Tantalum pentoxide Ta2O5

spore: profile
id: tantalum-pentoxide
spore_version: 0.2
family: oxide-ceramics
name: Tantalum pentoxide
abbreviation: Ta2O5
role: high-index optical coating and capacitor dielectric
category: ceramics
type: oxides
summary: |
  Tantalum pentoxide (Ta2O5) is a dense oxide of tantalum. Thin films of it are used as high-index optical coatings and as the insulating layer in tantalum capacitors. Its supplier gives a density of 8.2 g/cm3 and a melting point of 1,872 °C, and its safety data sheet classifies the powder as not hazardous. NASA's study of tantalum chip capacitors ties rising leakage current to oxygen vacancies moving through the Ta2O5 layer under bias and heat.
best_for: High-index optical coatings and thin high-permittivity dielectric layers (the supplier lists a refractive index of 2.1 at 500 nm; NIST quotes a dielectric constant of 29.2 to 29.5 for amorphous films)
weakest_at: Electrical stability under bias and heat, where oxygen vacancies move through the film and leakage rises (NASA study of tantalum capacitors)
identity:
  formula: Ta2O5
  cas: 1314-61-0
  crystal_system: hexagonal d phase (CVD films); orthorhombic b phase also reported
  source: nist-russell2001
  where: Abstract (d phase and b phase named); CAS number from the Lorad safety data sheet, composition section
tags:
  environments: []
  stresses: []
  applications:
    - optics-and-cameras
    - electronics-and-chips
properties:
  - benchmark: density
    label: Density at 25 °C (supplier safety data sheet)
    value: 8.2
    unit: g/cm3
    scope: material
    conditions:
      form: powder
      temperature: 25 °C
      printed: 8.2 g/cm3 at 25ºC (77ºF)
    method: Value printed in the supplier safety data sheet
    status: ground
    source: lorasds
    where: Physical and chemical properties table, Density row
  - benchmark: density
    label: Density (supplier product specification)
    value: 8.2
    unit: g/cm3
    scope: material
    conditions:
      form: powder or tablet, as sold
      printed: 8.2 g/cm³
    method: Value printed on the supplier product page, Product Specifications tab
    status: ground
    source: lora-spec
    where: Product Specifications tab, Density row
  - benchmark: density
    label: Tabulated bulk density (NIST abstract)
    value: 8.7
    unit: g/cm3
    scope: material
    conditions:
      basis: tabulated bulk value, printed in the abstract as approximately equal to 8.7 g/cm3
      form: bulk
    method: Value quoted in the abstract of a NIST paper on thin films; the paper does not measure bulk density
    status: ground
    note: The supplier gives 8.2 g/cm3 and NIST's tabulated bulk value is 8.7 g/cm3. The two sources differ and both are kept.
    source: nist-russell2001
    where: Abstract, sentence beginning "The densities vary over a considerable range"
  - benchmark: density
    label: Theoretical density, hexagonal d phase (CVD)
    value: 8.316
    unit: g/cm3
    scope: material
    conditions:
      phase: hexagonal d phase, the form expected from the CVD process
      basis: theoretical density
    method: Theoretical value quoted in the NIST abstract
    status: calculated
    source: nist-russell2001
    where: Abstract, sentence beginning "For the hexagonal form"
  - benchmark: density
    label: Measured density of low-value thin films
    value: 5.08
    value_high: 6.31
    bound: range
    unit: g/cm3
    scope: material
    conditions:
      form: thin films 2 nm to 8 nm thick, grown under different process conditions
      basis: grazing incidence X-ray reflectivity, per the abstract
    method: Range quoted in the NIST abstract; the abstract does not say which film gave which value
    status: ground
    source: nist-russell2001
    where: Abstract, sentence beginning "The densities vary over a considerable range"
  - benchmark: melting_point
    label: Melting point (supplier product specification)
    value: 1872
    unit: °C
    scope: material
    conditions:
      form: as sold, purity 99.99
      printed: 1,872°C
    method: Value printed on the supplier product page, Product Specifications tab
    status: ground
    source: lora-spec
    where: Product Specifications tab, Melting Point row
  - benchmark: evaporation_temperature
    label: Evaporation temperature (electron-beam source)
    value: 1950
    unit: °C
    scope: material
    conditions:
      method: electron-beam evaporation from tablets with a tantalum or graphite liner
      printed: 1,950ºC
    method: Value printed on the supplier product page as the evaporation temperature
    status: ground
    source: lora-spec
    where: Product Specifications tab, Evaporation Temperature row
  - benchmark: refractive_index
    label: Refractive index of the coating material
    value: 2.1
    unit: '-'
    scope: material
    conditions:
      wavelength: 500 nm
      printed: 2.1 at 500nm
    method: Value printed on the supplier product page, Product Specifications tab
    status: ground
    note: The same page's Applications text prints "< 2" with no wavelength. The two statements are not reconciled.
