Beryllium oxide BeO

spore: profile
id: beryllium-oxide
spore_version: 0.2
family: oxide-ceramics
name: Beryllium oxide
abbreviation: BeO
role: electrically insulating, high-thermal-conductivity ceramic (beryllia)
category: ceramics
type: oxides
summary: 'Beryllium oxide (BeO, beryllia) is an oxide ceramic that conducts heat better than almost any electrical insulator, second only to diamond according to Materion. PubChem and the CRC Handbook give a density of 3.01 g/cm3 and a melting point of 2578 °C. Materion gives Thermalox 995 (99.5% BeO) a thermal conductivity of 285 W/m°K and a flexural strength of 221 MPa. The material is used in RF and microwave devices, power packages and heat spreaders. Its dust is toxic: PubChem classifies the compound with H330 and H350i, and OSHA sets very low airborne beryllium limits.'
best_for: Heat spreaders and packages that must move a lot of heat while staying electrically insulating, where the beryllium dust hazard can be controlled
weakest_at: 'Health: beryllium dust, fume and mist are toxic and carcinogenic by inhalation. Mechanical strength is lower than alumina according to the American Beryllia page'
identity:
  formula: BeO (beryllium oxide)
  cas: 1304-56-9
  crystal_system: hexagonal
  space_group: P6_3mc
  source: pubchem-beo
  where: Names and Identifiers (CID 14775, Beryllium Oxide); Wikipedia infobox for crystal system and space group
  designations:
    - system: CAS
      code: 1304-56-9
      source: pubchem-beo
      where: Names and Identifiers > Other Identifiers > CAS
    - system: Name
      code: Beryllium oxide
      source: pubchem-beo
      where: Names and Identifiers > Record Title
    - system: Name
      code: Beryllia
      source: materion-beo
      where: Product description, first paragraph ("BeO (or beryllia)")
    - system: Trade name
      code: Thermalox 995
      note: Materion grade name (99.5% BeO); its values are kept separate
      source: materion-beo
      where: Technical Details table, Thermalox 995 Properties
tags:
  environments: []
  stresses:
    - extreme-heat
  applications:
    - thermal-control
    - electronics-and-chips
properties:
  - benchmark: density
    label: Density, beryllium oxide (CRC Handbook via PubChem)
    value: 3.01
    unit: g/cu cm
    scope: material
    conditions:
      grade: beryllium oxide, no grade or purity stated
      temperature: 25 °C (printed beside the value)
    method: Value from the CRC Handbook, 94th edition, as printed in the PubChem record
    status: ground
    source: pubchem-beo
    where: Experimental Properties > Density, CRC Handbook p. 4-51; second entry "3.01 @25 °C"
  - benchmark: density
    label: Density, beryllium oxide (Frontiers review, Table 1)
    value: 3.01
    unit: g/cm3
    scope: material
    conditions:
      grade: beryllium oxide as a neutron moderator; no grade stated
      temperature: not stated
    method: Table of moderator properties in an open-access review
    status: ground
    source: frontiers-beo-review
    where: Table 1 (Moderator, Density column), BeO row
  - benchmark: density
    label: Theoretical density, beryllium oxide (American Beryllia)
    value: 3.01
    unit: g/cc
    scope: material
    conditions:
      grade: unnamed beryllium oxide (vendor page does not name a grade)
      temperature: not stated
    method: Vendor comparison of theoretical density values, as printed
    status: ground
    source: americanberyllia-beo
    where: Physical properties list, bullet on density (BeO 3.01 g/cc, Al2O3 4.00 g/cc, AlN 3.26 g/cc)
  - benchmark: melting_point
    label: Melting point, beryllium oxide (CRC Handbook via PubChem)
    value: 2578
    unit: °C
    scope: material
    conditions:
      grade: beryllium oxide, no grade or purity stated
      pressure: atmospheric (standard)
    method: Value from the CRC Handbook, 94th edition, as printed in the Wikipedia infobox (which cites Haynes p. 4.51)
    status: ground
    source: wiki-beo
    where: Infobox, Melting point 2,578 °C (CRC Handbook cited)
  - benchmark: thermal_conductivity
    label: Thermal conductivity, Thermalox 995 (Materion)
    value: 285
    unit: W/m°K
    scope: material
    conditions:
      grade: Thermalox 995 (99.5% BeO, Materion)
