Barium metal Ba

spore: profile
id: barium
spore_version: 0.2
family: alkali-and-alkaline-earth-metals
name: Barium metal
abbreviation: Ba
role: getter
category: metals
type: heavy-metals
summary: |
  Barium is a soft, silvery alkaline earth metal. It reacts with water, giving off hydrogen, and it oxidizes readily in moist air. Its spaceflight role comes from barium oxide, which is pressed into the tungsten emitters of dispenser cathodes that supply the electrons used by ion and Hall thrusters and by plasma contactors. Barium alloys with aluminium or magnesium also serve as getters that remove residual gases in electronic vacuum tubes.
best_for: Getter alloys and barium-impregnated electron emitters inside a sealed vacuum, where the metal is never exposed to water or air
weakest_at: 'Any contact with water or moist air: it reacts at once and releases hydrogen, and powdered barium reacts violently with air'
identity:
  formula: Ba
  cas: 7440-39-3
  crystal_system: cubic
  source: atsdr-2007
  where: 'Table 4-2, Barium column: CAS registry and Physical description (silvery-yellow metal; cubic)'
tags:
  environments:
    - low-earth-orbit
  stresses:
    - vacuum-and-outgassing
  applications:
    - electronics-and-chips
    - propulsion-and-tanks
    - structures
properties:
  - benchmark: density
    value: 3.51
    unit: g/cm3
    scope: material
    conditions:
      temperature: 20 C
    method: Value printed in the supplier safety data sheet
    status: ground
    source: aci-ba-sds
    where: 'Section 9, Physical and chemical properties: Density at 20 C'
  - benchmark: density
    value: 3.62
    unit: g/cm3
    scope: material
    conditions:
      temperature: not stated by source
    method: Value printed in the ATSDR profile
    status: ground
    note: The supplier sheet gives 3.51 g/cm3 at 20 C. The profile keeps both values and does not average them.
    source: atsdr-2007
    where: 'Table 4-2, Barium column: Density'
  - benchmark: melting_point
    value: 727
    unit: °C
    scope: material
    conditions:
      pressure: not stated by source
    method: Value printed in the ATSDR profile
    status: ground
    source: atsdr-2007
    where: 'Table 4-2, Barium column: Melting point'
  - benchmark: melting_point
    value: 725
    unit: °C
    scope: material
    conditions:
      pressure: not stated by source
    method: Value printed in the supplier safety data sheet
    status: ground
    note: The supplier sheet gives 725 C, 2 C below the ATSDR value. Both are kept.
    source: aci-ba-sds
    where: Section 9, Melting point/Melting range
  - benchmark: boiling_point
    value: 1897
    unit: °C
    scope: material
    conditions:
      pressure: not stated by source
    method: Value printed in the ATSDR profile
    status: ground
    note: The ATSDR table prints the row label as Boling point. The University of Waterloo page gives the same 1897 C, citing the CRC Handbook 91st edition. The supplier sheet disagrees (1640 C).
    source: atsdr-2007
    where: 'Table 4-2, Barium column: boiling point row'
  - benchmark: boiling_point
    value: 1640
    unit: °C
    scope: material
    conditions:
      pressure: not stated by source
    method: Value printed in the supplier safety data sheet
    status: ground
    note: Conflicts with the 1897 C in ATSDR and the Waterloo page. The profile does not choose between them.
    source: aci-ba-sds
    where: Section 9, Boiling point/Boiling range
  - benchmark: electrical_resistivity
    value: 34.3
    unit: microohm cm
    scope: material
    conditions:
      temperature: 300 K
      unit_in_source: 34.3 x 10-8 ohm m
    method: 'Printed as 34.3 x 10-8 ohm m and converted: 1 microohm cm equals 10-8 ohm m, so the number is unchanged'
    status: ground
    note: The page is an aggregator that does not attribute each value to a handbook.
