Journal
JOURNAL OF MATERIOMICS
Volume 5, Issue 3, Pages 337-343Publisher
ELSEVIER
DOI: 10.1016/j.jmat.2019.03.002
Keywords
High-entropy ceramics; High-entropy silicide; Thermal conductivity; Hardness; C40 crystal structure
Funding
- Office of Naval Research MURI program [N00014-15-1-2863]
- National Science Foundation [CBET-1706388]
- Deparment of Defense (DoD) through the National Defense Science and Engineering Graduate Fellowship (NDSEG) program
- ARCS foundation
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A high-entropy metal disilicide, (Mo0.2Nb0.2Ta0.2Ti0.2W0.2)Si-2, has been successfully synthesized. X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), and electron backscatter diffraction (EBSD) collectively show the formation of a single high-entropy silicide phase. This high-entropy (Mo0.2Nb0.2Ta0.2Ti0.2W0.2)Si-2 possesses a hexagonal C40 crystal structure with ABC stacking sequence and a space group of P6(2)22. This discovery expands the known families of high-entropy materials from metals, oxides, borides, carbides, and nitrides to a silicide, for the first time to our knowledge, as well as demonstrating that a new, non-cubic, crystal structure (with lower symmetry) can be made into high-entropy phase. This(Mo0.2Nb0.2Ta0.2Ti0.2W0.2)Si-2 exhibits high nanohardness of 16.7 +/- 1.9 GPa and Vickers hardness of 11.6 +/- 0.5 GPa. Moreover, it has a low thermal conductivity of 6.9 +/- 1.1 W m(-1) K-1, which is approximately one order of magnitude lower than that of the widely-used tetragonal MoSi2 and similar to 1/3 of those reported values for the hexagonal NbSi2 and TaSi2 with the same crystal structure. (C) 2019 The Chinese Ceramic Society. Production and hosting by Elsevier B.V.
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