Beryllium oxide: Difference between revisions

| Verifiedfields = changed

| Watchedfields = changed

| verifiedrevid = 442353803

| ImageFile = Wurtzite polyhedra.png

| ImageFile_Ref = {{chemboximage|correct|??}}

| ImageName = Unit cell, ball and stick model of beryllium oxide

| ImageFile2 = BeO sample.jpg

| PIN = Beryllium(II) monoxide

| SystematicName = Oxoberyllium

| OtherNames = Beryllia, Thermalox, Bromellite, Thermalox 995.<ref>{{Cite web|title = beryllium oxide – Compound Summary|url = https://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=14775&loc=ec_rcs|work = PubChem Compound|publisher = National Center for Biotechnology Information|access-date = 8 November 2011|location = USA|date = 27 March 2005|at = Identification and Related records}}</ref>

| Section1 = {{Chembox Identifiers

| CASNo = 1304-56-9

| CASNo_Ref = {{cascite|correct|CAS}}

| UNII_Ref = {{fdacite|correct|FDA}}

| UNII = 2S8NLR37S3

| PubChem = 14775

| ChemSpiderID = 14092

| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

| EINECS = 215-133-1

| UNNumber = 1566

| MeSHName = beryllium+oxide

| ChEBI = 62842

| ChEBI_Ref = {{ebicite|changed|EBI}}

| RTECS = DS4025000

| Beilstein = 3902801

| SMILES = [Be]=[O]

| SMILES1 = [Be-]#[O+]

| StdInChI = 1S/Be.O

| StdInChI_Ref = {{stdinchicite|correct|chemspider}}

| InChI = 1/Be.O/rBeO/c1-2

| StdInChIKey = LTPBRCUWZOMYOC-UHFFFAOYSA-N

| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}

| InChIKey = LTPBRCUWZOMYOC-SRAGPBHZAE

}}

| Section2 = {{Chembox Properties

| Be=1 | O=1

| Appearance = Colourless, vitreous crystals

| Odor = Odourless

| Density = 3.01 g/cm³<ref name=crc>[[#Haynes|Haynes]], p. 4.51</ref>

| MeltingPtC = 2578

| MeltingPt_ref=<ref name=crc/>

| BoilingPtC =

| Solubility =

| SolubleOther =

| MagSus = −11.9·10⁻⁶ cm³/mol<ref>[[#Haynes|Haynes]], p. 4.126</ref>

| BandGap = 10.6 eV<ref>{{cite journal|doi=10.1063/1.2168040 |title=Wide-band gap oxide alloy: BeZnO |date=2006 |last1=Ryu |first1=Y. R. |last2=Lee |first2=T. S. |last3=Lubguban |first3=J. A. |last4=Corman |first4=A. B. |last5=White |first5=H. W. |last6=Leem |first6=J. H. |last7=Han |first7=M. S. |last8=Park |first8=Y. S. |last9=Youn |first9=C. J. |last10=Kim |first10=W. J. |journal=Applied Physics Letters |volume=88 |issue=5 |page=052103 |bibcode=2006ApPhL..88e2103R }}</ref>

| RefractIndex = n₁1.7184, n₂=1.733<ref>[[#Haynes|Haynes]], p. 10.248</ref><ref>[http://www.webmineral.com/data/Bromellite.shtml Bromellite Mineral Data]. webmineral</ref>

| ThermalConductivity = 210 W/(m·K)<ref>[[#Haynes|Haynes]], p. 12.222</ref>

}}

| Section3 = {{Chembox Structure

| Structure_ref=<ref>[[#Haynes|Haynes]], p. 4.139</ref>

| CrystalStruct = Hexagonal, [[zincite]]

| SpaceGroup = P6₃mc

| PointGroup = C_6v

| MolShape = Linear

| UnitCellFormulas = 2

| LattConst_a = 2.6979 Å

| LattConst_c = 4.3772 Å

}}

| Section4 = {{Chembox Thermochemistry

| Thermochemistry_ref =<ref>[[#Haynes|Haynes]], pp. 5.1, 5.6, 6.155</ref>

| DeltaHf = −609.4±2.5 kJ/mol

| DeltaGf = −580.1 kJ/mol

| Entropy = 13.77±0.04 J/(K·mol)

