@article{69ae0ad19866409c9a4c760c99bdbd96,
title = "Ultralow Thermal Conductivity in Nanoporous Crystalline Fe3O4",
abstract = "While there is no known fundamental lower limit to the thermal conductivity of a material, the lowest thermal conductivities are typically found in amorphous and strongly disordered materials, not highly crystalline materials. Here, we demonstrate a surprising nanostructuring route to ultralow thermal conductivity in a large-unit-cell oxide crystal (Fe3O4) containing close-packed nanoscale pores. The electrical conductivity of this material reduces by a factor of 5 relative to dense Fe3O4, independent of pore size. In contrast, thermal conductivity has a strong dependence on pore size with a factor of 40 of suppression relative to dense Fe3O4 for 40 nm pores vs a factor of 5 for 500 nm pores. The matrix thermal conductivity of Fe3O4 containing 40 nm pores falls below the predicted minimum thermal conductivity by a factor of 3. We attribute this to strong acoustic phonon scattering and intrinsically limited contributions to thermal conductivity from optical phonons with small dispersion.",
author = "Kang, {Jin Gu} and Hyejin Jang and Jun Ma and Qun Yang and Khalid Hattar and Zhu Diao and Renliang Yuan and Jianmin Zuo and Sanjiv Sinha and Cahill, {David G.} and Braun, {Paul V.}",
note = "Funding Information: This work was supported by the National Science Foundation Engineering Research Center for Power Optimization of Electro Thermal Systems (POETS) with cooperative Agreement No. EEC-1449548. Characterization and measurements were carried out in the Materials Research Laboratory and the Beckman Institute at the University of Illinois at Urbana–Champaign. This work was performed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. DOE{\textquoteright}s National Nuclear Security Administration under contract DE-NA-0003525. The views expressed in the article do not necessarily represent the views of the U.S. DOE or the United States Government. We thank C. Spence, A. Kulkarni, A. Patra, and C. Ocier for experimental assistance and helpful discussions. J.G.K. acknowledges the Kwanjeong Educational Foundation for fellowship support and the Institutional Program (2E31171) of Korea Institute of Science and Technology (KIST). Publisher Copyright: {\textcopyright} 2021 American Chemical Society.",
year = "2021",
month = apr,
day = "1",
doi = "10.1021/acs.jpcc.1c00411",
language = "English (US)",
volume = "125",
pages = "6897--6908",
journal = "Journal of Physical Chemistry C",
issn = "1932-7447",
publisher = "American Chemical Society",
number = "12",
}