spore: profile
id: cvd-diamond
spore_version: 0.2
family: diamond
name: CVD diamond (polycrystalline and single-crystal)
abbreviation: CVD diamond
role: heat spreader, optical window
category: carbon
type: diamond
summary: |
  CVD diamond is carbon grown from hydrocarbon gas by chemical vapour deposition, as polycrystalline plates or as single crystals. Element Six prints a thermal conductivity of greater than 2200 W m-1 K-1 at 300 K for its polycrystalline optical grade and for its single-crystal optical grade. The same brochure prints a density of 3.52 x 10³ kg m⁻³ and a coefficient of thermal expansion of 1.0 ppm/K at 300 K.
best_for: Heat spreaders and high-power laser windows, where thermal conductivity above 2000 W/(m·K) at 300 K matters most
weakest_at: 'Size and thickness: polycrystalline optical windows up to Ø 135 mm and 3 mm thick, single-crystal plates up to 7 x 7 x 2 mm (Element Six)'
identity:
  formula: C, carbon in the diamond cubic structure (eight atoms per unit cell, Wikipedia)
  crystal_system: cubic
  source: wikipedia-diamond
  where: 'Crystal structure section: diamond cubic, unit cell side 3.567 angstroms, eight atoms per unit cell'
tags:
  environments: []
  stresses:
    - dust-abrasion
  applications:
    - thermal-control
    - optics-and-cameras
    - electronics-and-chips
properties:
  - benchmark: thermal_conductivity
    label: Thermal conductivity, polycrystalline CVD diamond, optical grade, 300 K
    value: 2200
    bound: lower
    unit: W/(m·K)
    scope: material
    conditions:
      grade: polycrystalline CVD diamond, optical grade
      temperature: 300 K
      unit_in_source: W m-1 K-1, printed as >2200
    method: Lower limit printed in a manufacturer properties table
    status: ground
    source: e6-optics
    where: Page 5, table CVD diamond properties, row Thermal conductivity 300 K, column Polycrystalline Optical grade
  - benchmark: thermal_conductivity
    label: Thermal conductivity, polycrystalline CVD diamond, RF grade, 300 K
    value: 2000
    bound: lower
    unit: W/(m·K)
    scope: material
    conditions:
      grade: polycrystalline CVD diamond, RF grade
      temperature: 300 K
      unit_in_source: W m-1 K-1, printed as >2000
    method: Lower limit printed in a manufacturer properties table
    status: ground
    source: e6-optics
    where: Page 5, table CVD diamond properties, row Thermal conductivity 300 K, column RF grade
  - benchmark: thermal_conductivity
    label: Thermal conductivity, single-crystal CVD diamond, optical grade, 300 K
    value: 2200
    bound: lower
    unit: W/(m·K)
    scope: material
    conditions:
      grade: single-crystal CVD diamond, optical grade
      temperature: 300 K
      unit_in_source: W m-1 K-1, printed as >2200
    method: Lower limit printed in a manufacturer properties table
    status: ground
    source: e6-optics
    where: Page 5, table CVD diamond properties, row Thermal conductivity 300 K, column Single crystal Optical grade
  - benchmark: thermal_conductivity
    label: Thermal conductivity, polycrystalline CVD diamond, optical grade, 425 K
    value: 1600
    bound: lower
    unit: W/(m·K)
    scope: material
    conditions:
      grade: polycrystalline CVD diamond, optical grade
      temperature: 425 K
      unit_in_source: W m-1 K-1, printed as >1600
    method: Lower limit printed in a manufacturer properties table
    status: ground
    source: e6-optics
    where: Page 5, table CVD diamond properties, row Thermal conductivity 425 K, column Polycrystalline Optical grade
  - benchmark: thermal_conductivity
    label: Thermal conductivity, single-crystal CVD diamond sheet (SCD-O), temperature not stated
    value: 2200
    bound: lower
    unit: W/(m·K)
    scope: material
    conditions:
      grade: single-crystal CVD diamond, optical grade (SCD-O), table labels it Thermal Grade
      temperature: not stated on the datasheet
      unit_in_source: W/mK, printed as ≥2,200
    method: Lower limit printed in a manufacturer datasheet; no temperature given
    status: ground
    note: Matches the Element Six single-crystal optical grade value at 300 K, but the datasheet does not print the temperature.
    source: coherent-scd-o
    where: Material Properties table, row Thermal Conductivity
  - benchmark: thermal_conductivity
    label: Thermal conductivity, Element Six Diafilm TM100, 300 K
    value: 1000
    bound: lower
    unit: W/(m·K)
    scope: material
    conditions:
      grade: Element Six Diafilm TM100, polycrystalline CVD heat spreader
      temperature: 300 K
      unit_in_source: W/m-K, printed as better than 1,000
    method: Lower limit printed in a trade article that reports Element Six product data
    status: ground
    source: mwrf-diafilm
    where: Thermal conductivity table, row Diafilm TM100, column At 300 K
  - benchmark: thermal_conductivity
    label: Thermal conductivity, Element Six Diafilm TM200, 300 K
    value: 2000
    bound: lower
    unit: W/(m·K)
    scope: material
    conditions:
      grade: Element Six Diafilm TM200, polycrystalline CVD heat spreader
      temperature: 300 K
      unit_in_source: W/m-K, printed as better than 2,000
    method: Lower limit printed in a trade article that reports Element Six product data
    status: ground
    source: mwrf-diafilm
    where: Thermal conductivity table, row Diafilm TM200, column At 300 K
  - benchmark: cte
    label: Coefficient of thermal expansion, CVD diamond, 300 K
    value: 1
    unit: ppm/K
    scope: material
    conditions:
      grade: polycrystalline and single-crystal CVD diamond (same value printed for both)
      temperature: 300 K
      unit_in_source: ppm K-1
    method: Value printed in a manufacturer properties table
    status: ground
    note: The Diafilm article prints 1.0 ± 0.1 ppm/K at 300 K for four Diafilm grades, which agrees.
