Directional Phonon Suppression Function as a Tool for the Identification of Ultralow Thermal Conductivity Materials
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Directional phonon.pdf
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Author(s)
Romano, Giuseppe
Kolpak, Alexie M.
Date Issued
March 2017
Journal
Scientific Reports
Publisher
Nature Publishing Group
Citation
Romano, Giuseppe and Kolpak, Alexie M. “Directional Phonon Suppression Function as a Tool for the Identification of Ultralow Thermal Conductivity Materials.” Scientific Reports 7 (March 2017): 44379 © 2017 The Author(s)
Version
Final published version
Abstract
Boundary-engineering in nanostructures has the potential to dramatically impact the development of materials for high- efficiency conversion of thermal energy directly into electricity. In particular, nanostructuring of semiconductors can lead to strong suppression of heat transport with little degradation of electrical conductivity. Although this combination of material properties is promising for thermoelectric materials, it remains largely unexplored. In this work, we introduce a novel concept, the directional phonon suppression function, to unravel boundary-dominated heat transport in unprecedented detail. Using a combination of density functional theory and the Boltzmann transport equation, we compute this quantity for nanoporous silicon materials. We first compute the thermal conductivity for the case with aligned circular pores, confirming a significant thermal transport degradation with respect to the bulk. Then, by analyzing the information on the directionality of phonon suppression in this system, we identify a new structure of rectangular pores with the same porosity that enables a four-fold decrease in thermal transport with respect to the circular pores. Our results illustrate the utility of the directional phonon suppression function, enabling new avenues for systematic thermal conductivity minimization and potentially accelerating the engineering of next-generation thermoelectric devices.
MIT Department
Massachusetts Institute of Technology. Department of Mechanical Engineering
Terms of Use
Creative Commons Attribution 4.0 International License
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DOI of Published Version
https://doi.org/10.1038/srep44379