| HeatCapacity = 25.6 J/(K·mol)

| DeltaHfus = 86 kJ/mol

}}

| Section5 = {{Chembox Hazards

| MainHazards = Very toxic, Group 1B carcinogen

| GHSPictograms = {{GHS skull and crossbones}} {{GHS health hazard}}{{GHS environment}}

| GHSSignalWord = '''DANGER'''

| HPhrases = {{H-phrases|301|315|317|319|330|335|350|372}}

| PPhrases = {{P-phrases|201|260|280|284|301+310|305+351+338}}

| LD50 = 15 mg/kg (mouse, oral)<ref>Beryllium oxide toxicity</ref>

| REL = Ca C 0.0005 mg/m³ (as Be)<ref name=PGCH>{{PGCH|0054}}</ref>

| PEL = TWA 0.002 mg/m³<br/>C 0.005 mg/m³ (30 minutes), with a maximum peak of 0.025 mg/m³ (as Be)<ref name=PGCH/>

| IDLH = Ca [4 mg/m³ (as Be)]<ref name=PGCH/>

| Section6 = {{Chembox Related

| OtherCations = {{unbulleted list

| [[Magnesium oxide]]

| [[Calcium oxide]]

| [[Strontium oxide]]

| [[Barium oxide]]

| OtherAnions = [[Beryllium telluride]]

}}

'''Beryllium oxide''' ('''BeO'''), also known as '''beryllia''', is an [[inorganic compound]] with the [[chemical formula|formula]] BeO. This colourless solid is a [[Insulator (electricity)|electrical insulator]] with a higher [[Thermal conductivity and resistivity|thermal conductivity]] than any other non-metal except [[diamond]], and exceeds that of most metals.<ref name = "Greenwood">{{Greenwood&Earnshaw}}</ref> As an [[amorphous solid]], beryllium oxide is white. Its high melting point leads to its use as a [[refractory]] material.<ref>{{cite book |url=https://archive.org/details/materialsforengi0004higg |url-access=registration |page=[https://archive.org/details/materialsforengi0004higg/page/301 301] |author=Higgins, Raymond Aurelius |year=2006 |title=Materials for Engineers and Technicians |publisher=Newnes |isbn=0-7506-6850-4}}</ref> 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.

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

:BeCO₃ → BeO + CO₂

Igniting beryllium in air gives a mixture of BeO and the nitride [[Beryllium nitride|Be₃N₂]].<ref name = "Greenwood"/> Unlike the oxides formed by the other Group 2 elements ([[Alkaline earth metal|alkaline earth metals]]), beryllium oxide is [[amphoterism|amphoteric]] rather than basic.

Beryllium oxide formed at high temperatures (>800&nbsp;°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).

BeO crystallizes in the hexagonal [[Wurtzite crystal structure|wurtzite]] structure, featuring tetrahedral Be²⁺ and O²⁻ centres, like [[lonsdaleite]] and w-[[boron nitride|BN]] (with both of which it is [[Isoelectronicity|isoelectronic]]). In contrast, the oxides of the larger group-2 metals, i.e., [[magnesium oxide|MgO]], [[calcium oxide|CaO]], [[strontium oxide|SrO]], [[barium oxide|BaO]], crystallize in the cubic [[Rock-salt structure|rock salt motif]] with octahedral geometry about the dications and dianions.<ref name = "Greenwood"/> At high temperature the structure transforms to a tetragonal form.<ref>{{cite book |author=Wells, A. F. |year=1984 |title=Structural Inorganic Chemistry |edition=5 |publisher=Oxford Science Publications |isbn=0-19-855370-6}}</ref>

In the vapour phase, beryllium oxide is present as discrete [[diatomic molecule]]s. 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 2''s'' 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 [[Diatomic carbon|C₂]] molecule), where both bonds can be considered as [[dative bonds]] from oxygen towards beryllium.<ref>{{cite book |title=Fundamentals of Spectroscopy |url=https://books.google.com/books?id=gfM9B3JshegC&pg=PA234 |access-date=29 November 2011 |publisher=Allied Publishers |isbn=978-81-7023-911-6 |pages=234}}</ref>

