Abstract
Several thousand compounds from the Inorganic Crystal Structure Database have been considered as nanograined, sintered-powder thermoelectrics with the high-throughput ab-initio AFLOW framework. Regression analysis unveils that the power factor is positively correlated with both the electronic band gap and the carrier effective mass, and that the probability of having large thermoelectric power factors increases with the increasing number of atoms per primitive cell. Avenues for further investigation are revealed by this work. These avenues include the role of experimental and theoretical databases in the development of novel materials.
- Received 6 July 2011
DOI:https://doi.org/10.1103/PhysRevX.1.021012
This article is available under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Popular Summary
Thermoelectric materials convert heat flow into electric power. Solid-state devices based on such materials, silent, stable, and scalable, are envisioned as being ideal devices for small-scale, localized power generation that turns waste heat into electric power. Their efficiency is captured by two collective material parameters: thermoelectric power factor and thermal conductivity. The higher the former and the lower the latter, the more efficient a material is. But the conversion efficiency of most known bulk crystalline thermoelectric materials is too low for them to be cost effective in devices. Therefore, the search for high-efficiency thermoelectric materials is still on, exploiting different materials-engineering strategies. One of the strategies is based on sintered compounds that have a general material structure consisting of randomly oriented, similarly sized crystalline grains. However, an experimental search approach of trials and errors is expensive and time consuming. Theoretical predictions that can guide experimental efforts are therefore crucial. In this paper, we introduce a new high-throughput, quantum-mechanical computational approach, and we predict a large set of potential sintered inorganic compounds with high thermoelectric power factors.
The physical concept we introduce is based on an intuitive picture: Charge carriers (electrons or holes) in a nanosintered compound are scattered at the grain boundaries, and therefore, the mean free paths between collisions are roughly constant, of the order of the grain size. This picture is quite different from the commonly used “constant-relaxation-time” approach for bulk crystalline materials. Armed with a high-throughput computational method that incorporates this “constant-mean-free-path” idea, we have calculated the thermoelectric properties of several thousands of powder-sintered compounds extracted from the on-line repository consortium of electronic structure calculations, www.aflowlib.org. Guiding rules for searching for better materials are drawn by the correlations between the power factor and other physical properties. In particular, we have found that sintered thermoelectric compounds with large power factors tend to have large band gaps, heavy carrier effective masses, and many atoms per primitive cell. We have also established a supplemental table with all the thermoelectric properties for the 2 500 compounds.
We expect that our predictions will aid experimentalists considerably in terms of orienting their searches. We also hope that our “high-throughput electronic-structure formalism” will find broader use in studies of complex nanostructured thermoelectric materials.