    source: e6-optics
    where: Page 5, table CVD diamond properties, row Thermal expansion coefficient 300 K
  - benchmark: cte
    label: Coefficient of thermal expansion, CVD diamond, 1000 K
    value: 4.4
    unit: ppm/K
    scope: material
    conditions:
      grade: polycrystalline and single-crystal CVD diamond (same value printed for both)
      temperature: 1000 K
      unit_in_source: ppm K-1
    method: Value printed in a manufacturer properties table
    status: ground
    source: e6-optics
    where: Page 5, table CVD diamond properties, row Thermal expansion coefficient 1000 K
  - benchmark: density
    label: Density, CVD diamond
    value: 3.52
    unit: g/cm3
    scope: material
    conditions:
      grade: polycrystalline and single-crystal CVD diamond (same value printed for both)
      unit_in_source: 3.52 x 10³ kg m⁻³ (printed in the table heading, which equals 3.52 g/cm3)
    method: Value printed as 3.52 in a manufacturer properties table under the heading x 10³ kg m⁻³; the same figure is entered in g/cm3 (1 g/cm3 = 1000 kg/m3). The Diafilm article prints 3.52 x 10³ kg/m³ for its four grades.
    status: ground
    source: e6-optics
    where: Page 5, table CVD diamond properties, row Density
  - benchmark: specific_heat
    label: Specific heat capacity, CVD diamond, 500 K
    value: 520
    unit: J/(kg·K)
    scope: material
    conditions:
      grade: polycrystalline and single-crystal CVD diamond (same value printed for both)
      temperature: 500 K
      unit_in_source: J Kg-1 K-1
    method: Value printed in a manufacturer properties table
    status: ground
    source: e6-optics
    where: Page 5, table CVD diamond properties, row Specific heat capacity at 500 K
  - benchmark: specific_heat
    label: Specific heat capacity, Diafilm grades, 300 K
    value: 520
    unit: J/(kg·K)
    scope: material
    conditions:
      grade: Element Six Diafilm TM grades (printed for all four)
      temperature: 300 K
      unit_in_source: J/kg/K
    method: Value printed in a trade article that reports Element Six product data
    status: ground
    source: mwrf-diafilm
    where: Other properties list, Specific heat capacity
  - benchmark: specific_heat
    label: Specific heat capacity, single-crystal CVD diamond sheet (SCD-O), 25 °C
    value: 0.536
    unit: J/g-K
    scope: material
    conditions:
      grade: single-crystal CVD diamond, optical grade (SCD-O)
      temperature: 25 °C
      unit_in_source: J/g-K
    method: Value printed in a manufacturer datasheet
    status: ground
    note: Differs in unit form and temperature from the 520 J/(kg·K) values; 0.536 J/g-K is 536 J/(kg·K). Both are kept, with their temperatures.
    source: coherent-scd-o
    where: Material Properties table, row Specific Heat (25 °C)
  - benchmark: elastic_modulus
    label: Young's modulus, Element Six Diafilm grades
    value: 1000
    value_high: 1100
    bound: range
    unit: GPa
    scope: material
    conditions:
      grade: Element Six Diafilm TM grades (same printed range for all four)
      temperature: not stated
      unit_in_source: GPa, printed as 1,000 to 1,100
    method: Range printed in a trade article that reports Element Six product data
    status: ground
    note: The Element Six brochure prints 1050 in the Young's modulus row with no unit, so that value is not entered.
    source: mwrf-diafilm
    where: Other properties list, Young's modulus
  - benchmark: hardness
    label: Hardness, polycrystalline CVD diamond
    value: 81
    unit: GPa
    scope: material
    conditions:
      grade: polycrystalline CVD diamond (value spans the two polycrystalline columns)
      unit_in_source: GPa, printed as 81 ± 18
    method: Value printed in a manufacturer properties table, with a stated spread of ± 18 GPa
    status: ground
    note: The spread of ± 18 GPa is printed beside the mean; the brochure does not say whether it is a standard deviation.