      temperature: not stated on the product page
    method: Value from the Materion technical details table
    status: ground
    source: materion-beo
    where: 'Technical Details, Thermalox 995 Properties (''Thermal Conductivity: 285 W/m°K'')'
  - benchmark: thermal_conductivity
    label: Thermal conductivity, unnamed beryllium oxide (American Beryllia)
    value: 285
    unit: W/mK
    scope: material
    conditions:
      grade: unnamed beryllium oxide (vendor page does not name a grade)
      temperature: room temperature (page text)
    method: Vendor statement, as printed
    status: ground
    source: americanberyllia-beo
    where: Thermal properties bullet, "thermal conductivity of Beryllium Oxide at Room Temperature is 285 W/mK"
  - benchmark: flexural_strength
    label: Flexural strength, Thermalox 995 (Materion)
    value: 221
    unit: Mpa
    scope: material
    conditions:
      grade: Thermalox 995 (99.5% BeO, Materion)
      temperature: not stated on the product page
    method: Value from the Materion technical details table; test method not stated
    status: ground
    source: materion-beo
    where: 'Technical Details, Thermalox 995 Properties (''Flexural Strength: 221 Mpa'')'
  - benchmark: refractive_index
    label: Refractive index, beryllia (American Beryllia)
    value: 1.719
    unit: '-'
    scope: material
    conditions:
      grade: unnamed beryllium oxide
      wavelength: not stated
      temperature: not stated
    method: Vendor optical properties list, as printed
    status: ground
    source: americanberyllia-beo
    where: 'Selected Optical Properties of Beryllia, ''Refractive Index: 1.719'''
  - benchmark: band_gap
    label: Band gap, beryllium oxide (Wikipedia infobox)
    value: 10.6
    unit: eV
    scope: material
    conditions:
      grade: beryllium oxide, wurtzite phase
      temperature: not stated
    method: Infobox value in Wikipedia; the source of the infobox figure is not given on the page read
    status: ground
    note: The vendor page gives a wurtzite phase band gap of 10.4 to 10.6 eV; the infobox value is the upper end of that range.
    source: wiki-beo
    where: Properties infobox, "Band gap 10.6 eV"
  - benchmark: lattice_constant_a
    label: Lattice constant a, beryllium oxide (wurtzite cell)
    value: 2.6979
    unit: Å
    scope: material
    conditions:
      crystal: hexagonal wurtzite-type cell
      temperature: not stated
    method: Crystallographic value in the Wikipedia infobox, as printed
    status: ground
    source: wiki-beo
    where: Structure infobox, LattConst_a
  - benchmark: lattice_constant_c
    label: Lattice constant c, beryllium oxide (wurtzite cell)
    value: 4.3772
    unit: Å
    scope: material
    conditions:
      crystal: hexagonal wurtzite-type cell
      temperature: not stated
    method: Crystallographic value in the Wikipedia infobox, as printed
    status: ground
    source: wiki-beo
    where: Structure infobox, LattConst_c
  - benchmark: water_solubility
    label: Solubility in water, beryllium oxide at 30 °C (CRC Handbook via PubChem)
    value: 2
    unit: ug/100 mL
    scope: material
    conditions:
      solvent: water
      temperature: 30 °C
    method: Value from the CRC Handbook, 76th edition (1995 to 1996), as printed in the PubChem record; not a canonical property, so the name is a short snake_case name
    status: ground
    source: pubchem-beo
    where: Experimental Properties > Solubility, CRC Handbook p. 4-44, entry "2 ug/100 mL in water at 30 °C"
  - benchmark: abbe_number
    label: Abbe number, beryllia (American Beryllia)
    value: 93.25
    unit: '-'
    scope: material
    conditions:
      grade: unnamed beryllium oxide
      wavelength: not stated
    method: Vendor optical properties list, as printed ("Vd = 93.25")
    status: ground
    source: americanberyllia-beo
    where: 'Selected Optical Properties of Beryllia, ''Abbe number: Vd = 93.25'''
corrosion:
  - environment: Water
    headline: Very low solubility in water
    effect: The CRC Handbook figure in the PubChem record is 2 ug/100 mL at 30 °C. The PubChem record does not give a hydrolysis rate. Unlike aluminium nitride, no source read here says that water decomposes beryllium oxide.
