Beryllium oxide

Last updated
Beryllium oxide
Wurtzite polyhedra.png
BeO sample.jpg
Names
Preferred IUPAC name
Beryllium(II) monoxide
Systematic IUPAC name
Oxoberyllium
Other names
Beryllia, Thermalox, Bromellite, Thermalox 995. [1]
Identifiers
3D model (JSmol)
3902801
ChEBI
ChemSpider
ECHA InfoCard 100.013.758 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 215-133-1
MeSH beryllium+oxide
PubChem CID
RTECS number
  • DS4025000
UNII
UN number 1566
  • InChI=1S/Be.O Yes check.svgY
    Key: LTPBRCUWZOMYOC-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/Be.O/rBeO/c1-2
    Key: LTPBRCUWZOMYOC-SRAGPBHZAE
  • [Be]=[O]
  • [Be-]#[O+]
Properties
BeO
Molar mass 25.011 g·mol−1
AppearanceColourless, vitreous crystals
Odor Odourless
Density 3.01 g/cm3 [2]
Melting point 2,578 °C (4,672 °F; 2,851 K) [2]
Band gap 10.6 eV [3]
−11.9·10−6 cm3/mol [4]
Thermal conductivity 210 W/(m·K) [5]
n11.7184, n2=1.733 [6] [7]
Structure [8]
Hexagonal, zincite
P63mc
C6v
a = 2.6979 Å, c = 4.3772 Å
2
Linear
Thermochemistry [9]
25.6 J/(K·mol)
Std molar
entropy
(S298)
13.77±0.04 J/(K·mol)
−609.4±2.5 kJ/mol
−580.1 kJ/mol
Enthalpy of fusion fHfus)
86 kJ/mol
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
Very toxic, Group 1B carcinogen
GHS labelling:
GHS-pictogram-skull.svg GHS-pictogram-silhouette.svg GHS-pictogram-pollu.svg
Danger
H301, H315, H317, H319, H330, H335, H350, H372
P201, P260, P280, P284, P301+P310, P305+P351+P338
NFPA 704 (fire diamond)
NFPA 704.svgHealth 4: Very short exposure could cause death or major residual injury. E.g. VX gasFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
4
0
0
Lethal dose or concentration (LD, LC):
15 mg/kg (mouse, oral) [10]
NIOSH (US health exposure limits):
PEL (Permissible)
TWA 0.002 mg/m3
C 0.005 mg/m3 (30 minutes), with a maximum peak of 0.025 mg/m3 (as Be) [11]
REL (Recommended)
Ca C 0.0005 mg/m3 (as Be) [11]
IDLH (Immediate danger)
Ca [4 mg/m3 (as Be)] [11]
Related compounds
Other anions
Beryllium telluride
Other cations
Supplementary data page
Beryllium oxide (data page)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

Beryllium oxide (BeO), also known as beryllia, is an inorganic compound with the formula BeO. This colourless solid is a electrical insulator with a higher thermal conductivity than any other non-metal except diamond, and exceeds that of most metals. [12] As an amorphous solid, beryllium oxide is white. Its high melting point leads to its use as a refractory material. [13] It occurs in nature as the mineral bromellite. Historically and in materials science, beryllium oxide was called glucina or glucinium oxide, owing to its sweet taste.

Contents

Preparation and chemical properties

Beryllium oxide can be prepared by calcining (roasting) beryllium carbonate, dehydrating beryllium hydroxide, or igniting metallic beryllium:

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. [12] Unlike the oxides formed by the other Group 2 elements (alkaline earth metals), beryllium oxide is amphoteric rather than basic.

Beryllium oxide formed at high temperatures (>800 °C) is inert, but dissolves easily in hot aqueous ammonium bifluoride (NH4HF2) or a solution of hot concentrated sulfuric acid (H2SO4) and ammonium sulfate ((NH4)2SO4).