    source: e6-optics
    where: Page 5, table CVD diamond properties, row Hardness (GPa)
  - benchmark: hardness
    label: Hardness, single-crystal CVD diamond
    value: 70
    value_high: 120
    bound: range
    unit: GPa
    scope: material
    conditions:
      grade: single-crystal CVD diamond (value spans the two single-crystal columns)
      unit_in_source: GPa, printed as 70 - 120
    method: Range printed in a manufacturer properties table
    status: ground
    source: e6-optics
    where: Page 5, table CVD diamond properties, row Hardness (GPa)
  - benchmark: refractive_index
    label: Refractive index, CVD diamond at 10.6 µm
    value: 2.376
    unit: '-'
    scope: material
    conditions:
      grade: polycrystalline and single-crystal CVD diamond (same value printed for both)
      wavelength: 10.6 µm
    method: Value printed in a manufacturer properties table
    status: ground
    source: e6-optics
    where: Page 5, table CVD diamond properties, row Refractive index 10.6 µm
  - benchmark: refractive_index
    label: Refractive index, CVD diamond at 1550 nm
    value: 2.386
    unit: '-'
    scope: material
    conditions:
      grade: polycrystalline and single-crystal CVD diamond (same value printed for both)
      wavelength: 1550 nm
    method: Value printed in a manufacturer properties table
    status: ground
    source: e6-optics
    where: Page 5, table CVD diamond properties, row Refractive index 1550 nm
  - benchmark: refractive_index
    label: Refractive index, CVD diamond at 1064 nm
    value: 2.392
    unit: '-'
    scope: material
    conditions:
      grade: polycrystalline and single-crystal CVD diamond (same value printed for both)
      wavelength: 1064 nm
    method: Value printed in a manufacturer properties table
    status: ground
    note: The chart on page 3 of the same brochure reads 2.390 at 1064 nm, so the two values differ by 0.002. The table value is entered.
    source: e6-optics
    where: Page 5, table CVD diamond properties, row Refractive index 1064 nm; chart on page 3 for comparison
  - benchmark: refractive_index_temperature_coefficient
    label: Temperature coefficient of refractive index (dn/dT), CVD diamond
    value: 0.0000096
    unit: K-1
    scope: material
    conditions:
      grade: polycrystalline and single-crystal CVD diamond (same value printed for both)
      unit_in_source: 9.6 x 10-6 (K-1)
    method: Value printed in a manufacturer properties table
    status: ground
    source: e6-optics
    where: Page 5, table CVD diamond properties, row dn/dT
  - benchmark: birefringence
    label: Birefringence, single-crystal CVD diamond, optical plus grade
    value: 0.00005
    bound: upper
    unit: '-'
    scope: material
    conditions:
      grade: single-crystal CVD diamond, optical plus
      unit_in_source: <5 x 10-5 (Δn, dimensionless)
    method: Upper limit printed in a manufacturer properties table
    status: ground
    note: The Coherent SCD-O datasheet prints the same limit, <5 x 10-5 Δn, for its single-crystal optical grade.
    source: e6-optics
    where: Page 5, table CVD diamond properties, row Birefringence, column Optical plus
  - benchmark: birefringence
    label: Birefringence, single-crystal CVD diamond, optical grade
    value: 0.0001
    unit: '-'
    scope: material
    conditions:
      grade: single-crystal CVD diamond, optical grade
      unit_in_source: 1 x 10-4 (Δn, dimensionless)
    method: Value printed in a manufacturer properties table
    status: ground
    note: The Element Six table gives 1 x 10-4 for this grade, while the Coherent SCD-O datasheet gives less than 5 x 10-5 for its optical grade. Both are kept side by side and the grades may differ.
    source: e6-optics
    where: Page 5, table CVD diamond properties, row Birefringence, column Single crystal Optical grade
  - benchmark: absorption_coefficient
    label: Absorption coefficient at 10.6 µm, polycrystalline CVD diamond, optical grade
    value: 0.07
    bound: upper
    unit: cm-1
    scope: material
    conditions:
      grade: polycrystalline CVD diamond, optical grade
      wavelength: 10.6 µm
      unit_in_source: <0.07 cm-1
    method: Upper limit printed in a manufacturer properties table
    status: ground
    source: e6-optics
    where: Page 5, table CVD diamond properties, row Absorption coefficient 10.6 µm, column Polycrystalline Optical grade
  - benchmark: absorption_coefficient
    label: Absorption coefficient at 10.6 µm, single-crystal CVD diamond, optical grade
    value: 0.05
    bound: upper
    unit: cm-1
    scope: material
    conditions:
      grade: single-crystal CVD diamond, optical grade
      wavelength: 10.6 µm
      unit_in_source: <0.05 cm-1
    method: Upper limit printed in a manufacturer properties table
    status: ground
    note: The Coherent SCD-O datasheet prints the same limit, 10.6 µm ABS coefficient <0.05 (cm-1).
    source: e6-optics
    where: Page 5, table CVD diamond properties, row Absorption coefficient 10.6 µm, column Single crystal Optical grade
  - benchmark: absorption_coefficient
    label: Absorption coefficient at 1064 nm, single-crystal CVD diamond, optical plus grade
    value: 0.005
    bound: upper
    unit: cm-1
    scope: material
    conditions:
      grade: single-crystal CVD diamond, optical plus
      wavelength: 1064 nm
      unit_in_source: <0.005
    method: Upper limit printed in a manufacturer properties table
    status: ground
    note: The Coherent SCD-O datasheet prints 0.005 (cm-1) at 1.064 µm for its single-crystal optical grade, which agrees.
