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. Its high melting point leads to its use as a
refractoryA refractory material is one that retains its strength at high temperatures. ASTM C71 defines refractories as "non-metallic materials having those chemical and physical properties that made them applicable for structures, or as components of systems, that are exposed to environments above...
. It occurs in nature as the mineral
bromelliteBromellite, whose name derives from the Swedish chemist Magnus von Bromell , is a white oxide mineral, found in complex pegmatitic manganese-iron deposits, but is more frequently made synthetically...
. Historically beryllium oxide was called
glucina or glucinium oxide.
Beryllium oxide can be prepared by calcining (roasting) beryllium carbonate, dehydrating
beryllium hydroxideBeryllium hydroxide, Be2 is an amphoteric hydroxide, dissolving in both acids and alkalis. Industrially it is produced as a by-product in the extraction of beryllium metal from the ores, beryl and bertrandite. When alkali is added to beryllium salt solutions the α-form is formed. If...
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 Be
3N
2.
Unlike oxides formed by the other group 2 (alkaline earth metals), beryllium oxide is
amphotericIn chemistry, an amphoteric substance is one that can react as either an acid or base. The word is derived from the Greek prefix ampho- meaning "both"....
rather than basic.
Beryllium oxide formed at high temperatures (>800°C) is inert but may be easily dissolved in hot aqueous ammonium bifluoride (NH
4HF
2) or a hot solution of concentrated
sulfuric acidSulfuric acid, , is a strong mineral acid. It is soluble in water at all concentrations. Sulfuric acid has many applications, and is one of the top products of the chemical industry. World production in 2001 was 165 million tonnes, with an approximate value of US$8 billion...
(H
2SO
4) and
ammonium sulfateAmmonium sulfate , 2SO4, is an inorganic salt with a number of commercial uses. The most common use is as a soil fertilizer. It contains 21% nitrogen as ammonium cations, and 24% sulfur as sulfate anions...
((NH
4)
2SO
4).
BeO at normal temperatures has the hexagonal
wurtziteZinc sulfide is a chemical compound with the formula ZnS. Zinc sulfide is a white- to yellow-colored powder or crystal. It is typically encountered in the more stable cubic form, known also as zinc blende or sphalerite. The hexagonal form is also known both as a synthetic material and as the...
, form.
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. Its high melting point leads to its use as a
refractoryA refractory material is one that retains its strength at high temperatures. ASTM C71 defines refractories as "non-metallic materials having those chemical and physical properties that made them applicable for structures, or as components of systems, that are exposed to environments above...
. It occurs in nature as the mineral
bromelliteBromellite, whose name derives from the Swedish chemist Magnus von Bromell , is a white oxide mineral, found in complex pegmatitic manganese-iron deposits, but is more frequently made synthetically...
. Historically beryllium oxide was called
glucina or glucinium oxide.
Preparation and Chemistry
Beryllium oxide can be prepared by calcining (roasting) beryllium carbonate, dehydrating
beryllium hydroxideBeryllium hydroxide, Be2 is an amphoteric hydroxide, dissolving in both acids and alkalis. Industrially it is produced as a by-product in the extraction of beryllium metal from the ores, beryl and bertrandite. When alkali is added to beryllium salt solutions the α-form is formed. If...
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 Be
3N
2.
Unlike oxides formed by the other group 2 (alkaline earth metals), beryllium oxide is
amphotericIn chemistry, an amphoteric substance is one that can react as either an acid or base. The word is derived from the Greek prefix ampho- meaning "both"....
rather than basic.
Beryllium oxide formed at high temperatures (>800°C) is inert but may be easily dissolved in hot aqueous ammonium bifluoride (NH
4HF
2) or a hot solution of concentrated
sulfuric acidSulfuric acid, , is a strong mineral acid. It is soluble in water at all concentrations. Sulfuric acid has many applications, and is one of the top products of the chemical industry. World production in 2001 was 165 million tonnes, with an approximate value of US$8 billion...
(H
2SO
4) and
ammonium sulfateAmmonium sulfate , 2SO4, is an inorganic salt with a number of commercial uses. The most common use is as a soil fertilizer. It contains 21% nitrogen as ammonium cations, and 24% sulfur as sulfate anions...
((NH
4)
2SO
4).
Structure
BeO at normal temperatures has the hexagonal
wurtziteZinc sulfide is a chemical compound with the formula ZnS. Zinc sulfide is a white- to yellow-colored powder or crystal. It is typically encountered in the more stable cubic form, known also as zinc blende or sphalerite. The hexagonal form is also known both as a synthetic material and as the...
, form. This contrasts with other members of group 2, whose oxides,
MgOMagnesium oxide, or magnesia, is a white solid mineral that occurs naturally as periclase and is a source of magnesium . It has an empirical formula of . It is formed by an ionic bond between one magnesium and one oxygen atom. Magnesium oxide is hygroscopic in nature and care must be taken to...