Structure

BeO crystallizes in the hexagonal wurtzite structure, featuring tetrahedral Be2+ and O2− centres, like lonsdaleite and w-BN (with both of which it is isoelectronic). In contrast, the oxides of the larger group-2 metals, i.e., MgO, CaO, SrO, BaO, crystallize in the cubic rock salt motif with octahedral geometry about the dications and dianions. [12] At high temperature the structure transforms to a tetragonal form. [14]

In the vapour phase, beryllium oxide is present as discrete diatomic molecules. In the language of valence bond theory, these molecules can be described as adopting sp orbital hybridisation on both atoms, featuring one σ bond (between one sp orbital on each atom) and one π bond (between aligned p orbitals on each atom oriented perpendicular to the molecular axis). Molecular orbital theory provides a slightly different picture with no net σ bonding (because the 2s orbitals of the two atoms combine to form a filled sigma bonding orbital and a filled sigma* anti-bonding orbital) and two π bonds formed between both pairs of p orbitals oriented perpendicular to the molecular axis. The sigma orbital formed by the p orbitals aligned along the molecular axis is unfilled. The corresponding ground state is ...(2sσ)2(2sσ*)2(2pπ)4 (as in the isoelectronic C2 molecule), where both bonds can be considered as dative bonds from oxygen towards beryllium. [15]

Applications

High-quality crystals may be grown hydrothermally, or otherwise by the Verneuil method. For the most part, beryllium oxide is produced as a white amorphous powder, sintered into larger shapes. Impurities, like carbon, can give rise to a variety of colours to the otherwise colourless host crystals.

Sintered beryllium oxide is a very stable ceramic. [16] Beryllium oxide is used in rocket engines[ citation needed ] and as a transparent protective over-coating on aluminised telescope mirrors.

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. [17] Some power semiconductor devices have used beryllium oxide ceramic between the silicon chip and the metal mounting base of the package to achieve a lower value of thermal resistance than a similar construction of aluminium oxide. It is also used as a structural ceramic for high-performance microwave devices, vacuum tubes, cavity magnetrons, and gas lasers. BeO has been proposed as a neutron moderator for naval marine high-temperature gas-cooled reactors (MGCR), as well as NASA's Kilopower nuclear reactor for space applications. [18]

Safety

BeO is carcinogenic in powdered form [19] and may cause a chronic allergic-type lung disease berylliosis. Once fired into solid form, it is safe to handle if not subjected to machining that generates dust. Clean breakage releases little dust, but crushing or grinding actions can pose a risk. [20]

Related Research Articles

<span class="mw-page-title-main">Beryllium</span> Chemical element with atomic number 4 (Be)

Beryllium is a chemical element; it has symbol Be and atomic number 4. It is a steel-gray, strong, lightweight and brittle alkaline earth metal. It is a divalent element that occurs naturally only in combination with other elements to form minerals. Gemstones high in beryllium include beryl and chrysoberyl. It is a relatively rare element in the universe, usually occurring as a product of the spallation of larger atomic nuclei that have collided with cosmic rays. Within the cores of stars, beryllium is depleted as it is fused into heavier elements. Beryllium constitutes about 0.0004 percent by mass of Earth's crust. The world's annual beryllium production of 220 tons is usually manufactured by extraction from the mineral beryl, a difficult process because beryllium bonds strongly to oxygen.

<span class="mw-page-title-main">Carbon monoxide</span> Colourless, odourless, tasteless and toxic gas

Carbon monoxide is a poisonous, flammable gas that is colorless, odorless, tasteless, and slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simplest carbon oxide. In coordination complexes, the carbon monoxide ligand is called carbonyl. It is a key ingredient in many processes in industrial chemistry.

<span class="mw-page-title-main">Metallic bonding</span> Type of chemical bond in metals

Metallic bonding is a type of chemical bonding that arises from the electrostatic attractive force between conduction electrons and positively charged metal ions. It may be described as the sharing of free electrons among a structure of positively charged ions (cations). Metallic bonding accounts for many physical properties of metals, such as strength, ductility, thermal and electrical resistivity and conductivity, opacity, and lustre.