    source: e6-optics
    where: Page 5, table CVD diamond properties, row Absorption coefficient 1064 nm, column Single crystal Optical plus
  - benchmark: transmittance
    label: Transmittance at 1 mm thickness, polycrystalline CVD diamond, optical grade, 8 to 200 µm
    value: 71.4
    unit: '%'
    scope: material
    conditions:
      grade: polycrystalline CVD diamond, optical grade
      thickness: 1 mm
      wavelength: 8 to 200 µm
    method: Value printed in a manufacturer properties table
    status: ground
    source: e6-optics
    where: Page 5, table CVD diamond properties, row Transmittance 8-200 µm, column Polycrystalline Optical grade
  - benchmark: dielectric_constant
    label: Dielectric constant, polycrystalline CVD diamond, 35 GHz
    value: 5.68
    unit: '-'
    scope: material
    conditions:
      grade: polycrystalline CVD diamond (value spans the two polycrystalline columns)
      frequency: 35 GHz
    method: Value printed in a manufacturer properties table, with a stated spread of ± 0.15
    status: ground
    note: The spread of ± 0.15 is printed beside the value. The brochure gives 4.3 % increase in D at 773 K and does not give the value at that temperature.
    source: e6-optics
    where: Page 5, table CVD diamond properties, row Dielectric constant D (35 GHz)
  - benchmark: dissipation_factor
    label: Loss tangent at 145 GHz, polycrystalline CVD diamond, optical grade
    value: 0.000008
    value_high: 0.00002
    bound: range
    unit: '-'
    scope: material
    conditions:
      grade: polycrystalline CVD diamond, optical grade
      frequency: 145 GHz
      unit_in_source: 8 - 20 (x 10-6)
    method: Range printed in a manufacturer properties table
    status: ground
    source: e6-optics
    where: Page 5, table CVD diamond properties, row Loss tangent 145 GHz, column Optical grade
  - benchmark: dissipation_factor
    label: Loss tangent at 145 GHz, polycrystalline CVD diamond, RF grade
    value: 0.00001
    value_high: 0.0001
    bound: range
    unit: '-'
    scope: material
    conditions:
      grade: polycrystalline CVD diamond, RF grade
      frequency: 145 GHz
      unit_in_source: 10 - 100 (x 10-6)
    method: Range printed in a manufacturer properties table
    status: ground
    source: e6-optics
    where: Page 5, table CVD diamond properties, row Loss tangent 145 GHz, column RF grade
  - benchmark: fracture_stress
    label: Fracture stress, single-crystal CVD diamond, optical grade and optical plus
    value: 3500
    unit: MPa
    scope: material
    conditions:
      grade: single-crystal CVD diamond, optical grade and optical plus (same value printed for both)
      weibull_modulus: '2.5'
      unit_in_source: MPa, Weibull modulus printed in brackets
    method: Value printed in a manufacturer properties table with its Weibull modulus
    status: ground
    source: e6-optics
    where: Page 5, table CVD diamond properties, row Fracture stress (MPa) [Weibull modulus]
  - benchmark: sand_erosion
    label: Sand erosion, polycrystalline CVD diamond, optical grade
    value: 2.1
    unit: mg/kg
    scope: material
    conditions:
      grade: polycrystalline CVD diamond, optical grade
      sand: C300/600
      velocity: 100 m/s
      unit_in_source: mg kg-1 at 100 ms-1 C300/600 sand
    method: Value printed in a manufacturer properties table, with a stated spread of ± 0.6
    status: ground
    note: The brochure gives no single-crystal value for sand erosion.
    source: e6-optics
    where: Page 5, table CVD diamond properties, row Sand erosion
  - benchmark: emittance
    label: Emittance at 10 µm, CVD diamond, 573 K
    value: 0.02
    unit: '-'
    scope: material
    conditions:
      grade: polycrystalline and single-crystal CVD diamond (same value printed for both)
      wavelength: 10 µm
      temperature: 573 K
    method: Value printed in a manufacturer properties table
    status: ground
    note: At 773 K the same table prints 0.03.
    source: e6-optics
    where: Page 5, table CVD diamond properties, row Emittance at 10 µm, 573 K
  - benchmark: thermal_diffusivity
    label: Thermal diffusivity, Element Six Diafilm TM200, 300 K
    value: 11.1
    bound: lower
    unit: cm2/s
    scope: material
    conditions:
      grade: Element Six Diafilm TM200, polycrystalline CVD heat spreader
      temperature: 300 K
      unit_in_source: cm²/s, printed as greater than 11.1
    method: Lower limit printed in a trade article that reports Element Six product data
    status: ground
    source: mwrf-diafilm
    where: Thermal diffusivity at 300 K list, row TM200
corrosion:
  - environment: Corrosive chemicals and hostile environments
    headline: CVD diamond is chemically inert and the manufacturer says it can operate in corrosive environments.
    effect: Element Six says its CVD diamond components can operate in highly corrosive and hostile environments and that diamond ATR prisms give the longest lifetimes. The brochure gives no test data, so this is a manufacturer statement, not a measured corrosion rate.
    rating: none
    conditions:
      basis: manufacturer statement; no chemical, temperature or time given
    source: e6-optics
    where: Page 2, section Unparalleled chemical inertness
  - environment: Rain impact
    headline: Rain impact damage threshold velocity is printed as 525 m/s for polycrystalline optical grade.
    effect: Element Six prints a rain impact DTV of 525 m/s for polycrystalline optical grade and of 457 - 533 m/s for single crystal. The brochure does not define the abbreviation DTV or give the test set-up in its printed text.
    rating: low
    conditions:
      grade: polycrystalline optical grade (525) and single crystal (457 - 533)
      unit_in_source: m s-1
    source: e6-optics
    where: Page 5, table CVD diamond properties, row Rain impact DTV (m s-1)
  - environment: Sand erosion
    headline: Sand erosion is 2.1 ± 0.6 mg/kg at 100 m/s for polycrystalline optical grade.
