View source for Molybdenum disilicide

{{chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 428632177
| ImageFile = MoSi2structure.png
| ImageSize = 
| IUPACName = Molybdenum disilicide
| OtherNames = Molybdenum(VIII) silicide
|Section1={{Chembox Identifiers
| CASNo = 12136-78-6
| CASNo_Ref = {{cascite|correct|CAS}}
| PubChem = 6336985
  }}
|Section2={{Chembox Properties
| Formula = MoSi<sub>2</sub>
| MolarMass = 152.11 g/mol
| Appearance = gray metallic solid
| Density = 6.26 g/cm<sup>3</sup><ref name=j1/><ref name=b1/>
| MeltingPtC = 2030
| MeltingPt_ref = <ref name=b1>{{cite book|author1=Soo-Jin Park|author2=Min-Kang Seo|title=Interface Science and Composites|url=https://books.google.com/books?id=DewhZ53WgLwC&pg=PA563|date=2011|publisher=Academic Press|isbn=978-0-12-375049-5|pages=563–}}</ref>
| BoilingPt = 
| Solubility = 
 }}
|Section3={{Chembox Structure
| CrystalStruct = [[Tetragonal]]<ref name=j1>{{cite journal|doi=10.1016/0022-0248(93)90456-7 |title=Crystal growth and characterization of the transition metal silicides MoSi<sub>2</sub> and WSi<sub>2</sub>|journal=Journal of Crystal Growth|volume=129|issue =1–2|year= 1993|pages= 266–268|author=A. Nørlund Christensen |bibcode=1993JCrGr.129..266N}}</ref>
| SpaceGroup = I4/mmm (No. 139), [[Pearson symbol|tI6]]
| LattConst_a = 0.32112 nm
| LattConst_c = 0.7845 nm
| UnitCellFormulas = 2
}}
|Section7={{Chembox Hazards
| ExternalSDS = 
| MainHazards = 
| FlashPt = Non-flammable
  }}
  | Section8 = {{Chembox Related
| OtherCations = [[Chromium disilicide]]<br>[[Tungsten disilicide]]
}}
}}

'''Molybdenum disilicide''' ('''MoSi<sub>2</sub>''', or '''molybdenum silicide'''), an [[intermetallic compound]], a [[silicide]] of [[molybdenum]], is a [[refractory material|refractory]] [[ceramic]] with primary use in [[heating element]]s. It has moderate [[density]], melting point 2030&nbsp;°C, and is [[electrically conductive]]. At high temperatures it forms a [[Passivation (chemistry)|passivation layer]] of [[silicon dioxide]], protecting it from further oxidation. The thermal stability of MoSi<sub>2</sub> alongside its high [[emissivity]] make this material, alongside [[tungsten disilicide|WSi<sub>2</sub>]] attractive for applications as a high emissivity coatings in [[heat shield]]s for [[atmospheric entry]].<ref>[https://arxiv.org/ftp/arxiv/papers/1902/1902.03943.pdf High emissivity coatings on fibrous ceramics for reusable space systems] Corrosion Science 2019 </ref> 
MoSi<sub>2</sub> is a gray metallic-looking material with [[tetragonal]] [[crystal structure]] (alpha-modification); its beta-modification is [[hexagonal (crystal system)|hexagonal]] and unstable.<ref>{{cite journal|journal=J. Appl. Phys. |volume=51|issue=11|pages= 5976–5980 |year=1980|doi=10.1063/1.327517 |title=Observations on the hexagonal form of MoSi<sub>2</sub> and WSi<sub>2</sub> films produced by ion implantation and on related snowplow effects|author=F. M. d’Heurle, C. S. Petersson, and M. Y. Tsai |bibcode=1980JAP....51.5976D}}</ref> It is insoluble in most acids but soluble in [[nitric acid]] and [[hydrofluoric acid]].

While MoSi<sub>2</sub> has excellent resistance to oxidation and high [[Young's modulus]] at temperatures above 1000&nbsp;°C, it is [[brittle]] in lower temperatures. Also, at above 1200&nbsp;°C it loses [[creep (deformation)|creep]] resistance. These properties limits its use as a [[structural material]], but may be offset by using it together with another material as a [[composite material]].

Molybdenum disilicide and MoSi<sub>2</sub>-based materials are usually made by [[sintering]]. [[Plasma spraying]] can be used for producing its dense monolithic and composite forms; material produced this way may contain a proportion of β-MoSi<sub>2</sub> due to its rapid cooling.

Molybdenum disilicide heating elements can be used for temperatures up to 1800&nbsp;°C, in electric [[Industrial furnace|furnace]]s used in laboratory and production environment in production of [[glass]], [[steel]], [[electronics]], [[ceramic]]s, and in [[heat treatment]] of materials. While the elements are brittle, they can operate at high power without aging, and their electrical resistivity does not increase with operation time. Their maximum [[operating temperature]] has to be lowered in atmospheres with low oxygen content due to breakdown of the passivation layer.<ref name="Park Seo 2011 p. 563">{{cite book |last1=Park |first1=S.J. |url=https://books.google.com/books?id=DewhZ53WgLwC&pg=PA563 |title=Interface Science and Composites |last2=Seo |first2=M.K. |publisher=Elsevier Science |year=2011 |isbn=978-0-12-375049-5 |series=Interface Science and Technology |page=563 |access-date=2023-09-09}}</ref>

Other ceramic materials used for heating elements include [[silicon carbide]], [[barium titanate]], and [[lead titanate]] [[composite material]]s.

Molybdenum disilicide is used in [[microelectronics]] as a contact material. It is often used as a [[shunt (electrical)|shunt]] over [[polysilicon]] lines to increase their conductivity and increase signal speed.

==References==
{{reflist}}

{{Molybdenum compounds}}
{{Silicides}}

[[Category:Ceramic materials]]
[[Category:Group 6 silicides]]
[[Category:Molybdenum(II) compounds]]
[[Category:Refractory materials]]
[[Category:Semiconductor materials]]