Beryllium oxide
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2008-06-11T21:11:06Z
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{{Chembox new
| ImageFile = Beryllium-oxide-3D-balls.png
| Name = Beryllium oxide
| OtherNames = Beryllia, Thermalox, Super Beryllia, Beryllia Ceramic, bromellite
| Section1 = {{Chembox Identifiers
| CASNo = 1304-56-9
}}
| Section2 = {{Chembox Properties
| Formula = BeO
| MolarMass = 25.01
| Appearance = white solid
| Density = 3.0 g/cm³ (solid)
| SolubilityOther = insoluble
| Solvent = water
| MeltingPt = 2530 °C
| BoilingPt = 3900 °C
}}<!--
{{Chembox/DeltaHf298|−609}}
{{Chembox/S298|13.8}}
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| Section7 = {{Chembox Hazards
| EUClass = Highly toxic ('''T+''')<br />Carc. Cat. 2
| NFPA-H = 4
| NFPA-F = 4 ox
| NFPA-R = 0
| RPhrases = {{R49}}, {{R25}}, {{R26}},<br />{{R36/37/38}}, {{R43}}, {{R48/23}}
| SPhrases = {{S53}}, {{S45}}
| FlashPt = Non-flammable
}}
| Section8 = {{Chembox Related
| OtherAnions = [[Beryllium telluride]]
| OtherCations = [[Magnesium oxide]]<br />[[Calcium oxide]]
}}
}}
'''Beryllium oxide''' ('''BeO''') is a white crystalline oxide. It is notable as it is an electrical insulator with a thermal conductivity higher than any other non-metal, that actually exceeds that of some metals.<ref name = "Greenwood">{{Greenwood&Earnshaw}}</ref> Its high melting point leads to its use as a [[refractory]]<ref>Raymond Aurelius Higgins,
(2006), Materials for Engineers and Technicians, Newnes, ISBN 0750668504</ref>. It occurs in nature as the mineral [[bromellite]]. Historically beryllium oxide was called '''glucina''' or glucinium oxide.
==Preparation and Chemistry==
Beryllium oxide can be prepared by calcining (roasting) beryllium carbonate, dehydrating [[beryllium hydroxide]] or igniting the metal:
:BeCO<sub>3</sub>→ BeO + CO<sub>2</sub>
:Be(OH)<sub>2</sub> → BeO + H<sub>2</sub>O
:2Be + O<sub>2</sub> → 2BeO
Igniting beryllium in air gives a mixture of BeO and the nitride Be<sub>3</sub>N<sub>2</sub>.<ref name = "Greenwood"/><br />
Unlike oxides formed by the other group 2 (alkaline earth metals), beryllium oxide is [[amphoterism|amphoteric]] rather than basic.
Beryllium oxide formed at high temperatures (>800°C) is inert but may be easily dissolved in hot aqueous [[ammonium bifluoride]] (NH<sub>4</sub>HF<sub>2</sub/>) or a hot solution of concentrated [[sulfuric acid]] (H<sub>2</sub>SO<sub>4</sub>) and [[ammonium sulfate]] ((NH<sub>4</sub>)<sub>2</sub>SO<sub>4</sub>).
==Structure==
BeO at normal temperatures has the hexagonal [[zinc sulfide|wurtzite]], form.<ref name = "Greenwood"/> This contrasts with other members of group 2, whose oxides, [[magnesium oxide|MgO]], [[calcium oxide|CaO]], [[strontium oxide|SrO]], [[barium oxide|BaO]] have the cubic rock salt structure.<ref name = "Greenwood"/>. At high temperature the structure transforms to a tetragonal form.<ref> Wells A.F. (1984) ''Structural Inorganic Chemistry'' 5th edition Oxford Science Publications ISBN 0-19-855370-6 </ref>
==Applications==
[[Sintered]] beryllium oxide, which is very stable, has [[ceramic]] characteristics. Beryllium oxide is used for rocket engines, [[catalysts]], [[semiconductors]], [[Neutron moderator|moderators]] of atomic reactors, and neutron reflectors.
Beryllium oxide is used in many high-performance semiconductor parts for applications such as radio equipment because it has good [[thermal conductivity]] while also being a good electrical insulator. It is used as a filler in some thermal interface materials such as [[thermal grease]].<ref name="apmag">{{cite journal | author=Greg Becker, Chris Lee, and Zuchen Lin | title=Thermal conductivity in advanced chips — Emerging generation of thermal greases offers advantages | journal=Advanced Packaging | month=Jul | year=2005 | pages=pp.2–4 | url=http://www.apmag.com/ | accessdate=2008-03-04 }}</ref> Some [[power semiconductor device]]s have used beryllium oxide ceramic between the [[silicon]] chip and the metal mounting base of the package in order to achieve a lower value of [[Thermal resistance in electronics|thermal resistance]] than for a similar construction made with [[aluminium oxide]]. It is also used as a structural [[ceramic]] for high-performance [[vacuum tube]]s, [[magnetron]]s, and [[gas laser]]s.
Currently there are only two companies in the United States that manufacture Beryllium Oxide. they are [[American Beryllia Inc.]] of [[Haskell,_New_Jersey|Haskell]] [[New Jersey]], and Brush Ceramics of [[Tucson]] [[Arizona]].
==Safety==
BeO is [[carcinogen]]ic if the powder is ingested or inhaled and may cause chronic [[Berylliosis|beryllium disease]].
==References==
{{Refimprove|date=March 2008}}
{{reflist}}
==External links==
*[http://www-cie.iarc.fr/htdocs/monographs/vol58/mono58-1.htm IARC Monograph "Beryllium and Beryllium Compounds"]
*[http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc13/icsc1325.htm International Chemical Safety Card 1325]
* [http://www.npi.gov.au/database/substance-info/profiles/13.html National Pollutant Inventory - Beryllium and compounds]
*[http://www.cdc.gov/niosh/npg/npgd0054.html NIOSH Pocket guide to Chemical Hazards]
[[Category:Beryllium compounds]]
[[Category:Oxides]]
[[Category:IARC Group 1 carcinogens]]
[[Category:Ceramic materials]]
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