Graphical 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.
Tsai M-H, Yeh J-W. High-entropy alloys: a critical review. Materials Research Letters 2014;2:107–23. https://doi.org/10.1080/21663831.2014.912690.
Zhang Y, Zuo TT, Tang Z, Gao MC, Dahmen KA, Liaw PK, Lu ZP. Microstructures and properties of high-entropy alloys. Prog Mater Sci 2014;61:1–93. https://doi.org/https://doi.org/10.1016/j.pmatsci.2013.10.001.
Yeh J-W, Lin S-J, Chin T-S, Gan J-Y, Chen S-K, Shun T-T, Tsau C-H, Chou S-Y. Formation of simple crystal structures in Cu-Co-Ni-Cr-Al-Fe-Ti-V alloys with multiprincipal metallic elements. Metall Mater Trans 2004;35:2533–6.
Yeh JW, Chen SK, Lin SJ, Gan JY, Chin TS, Shun TT, Tsau CH, Chang SY. Nanostructured high-entropy alloys with multiple principal elements: novel alloy design concepts and outcomes. Adv Eng Mater 2004;6:299–303. https://doi.org/10.1002/adem.200300567.
Senkov ON, Miracle DB, Chaput KJ, Couzinie J-P. Development and exploration of refractory high entropy alloys–a review. J Mater Res 2018;33:3092–128. https://doi.org/10.1557/jmr.2018.153.
Cantor B, Chang I, Knight P, Vincent A. Microstructural development in equiatomic multicomponent alloys. Mater Sci Eng, A 2004;375:213–8.
Miracle DB, Senkov ON. A critical review of high entropy alloys and related concepts. Acta Mater 2017;122:448–511. https://doi.org/10.1016/j.actamat. 2016.08.081.
Rost CM, Sachet E, Borman T, Moballegh A, Dickey EC, Hou D, Jones JL, Curtarolo S, Maria J-P. Entropy-stabilized oxides. Nat Commun 2015;6. https://doi.org/10.1038/ncomms9485.
Gild J, Zhang Y, Harrington T, Jiang S, Hu T, Quinn MC, Mellor WM, Zhou N, Vecchio K, Luo J. High-entropy metal diborides: a new class of high-entropy materials and a new type of ultrahigh temperature ceramics. Sci Rep 2016;6:37946. https://doi.org/10.1038/srep37946.
Giri A, Braun JL, Hopkins PE. Reduced dependence of thermal conductivity on temperature and pressure of multi-atom component crystalline solid solutions. J Appl Phys 2018;123:015106.
Braun JL, Rost CM, Lim M, Giri A, Olson DH, Kotsonis GN, Stan G, Brenner DW, Maria JP, Hopkins PE. Charge-induced disorder controls the thermal conductivity of entropy-stabilized oxides. Adv Mater 2018;30:1805004.
Giri A, Braun JL, Rost CM, Hopkins PE. On the minimum limit to thermal conductivity of multi-atom component crystalline solid solutions based on impurity mass scattering. Scripta Mater 2017;138:134–8.
Bérardan D, Franger S, Dragoe D, Meena AK, Dragoe N. Colossal dielectric constant in high entropy oxides. Phys Status Solidi Rapid Res Lett 2016;10:328–33. https://doi.org/10.1002/pssr.201600043.
Sarkar A, Velasco L, Wang D, Wang Q, Talasila G, de Biasi L, Kübel C, Brezesinski T, Bhattacharya SS, Hahn H, Breitung B. High entropy oxides for reversible energy storage. Nat Commun 2018;9:3400. https://doi.org/10.1038/s41467-018-05774-5.
Bérardan D, Franger S, Meena A, Dragoe N. Room temperature lithium superionic conductivity in high entropy oxides. J Mater Chem 2016;4:9536–41.
Tallarita G, Licheri R, Garroni S, Orrù R, Cao G. Novel processing route for the fabrication of bulk high-entropy metal diborides. Scripta Mater 2019;158:100–4. https://doi.org/https://doi.org/10.1016/j.scriptamat.2018.08.039.
Mansouri Tehrani A, Brgoch J. Hard and superhard materials: a computational perspective. J Solid State Chem 2019;271:47–58. https://doi.org/https://doi.org/10.1016/j.jssc.2018.10.048.
Mayrhofer PH, Kirnbauer A, Ertelthaler P, Koller CM. High-entropy ceramic thin films; A case study on transition metal diborides. Scripta Mater 2018;149:93–7.
Harrington TJ, Gild J, Sarker P, Toher C, Rost CM, Dippo OF, McElfresh C, Kaufmann K, Marin E, Borowski L, Hopkins PE, Luo J, Curtarolo S, Brenner DW, Vecchio KS. Phase stability and mechanical properties of novel high entropy transition metal carbides. Acta Mater 2019;166:271–80. https://doi.org/https://doi.org/10.1016/j.actamat.2018.12.054.
