Planar defects-induced low thermal conductivity in a superhard material SiB6

Generally materials with low thermal conductivity require weaker interatomic bonding, considered as soft materials. Here we demonstrate that SiB6 with planar structural defects shows low thermal conductivity, but uncommonly high strength. Planar defects-induced polycrystalline SiB6 (PD-SiB6) has a relatively large Vickers hardness, which is comparable to those of well-known superhard materials, despite of relatively low thermal conductivity (< 10 W m-1 K-1at 300 K). Transmission electron microscopy observations con-firmed the presence of numerous planar defects, which were thought to contribute to the improvement of hardness. Thanks to the special characteristics of a trade-off relationship between low thermal conductivity and high strength, we believe that PD-SiB6 can be used in new strategies of controlling thermal and me-chanical properties in various functional materials.(c) 2023 Elsevier B.V. All rights reserved.