    effect: Element Six prints a sand erosion value of 2.1 ± 0.6 mg kg-1 at 100 m s-1 with C300/600 sand for polycrystalline optical grade. The brochure gives no value for single crystal, and no exposure time is printed.
    rating: low
    conditions:
      grade: polycrystalline CVD diamond, optical grade
      sand: C300/600
      velocity: 100 m/s
    source: e6-optics
    where: Page 5, table CVD diamond properties, row Sand erosion
risks:
  hazards:
    - text: PubChem's record for the element carbon (CID 5462310) aggregates ECHA C&L notifications for carbon, EC 231-153-3, with GHS07, signal word 'Warning', H319 'Causes serious eye irritation' and H335 'May cause respiratory irritation'. A second ECHA notification for carbon, EC 610-410-7, is listed as Not Classified. These are element-level notifications, not a classification of CVD diamond.
      ghs:
        - H319
        - H335
      source: pubchem-carbon-ghs
      where: GHS Classification section, ECHA C&L entries (Reference 26 and Reference 29)
    - text: PACE Technologies safety data sheet for Diamond Powders (date revised 7/21/2025) is a metallographic abrasive SDS. It states 'Not a hazardous substance or mixture' under GHS, with pictogram, signal word and hazard statements all N/A, and gives precautionary statement 'P261-Avoid breathing dust.' Section 4 says the material is 'not likely to be hazardous by inhalation'. The SDS does not say the diamond is synthetic or CVD-grown.
      ghs: []
      source: pace-diamond-sds
      where: Section 2 Hazard(s) Identification; Section 4 First-Aid Measures, Inhalation; header date revised
  failure_risks:
    - mode: Sand erosion of an exposed diamond surface
      trigger: Sand impacting at 100 m/s, in the test used by Element Six
      consequence: Element Six prints 2.1 ± 0.6 mg/kg of mass loss for polycrystalline optical grade. The brochure does not say how much erosion would matter for a given part.
      severity: low
      source: e6-optics
      where: Page 5, row Sand erosion
    - mode: Fracture under load, with wide strength spread
      trigger: Tensile stress on a single-crystal part
      consequence: Element Six prints a fracture stress of 3500 MPa with a Weibull modulus of 2.5 for single-crystal optical grade and optical plus. The brochure does not explain what the modulus means for a part's strength.
      severity: moderate
      source: e6-optics
      where: Page 5, row Fracture stress (MPa) [Weibull modulus]
  side_effects: []
  handling:
    - text: Element Six says CVD diamond can be processed to virtually any shape, and that windows and mounts can be made with water or air cooling if required.
      source: e6-optics
      where: Page 2 section Sizes and shapes; page 4 section Collaboration in applications development
    - text: Element Six lists maximum sizes of up to Ø 135 mm and 3 mm thick for polycrystalline optical grades, and plates up to 7 x 7 x 2 mm for single crystal.
      source: e6-optics
      where: Page 2 section Sizes and shapes
  mitigations: []
uses:
  - application: thermal-control
    device: Heat spreaders for high-power GaN transistors, MMICs and laser diodes
    example: Element Six Diafilm heat spreaders are stated for high-power, high-density circuits, including GaN discrete transistors, MMICs and laser diodes.
    source: mwrf-diafilm
    where: Article, applications paragraph
  - application: optics-and-cameras
    device: Optical windows for high-power CO2 and solid-state lasers
    example: Element Six lists optical windows and lenses for high-power CO2 lasers and high-power solid-state lasers, and says CVD diamond windows allow much higher laser power densities than other materials.
    source: e6-optics
    where: Page 3, section Optical windows in high power lasers; page 4, table Example applications
  - application: electronics-and-chips
    device: RF and microwave windows in high-power gyrotrons
    example: Element Six says CVD RF diamond windows are used in nuclear fusion experiments, in gyrotrons above 2 MW and as containment windows in waveguides.
    source: e6-optics
    where: Page 4, section Optical microwave CVD diamond at the frontiers of science
  - application: thermal-control
    device: Heat sinks for high-power laser diodes and AlGaN/GaN HEMT transistors
    example: A 2019 open-access chapter lists CVD diamond heat sinking components for transistor high power devices and high power laser diodes, and names AlGaN/GaN HEMTs produced on CVD diamond substrates.
    source: intech-cvd-heat-sinks
    where: Section CVD diamond as a heat spreader or in devices
supply:
  - subject: Synthetic industrial diamond (manufactured bort, grit, dust and powder)
    producers: []
    ranking: China was the leading producer of synthetic industrial diamond in 2025, followed by the United States and Russia; these three produced about 99 % of the world's synthetic industrial diamond. Per-country shares are not printed.
    critical_lists: []
    recycling: 'USGS: in 2025 about 15 million carats of diamond bort, grit, dust and powder were recycled, and at least two companies recovered used industrial diamond material. Manufactured production was estimated at 160 million carats.'
    substitutes:
      - 'USGS: cubic boron nitride, fused aluminum oxide and silicon carbide can compete with industrial diamond in some applications.'