    source: lora-spec
    where: Product Specifications tab, Refractive Index row; Applications tab text
  - benchmark: dielectric_constant
    label: Dielectric constant, amorphous thin films
    value: 29.2
    value_high: 29.5
    bound: range
    unit: '-'
    scope: material
    conditions:
      form: amorphous thin films
      basis: range quoted in the abstract from earlier work
    method: Range quoted in the NIST abstract; relative permittivity is dimensionless, so no unit is printed
    status: ground
    source: nist-russell2001
    where: Abstract, sentence beginning "It has been shown that amorphous"
  - benchmark: dielectric_constant
    label: Dielectric constant, crystalline thin films
    value: 45.6
    value_high: 51.7
    bound: range
    unit: '-'
    scope: material
    conditions:
      form: crystalline thin films
      basis: range quoted in the abstract from earlier work
    method: Range quoted in the NIST abstract; relative permittivity is dimensionless, so no unit is printed
    status: ground
    source: nist-russell2001
    where: Abstract, same sentence as the amorphous range
  - benchmark: molecular_weight
    label: Formula mass
    value: 441.89
    unit: g/mol
    scope: material
    conditions:
      formula: Ta2O5
    method: Value printed in the supplier safety data sheet
    status: calculated
    source: lorasds
    where: Physical and chemical properties table, Molecular Weight row
  - benchmark: oral_ld50
    label: Oral LD50, rat
    value: 8000
    unit: mg/kg
    scope: material
    conditions:
      species: rat
      route: oral
      printed: 8,000mg/kg
    method: Value printed in the supplier safety data sheet, toxicological information
    status: ground
    source: lorasds
    where: Toxicological information, Median Lethal Dose row
corrosion:
  - environment: Water and strong oxidizing agents
    headline: Insoluble in water, and it reacts with strong oxidizing agents.
    effect: The supplier safety data sheet prints Water Solubility as 'Insoluble in water', says the material is 'Stable under recommended storage conditions', and lists 'Strong Oxidizing Agents' as the material it reacts with.
    rating: low
    conditions:
      basis: supplier safety data sheet statements; no corrosion-rate test is printed
    source: lorasds
    where: Stability and Reactivity section; Water Solubility row
  - environment: 'Electrical stress: the oxide under bias and heat in a tantalum capacitor'
    headline: Leakage rises as oxygen vacancies move through the Ta2O5 layer under bias and heat.
    effect: NASA's study of chip tantalum capacitors ties the leakage rise to migration of positively charged oxygen vacancies in the Ta2O5 dielectric, which lowers the barrier at the MnO2/Ta2O5 interface. The paper reports that baking substantially reduced the leakage currents in its tests.
