Theoretical search for Chevrel phase based thermoelectric materials

TL;DR

This study uses theoretical calculations to explore the thermoelectric potential of Chevrel phases, identifying promising compositions like Li and Cu fillings for high thermopower and mobility.

Contribution

It provides a theoretical assessment of various Chevrel phase compositions, highlighting promising alloying strategies for thermoelectric applications.

Findings

Alloying Mo with Re, Ru, or Tc reduces carrier mobility.

Filling with Zn, Cu, and especially Li is favorable for thermoelectric performance.

Li-rich (Li,Cu)$_4$Mo$_6$Se$_8$ is predicted to have high thermopower and good mobility.

Abstract

We investigate the thermoelectric properties of some semiconducting Chevrel phases. Band structure calculations are used to compute thermopowers and to estimate of the effects of alloying and disorder on carrier mobility. Alloying on the Mo site with transition metals like Re, Ru or Tc to reach a semiconducting composition causes large changes in the electronic structure at the Fermi level. Such alloys are expected to have low carrier mobilities. Filling with transition metals was also found to be incompatible with high thermoelectric performance based on the calculated electronic structures. Filling with Zn, Cu, and especially with Li was found to be favorable. The calculated electronic structures of these filled Chevrel phases are consistent with low scattering of carriers by defects associated with the filling. We expect good mobility and high thermopower in materials with the composition close to (Li,Cu)$_4$Mo$_6$Se$_8$, particularly when Li-rich, and recommend this system for experimental investigation.