High-quality crystals may be grown [[Hydrothermal synthesis|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]].<ref>Petzow, Günter; Aldinger, Fritz; Jönsson, Sigurd; Welge, Peter; van Kampen, Vera; Mensing, Thomas; Brüning, Thomas (2005) "Beryllium and Beryllium Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim. {{doi|10.1002/14356007.a04_011.pub2}}</ref> Beryllium oxide is used in rocket engines{{cn|date=September 2023}} and as a transparent [[Anti-corrosion|protective over-coating]] on [[Silvering|aluminised]] [[Curved mirror|telescope mirrors]]. Metal-coated beryllium oxide (BeO) plates are used in the control systems of aircraft drive devices.<ref>{{cite web |url=https://www.samaterials.com/content/what-are-the-ceramic-materials-with-high-thermal-conductivity.html |title=What Are the Ceramic Materials With High Thermal Conductivity? |last=Trento |first=Chin |date=Dec 27, 2023 |website=Stanford Advanced Materials |access-date=Sep 3, 2024}}</ref>

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]].<ref name="apmag">{{cite journal |author1=Greg Becker |author2=Chris Lee |author3=Zuchen Lin |title=Thermal conductivity in advanced chips — Emerging generation of thermal greases offers advantages |journal=Advanced Packaging |year=2005 |pages=2–4 |url=http://www.apmag.com/ |access-date=2008-03-04 |url-status=dead |archive-url=https://web.archive.org/web/20000621233638/http://www.apmag.com/ |archive-date=June 21, 2000 }}</ref> Some [[power semiconductor device]]s 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 in electronics|thermal resistance]] than a similar construction of [[aluminium oxide]]. It is also used as a structural [[ceramic]] for high-performance microwave devices, [[vacuum tube]]s, [[cavity magnetron]]s, and [[gas laser]]s. BeO has been proposed as a [[neutron moderator]] for naval marine high-temperature [[gas-cooled reactor]]s (MGCR), as well as [[NASA]]'s [[Kilopower]] [[nuclear reactor]] for space applications.<ref name="KiloPower Reactor Materials Study">{{cite web| last1=McClure |first1=Patrick |last2=Poston |first2=David |last3=Gibson |first3=Marc |last4=Bowman |first4=Cheryl |last5=Creasy |first5=John |title=KiloPower Space Reactor Concept – Reactor Materials Study |date=14 May 2014 |url=http://permalink.lanl.gov/object/tr?what=info:lanl-repo/lareport/LA-UR-14-23402 |access-date=21 November 2017}}</ref>

BeO is [[carcinogen]]ic in powdered form<ref>{{cite web|url=https://nj.gov/health/eoh/rtkweb/documents/fs/0226.pdf|title=Hazardous Substance Fact Sheet|publisher=New Jersey Department of Health and Senior Services|access-date=August 17, 2018}}</ref> 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.<ref>{{cite web |url=https://www.americanberyllia.com/safety |title=Beryllium Oxide Safety |website=American Beryllia |access-date=2018-03-29}}</ref>

{{Reflist|30em}}

==Cited sources==

*{{cite book |ref=Haynes| editor= Haynes, William M. | date = 2016| title = [[CRC Handbook of Chemistry and Physics]] | edition = 97th | publisher = [[CRC Press]] | isbn = 9781498754293}}

*[https://web.archive.org/web/20090828053542/http://americanberyllia.com/tech_info1.html Beryllium Oxide MSDS from American Beryllia]

*[https://web.archive.org/web/20051015082353/http://www-cie.iarc.fr/htdocs/monographs/vol58/mono58-1.htm IARC Monograph "Beryllium and Beryllium Compounds"]

*[https://web.archive.org/web/20051214061938/http://www.npi.gov.au/database/substance-info/profiles/13.html National Pollutant Inventory – Beryllium and compounds]

*[https://www.cdc.gov/niosh/npg/npgd0054.html NIOSH Pocket guide to Chemical Hazards]

{{Oxides}}

{{oxygen compounds}}

{{Authority control}}

[[Category:Nuclear technology]]

[[Category:II-VI semiconductors]]

[[Category:Wurtzite structure type]]