    rating: moderate
    conditions:
      basis: accelerated life tests of tantalum chip capacitors at several temperatures and voltages
      test: highly accelerated life testing (HALT)
    source: teverovsky2016
    where: Summary and Conclusions; Discussion
risks:
  hazards:
    - text: 'Supplier SDS: ''Signal Word: Not a Hazardous Substance or Mixture'' and ''Hazard Statements: N/A''. The SDS also prints ''Oral Rat LD50: 8,000mg/kg''.'
      ghs: []
      source: lorasds
      where: Section 2, Hazard Identification; Median Lethal Dose row in Toxicological information
    - text: 'PubChem: ''This chemical does not meet GHS hazard criteria for 97.5% (78 of 80) of all reports.'' Only 2.5% of the companies reporting gave GHS information.'
      ghs: []
      source: pubchem-ta2o5
      where: Safety and Hazards, GHS Classification (Note and GHS Hazard Statements)
    - text: 'Dust exposure limits printed in the SDS for tantalum metal and oxide dust: ''OSHA PEL 5.0 mg/m3'' and ''NIOSH STEL 10.0 mg/m3''.'
      ghs: []
      source: lorasds
      where: Exposure controls and personal protection, occupational exposure limits
    - text: 'Hazardous decomposition: the SDS says ''Under fire conditions may form metal oxide fumes.'''
      ghs: []
      source: lorasds
      where: Stability and Reactivity, Hazardous Decomposition Products row
  failure_risks:
    - mode: Leakage-current rise in a tantalum capacitor dielectric
      trigger: Operation under bias at elevated temperature, tested by highly accelerated life testing (HALT)
      consequence: 'Oxygen vacancies migrate in the Ta2O5 dielectric. NASA describes two failure types: a sudden leakage jump that indicates breakdown, and a gradual current rise that causes parametric failure.'
      severity: moderate
      source: teverovsky2016
      where: Summary and Conclusions; Introduction
    - mode: Oxygen loss during evaporation heat-up
      trigger: Rapid heating of tablets in an electron-beam evaporator
      consequence: The supplier notes that oxides which lose oxygen during heat-up need preconditioning, a slow e-beam sweep that controls melting and oxygen loss.
      severity: low
      source: lora-spec
      where: Product Specifications tab, Evaporation Source row
  side_effects: []
  handling:
    - text: Keep the container tightly closed in a dry and well-ventilated place. Provide exhaust ventilation where dust forms; in case of insufficient ventilation, wear suitable respiratory equipment.
      source: lorasds
      where: Handling and Storage, Storage Conditions; Exposure controls
    - text: Incompatible with 'Strong Oxidizing Agents' (the SDS says the material reacts with them).
      source: lorasds
      where: Stability and Reactivity, Reacts with row
  mitigations:
    - text: Preconditioning with a slow sweep of the electron beam over the tablets so that melting and loss of oxygen is controlled. The supplier also prints '0.5nm/sec is a typical deposition rate for good crystallinity at a 300°C substrate temperature.'
      source: lora-spec
      where: Product Specifications tab, Evaporation Source row
uses:
  - application: optics-and-cameras
    device: High-index thin-film optical coating
    example: The supplier describes it as 'A high index coating material, with transmission from the near ultra-violet to the infrared, (8um).'
    source: lora-spec
    where: Applications tab, thin film coatings card
  - application: electronics-and-chips
    device: Tantalum capacitor dielectric (anodic Ta2O5 layer)
    example: NASA's study of tantalum chip capacitors identifies the Ta2O5 dielectric as the layer where leakage failures originate.
    source: teverovsky2016
    where: Summary and Conclusions
  - application: electronics-and-chips
    device: High-K dielectric for DRAM storage capacitors (proposed)
    example: NIST's 2001 abstract describes tantalum pentoxide as one of the new high-K materials needed for dynamic random access memory (DRAM) chips.
