Limitations of zT as a Figure of Merit for Nanostructured Thermoelectric Materials

Authors

Xufeng Wang, Purdue UniversityFollow
Mark Lundstrom, Purdue UniversityFollow

Abstract

Thermoelectric properties of nanocomposites are numerically studied as a function of average grain size or nanoparticle density by simulating the measurements as they would be done experimentally. In accordance with previous theoretical and experimental results, we find that the Seebeck coefficient, power factor and figure of merit, zT, can be increased by nanostructuring when energy barriers exist around the grain boundaries or embedded nanoparticles. When we simulate the performance of a thermoelectric cooler with the same material, however, we find that the maximum temperature difference is much less than expected from the given zT. This occurs because the measurements are done in a way that minimizes Joule heating, but the Joule heating that occurs in operating devices has a large effect for these kinds of materials. The same nanocomposite but without energy barriers at the grain boundaries has a lower measured zT but a higher maximum temperature difference. The physical reason for these results is explained. The results illustrate the limitations of zT as a figure of merit for nanocomposites with electrically active grain boundaries.

Comments

This is the PDF of Wang, X and Lundstrom, M. "Limitations of zT as a figure of merit for nanostructured thermoelectric materials" J. Appl. Phys. 126, 195703 (2019); doi: 10.1063/1.5127175. It is made available here CC-BY

Keywords

thermoelectrics, Seebeck coefficient, Figure of Merit

Date of this Version

2019

Published in:

Journal of Applied Physics