Beryllium oxide

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Beryllium oxide
General
Other names	Beryllia
Molecular formula	BeO
Molar mass	25.01 g/mol
Appearance	white solid
CAS number	1304-56-9
Properties
Density and phase	3.0 g/cm³, solid
Solubility in water	insoluble
Melting point	2530 °C
Boiling point	3900 °C
Structure
Coordination geometry	?
Crystal structure	?
Thermodynamic data
Std enthalpy of formation Δ_fH^o₂₉₈	−609 kJ/mol
Standard molar entropy S^o₂₉₈	13.8 J·K⁻¹·mol⁻¹
Hazards
MSDS	External MSDS
EU classification	Highly toxic (T+) Carc. Cat. 2
R-phrases	R49, R25, R26, R36/37/38, R43, R48/23
S-phrases	S53, S45
Flash point	non-flammable
Supplementary data page
Structure and properties	n, ε_r, etc.
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
Related compounds
Other anions	Beryllium telluride
Other cations	Magnesium oxide Calcium oxide
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Beryllium oxide (BeO) is a white crystalline oxide. It is obtained from beryllium or beryllium compounds by ignition in the air. The sintered beryllium oxide (beryllia), which is very stable, has ceramic characteristics. It is similar to aluminium oxide (Al₂O₃), is highly fire resistant (melting point: 2570°C), and has polymorphism. Beryllium oxide was previously called glucina.

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] Applications

This complex 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. Some power semiconductor devices have used beryllium oxide ceramic to insulate the silicon chip from the metal mounting base of the package in order to achieve a lower value 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.