    rating: low
    conditions:
      medium: water
      temperature: 30 °C
    source: pubchem-beo
    where: Experimental Properties > Solubility, CRC Handbook p. 4-44
  - environment: Concentrated sulfuric acid and fused potassium hydroxide
    headline: Soluble in hot strong acid and fused alkali
    effect: The CRC Handbook entry in PubChem says beryllium oxide is soluble in concentrated sulfuric acid and in fused potassium hydroxide. No rate, temperature or concentration is printed.
    rating: severe
    conditions:
      medium: concentrated sulfuric acid; fused potassium hydroxide
      temperature: not stated
    source: pubchem-beo
    where: Experimental Properties > Solubility, CRC Handbook p. 4-44
  - environment: Oxidizing chemicals
    headline: More chemically stable than aluminium nitride in oxidizing environments
    effect: Materion says BeO is more chemically stable than AlN ceramic in environments that contain oxidizing chemicals. No test data are given.
    rating: low
    source: materion-beo
    where: Beryllium Oxide Ceramics Outperform Competitive Products' section
  - environment: Oxygen and hydrogen at high temperature
    headline: Very stable with O2 and H2 at 2000 °C
    effect: The Frontiers review says BeO has a very stable performance with O2 and H2 even at a temperature of 2000 °C. The review gives no rate or test method.
    rating: low
    conditions:
      atmosphere: oxygen and hydrogen
      temperature: 2000 °C
    source: frontiers-beo-review
    where: Section on physical and chemical properties
risks:
  hazards:
    - text: PubChem aggregates 49 company reports from 7 ECHA C&L notifications for beryllium oxide. Its GHS hazard statements are H301, H315, H317, H319, H330, H335, H350i and H372, with signal word Danger. The statements include H330 (fatal if inhaled) and H350i (may cause cancer by inhalation).
      ghs:
        - H301
        - H315
        - H317
        - H319
        - H330
        - H335
        - H350i
        - H372
      source: pubchem-beo
      where: Safety and Hazards > Hazards Identification > GHS Classification
    - text: 'PubChem hazards summary: beryllium oxide is a severe skin, eye and respiratory tract irritant; dust or fume inhalation may cause chemical pneumonitis; repeated or prolonged exposure may cause chronic beryllium disease; and prolonged contact may cause beryllium sensitization.'
      ghs: []
      source: pubchem-beo
      where: Safety and Hazards > Hazards Identification > Hazards Summary
    - text: Wikipedia lists an oral LD50 of 15 mg/kg in mice and says beryllium oxide is carcinogenic in powdered form and may cause berylliosis, a chronic allergic-type lung disease.
      ghs: []
      source: wiki-beo
      where: Infobox (LD50) and Safety section
  failure_risks:
    - mode: Airborne beryllium from machining or crushing fired parts
      trigger: Machining, grinding or crushing of fired beryllium oxide that generates dust
      consequence: Airborne beryllium dust, which is the main inhalation hazard in the material's handling. Wikipedia says clean breakage releases little dust, but crushing or grinding can pose a risk.
