A high-entropy silicide: (Mo0.2Nb0.2Ta0.2Ti0.2W0.2)Si2

Joshua Gild; Jeffrey Braun; Kevin Kaufmann; Eduardo Marin; Tyler Harrington; Patrick Hopkins; Kenneth Vecchio; Jian Luo

Journal of Materiomics (Sep 2019)

A high-entropy silicide: (Mo0.2Nb0.2Ta0.2Ti0.2W0.2)Si2

Joshua Gild,
Jeffrey Braun,
Kevin Kaufmann,
Eduardo Marin,
Tyler Harrington,
Patrick Hopkins,
Kenneth Vecchio,
Jian Luo

Affiliations

Joshua Gild: Program of Materials Science and Engineering, University of California, San Diego, La Jolla, CA, 92093-0418, USA
Jeffrey Braun: Department of Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, VA, 22904, USA
Kevin Kaufmann: Department of NanoEngineering, University of California, San Diego, La Jolla, CA, 92093-0448, USA
Eduardo Marin: Department of NanoEngineering, University of California, San Diego, La Jolla, CA, 92093-0448, USA
Tyler Harrington: Program of Materials Science and Engineering, University of California, San Diego, La Jolla, CA, 92093-0418, USA
Patrick Hopkins: Department of Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, VA, 22904, USA
Kenneth Vecchio: Program of Materials Science and Engineering, University of California, San Diego, La Jolla, CA, 92093-0418, USA; Department of NanoEngineering, University of California, San Diego, La Jolla, CA, 92093-0448, USA
Jian Luo: Program of Materials Science and Engineering, University of California, San Diego, La Jolla, CA, 92093-0418, USA; Department of NanoEngineering, University of California, San Diego, La Jolla, CA, 92093-0448, USA; Corresponding author. University of California, San Diego, La Jolla, CA, 92093-0418, USA.

Journal volume & issue: Vol. 5, no. 3
pp. 337 – 343

Abstract

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A high-entropy metal disilicide, (Mo0.2Nb0.2Ta0.2Ti0.2W0.2)Si2, 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)Si2 possesses a hexagonal C40 crystal structure with ABC stacking sequence and a space group of P6222. 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)Si2 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 ∼1/3 of those reported values for the hexagonal NbSi2 and TaSi2 with the same crystal structure. Keywords: High-entropy ceramics, High-entropy silicide, Thermal conductivity, Hardness, C40 crystal structure

Published in Journal of Materiomics

ISSN: 2352-8478 (Print); 2352-8486 (Online)
Publisher: Elsevier
Country of publisher: Netherlands
LCC subjects: Technology: Electrical engineering. Electronics. Nuclear engineering: Materials of engineering and construction. Mechanics of materials
Website: https://www.sciencedirect.com/journal/journal-of-materiomics

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