    source: knowledgedoor-barium
    where: Electrical Resistivity (solid) entry at 300 K
  - benchmark: thermal_conductivity
    value: 18.4
    unit: W/(m·K)
    scope: material
    conditions:
      temperature: 295 K
    method: Value printed on the page, which marks each thermal conductivity entry as estimated
    status: calculated
    source: knowledgedoor-barium
    where: Thermal Conductivity (solid) entry at 295 K
  - benchmark: specific_heat
    value: 0.204
    unit: J/(g K)
    scope: material
    conditions:
      temperature: 298.15 K
      pressure: 1 bar
    method: Isobaric specific heat capacity printed on the page
    status: ground
    source: knowledgedoor-barium
    where: 'Specific heat: Isobaric Specific Heat Capacity row'
  - benchmark: cte
    value: 20.6
    unit: ppm/K
    scope: material
    conditions:
      temperature: not stated by source
    method: Printed as 20.6 x 10-6 K-1, which is the same as ppm/K
    status: ground
    source: webelements-physics
    where: 'Heat and conduction: Coefficient of linear thermal expansion'
  - benchmark: elastic_modulus
    value: 13
    unit: GPa
    scope: material
    conditions:
      temperature: not stated by source
    method: Young's modulus printed on the page
    status: ground
    source: webelements-physics
    where: 'Elastic properties: Young''s modulus'
  - benchmark: pauling_electronegativity
    label: Pauling electronegativity
    value: 0.89
    unit: '-'
    scope: material
    conditions:
      scale: Pauling
    method: Value printed on the page, which cites the CRC Handbook 91st edition
    status: ground
    note: Not in the canonical property file, so this snake_case name is used. Listed in gaps.
    source: uwaterloo-barium
    where: 'Atomic properties: Electronegativity'
  - benchmark: first_ionization_energy
    label: First ionization energy
    value: 5.211664
    unit: eV
    scope: material
    conditions:
      order: first ionization
    method: Value printed on the page
    status: ground
    note: Not in the canonical property file, so this snake_case name is used. Listed in gaps.
    source: knowledgedoor-barium
    where: 'Ionization Energies: I (1)'
  - benchmark: enthalpy_of_fusion
    label: Enthalpy of fusion
    value: 7.66
    unit: kJ/mol
    scope: material
    conditions:
      pressure: 1 atm
    method: Value printed on the page
    status: ground
    source: knowledgedoor-barium
    where: Enthalpy of Fusion entry
corrosion:
  - environment: Liquid water
    headline: Barium reacts violently with water and releases flammable hydrogen gas.
    effect: The supplier sheet says barium reacts violently with water and that contact liberates extremely flammable gases. ATSDR says the metal decomposes in water and evolves hydrogen gas.
    rating: severe
    conditions:
      form: bulk metal
    source: aci-ba-sds
    where: 'Section 2 (R14 Reacts violently with water) and Section 10 (Water: reacts violently)'
  - environment: Moist air
    headline: Barium oxidizes readily in moist air and takes on a silver-yellow colour.
    effect: Metallic barium is silvery-white but takes on a silver-yellow colour when exposed to air. It oxidizes readily in moist air, and in powdered form it reacts violently with air.
    rating: severe
    conditions:
      atmosphere: moist air
    source: atsdr-2007
    where: Section 4.2, Physical and chemical properties
  - environment: Air, once ignited
    headline: Once ignited, barium burns in air to give barium oxide and barium nitride.
    effect: Once ignited, barium metal burns in air to give a mixture of white barium oxide and barium nitride, Ba3N2.
    rating: severe
    conditions:
      temperature: not stated; the page describes ignition only
    source: webelements-chemistry
    where: Reaction of barium with air
  - environment: Dry argon
    headline: The supplier recommends handling under dry argon.
    effect: 'The supplier sheet gives a handling instruction only: handle under dry argon. It states no corrosion rate in dry argon.'
    rating: low
    conditions:
      atmosphere: dry argon
    source: aci-ba-sds
    where: Section 7, Handling and storage
  - environment: Fire-fighting media
    headline: Water, carbon dioxide and halogenated extinguishers are unsuitable for barium fires.
    effect: The supplier sheet lists water, carbon dioxide and halogenated extinguishers as unsuitable. Extinguishing powder is the suitable agent, and contact with water releases hydrogen.
    rating: severe
    conditions:
      state: burning or hot barium
    source: aci-ba-sds
    where: Section 5, Fire-fighting measures
risks:
  hazards:
    - text: Reacts violently with water. Contact with water liberates extremely flammable gases, and the sheet notes that the released hydrogen is explosive.
