Beryllium oxide
From Wikipedia, the free encyclopedia
| Beryllium oxide | |
|---|---|
 |
|
| Other names | Beryllia, Thermalox, Super Beryllia, Beryllia Ceramic, bromellite |
| Identifiers | |
| CAS number | [1304-56-9] |
| Properties | |
| Molecular formula | BeO |
| Molar mass | 25.01 |
| Appearance | white solid |
| Density | 3.0 g/cm³ (solid) |
| Melting point |
2530 °C |
| Boiling point |
3900 °C |
| Hazards | |
| MSDS | External MSDS |
| EU classification | Highly toxic (T+) Carc. Cat. 2 |
| NFPA 704 |
 4
0
|
| R-phrases | R49, R25, R26, R36/37/38, R43, R48/23 |
| S-phrases | S53, S45 |
| Flash point | Non-flammable |
| Related compounds | |
| Other anions | Beryllium telluride |
| Other cations | Magnesium oxide Calcium oxide |
| Supplementary data page | |
| Structure and properties |
n, εr, etc. |
| Thermodynamic data |
Phase behaviour Solid, liquid, gas |
| Spectral data | UV, IR, NMR, MS |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references |
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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.[1] Its high melting point leads to its use as a refractory[2]. It occurs in nature as the mineral bromellite. Historically beryllium oxide was called glucina or glucinium oxide.
Contents |
[edit] Preparation and Chemistry
Beryllium oxide can be prepared by calcining (roasting) beryllium carbonate, dehydrating beryllium hydroxide or igniting the metal:
- BeCO3→ BeO + CO2
- Be(OH)2 → BeO + H2O
- 2Be + O2 → 2BeO
Igniting beryllium in air gives a mixture of BeO and the nitride Be3N2.[1]
Unlike oxides formed by the other group 2 (alkaline earth metals), beryllium oxide is amphoteric rather than basic.
Beryllium oxide formed at high temperatures (>800°C) is inert but may be easily dissolved in hot aqueous ammonium bifluoride (NH4HF2) or a hot solution of concentrated sulfuric acid (H2SO4) and ammonium sulfate ((NH4)2SO4).
[edit] Structure
BeO at normal temperatures has the hexagonal wurtzite, form.[1] This contrasts with other members of group 2, whose oxides, MgO, CaO, SrO, BaO have the cubic rock salt structure.[1]. At high temperature the structure transforms to a tetragonal form.[3]
[edit] Applications
Sintered beryllium oxide, which is very stable, has ceramic characteristics. Beryllium oxide is used for rocket engines, catalysts, semiconductors, 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.[4] Some power semiconductor devices 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 than for a similar construction made with aluminium oxide. It is also used as a structural ceramic for high-performance vacuum tubes, magnetrons, and gas lasers.
Currently there are only two companies in the United States that manufacture Beryllium Oxide. they are American Beryllia Inc. of Haskell New Jersey, and Brush Ceramics of Tucson Arizona.
[edit] Safety
BeO is carcinogenic if the powder is ingested or inhaled and may cause chronic beryllium disease.
[edit] References
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This article needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (March 2008) |
- ^ a b c d Greenwood, N. N.; Earnshaw, A. (1997). Chemistry of the Elements, 2nd Edition, Oxford:Butterworth-Heinemann. ISBN 0-7506-3365-4.
- ^ Raymond Aurelius Higgins, (2006), Materials for Engineers and Technicians, Newnes, ISBN 0750668504
- ^ Wells A.F. (1984) Structural Inorganic Chemistry 5th edition Oxford Science Publications ISBN 0-19-855370-6
- ^ Greg Becker, Chris Lee, and Zuchen Lin (Jul 2005). "Thermal conductivity in advanced chips — Emerging generation of thermal greases offers advantages". Advanced Packaging: pp.2–4.