Zhou J, Zhang J, Zhang F, Niu B, Lei L, Wang W. High-entropy carbide: a novel class of multicomponent ceramics. Ceram Int 2018;44:22014–8. https://doi.org/https://doi.org/10.1016/j.ceramint.2018.08.100.
Yan X, Constantin L, Lu Y, Silvain J-F, Nastasi M, Cui B. Hf0.2Zr0.2Ta0.2Nb0.2Ti0.2)C high-entropy ceramics with low thermal conductivity. J Am Ceram Soc 2018;101:4486–91. https://doi.org/10.1111/jace. 15779.
Sarker P, Harrington T, Toher C, Oses C, Samiee M, Maria J-P, Brenner DW, Vecchio KS, Curtarolo S. High-entropy high-hardness metal carbides discovered by entropy descriptors. Nat Commun 2018;9:4980. https://doi.org/10.1038/s41467-018-07160-7.
Castle E, Csanádi T, Grasso S, Dusza J, Reece M. Processing and properties of high-entropy ultra-high temperature carbides. Sci Rep 2018;8:8609.
Dusza J, Švec P, Girman V, Sedlák R, Castle EG, Csanádi T, Kovalčíková A, Reece MJ. Microstructure of (Hf-Ta-Zr-Nb) C high-entropy carbide at micro and nano/atomic level. J Eur Ceram Soc 2018;38:4303–7.
Demirskyi D, Borodianska H, Suzuki T, Sakka Y, Yoshimi K, Vasylkiv O. High-temperature flexural strength performance of ternary high-entropy carbide consolidated via spark plasma sintering of TaC, ZrC and NbC. Scripta Mater 2019;164:12–6.
Yang Y, Wang W, Gan G-Y, Shi X-F, Tang B-Y. Structural, mechanical and electronic properties of (TaNbHfTiZr) C high entropy carbide under pressure: Ab initio investigation. Phys B Condens Matter 2018;550:163–70.
Ye B, Wen T, Huang K, Wang CZ, Chu Y. First-principles study, fabrication and characterization of (Hf0. 2Zr0. 2Ta0. 2Nb0. 2Ti0. 2) C high-entropy ceramic. J Am Ceram Soc 2019;00:1–9. https://doi.org/10.1111/jace.16295.
Feng L, Fahrenholtz WG, Hilmas GE, Zhou Y. Synthesis of single-phase high-entropy carbide powders. Scripta Mater 2019;162:90–3.
Jiang S, Hu T, Gild J, Zhou N, Nie J, Qin M, Harrington T, Vecchio K, Luo J. A new class of high-entropy perovskite oxides. Scripta Mater 2018;142:116–20.
Sharma Y, Musico BL, Gao X, Hua C, May AF, Herklotz A, Rastogi A, Mandrus D, Yan J, Lee HN. Single-crystal high entropy perovskite oxide epitaxial films. Physical Review Materials 2018;2:060404.
Sarkar A, Djenadic R, Wang D, Hein C, Kautenburger R, Clemens O, Hahn H. Rare earth and transition metal based entropy stabilised perovskite type oxides. J Eur Ceram Soc 2018;38:2318–27. https://doi.org/https://doi.org/10.1016/j.jeurceramsoc.2017.12.058.
Dąbrowa J, Stygar M, Mikuła A, Knapik A, Mroczka K, Tejchman W, Danielewski M, Martin M. Synthesis and microstructure of the (Co, Cr, Fe, Mn, Ni)3O4 high entropy oxide characterized by spinel structure. Mater Lett 2017;216:32–6.
Gild J, Samiee M, Braun JL, Harrington T, Vega H, Hopkins PE, Vecchio K, Luo J. High-entropy fluorite oxides. J Eur Ceram Soc 2018;38:3578–84.
Chen K, Pei X, Tang L, Cheng H, Li Z, Li C, Zhang X, An L. A five-component entropy-stabilized fluorite oxide. J Eur Ceram Soc 2018;38:4161–4.
Djenadic R, Sarkar A, Clemens O, Loho C, Botros M, Chakravadhanula VS, Kübel C, Bhattacharya SS, Gandhi AS, Hahn H. Multicomponent equiatomic rare earth oxides. Materials Research Letters 2017;5:102–9.
Jin T, Sang X, Unocic RR, Kinch RT, Liu X, Hu J, Liu H, Dai S. Mechanochemical-assisted synthesis of high-entropy metal nitride via a soft urea strategy. Adv Mater 2018;30:1707512.