      ghs: []
      source: aci-ba-sds
      where: Section 2 (R14), Section 5 (Special hazard)
    - text: Classified with the old EU irritant symbol Xi. The sheet prints no GHS hazard statement (H-code).
      ghs: []
      source: aci-ba-sds
      where: Section 2, Hazard description
    - text: UN1400, Barium, hazard class 4.3.
      ghs: []
      source: aci-ba-sds
      where: Section 14, Transport information
    - text: In powdered form, barium reacts violently with air.
      ghs: []
      source: atsdr-2007
      where: Section 4.2, Physical and chemical properties
  failure_risks:
    - mode: Barium depletion ends cathode life
      trigger: Evolution and transport of barium away from the emitter surface of a barium-impregnated thermionic cathode
      consequence: NASA Glenn states that this process determines the entitlement lifetime of the cathode.
      severity: high
      source: nasa-kovaleski
      where: Abstract
    - mode: Hydrogen release on contact with water
      trigger: Water or moisture reaching bulk barium
      consequence: Liberates extremely flammable gas, which the sheet calls explosive hydrogen.
      severity: high
      source: aci-ba-sds
      where: Section 5 (Special hazard)
    - mode: Ignition of powdered barium
      trigger: Powdered barium exposed to air
      consequence: Reacts violently with air, so the powder is a fire hazard.
      severity: high
      source: atsdr-2007
      where: Section 4.2, Physical and chemical properties
  side_effects:
    - text: Reaction with water releases hydrogen gas, which can ignite.
      affects: Storage area and fire response
      source: aci-ba-sds
      where: Section 5 and Section 10
    - text: Burning barium gives barium oxide and barium nitride as fire residues.
      affects: Fire area
      source: webelements-chemistry
      where: Reaction of barium with air
  handling:
    - text: Handle and store under dry argon.
      source: aci-ba-sds
    - text: Keep water away. Use extinguishing powder for fires and do not use water.
      source: aci-ba-sds
    - text: Ship as UN1400, hazard class 4.3.
      source: aci-ba-sds
  mitigations:
    - text: Barium oxide pressed with tungsten in a matrix is the best-performing reservoir cathode material in the NASA Glenn work. The reservoir design aims at more than 100,000 hours of life.
      source: nasa-reservoir
      where: Abstract
uses:
  - application: electronics-and-chips
    device: Getter alloy in an electronic vacuum tube
    example: Barium alloys with aluminium or magnesium are used as getters in electronic tubes to remove residual gases.
    source: atsdr-2007
    where: Section 4.1, Chemical identity
  - application: propulsion-and-tanks
    device: Barium-impregnated hollow cathode in ion and Hall thrusters
    example: Hollow cathodes provide electrons for propellant ionization and neutralization in ion and Hall thrusters, and emit electron current in International Space Station plasma contactors.
    source: nasa-kovaleski
    where: Introduction, first paragraph
  - application: propulsion-and-tanks
    device: Miniature reservoir dispenser cathode
    example: NASA Glenn and FDE report a miniature reservoir cathode with an objective of more than 100,000 hours of life at high loading.
    source: nasa-reservoir
    where: Abstract
  - application: structures
    device: Deoxidizer for steel and other metals
    example: Barium is used as a deoxidizer for steel and other metals.
    source: atsdr-2007
    where: Section 4.1, Chemical identity
supply:
  - subject: Barium, mined as barite (barium sulfate)
    abundance: 'World barite mine production was 8,700 thousand metric tons in 2025 (rounded total; the United States is withheld). Reserves in thousand metric tons: China 120,000; India 51,000; Iran 100,000; Kazakhstan 85,000; Russia 12,000; Turkey 34,000. Identified barite resources in the United States are 150 million tons. Net import reliance is more than 75 percent. More than 90 percent of barite sold in the United States is a weighting agent in oil and gas drilling fluids. Barium metal is not a separate line in the USGS data.'
