On the wiedemann-franz law in thermoelectric composites

TL;DR

This paper theoretically investigates how thermoelectric effects influence the effective electrical and thermal conductivity in inhomogeneous media, revealing potential impacts on thermoelectric device efficiency.

Contribution

It provides a theoretical analysis of the Wiedemann-Franz law in thermoelectric composites, considering various inhomogeneous structures and high thermoelectric figures of merit.

Findings

Effective electrical to thermal conductivity ratio can differ significantly from local values in high figure of merit media.

The ratio may decrease, negatively affecting the composite's thermoelectric efficiency.

The relation depends on the structure and thermoelectric properties of the composite.

Abstract

Theoretical analysis of the effect of thermoelectric phenomena on the relation of effective electrical and thermal conductivity in the macroscopically inhomogeneous media is carried out. Plane-layered structures, two-dimensional self-dual and three-dimensional randomly inhomogeneous media are examined. It is shown that the relation of effective electrical to thermal conductivity, which is independent of concentration in so-called Wiedemann-Franz media, in the case of high values of internal thermoelectric figure of merit can be considerably different from the one for the local values in each phase. The decrease of the relation may have negative impact on the effective figure of merit of composites and thus lead to the decrease of thermoelectric devices efficiency.