound ZrNiSn

TL;DR

This study uses ab-initio calculations to identify Ni/vacancy antisites as the main phonon scattering defects in ZrNiSn, challenging previous assumptions and providing a method to assess defect types via thermal conductivity.

Contribution

It reveals the dominant defect type affecting thermal transport in ZrNiSn using ab-initio calculations, correcting prior claims and establishing a quantitative defect assessment approach.

Findings

Ni/vacancy antisites are the main defects affecting thermal conductivity.

The phonon-antisite scattering rate scales with the sixth power of phonon frequency.

The calculations match experimental thermal conductivity data.

Abstract

Determining defect types and concentrations remains a big challenge of semiconductor materials science. By using ab-initio thermal conductivity calculations we reveal that Ni/vacancy antisites, and not the previously claimed Sn/Zr antisites, are the dominant defects affecting thermal transport in half-Heusler compound ZrNiSn. Our calculations correctly predict the thermal conductivity dependence with temperature and concentration, in quantitative agreement with published experimental results. Furthermore, we find a characteristic proportionality between phonon-antisite scattering rates and the sixth power of phonon frequency, for which we provide an analytic derivation. These results suggest that thermal conductivity measurements in combination with ab-initio calculations can be used to quantitatively assess defect types and concentrations in semiconductors.