    source: usgs-mcs2026-diamond
    where: Domestic Production and Use; Events, Trends, and Issues; Recycling; Substitutes
  - subject: Natural industrial diamond (mine production, shown for contrast)
    producers:
      - country: Russia
        share_percent: 42
        year: 2025
      - country: Congo (Kinshasa)
        share_percent: 18
        year: 2025
      - country: Botswana
        share_percent: 14
        year: 2025
      - country: Zimbabwe
        share_percent: 13
        year: 2025
      - country: South Africa
        share_percent: 8
        year: 2025
    critical_lists: []
    recycling: Synthetic diamond accounts for more than 99 % of global industrial diamond production and consumption, and natural diamond for less than 1 % of industrial diamond used (USGS).
    substitutes: []
    source: usgs-mcs2026-diamond
    where: Events, Trends, and Issues (natural production shares as printed, 16 of 38 million carats worldwide); World Natural Industrial Diamond Mine Production and Reserves; World Resources
documents:
  - title: 'Element Six, Optics: CVD diamond brochure (March 2021)'
    type: datasheet
    url: https://terpconnect.umd.edu/~antonsen/ENEE681-lectures/element_six_optics_brochure_1.pdf
    year: 2021
  - title: Coherent, Single Crystal Diamond, Optical Grade (SCD-O) datasheet
    type: datasheet
    url: https://www.coherent.com/content/dam/coherent/site/en/resources/datasheet/optics/single-crystal-diamond-optical-grade.pdf
    year: 2026
  - title: Jack Browne, Diamond is precious for thermal dissipation (Microwaves & RF, 2 March 2017)
    type: report
    url: https://www.mwrf.com/technologies/article/21848133/diamond-is-precious-for-thermal-dissipation
    year: 2017
  - title: 'USGS Mineral Commodity Summaries 2026: Diamond (Industrial)'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-diamond.pdf
    year: 2026
  - title: 'Wikipedia: Diamond (crystal structure, synthesis)'
    type: database
    url: https://en.wikipedia.org/wiki/Diamond
  - title: PubChem compound record CID 5462310 (carbon element record)
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/compound/5462310
  - title: PACE Technologies, Safety Data Sheet, Diamond Powders (date revised 7/21/2025)
    type: sds
    url: https://www.metallographic.com/sds/Diamond-powders.pdf
    year: 2025
  - title: PubChem GHS Classification, compound record CID 5462310 (carbon), JSON view
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/5462310/JSON?heading=GHS+Classification
  - title: Vieira da Silva Neto, Fraga and Trava-Airoldi (2019), Development, Properties, and Applications of CVD Diamond-Based Heat Sinks
    type: paper
    url: https://intechopen.com/chapters/66249
    year: 2019
gaps:
  - No hazard classification for CVD diamond itself was found. The hazard entries use an SDS for a diamond abrasive powder, which does not say the diamond is synthetic, and PubChem's element-level ECHA notifications for carbon, which conflict with the SDS. Both are recorded side by side.
  - No CAS number for synthetic diamond was read. The PubChem name lookup returned CID 5462310, which is the carbon element record and not a diamond-specific entry.
  - No atomic-oxygen erosion or reaction data, and no outgassing or total mass loss test for CVD diamond, were found in the pages read in this run.
  - No oxidation limit or graphitisation temperature in air was found in the pages read, so the maximum service temperature is not recorded.
  - No radiation (total dose or displacement damage) data for CVD diamond were looked up.
  - The Element Six Diamond Handbook is cited on page 5 of the brochure but was not opened, so its references are not recorded.
  - The Diafilm TM150 and TM180 thermal conductivity values at 300 K and 425 K (printed in the trade article) were not entered; only TM100 and TM200 at 300 K are recorded. Thermal conductivity at 425 K is recorded for the Element Six optical and RF grades only.
  - Thermal conductivity at cryogenic temperatures and at 1000 K was not found in the pages read.
  - Wikipedia gives 900 to 2320 W m-1 K-1 as a range for identifying diamond with no temperature or condition stated, so it is not entered as a property.
  - Critical-mineral list status for industrial diamond was not read. The USGS diamond summary does not state a critical-mineral listing, and the 2025 USGS critical list was not checked in this run.
  - Per-country shares of synthetic industrial diamond production are not printed in the USGS summary; only the rank order and the combined share of about 99 % are recorded.
  - Element Six lists 1050 for Young's modulus with no unit on page 5; the GPa range from the Diafilm article is entered instead.
  - The Element Six nucleation and growth values (800 [10], 400 [15] and so on) and the 633 transmittance row were left out because the brochure does not print a clear unit or meaning for them.
  - Property names not in the canonical list (hardness, absorption_coefficient, birefringence, emittance, fracture_stress, sand_erosion, thermal_diffusivity, refractive_index_temperature_coefficient) use snake_case names. The Element Six rain impact DTV abbreviation is not defined in the brochure.