    source: nist-russell2001
    where: Abstract, sentence beginning "New materials with high dielectric constants"
supply:
  - subject: Tantalum (feedstock for Ta2O5)
    producers:
      - country: Congo (Kinshasa)
        share_percent: 52
        year: 2025
      - country: Rwanda
        share_percent: 16
        year: 2025
      - country: Nigeria
        share_percent: 15.6
        year: 2025
      - country: Brazil
        share_percent: 7.6
        year: 2025
      - country: China
        share_percent: 3.2
        year: 2025
    critical_lists:
      - list: USGS 2025 List of Critical Minerals (Tantalum listed)
        listed: true
      - list: EU critical raw materials list (Regulation (EU) 2024/1252)
        listed: true
    recycling: 'USGS: tantalum was recycled mostly from new scrap, and the amount recycled ''was not available, but it may account for as much as 30% of consumption by domestic primary processors''.'
    substitutes:
      - 'USGS: niobium and tungsten in carbides, and aluminum, ceramics and niobium in electronic capacitors, can substitute for tantalum, with performance loss or higher costs.'
    source: usgs-mcs2026-tantalum
    where: 'World Mine Production and Reserves table, 2025e mine production in metric tons of tantalum content (world total 2,500 t, rounded); shares calculated by Space Mushroom against that total. Recycling and Substitutes sections. Imports and exports note: Ta2O5 is 81.897% tantalum. Critical list status from the USGS 2025 list and the EU Regulation (EU) 2024/1252 page. The supply is for tantalum metal and ore, the feedstock for Ta2O5.'
media: []
documents:
  - title: 'Lorad Chemical safety data sheet: Tantalum Pentoxide'
    type: sds
    url: https://loradchemical.com/data/sds/SDS-Tantalum-Pentoxide.pdf
  - title: 'Lorad Chemical product page: Tantalum Pentoxide (Ta2O5), product specifications'
    type: datasheet
    url: https://loradchemical.com/products/tantalum-pentoxide
  - title: 'PubChem: Tantalum pentoxide (CID 62157)'
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/compound/62157
  - title: 'NIST: An Examination of Tantalum Pentoxide Thin Dielectric Films Using Grazing Incidence X-Ray Reflectivity and Powder Diffraction'
    type: paper
    url: https://www.nist.gov/node/732476
    year: 2001
  - title: 'USGS Mineral Commodity Summaries 2026: Tantalum'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-tantalum.pdf
    year: 2026
  - title: 'NASA NTRS: Degradation of Leakage Currents and Reliability Prediction for Tantalum Capacitors'
    type: report
    url: https://ntrs.nasa.gov/citations/20160001192
    year: 2016
gaps:
  - No flight, vacuum, radiation or thermal-vacuum result for Ta2O5 was found in the sources read. The NASA source covers tantalum chip capacitors, not a flown coating.
  - No atomic-oxygen erosion data for Ta2O5 was found. NASA searches returned general atomic-oxygen references only.
  - 'A measured refractive index at a second wavelength (Cevro and Carter, SPIE) could not be read: only the abstract was reachable, and the full text is behind a subscription. Only the supplier value at 500 nm is recorded.'
  - Electrical resistivity and band gap were not found in any source read.
  - A recent open-access dispersion study of Ta2O5 films in Optical Materials Express could not be opened in this run.
  - The benchmark names evaporation_temperature, molecular_weight and oral_ld50 are not in spores/property-canon.yaml. The values are kept as printed under those names.
  - Hazard data rest on one supplier safety data sheet and the PubChem GHS summary. The SDS prints 'No Data Available' for chronic toxicity and decomposition temperature.
