Ab initio study of the strain dependence of thermopower in electron-doped SrTiO$_3$

TL;DR

This study uses ab initio calculations to analyze how strain affects the thermopower of electron-doped SrTiO$_3$, revealing that tensile strain can enhance thermopower without significant detrimental effects, aiding thermoelectric optimization.

Contribution

The paper provides a detailed ab initio analysis of strain effects on thermopower in SrTiO$_3$, highlighting the minor impact of band splitting and the potential for thermopower enhancement through tensile strain.

Findings

Strain has a small effect on high-temperature Seebeck coefficient.

Effective mass changes significantly with strain, influencing thermopower.

Tensile strain can enhance thermopower in certain regimes.

Abstract

In this paper we explore the different mechanisms that affect the thermopower of a band insulating perovskite (in this case, SrTiO$_3$) when subject to strain (both compressive or tensile). We analyze the high temperature, entropy dominated limit and the lower temperature, energy-transport regime. We observe that the effect of strain in the high-temperature Seebeck coefficient is small at the concentration levels of interest for thermoelectric applications. However, the effective mass changes substantially with strain, which produces an opposite effect to that of the degeneracy-breakups produced by strain. In particular, we find that the thermopower can be enhanced by applying tensile strain in the adequate regime. We conclude that the detrimental effect of strain in thermopower due to band splitting is a minor effect that will not hamper the optimization of the thermoelectric properties of oxides with t$_{2g}$-active bands by applying strain.