  - Only one open-access chapter (2019, IntechOpen) was read for CVD diamond heat sinks, and no peer-reviewed journal paper with measured CVD diamond data was read. A 2019 MDPI article (DOI path 2571-9637/5/1/8) appeared in search but could not be fetched, so it is not used.
sources:
  e6-optics:
    title: 'Element Six, Optics: CVD diamond brochure (March 2021), pages 2 to 5'
    url: https://terpconnect.umd.edu/~antonsen/ENEE681-lectures/element_six_optics_brochure_1.pdf
    year: 2021
    kind: datasheet
    license: Manufacturer brochure, cited, not reproduced
  coherent-scd-o:
    title: Coherent, Single Crystal Diamond, Optical Grade (SCD-O) datasheet
    url: https://www.coherent.com/content/dam/coherent/site/en/resources/datasheet/optics/single-crystal-diamond-optical-grade.pdf
    year: 2026
    kind: datasheet
    license: Manufacturer datasheet, cited, not reproduced
  mwrf-diafilm:
    title: Jack Browne, Diamond is precious for thermal dissipation, Microwaves & RF, 2 March 2017
    url: https://www.mwrf.com/technologies/article/21848133/diamond-is-precious-for-thermal-dissipation
    year: 2017
    kind: web
    license: Trade article reporting Element Six Diafilm data, cited, not reproduced
  usgs-mcs2026-diamond:
    title: Mineral Commodity Summaries 2026, Diamond (Industrial)
    id: USGS MCS 2026, February 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-diamond.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  wikipedia-diamond:
    title: Diamond (crystal structure, synthesis), Wikipedia
    url: https://en.wikipedia.org/wiki/Diamond
    kind: web
    license: CC BY-SA 4.0 (cited, not reproduced)
  pubchem-carbon:
    title: PubChem compound record CID 5462310 (carbon element record)
    id: CID 5462310
    url: https://pubchem.ncbi.nlm.nih.gov/compound/5462310
    kind: database
    license: public domain (NCBI)
  pace-diamond-sds:
    title: PACE Technologies, Safety Data Sheet, Diamond Powders (date revised 7/21/2025)
    url: https://www.metallographic.com/sds/Diamond-powders.pdf
    year: 2025
    kind: datasheet
    license: Manufacturer SDS, cited, not reproduced
  pubchem-carbon-ghs:
    title: PubChem compound record CID 5462310 (carbon), GHS Classification section, JSON view
    id: CID 5462310
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/5462310/JSON?heading=GHS+Classification
    kind: database
    license: public domain (NCBI)
  intech-cvd-heat-sinks:
    title: Vieira da Silva Neto, Fraga and Trava-Airoldi (2019), Development, Properties, and Applications of CVD Diamond-Based Heat Sinks
    id: DOI 10.5772/intechopen.85349
    url: https://intechopen.com/chapters/66249
    year: 2019
    kind: paper
    license: open-access chapter (IntechOpen), cited, not reproduced
license: CC-BY-4.0
updated: '2026-11-01'
review:
  status: draft
  method: assistant
  checked_values: 33
  unreachable: 1
  caveats: 5
  note: 'Values were read by an AI assistant on 2026-11-01 from the Element Six brochure (page 5 table read from a rendered image), the Coherent SCD-O datasheet, the Microwaves & RF article (WebFetch), the USGS Mineral Commodity Summaries 2026 diamond text, and Wikipedia (WebFetch). Added in the hazard and use pass: the PACE diamond powder SDS (rev. 7/21/2025), the PubChem GHS Classification JSON for CID 5462310, and the 2019 IntechOpen CVD diamond heat sink chapter. Unreachable: PubChem diamond page (browser check); MDPI page (403, and a mirror refused connection). Caveats: the Element Six and Coherent sources disagree on single-crystal birefringence and on the 1064 nm refractive index; the Young''s modulus unit comes from a trade article; the Diafilm values are from a trade article, not the datasheet; no peer-reviewed paper was read.'
story:
  risk_groups:
    - title: For people
      lead: The sources give two different pictures. An SDS for a diamond abrasive powder says the material is not a hazardous substance, and PubChem's element-level notifications for carbon carry eye and respiratory irritation statements.
      level: 1
      verdict: Mixed; no classification for CVD diamond itself was read
      points:
        - label: Substance
          line: PubChem's carbon element record aggregates ECHA notifications with GHS07, signal word Warning, H319 "Causes serious eye irritation" and H335 "May cause respiratory irritation". These are for carbon, not for CVD diamond.
        - label: Dust and handling
          line: The PACE SDS for diamond powders gives precautionary statement P261 "Avoid breathing dust." and says the material is not likely to be hazardous by inhalation. The brochure does not describe dust or powder hazards for the optical and RF grades; it describes the material as chemically inert.
    - title: If it fails
      lead: These are failure routes found in the sources. The sand erosion and fracture figures are measurements printed by the manufacturer.
      points:
        - label: Sand erosion
          line: Element Six prints 2.1 ± 0.6 mg/kg of sand erosion at 100 m/s for polycrystalline optical grade, with C300/600 sand.
        - label: Fracture
          line: Element Six prints a fracture stress of 3500 MPa for single-crystal optical grade, with a Weibull modulus of 2.5, and does not say what the modulus means for a part.
        - label: Rain
          line: Element Six prints a rain impact DTV of 525 m/s for polycrystalline optical grade and of 457 - 533 m/s for single crystal.
    - title: Handling and storage
      points:
        - label: Size
          line: Element Six lists polycrystalline optical windows up to Ø 135 mm and 3 mm thick, and single-crystal plates up to 7 x 7 x 2 mm.
        - label: Mounting
          line: Element Six says windows and mounts can be made with water or air cooling if required.
  why: CVD diamond has the highest thermal conductivity of any material, according to Element Six. Its polycrystalline optical grade is printed at greater than 2200 W/(m·K) at 300 K, and its RF grade at greater than 2000 W/(m·K) at 300 K. A Coherent single-crystal optical grade sheet prints at least 2200 W/(m·K) with no temperature given. That is why the material is used as a heat spreader under high-power electronics and as a window in high-power lasers.
  uses:
    - where: Heat spreaders
      line: Element Six Diafilm heat spreaders are stated for high-power, high-density circuits, including GaN discrete transistors, MMICs and laser diodes. The Diafilm TM200 grade is printed at greater than 2000 W/(m·K) at 300 K.