      severity: high
      source: wiki-beo
      where: Safety section
  side_effects: []
  handling:
    - text: OSHA sets the beryllium permissible exposure limit at 0.2 µg/m3 as an 8-hour time-weighted average and 2.0 µg/m3 as a 15-minute short-term exposure limit. The action level is 0.1 µg/m3 as an 8-hour TWA.
      source: osha-beryllium-1910-1024
      where: 29 CFR 1910.1024 paragraphs (c)(1), (c)(2) and (b), Action level definition
    - text: Once fired into solid form, beryllium oxide is safe to handle if it is not machined to produce dust. Crushing or grinding poses a risk (Wikipedia).
      source: wiki-beo
      where: Safety section
    - text: Keep beryllium oxide powder and dust out of the air. PubChem's hazards summary warns that dust or fume inhalation may cause chemical pneumonitis.
      source: pubchem-beo
      where: Safety and Hazards > Hazards Identification > Hazards Summary
  mitigations: []
uses:
  - application: electronics-and-chips
    device: Aerospace electronics
    example: Materion lists aerospace electronics among the applications of its beryllium oxide ceramics, along with laser systems, medical equipment and electronics manufacturing.
    source: materion-beo
    where: Benefits and Applications section
  - application: electronics-and-chips
    device: Microwave devices, vacuum tubes, gas lasers and magnetrons
    example: Materion says its BeO powder is used to form critical thermally conductive components for high-performance semiconductor applications, microwave devices, vacuum tubes, gas lasers and magnetrons.
    source: materion-beo
    where: Beryllium Oxide Powder for Thermally Conductive Components section
  - application: thermal-control
    device: Heat sinks and spreaders for CPUs, lasers and power amplifiers
    example: Wikipedia says beryllium oxide is used in heat sinks and spreaders that cool electronic devices, such as CPUs, lasers and power amplifiers, and that some power semiconductor packages use it between the chip and the mounting base.
    source: wiki-beo
    where: Uses section, Electronics paragraph
supply:
  - subject: Beryllium (feedstock for beryllium oxide)
    abundance: 'USGS: identified world resources of beryllium are more than 100,000 tons, and about 60% of them are in the United States.'
    producers:
      - country: United States
        share_percent: 53.5
        year: 2025
      - country: Brazil
        share_percent: 18.6
        year: 2025
      - country: China
        share_percent: 17.9
        year: 2025
      - country: Nigeria
        share_percent: 9.3
        year: 2025
      - country: Mozambique
        share_percent: 0.7
        year: 2025
    critical_lists: []
    recycling: 'USGS: recovered beryllium from new and old scrap may account for as much as 20% to 25% of total beryllium consumption.'
    substitutes:
      - 'USGS: aluminum nitride or boron nitride may be substituted for beryllium oxide.'
    source: usgs-mcs2026-beryllium
    where: 'World Mine Production and Reserves table, 2025e column (beryllium content, metric tons). Shares are calculated by Space Mushroom against the printed world total of 430 t: United States 230, Brazil 80, China 77, Nigeria 40, Mozambique 3. Recycling and Substitutes sections; World Resources paragraph.'
documents:
  - title: PubChem PUG-View record, Beryllium Oxide (CID 14775)
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/14775/JSON
    year: 2026
  - title: Materion, Beryllium Oxide Ceramics and Powder (product page with Thermalox 995 table)
    type: datasheet
    url: https://materion.com/products/technical-ceramics/beryllium-oxide-ceramics
  - title: American Beryllia, Beryllium Oxide (vendor properties page)
    type: datasheet
    url: https://americanberyllia.com/beryllium-oxide
  - title: BeO Utilization in Reactors for the Improvement of Extreme Reactor Environments - A Review (open access)
    type: paper
    url: https://www.frontiersin.org/articles/10.3389/fenrg.2021.669832/full
    year: 2021
  - title: USGS Mineral Commodity Summaries 2026, Beryllium
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-beryllium.pdf
    year: 2026
  - title: CIAAW Abridged Standard Atomic Weights 2024
    type: database
    url: https://www.ciaaw.org/abridged-atomic-weights.htm
    year: 2024
  - title: 29 CFR 1910.1024, Beryllium (OSHA general industry standard, text via Cornell LII)
    type: standard
    url: https://www.law.cornell.edu/cfr/text/29/1910.1024
gaps:
  - Electrical resistivity is not entered. American Beryllia prints the bulk resistivity as 10 16 Ωcm, with the exponent lost from the text, so the number cannot be matched to the page.
