Work

Limitations of zT as a figure of merit for nanostructured thermoelectric materials

Year: 2019

Type: article

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, ΔTmax, 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 ΔTmax. 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.

Source: Journal of Applied Physics

DOI: 10.1063/1.5127175

Authors: Xufeng Wang, Mark Lundstrom

Institution: Purdue University West Lafayette

Language: English

Topic: Advanced Thermoelectric Materials and Devices

Subfield: Materials Chemistry

Field: Materials Science

Domain: Physical Sciences

SDG: Affordable and clean energy

Open Access status: hybrid

Estimated APC paid: $3,500