<span class="mw-page-title-main">Nitrogen</span> Chemical element with atomic number 7 (N)

Nitrogen is a chemical element; it has symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at seventh in total abundance in the Milky Way and the Solar System. At standard temperature and pressure, two atoms of the element bond to form N2, a colorless and odorless diatomic gas. N2 forms about 78% of Earth's atmosphere, making it the most abundant chemical species in air. Because of the volatility of nitrogen compounds, nitrogen is relatively rare in the solid parts of the Earth.

A period 2 element is one of the chemical elements in the second row of the periodic table of the chemical elements. The periodic table is laid out in rows to illustrate recurring (periodic) trends in the chemical behavior of the elements as their atomic number increases; a new row is started when chemical behavior begins to repeat, creating columns of elements with similar properties.

<span class="mw-page-title-main">Conjugated system</span> System of connected p-orbitals with delocalized electrons in a molecule

In theoretical chemistry, a conjugated system is a system of connected p-orbitals with delocalized electrons in a molecule, which in general lowers the overall energy of the molecule and increases stability. It is conventionally represented as having alternating single and multiple bonds. Lone pairs, radicals or carbenium ions may be part of the system, which may be cyclic, acyclic, linear or mixed. The term "conjugated" was coined in 1899 by the German chemist Johannes Thiele.

<span class="mw-page-title-main">Pi bond</span> Type of chemical bond

In chemistry, pi bonds are covalent chemical bonds, in each of which two lobes of an orbital on one atom overlap with two lobes of an orbital on another atom, and in which this overlap occurs laterally. Each of these atomic orbitals has an electron density of zero at a shared nodal plane that passes through the two bonded nuclei. This plane also is a nodal plane for the molecular orbital of the pi bond. Pi bonds can form in double and triple bonds but do not form in single bonds in most cases.

<span class="mw-page-title-main">Catenation</span> Bonding of atoms of the same element into chains or rings

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<span class="mw-page-title-main">Aluminium nitride</span> Chemical compound

Aluminium nitride (AlN) is a solid nitride of aluminium. It has a high thermal conductivity of up to 321 W/(m·K) and is an electrical insulator. Its wurtzite phase (w-AlN) has a band gap of ~6 eV at room temperature and has a potential application in optoelectronics operating at deep ultraviolet frequencies.

In chemistry, orbital hybridisation is the concept of mixing atomic orbitals to form new hybrid orbitals suitable for the pairing of electrons to form chemical bonds in valence bond theory. For example, in a carbon atom which forms four single bonds, the valence-shell s orbital combines with three valence-shell p orbitals to form four equivalent sp3 mixtures in a tetrahedral arrangement around the carbon to bond to four different atoms. Hybrid orbitals are useful in the explanation of molecular geometry and atomic bonding properties and are symmetrically disposed in space. Usually hybrid orbitals are formed by mixing atomic orbitals of comparable energies.

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<span class="mw-page-title-main">Zirconium carbide</span> Chemical compound

Zirconium carbide (ZrC) is an extremely hard refractory ceramic material, commercially used in tool bits for cutting tools. It is usually processed by sintering.

<span class="mw-page-title-main">Uranium nitrides</span> Chemical compound

Uranium nitrides is any of a family of several ceramic materials: uranium mononitride (UN), uranium sesquinitride (U2N3) and uranium dinitride (UN2). The word nitride refers to the −3 oxidation state of the nitrogen bound to the uranium.

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<span class="mw-page-title-main">Niobium monoxide</span> Chemical compound

Niobium monoxide is the inorganic compound with the formula NbO. It is a grey solid with metallic conductivity.

<span class="mw-page-title-main">Solid</span> State of matter

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References

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  2. 1 2 Haynes, p. 4.51
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  4. Haynes, p. 4.126
  5. Haynes, p. 12.222
  6. Haynes, p. 10.248
  7. Bromellite Mineral Data. webmineral
  8. Haynes, p. 4.139
  9. Haynes, pp. 5.1, 5.6, 6.155
  10. Beryllium oxide toxicity
  11. 1 2 3 NIOSH Pocket Guide to Chemical Hazards. "#0054". National Institute for Occupational Safety and Health (NIOSH).
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  19. "Hazardous Substance Fact Sheet" (PDF). New Jersey Department of Health and Senior Services. Retrieved August 17, 2018.
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Cited sources