  - Coefficient of thermal expansion is not entered. American Beryllia prints 7.5 in./in./°C for 25 to 1000 °C with no 10 to the minus 6 exponent, so the unit as printed is not usable. No other source read gives a number.
  - 'Dielectric constant: Materion says its four BeO grades (purity 99.5% to 99.7%) have a dielectric constant of 6.7 against 9.7 for AlN. This is a family figure with no frequency and no single grade, so it is not entered as a property.'
  - Hardness, dielectric strength, specific heat and water absorption are not printed on any page read. The Materion Thermalox 995 density of 2.85 g/cm3 appeared only in a search snippet, not on a fetched page, so it is not entered.
  - Flexural strength is given for one grade only (Thermalox 995, 221 MPa). No test method or temperature is printed.
  - The Wikipedia thermal conductivity of 210 W/(m·K) is an unlabelled figure with no grade or temperature, so it is not entered. The Frontiers review gives a melting point of 2570 °C (Rothman, 1962), which differs from the CRC value of 2578 °C; the CRC value is used.
  - Mouse oral LD50 of 15 mg/kg comes from the Wikipedia infobox, which cites an unnamed source. It is not in the PubChem record, so it is not entered as a property.
  - 'Synthesis route: the calcining, dehydrating and metal-burning routes come from Wikipedia, and the calcination temperatures from the PubChem record. No manufacturer process description was read.'
  - Critical-mineral listing for beryllium was not in the USGS chapter text read; the EU list was not checked.
  - 'Trade names: only Thermalox 995 was found on the Materion page read. Other grades (for example BW3250 and Thermalox V) are not covered.'
  - 'Space use: no flight or vacuum result was found. The Kilopower mention is a proposal in Wikipedia, not a flown use.'
  - The OSHA page on osha.gov returned HTTP 403, so the exposure limits were read from the 29 CFR 1910.1024 text at Cornell LII instead.
  - Failure-risk severity labels and corrosion ratings are assistant judgement; no fetched source ranks them.
  - Lattice constants and band gap come from the Wikipedia infobox, which does not name its primary source.
sources:
  pubchem-beo:
    title: PubChem PUG-View record, Beryllium Oxide (CID 14775)
    id: CID 14775; CAS 1304-56-9
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/14775/JSON
    year: 2026
    kind: database
    license: Public domain (NCBI), cited
  wiki-beo:
    title: Wikipedia, Beryllium oxide (used for composition, structure, uses and toxicity only)
    url: https://en.wikipedia.org/wiki/Beryllium_oxide
    kind: web
    license: CC BY-SA 4.0, cited
  materion-beo:
    title: Materion, Beryllium Oxide Ceramics and Powder (product page)
    url: https://materion.com/products/technical-ceramics/beryllium-oxide-ceramics
    kind: datasheet
    license: Manufacturer web page, cited
  americanberyllia-beo:
    title: American Beryllia, Beryllium Oxide (vendor properties page)
    url: https://americanberyllia.com/beryllium-oxide
    kind: datasheet
    license: Manufacturer web page, cited
  frontiers-beo-review:
    title: BeO Utilization in Reactors for the Improvement of Extreme Reactor Environments - A Review
    id: doi:10.3389/fenrg.2021.669832 (Frontiers in Energy Research)
    url: https://www.frontiersin.org/articles/10.3389/fenrg.2021.669832/full
    year: 2021
    kind: paper
    license: CC BY (Frontiers open access)
  usgs-mcs2026-beryllium:
    title: Mineral Commodity Summaries 2026, Beryllium
    id: USGS MCS 2026, February 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-beryllium.pdf
    year: 2026
    kind: report
    license: Public domain (USGS)
  ciaaw-atomic-weights:
    title: Commission on Isotopic Abundances and Atomic Weights, 2024 Abridged Standard Atomic Weights
    url: https://www.ciaaw.org/abridged-atomic-weights.htm
    year: 2024
    kind: database
    license: CIAAW reference table, cited
  osha-beryllium-1910-1024:
    title: 29 CFR 1910.1024, Beryllium (OSHA general industry standard)
    url: https://www.law.cornell.edu/cfr/text/29/1910.1024
    kind: standard
    license: US federal regulation, public domain
license: CC-BY-4.0
updated: '2026-10-26'
review:
  status: draft
  method: assistant
  checked_values: 13
  unreachable: 1
  caveats: 3
  note: Values were read in this run from the PubChem record, the Materion and American Beryllia pages, the Frontiers review, the USGS chapter, the Wikipedia infobox, the CIAAW table and the OSHA standard text. Materion values are for Thermalox 995 only. The American Beryllia values name no grade. The osha.gov page returned HTTP 403 and was not used.
