Origin of large thermopower in LiRh$_2$O$_4$

TL;DR

This paper investigates the origin of large thermopower in LiRh₂O₄ using LDA+DMFT and Boltzmann approaches, revealing similarities with NaₓCoO₂ and suggesting doping to enhance thermoelectric performance.

Contribution

It demonstrates that the large thermopower in LiRh₂O₄ can be explained by electronic structure calculations and identifies potential ways to improve its thermoelectric efficiency.

Findings

LDA+DMFT reproduces experimental thermopower values.

Boltzmann approach reveals common origin with NaₓCoO₂.

Doping can further increase the power factor.

Abstract

Motivated by the newly synthesized mixed-valent spinel LiRh$_2$O$_4$ for which a large thermopower is observed in the metallic cubic phase above 230K [Okamoto {\it et al.} (arXiv:0806.2504)], we calculate the Seebeck coefficient by the combination of local density approximation and dynamical mean field theory (LDA+DMFT). The experimental values are well reproduced not only by LDA+DMFT but also by the less involved Boltzmann equation approach. A careful analysis of the latter shows unexpectedly that the origin of the large thermopower shares a common root with a very different oxide: Na$_x$CoO$_2$. We also discuss how it is possible to further increase the powerfactor of LiRh$_2$O$_4$ through doping, which makes the material even more promoising for technological applications.