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Beryllium oxide
Wurtzite polyhedra.png
Other names Beryllia, Thermalox, Berlox, Super beryllia, Beryllia ceramic, Bromellite
Identifiers
CAS number 1304-56-9 Yes check.svgY
PubChem 14775
EC number 215-133-1
RTECS number DS4025000
Properties
Molecular formula BeO
Molar mass 25.0116 g/mol
Appearance white solid
Density 3.02 g/cm3 [1]
Melting point

2507 °C
Boiling point

3900 °C
Solubility in water soluble (powder)
Solubility in KOH, NH4CO3 soluble
Band gap 10.6 eV
Thermal conductivity 4 W/(cm·K)
Refractive index (nD) 1.7
Structure
Crystal structure hexagonal, hP4
Space group P63/mc, No. 186
Hazards
MSDS External MSDS
EU Index 004-003-00-8
EU classification Carc. Cat. 2
Highly toxic (T+)
Irritant (Xi)
R-phrases R49, R25, R26, R36/37/38, R43, R48/23
S-phrases S53, S45
NFPA 704
NFPA 704.svg
0
4
0
 
Flash point Non-flammable
LD50 2062 mg/kg (mouse, oral)
Related compounds
Other anions Beryllium sulfide
Beryllium selenide
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
 Yes check.svgY (what is this?)  (verify)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

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 except diamond, and actually exceeds that of some metals.[2] Its high melting point leads to its use as a refractory[3]. It occurs in nature as the mineral bromellite. Historically beryllium oxide was called glucina or glucinium oxide.

Contents

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
2 Be + O2 → 2 BeO

Igniting beryllium in air gives a mixture of BeO and the nitride Be3N2.[2] 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).

Structure

BeO at normal temperatures has the hexagonal wurtzite, form.[2] This contrasts with other members of group 2, whose oxides, MgO, CaO, SrO, BaO have the cubic rock salt structure.[2]. At high temperature the structure transforms to a tetragonal form.[4]. BeO is a unique metallic compound in that it is a non-ionic oxide.

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.[5] 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 microwave devices, vacuum tubes, magnetrons, and gas lasers.

Currently there are only two companies in the United States that manufacture beryllium oxide which are American Beryllia Inc. of Haskell New Jersey, and Brush Ceramics of Tucson Arizona.

Safety

BeO powder is carcinogenic if the powder is ingested or inhaled and may cause chronic beryllium disease. However, once fired into solid form, it is safe to handle as long as it is not subjected to any machining that creates dust.[6]

Beryllium oxide ceramic is not a hazardous waste under Federal law and its use is not banned, restricted or otherwise limited by any country worldwide.

References

  1. ^ Patnaik, Pradyot (2003). Handbook of Inorganic Chemical Compounds. McGraw-Hill. pp. 104. ISBN 0070494398. http://books.google.com/books?id=Xqj-TTzkvTEC&pg=PA104. Retrieved 2009-06-06.  
  2. ^ a b c d Greenwood, Norman N.; Earnshaw, A. (1997), Chemistry of the Elements (2nd ed.), Oxford: Butterworth-Heinemann, ISBN 0-7506-3365-4  
  3. ^ Raymond Aurelius Higgins (2006). Materials for Engineers and Technicians. Newnes. p. 301. ISBN 0750668504. http://books.google.com/books?id=6TKSG6LWIEQC&pg=PA301.  
  4. ^ A.F. Wells (1984). Structural Inorganic Chemistry (5 ed.). Oxford Science Publications. ISBN 0-19-855370-6.  
  5. ^ Greg Becker, Chris Lee, and Zuchen Lin (2005). "Thermal conductivity in advanced chips — Emerging generation of thermal greases offers advantages". Advanced Packaging: 2–4. http://www.apmag.com/. Retrieved 2008-03-04.  
  6. ^ Beryllium Oxide Safety

External links








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