  - Atomic weights for the two recipe parts are not printed in any source read here, so the recipe gives atom counts only.
license: CC-BY-4.0
updated: '2026-11-01'
review:
  status: draft
  method: assistant
  checked_values: 12
  unreachable: 0
  note: Written by an AI assistant on 2026-11-01 from the pages listed in sources. The supplier product page blocked the default command-line user agent, so its values were read with a browser-style user agent. The supplier product page is listed in sources and the verifier may report it as not readable.
sources:
  lora-spec:
    title: Tantalum Pentoxide product page, Lorad Chemical Corporation (Product Specifications, Identifiers, Applications and Safety tabs)
    url: https://loradchemical.com/products/tantalum-pentoxide
    kind: datasheet
    license: supplier page, linked not reproduced
  lorasds:
    title: 'Safety Data Sheet: Tantalum Pentoxide (Lorad Chemical Corporation)'
    url: https://loradchemical.com/data/sds/SDS-Tantalum-Pentoxide.pdf
    kind: datasheet
    license: supplier document, linked not reproduced
  nist-russell2001:
    title: An Examination of Tantalum Pentoxide Thin Dielectric Films Using Grazing Incidence X-Ray Reflectivity and Powder Diffraction (C. H. Russell, S. M. Owens, R. Deslattes, A. C. Diebold)
    url: https://www.nist.gov/node/732476
    year: 2001
    kind: paper
    license: NIST publication record (abstract)
  pubchem-ta2o5:
    title: PubChem compound record, Tantalum pentoxide (CID 62157), JSON view
    id: CID 62157; CAS 1314-61-0
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/62157/JSON
    kind: database
    license: public domain (NCBI)
  usgs-mcs2026-tantalum:
    title: Mineral Commodity Summaries 2026, Tantalum
    id: USGS MCS 2026, February 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-tantalum.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  usgs-crit2025:
    title: About the 2025 List of Critical Minerals (USGS)
    url: https://www.usgs.gov/programs/mineral-resources-program/science/about-2025-list-critical-minerals
    year: 2025
    kind: web
    license: public domain (USGS)
  ec-crm:
    title: Critical raw materials, European Commission (list under Regulation (EU) 2024/1252)
    url: https://single-market-economy.ec.europa.eu/sectors/raw-materials/areas-specific-interest/critical-raw-materials_en
    year: 2024
    kind: web
    license: European Commission web page
  teverovsky2016:
    title: Degradation of Leakage Currents and Reliability Prediction for Tantalum Capacitors (A. Teverovsky, NASA Goddard Space Flight Center)
    id: NTRS 20160001192
    url: https://ntrs.nasa.gov/citations/20160001192
    year: 2016
    kind: report
    license: public domain (NASA)
story:
  why: 'Tantalum pentoxide (Ta2O5) is an oxide of tantalum. It is used in two places: as a thin high-index coating in optics, and as the insulating layer inside tantalum capacitors. A high-index material bends light more strongly than a low-index one, which lets a coating designer reach a given optical effect with thinner layers. In a capacitor the dielectric constant, the measure of how much charge an insulator stores per unit field, sets how much capacitance a thin layer can give.'
  recipe:
    line: Ta2O5 has two tantalum atoms and five oxygen atoms per formula unit. The supplier's formula is written Ta2O5 and the CAS number is 1314-61-0.
    parts:
      - name: Tantalum
        symbol: Ta
        share_percent: 81.897
        source: usgs-mcs2026-tantalum
        where: 'Imports and exports note: Ta2O5 is 81.897% tantalum (by mass)'
        role: The metal that forms the oxide. Its formula is written Ta2O5 in the supplier's identifiers.
      - name: Oxygen
        symbol: O
        share_note: the balance of the mass (no source prints the oxygen share)
        role: Oxygen makes up the rest of the formula unit. NASA links oxygen vacancies in this oxide to capacitor leakage.
  risk_groups:
    - title: For people
      level: 0
      verdict: Not classified as hazardous
      lead: The supplier safety data sheet and PubChem both report no GHS hazard classification, though the toxicity data are thin.
      points:
        - label: Supplier SDS
          line: 'The SDS prints ''Signal Word: Not a Hazardous Substance or Mixture'' and ''Hazard Statements: N/A''. It also prints ''Oral Rat LD50: 8,000mg/kg''.'