,
CaOCalcium oxide , commonly known as burnt lime, lime or quicklime, is a widely used chemical compound. It is a white, caustic and alkaline crystalline solid at room temperature. As a commercial product, lime often also contains magnesium oxide, silicon oxide and smaller amounts of aluminium oxide and...
,
SrOStrontium oxide or strontia, SrO, is formed when strontium reacts with oxygen. Burning strontium in air results in a mixture of strontium oxide and strontium nitride. It also forms from the decomposition of strontium carbonate SrCO3...
,
BaOBarium oxide, BaO, is a white hygroscopic compound formed by the burning of barium in oxygen, although it is often formed through the decomposition of other barium salts.It transforms into barium hydroxide on contact with water.-Uses:...
have the cubic rock salt structure.. At high temperature the structure transforms to a tetragonal form.. BeO is a unique metallic compound in that it is a non-ionic oxide.
Applications
Sintered beryllium oxide, which is very stable, has
ceramicA ceramic is an inorganic, non-metallic solid prepared by the action of heat and subsequent cooling. Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous...
characteristics. Beryllium oxide is used for rocket engines, catalysts, semiconductors,
moderatorsIn nuclear engineering, a neutron moderator is a medium which reduces the speed of fast neutrons, thereby turning them into thermal neutrons capable of sustaining a nuclear chain reaction involving uranium-235....
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 conductivityIn physics, thermal conductivity, , is the property of a material that indicates its ability to conduct heat. It appears primarily in Fourier's Law for heat conduction.-Measurement:...
while also being a good electrical insulator. It is used as a filler in some thermal interface materials such as
thermal greaseThermal grease is a fluid substance, originally with properties akin to grease, which increases the thermal conductivity of a thermal interface by compensating for the irregular surfaces of the components...
. Some
power semiconductor devicePower semiconductor devices are semiconductor devices used as switches or rectifiers in power electronic circuits...
s have used beryllium oxide ceramic between the
siliconSilicon is the most common metalloid. It is a chemical element, which has the symbol Si and atomic number 14. A tetravalent metalloid, silicon is less reactive than its chemical analog carbon...
chip and the metal mounting base of the package in order to achieve a lower value of
thermal resistanceThermal resistance is the temperature difference across a structure when a unit of heat energy flows through it in unit time. It is the reciprocal of thermal conductance...
than for a similar construction made with
aluminium oxideAluminium oxide is an amphoteric oxide of aluminium with the chemical formula
23. It is also commonly referred to as alumina, corundum, sapphire, ruby or aloxite in the mining, ceramic and materials science communities. It is produced by the Bayer process from bauxite...
. It is also used as a structural
ceramicA ceramic is an inorganic, non-metallic solid prepared by the action of heat and subsequent cooling. Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous...
for high-performance microwave devices,
vacuum tubeIn electronics, a vacuum tube, electron tube , thermionic valve, or valve is a device used to amplify, switch, otherwise modify, or create an electrical signal by controlling the movement of electrons in a low-pressure space...
s, magnetrons, and
gas laserA gas laser is a laser in which an electric current is discharged through a gas to produce light. The first gas laser, the Helium-neon, was co-invented by Iranian physicist Ali Javan and American physicist William R. Bennett, Jr...
s.
Currently there are only two companies in the United States that manufacture Beryllium Oxide which are American Beryllia Inc. of
HaskellHaskell is an unincorporated area of Wanaque Borough, in Passaic County, New Jersey. The area is served by the United States Postal Service as part of ZIP Code 07420. The community is located in suburban Northern New Jersey....
New JerseyNew Jersey is a state in the Mid-Atlantic region of the United States. It is bordered on the north by New York, and to the east by the Hudson River, Upper New York Bay, the Kill Van Kull, Newark Bay, the Arthur Kill, Raritan Bay, Sandy Hook Bay, Westchester County, New York City, Long Island, and...
, and Brush Ceramics of Tucson
ArizonaThe State of Arizona is a state located in the southwestern region of the United States. The capital and largest city is Phoenix. The second largest city is Tucson, followed in size by the four Phoenix metropolitan area cities of Mesa, Glendale, Chandler, and Scottsdale.Arizona was the 48th and...
.
Safety
BeO powder is
carcinogenA carcinogen is any substance, radionuclide or radiation that is an agent directly involved in the promotion of cancer or in the increase of its propagation. This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes...
ic if the powder is ingested or inhaled and may cause chronic
beryllium diseaseBerylliosis, or chronic beryllium disease , is an occupational lung disease that is most classically associated with exposure to fluorescent lighting and missile silos. It is a chronic allergic-type lung response and chronic lung disease caused by exposure to beryllium and its compounds...
. However, once fired into solid form, it is safe to handle as long as it is not subjected to any machining that creates dust.
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.
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