story:
  recipe:
    line: BeO is beryllium oxide, with one beryllium atom bonded to one oxygen atom per formula unit . CIAAW 2024 standard atomic weights are 9.0122 for beryllium and 15.999 for oxygen. Commercial BeO is made by calcining beryllium hydroxide, carbonate or sulfate. PubChem says practically all commercial BeO is calcined at 1000 °C or higher ('high-fired'), and beryllium sulfate is calcined at carefully controlled temperatures to tailor its properties. Wikipedia also lists dehydration of the hydroxide and burning of the metal in air, which gives some beryllium nitride.
    parts:
      - name: Beryllium
        symbol: Be
        atoms: 1
        atomic_weight: 9.0122
        role: Metal atom in each BeO formula unit
        source: ciaaw-atomic-weights
        where: 2024 Abridged Standard Atomic Weights, beryllium row (9.0122)
      - name: Oxygen
        symbol: O
        atoms: 1
        atomic_weight: 15.999
        role: Oxide anion in each BeO formula unit
        source: ciaaw-atomic-weights
        where: 2024 Abridged Standard Atomic Weights, oxygen row (15.999)
  risk_groups:
    - title: For people
      verdict: Toxic dust, a carcinogen by inhalation
      lead: The hazard comes from dust, fume and mist. The fired solid is much less of a hazard, but PubChem's aggregate of ECHA reports classifies the compound as fatal if inhaled.
      points:
        - label: Inhalation
          line: PubChem lists H330 (fatal if inhaled) and H350i (may cause cancer by inhalation), with H372 for organ damage from prolonged or repeated exposure.
        - label: Chronic disease
          line: PubChem says repeated or prolonged exposure may cause chronic beryllium disease. Wikipedia names berylliosis, a chronic allergic-type lung disease.
        - label: Exposure limits
          line: OSHA sets 0.2 µg/m3 as an 8-hour TWA and 2.0 µg/m3 as a 15-minute limit, with an action level of 0.1 µg/m3.
    - title: Fired parts
      lead: Once fired into a solid, the ceramic is safe to handle unless machining creates dust.
      verdict: Dust control during machining
      points:
        - label: Machining
          line: Wikipedia says crushing or grinding poses a risk, while clean breakage releases little dust.
    - title: If the part gets wet
      lead: Beryllium oxide is almost insoluble in water, and it dissolves only in strong acid or fused alkali.
      verdict: Very low water solubility
      points:
        - label: Water
          line: The CRC Handbook gives 2 ug/100 mL at 30 °C in water.
        - label: Acid and alkali
          line: It is soluble in concentrated sulfuric acid and in fused potassium hydroxide, according to the CRC Handbook.