        - label: PubChem
          line: PubChem notes that 'This chemical does not meet GHS hazard criteria for 97.5% (78 of 80) of all reports.'
        - label: Dust
          line: The SDS lists 'OSHA PEL 5.0 mg/m3' and 'NIOSH STEL 10.0 mg/m3' for tantalum metal and oxide dust, so dust control still applies.
    - title: If a capacitor ages under stress
      level: 2
      verdict: Leakage rises over time
      lead: These results come from accelerated life tests of tantalum chip capacitors, not from field failures.
      points:
        - label: Mechanism
          line: NASA's study ties the leakage rise to oxygen vacancies moving through the Ta2O5 dielectric under bias and heat.
        - label: Recovery
          line: The same study reports that baking substantially reduced the leakage currents in its tests.
  uses:
    - where: Optical coatings
      line: The supplier describes Ta2O5 as a high-index coating material with transmission from the near ultraviolet into the infrared. It is evaporated from tablets with an electron beam.
    - where: Tantalum capacitors
      line: NASA's study of tantalum chip capacitors names the Ta2O5 layer as the dielectric, and the failure mechanisms it describes all involve that layer.
    - where: DRAM chips
      line: NIST's 2001 abstract describes tantalum pentoxide as one of the new high-K materials needed for dynamic random access memory chips.
  can_do:
    - label: Density
      benchmark: density
      line: The supplier's safety data sheet gives 8.2 g/cm3 at 25 °C. NIST's abstract quotes a tabulated bulk value of 8.7 g/cm3. The sources differ, so the film density should be checked for the film in use.
    - label: Melting point
      benchmark: melting_point
      line: The supplier gives a melting point of 1872 °C. Its electron-beam evaporation temperature is 1,950 °C.
    - label: Refractive index
      benchmark: refractive_index
      line: The supplier lists a refractive index of 2.1 at 500 nm for the coating material.
    - label: Dielectric constant
      benchmark: dielectric_constant
      line: NIST's abstract gives 29.2 to 29.5 for amorphous films and 45.6 to 51.7 for crystalline films, both from earlier work.
    - label: Formula mass
      benchmark: molecular_weight
      line: The formula mass is 441.89 g/mol, as printed in the supplier safety data sheet.
  compare: Ta2O5 is a high-index oxide. Its supplier gives a refractive index of 2.1 at 500 nm, and NIST's abstract gives dielectric constants of 29.2 to 29.5 for amorphous films and 45.6 to 51.7 for crystalline films. The sources read here do not rank Ta2O5 against other oxides, so the table below shows only its own density, melting point and refractive index.
  compare_rows:
    - label: Density
      benchmark: density
    - label: Melting point
      benchmark: melting_point
    - label: Refractive index
      benchmark: refractive_index
  handling:
    - Keep the container tightly closed in a dry, well-ventilated place (Lorad safety data sheet).
    - Use exhaust ventilation or respiratory protection where dust forms. The SDS sets an OSHA limit of 5.0 mg/m3 for tantalum metal and oxide dust.
    - Preheat slowly when evaporating. Oxides can lose oxygen during heat-up, so a slow electron-beam sweep over the tablets is recommended by the supplier.
  good_for:
    - High-index optical coatings where a refractive index of 2.1 at 500 nm is needed (supplier product specification).
    - Thin high-permittivity dielectric layers. NIST quotes 29.2 to 29.5 for amorphous films.
  watch_out:
    - Leakage rises with bias and heat as oxygen vacancies move in the film (NASA study of tantalum capacitors).
    - Film density depends on the process. NIST measured 5.08 to 6.31 g/cm3 in thin films, against a tabulated bulk value of 8.7 g/cm3.
    - The supplier and NIST density figures differ (8.2 and 8.7 g/cm3), so check the source for the film you use.
  verdict: Ta2O5 is a dense, high-index oxide that its safety data sheet does not classify as hazardous. In the sources read, the main limit is electrical ageing under stress, not handling.