Kang, Jin Gu Jang, Hyejin Ma, Jun Yang, Qun Hattar, Khalid Diao, Zhu Yuan, Renliang Zuo, Jianmin Sinha, Sanjiv Cahill, David G. Braun, Paul, V 2024-01-19T15:01:57Z 2024-01-19T15:01:57Z 2022-01-10 2021-04-01 1932-7447 https://pubs.kist.re.kr/handle/201004/117151 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. English American Chemical Society Ultralow Thermal Conductivity in Nanoporous Crystalline Fe3O4 Article 10.1021/acs.jpcc.1c00411 1 The Journal of Physical Chemistry C, v.125, no.12, pp.6897 - 6908 The Journal of Physical Chemistry C 125 12 6897 6908 scie scopus 000636924700041 2-s2.0-85104973802 Chemistry, Physical Nanoscience & Nanotechnology Materials Science, Multidisciplinary Chemistry Science & Technology - Other Topics Materials Science Article