    - title: Hot oxidizing air
      lead: Beryllium oxide is chemically stable in oxygen and hydrogen.
      verdict: Stable to 2000 °C in O2 and H2
      points:
        - label: Stability
          line: The Frontiers review says BeO performs very stably with O2 and H2 even at 2000 °C. Materion says it is more chemically stable than AlN in oxidizing environments.
  why: 'Beryllium oxide combines high thermal conductivity with electrical insulation. Materion says it is the second highest thermal conductivity of any electrical insulator after diamond, nine times that of alumina, and up to 80 percent higher than aluminium nitride. The Frontiers review adds high-temperature radiation stability and high strength. The same properties make it attractive in electronics and reactors. The price is the toxicity of beryllium: the grade must be chosen with the dust hazard in mind.'
  uses:
    - where: Aerospace and defense electronics
      line: Materion lists aerospace electronics as an application of its beryllium oxide ceramics. It also lists microwave devices, vacuum tubes, gas lasers and magnetrons among the uses of its BeO powder.
    - where: Heat spreaders and power packages
      line: Wikipedia says BeO is used in heat sinks and spreaders for CPUs, lasers and power amplifiers, and in some power semiconductor packages between the chip and the mounting base.
    - where: Reactors and proposed space power
      line: The Frontiers review describes BeO as a candidate reflector and moderator in reactors. Wikipedia says it has been proposed as a moderator for naval gas-cooled reactors and for NASA's Kilopower reactor for space applications. These are reactor and proposal uses, not flown ones.
  can_do:
    - label: Carry heat away
      benchmark: thermal_conductivity
      line: Materion gives 285 W/m°K for Thermalox 995 (99.5% BeO). American Beryllia gives 285 W/mK at room temperature for an unnamed grade. Both are in the properties table.
    - label: Insulate electrically
      benchmark: electrical_resistivity
      line: American Beryllia calls BeO an electrical insulator with bulk resistivity on the order of 10 16 Ωcm. The exponent is lost in the printed text, so no number is entered.
    - label: Stay strong
      benchmark: flexural_strength
      line: Materion gives 221 MPa flexural strength for Thermalox 995. American Beryllia says BeO strength is normally lower than that of alumina.
  compare: Materion says BeO is nine times more thermally conductive than alumina and up to 80 percent more than aluminium nitride, and that it is more chemically stable than AlN in oxidizing environments. Its density is 3.01 g/cm3 against 4.00 g/cm3 for alumina and 3.26 g/cm3 for AlN, both from American Beryllia. Its melting point of 2578 °C is from the CRC Handbook. The compared numbers come from different sources and grades, so they should be read as direction, not as exact ratios.
  compare_rows:
    - label: Thermal conductivity
      benchmark: thermal_conductivity
    - label: Flexural strength
      benchmark: flexural_strength
    - label: Density
      benchmark: density
  handling:
    - Keep dust and fume out of the air. OSHA's limits are 0.2 µg/m3 as an 8-hour TWA and 2.0 µg/m3 over 15 minutes, with an action level of 0.1 µg/m3.
    - Do not machine, grind or crush fired parts without dust control, because the dust carries the beryllium hazard.
    - Treat powder and dust as toxic beryllium material. PubChem warns that dust or fume inhalation may cause chemical pneumonitis.
  good_for:
    - Heat spreaders and packages that must move heat while staying electrically insulating, as in aerospace electronics and power packages.
    - Microwave, vacuum-tube, magnetron and gas-laser parts, as Materion lists them.
  watch_out:
    - Beryllium dust is toxic and carcinogenic by inhalation. Handling needs dust control at every step.
    - Grade data differ. The Materion values are for Thermalox 995 only, and the American Beryllia values name no grade.
    - Electrical resistivity and thermal expansion are not entered, because the printed values lost their exponents.
  verdict: Beryllium oxide is one of the best electrical insulators for conducting heat, and it suits electronics where aluminium nitride is not enough. Its toxicity is serious, so it suits only applications where the dust hazard can be controlled, and the grade should be checked on its own data sheet.