Optimizing thermoelectric properties of filled MPt$_4$Ge$_{12-x}$Sb$_x$ skutterudites by band engineering

TL;DR

This study uses density functional theory to optimize the thermoelectric properties of Sb-doped skutterudites, predicting significant improvements in Seebeck coefficients and thermal properties, supported by experimental validation.

Contribution

It introduces a band engineering approach to enhance thermoelectric performance in filled MPt4Ge12-xSbx skutterudites, identifying optimal doping levels for improved efficiency.

Findings

Seebeck coefficient increased by over 10 times with doping

Optimal doping aligns with a 'magic' valence electron count

La-based skutterudites show low thermal conductivity and high thermoelectric potential

Abstract

On the basis of density functional theory (DFT) calculations thermoelectric properties are derived for Sb-doped skutterudites MPt$_4$Ge$_{12-x}$Sb$_x$ with M=Ba,La,Th. It is predicted that the originally very small absolute values of Seebeck coefficients $|S|$ of the undoped compounds is increased by factors of 10 or more for suitable dopings. The optimal dopings correspond to a "magic" valence electron number for which all electronic states up to a (pseudo)gap are filled. The theoretical findings are corroborated by measurements of $S$ for LaPt$_4$Ge$_{12-x}$Sb$_x$ skutterudites. DFT derived vibrational rattling-like modes for LaPt$_4$Ge$_{12}$ indicate a small value for the lattice thermal conductivity which in combination with a large value of $S^2$ makes the La-based skutterudites appear as promising thermoelectric materials.