    producers:
      - country: India
        share_percent: 34.5
        year: 2025
      - country: China
        share_percent: 25.3
        year: 2025
      - country: Morocco
        share_percent: 11.5
        year: 2025
      - country: Kazakhstan
        share_percent: 8
        year: 2025
      - country: Iran
        share_percent: 3.4
        year: 2025
      - country: Mexico
        share_percent: 3.4
        year: 2025
      - country: Laos
        share_percent: 3
        year: 2025
      - country: Turkey
        share_percent: 3
        year: 2025
      - country: Russia
        share_percent: 2.6
        year: 2025
      - country: Pakistan
        share_percent: 1.1
        year: 2025
    critical_lists:
      - list: 'USGS 2025 final list of critical minerals: barite is listed; barium is not named separately'
        listed: true
    recycling: No recycling figure for barium was found in the sources read for this profile.
    substitutes:
      - 'For barite in drilling fluids (USGS): calcium carbonate, hematite, ilmenite and manganese tetroxide.'
    source: usgs-barite-2026
    where: Salient statistics and World Mine Production and Reserves table (2025 values); Substitutes section. Shares are computed by the editors as 2025 mine production divided by the rounded world total of 8,700 thousand tons. Critical list status from usgs-critical-2025.
story:
  recipe:
    line: Barium metal is the pure element, Ba, with one atom per formula unit. It is not an alloy in this profile. The supplier sheet says to handle it under dry argon.
    parts:
      - name: Barium
        symbol: Ba
        atoms: 1
        atomic_weight: 137.327
        role: The only element in the metal. The atomic weight is the value given by ATSDR for the element (molecular weight row, Table 4-2).
  why: Barium is a soft, silvery alkaline earth metal. Because it is so reactive, ATSDR says it does not exist as the metal in the environment. Its useful forms in the sources read are its getter alloys and its oxide. Barium alloys with aluminium or magnesium remove residual gases in electronic vacuum tubes. Barium oxide is pressed into the tungsten emitters of dispenser cathodes, which give electrons for ion and Hall thrusters. The metal must never meet water.
  uses:
    - where: Electron emitters for electric propulsion
      line: NASA reports that hollow cathodes with barium calcium aluminate impregnated tungsten emitters provide electrons for ion and Hall thrusters, and emit electron current in International Space Station plasma contactors. The lifetime of the cathode is set by the transport of barium away from its emitter surface.
    - where: Vacuum tubes and getters
      line: Barium alloys with aluminium or magnesium are used as getters in electronic tubes to remove residual gases. Barium is also used as a deoxidizer for steel and other metals.
  can_do:
    - label: Density
      value: 3.51 g/cm3
      line: The supplier sheet gives 3.51 g/cm3 at 20 C and ATSDR gives 3.62 g/cm3. The two sources differ, and the profile keeps both.
    - label: Melting point
      value: 727 °C
      line: ATSDR gives 727 C and the supplier sheet 725 C. The heat of fusion is 7.66 kJ/mol, as printed on the aggregator page.
    - label: Electrical resistivity
      value: 34.3 microohm cm at 300 K
      line: Resistivity as printed on the aggregator page, converted from 34.3 x 10-8 ohm m.
    - label: Specific heat
      value: 0.204 J/(g K)
      line: Isobaric specific heat capacity at 298.15 K and 1 bar, as printed on the aggregator page.
  compare: Barium is not a battery material, so the collection does not compare it with lithium cells. In the sources read for this profile, barium is used for its getter alloys and for barium oxide in emitters inside sealed vacuum systems. Its two sources give densities of 3.51 and 3.62 g/cm3, and its melting point is 727 C (ATSDR) or 725 C (supplier sheet).
  compare_rows:
    - label: Density
      benchmark: density
      scope: material
    - label: Melting point
      benchmark: melting_point
      scope: material
    - label: Electrical resistivity
      benchmark: electrical_resistivity
      scope: material
  handling:
    - Handle and store under dry argon. Keep it away from water and moist air.
    - Use extinguishing powder for fires. Water, carbon dioxide and halogenated extinguishers are unsuitable.
    - Ship as UN1400, hazard class 4.3.
  good_for:
    - Electron emitters in dispenser cathodes, which NASA has used for ion and Hall thrusters.
    - Getter alloys that remove residual gases in electronic vacuum tubes.
  watch_out:
    - It reacts violently with water and releases flammable hydrogen.
    - Powdered barium reacts violently with air.