Braic V, Vladescu A, Balaceanu M, Luculescu CR, Braic M. Nanostructured multi-element (TiZrNbHfTa)N and (TiZrNbHfTa)C hard coatings. Surf Coating Technol 2012;211:117–21. https://doi.org/https://doi.org/10.1016/j.surfcoat.2011.09.033.
Petrovic JJ. MoSi 2-based high-temperature structural silicides. MRS Bull 1993;18:35–41.
Petrovic J, Vasudevan A. Overview of high temperature structural silicides. MRS Online Proceedings Library Archive 1993:322.
Petrovic JJ. Mechanical behavior of MoSi2 and MoSi2 composites. Mater Sci Eng, A 1995;192:31–7.
Raj S. A preliminary assessment of the properties of a chromium silicide alloy for aerospace applications. Mater Sci Eng, A 1995;192:583–9.
Samsonov G, Lavrenko V, Glebov L. Oxidation of chromium disilicide in oxygen. Sov Powder Metall Met Ceram 1974;13:36–8.
Song B, Feng P, Wang J, Ge Y, Wu G, Wang X, Akhtar F. Oxidation properties of self-propagating high temperature synthesized niobium disilicide. Corros Sci 2014;85:311–7.
Yao Z, Stiglich J, Sudarshan T. Molybdenum silicide based materials and their properties. J Mater Eng Perform 1999;8:291–304.
Jiang P, Qian X, Yang R. Tutorial: time-domain thermoreflectance (TDTR) for thermal property characterization of bulk and thin film materials. J Appl Phys 2018;124:161103.
Touloukian Y, Makita M. Plenum. 1976. New York.
d'Heurle F, Petersson C, Tsai M. Observations on the hexagonal form of MoSi2 and WSi2 films produced by ion implantation and on related snowplow effects. J Appl Phys 1980;51:5976–80.
Jeitschko W. Refinement of the crystal structure of TiSi2 and some comments on bonding in TiSi2 and related compounds. Acta Crystallogr B Struct Crystallogr Cryst Chem 1977;33:2347–8.
Murarka S, Read M, Chang C. Hexagonal WSi2 in cosputtered (tungsten and silicon) mixture. J Appl Phys 1981;52:7450–2.
Sonber J, Murthy TC, Subramanian C, Kumar S, Fotedar R, Suri A. Investigations on synthesis of ZrB2 and development of new composites with HfB2 and TiSi2. Int J Refract Metals Hard Mater 2011;29:21–30.
Raju GB, Basu B. Densification, sintering reactions, and properties of titanium diboride with titanium disilicide as a sintering aid. J Am Ceram Soc 2007;90:3415–23.
Nakamura M, Matsumoto S, Hirano T. Elastic constants of MoSi2 and WSi2 single crystals. J Mater Sci 1990;25:3309–13.
Newman A, Jewett T, Sampath S, Berndt C, Herman H. Indentation response of molybdenum disilicide. J Mater Res 1998;13:2662–71.
Haji-Mahmood M, Chumbley L. Processing and characterization of nanocrystalline molybdenum disilicide consolidated by hot isostatic pressing (HIP). Nanostruct Mater 1996;7:95–112.
Schwarz R, Srinivasan S, Petrovic JJ, Maggiore C. Synthesis of molybdenum disilicide by mechanical alloying. Mater Sci Eng, A 1992;155:75–83.
Wade RK, Petrovic JJ. Processing temperature effects on molybdenum disilicide. J Am Ceram Soc 1992;75:3160–2.
Vasudevan A, Petrovic J. A comparative overview of molybdenum disilicide composites. Mater Sci Eng, A 1992;155:1–17.
Neshpor V. The thermal conductivity of the silicides of transition metals. J Eng Phys Thermophys 1968;15:750–2.
Cahill DG. Analysis of heat flow in layered structures for time-domain thermoreflectance. Rev Sci Instrum 2004;75:5119–22.
Yazdani Z, Karimzadeh F, Abbasi M-H. Characterization of nanostructured NbSi2 intermetallic coatings obtained by plasma spraying of mechanically alloyed powders. J Therm Spray Technol 2015;24:947–52.
Vorotilo S, Potanin AY, Iatsyuk IV, Levashov EA. SHS of silicon-based ceramics for the high-temperature applications. Adv Eng Mater 2018;20:1800200.
Shon I-J, Ko I-Y, Chae S-M. Na K-i. Rapid consolidation of nanostructured TaSi2 from mechanochemically synthesized powder by high frequency induction heated sintering. Ceram Int 2011;37:679–82.
Frommeyer G, Rosenkranz R. In metallic Materials with high structural efficiency 287-308. Springer; 2004.
Shon I, Rho D, Kim H, Munir Z. Dense WSi2 and WSi2–20 vol.% ZrO2 composite synthesized by pressure-assisted field-activated combustion. J Alloy Comp 2001;322:120–6.
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