    - where: Laser windows
      line: Element Six lists optical windows for high-power CO2 and solid-state lasers, and says CVD diamond windows allow much higher laser power densities than other materials.
    - where: RF windows
      line: Element Six says CVD RF diamond windows are used in nuclear fusion experiments, in gyrotrons above 2 MW and as containment windows in waveguides.
    - where: Laser and power-electronics heat sinks
      line: A 2019 open-access chapter says CVD diamond heat sinks are used for high-power laser diodes and transistor high power devices, and names AlGaN/GaN HEMTs on CVD diamond substrates (Vieira da Silva Neto et al., 2019).
  can_do:
    - label: Carry heat
      value: greater than 2200 W/(m·K) at 300 K
      benchmark: thermal_conductivity
      line: Element Six prints greater than 2200 W/(m·K) at 300 K for polycrystalline optical grade and for single-crystal optical grade. At 425 K it prints greater than 1600 W/(m·K) for the polycrystalline optical grade.
    - label: Stay dimensionally stable
      value: 1.0 ppm/K at 300 K
      benchmark: cte
      line: The coefficient of thermal expansion is 1.0 ppm/K at 300 K and 4.4 ppm/K at 1000 K, per Element Six. The Diafilm article prints 1.0 ± 0.1 ppm/K at 300 K.
    - label: Weight
      value: 3.52 g/cm3
      benchmark: density
      line: Density is printed as 3.52 x 10³ kg m⁻³ in the Element Six brochure and as 3.52 x 10³ kg/m³ in the Diafilm article.
    - label: Pass light
      value: 71.4 % at 1 mm
      benchmark: transmittance
      line: Polycrystalline optical grade transmits 71.4 % through 1 mm of material over 8 to 200 µm, per Element Six.
    - label: Hard
      value: 81 ± 18 GPa
      benchmark: hardness
      line: Polycrystalline CVD diamond is printed at a hardness of 81 ± 18 GPa, and single crystal at 70 - 120 GPa.
  compare: The Element Six brochure prints thermal conductivity above 2000 W/(m·K) at 300 K for the RF and optical grades, and the Coherent single-crystal sheet prints at least 2200 W/(m·K), and the Diafilm article gives 1000 and 2000 W/(m·K) for the TM100 and TM200 grades. The two sources give different specific heat figures, 520 J/(kg·K) at 300 K in the trade article and 0.536 J/g-K at 25 °C on the Coherent sheet, so read them with their temperatures in view. For birefringence the Element Six table gives 1e-4 for its single-crystal optical grade, while the Coherent sheet gives less than 5e-5, so grades and sources need to be matched before comparing.
  compare_rows:
    - label: Thermal conductivity
      benchmark: thermal_conductivity
    - label: Density
      benchmark: density
    - label: Thermal expansion
      benchmark: cte
  handling:
    - Specify the grade, because polycrystalline and single-crystal values differ, and the RF grade is lower than the optical grade for thermal conductivity.
    - 'Check the size limits before design: Ø 135 mm by 3 mm for polycrystalline optical grade, and 7 x 7 x 2 mm for single crystal.'
    - Read the supplier's SDS for the exact product before use. The PACE SDS covers a diamond abrasive powder, not CVD plate or window material.
  good_for:
    - 'Heat spreading: greater than 2200 W/(m·K) at 300 K for the optical grades, per Element Six.'
    - 'High-power laser windows: absorption at 10.6 µm below 0.07 cm-1 for polycrystalline optical grade.'
    - 'Erosion resistance: sand erosion of 2.1 ± 0.6 mg/kg at 100 m/s for polycrystalline optical grade.'
  watch_out:
    - 'Size: polycrystalline optical windows top out at Ø 135 mm and 3 mm thick, and single-crystal plates at 7 x 7 x 2 mm.'
    - 'Strength spread: a Weibull modulus of 2.5 with a fracture stress of 3500 MPa for single crystal, and the brochure does not explain the scatter.'
    - No atomic-oxygen, oxidation or radiation data were read for this profile. The hazard entries come from an abrasive-powder SDS and element-level PubChem notifications, not from a CVD plate SDS.
  verdict: CVD diamond is printed at greater than 2200 W/(m·K) at 300 K for the Element Six optical grades and at least 2200 W/(m·K) on the Coherent sheet, and the Diafilm article gives greater than 2000 W/(m·K) at 300 K for the TM200 grade. Its size limits, the 2.5 Weibull modulus on fracture stress, and the missing CVD-specific hazard and space-environment data are the main gaps.
  recipe:
    line: Diamond is pure carbon with a cubic crystal structure (Wikipedia). Synthetic diamond can be grown from hydrocarbon gases by chemical vapour deposition (Wikipedia). Coherent describes its single-crystal optical grade as made by plasma-enhanced chemical vapour deposition (Coherent datasheet).
    parts:
      - name: Carbon
        symbol: C
        atoms: 1
        atomic_weight: 12.011
        role: The whole material. The PubChem carbon element record prints a molecular weight of 12.011.