    - The handbook values for the boiling point do not agree (1897 C and 1640 C), so check a primary table before using it.
  verdict: Barium is a useful getter metal, but it is hazardous to handle. The space uses in the sources read are of barium oxide in emitters inside vacuum hardware, not of bare barium metal.
  risk_groups:
    - title: For people
      level: 3
      verdict: Reacts violently with water; releases hydrogen
      lead: The supplier sheet describes barium as reacting violently with water and gives the old EU irritant classification. It prints no GHS hazard codes.
      points:
        - label: Water reaction
          line: Contact with water releases extremely flammable gas, which the sheet calls explosive hydrogen (R14 and Section 5).
        - label: Powder
          line: In powdered form barium reacts violently with air (ATSDR).
        - label: Transport
          line: Shipped as UN1400, hazard class 4.3.
    - title: Fire
      level: 3
      verdict: Use dry powder; never use water
      lead: Burning barium forms oxides and nitrides, and water, carbon dioxide and halogenated extinguishers are unsuitable.
      points:
        - label: Extinguishing
          line: Extinguishing powder is the suitable agent (Section 5 of the supplier sheet).
        - label: Residues
          line: Once ignited, barium burns in air to give barium oxide and barium nitride (WebElements).
    - title: Handling and storage
      points:
        - label: Storage
          line: Handle and store under dry argon, away from water and moist air (Section 7 of the supplier sheet).
        - label: Shipping
          line: Ship as UN1400, hazard class 4.3 (Section 14 of the supplier sheet).
license: CC-BY-4.0
updated: '2026-10-26'
review:
  status: draft
  method: assistant
  checked_values: 14
  unreachable: 2
  caveats: 3
  note: 'Read by an AI assistant on 2026-10-26: 14 property rows from 10 sources. Two melting points, two boiling points and two densities are kept as printed. PubChem and the UNR safety data sheet could not be opened.'
documents:
  - title: Barium safety data sheet (ACI Alloys)
    type: sds
    url: https://www.acialloys.com/wp-content/uploads/msds/ba.html
  - title: ATSDR Toxicological Profile for Barium
    type: report
    url: https://www.atsdr.cdc.gov/ToxProfiles/tp24-c4.pdf
    year: 2007
  - title: 'WebElements: Barium, physical properties'
    type: database
    url: https://www.webelements.com/barium/physics.html
  - title: 'WebElements: Barium, chemistry'
    type: database
    url: https://www.webelements.com/barium/chemistry.html
  - title: University of Waterloo chemistry page on barium (CRC Handbook 91st edition)
    type: database
    url: https://uwaterloo.ca/chemistry/node/700
  - title: 'Elements handbook: barium (aggregator page)'
    type: database
    url: https://www.knowledgedoor.com/2/elements_handbook/barium.html
  - title: 'USGS Mineral Commodity Summaries 2026: Barite'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-barite.pdf
    year: 2026
  - title: 'USGS: Final 2025 list of critical minerals (science snippet)'
    type: report
    url: https://www.usgs.gov/news/science-snippet/interior-department-releases-final-2025-list-critical-minerals
    year: 2025
  - title: 'NASA NTRS 20020013325: Life model of hollow cathodes using a barium calcium aluminate impregnated emitter'
    type: report
    url: https://ntrs.nasa.gov/api/citations/20020013325/downloads/20020013325.pdf
  - title: 'NASA NTRS 20020072844: Miniature reservoir cathode, an update (Vancil and Wintucky)'
    type: report
    url: https://ntrs.nasa.gov/api/citations/20020072844/downloads/20020072844.pdf
gaps:
  - 'Electrode potential against the standard hydrogen electrode: no source with the number was read in this run.'
  - 'Specific heat, vapour pressure at room temperature and heat of vaporization: the aggregator page lists them without a handbook attribution, so they are left out apart from specific heat.'
  - 'Lattice type and space group: the aggregator page gives allotropes and a nearest-neighbour distance (435 pm) but no lattice type. Only cubic is given, from ATSDR.'
  - 'GHS hazard codes (H-codes) for barium metal: the supplier sheet uses the old EU classification only. No GHS table for barium metal was read in this run.'
  - 'Health effects and toxicity of the metal and of soluble barium compounds: the ATSDR PDF could not be extracted beyond its physical and chemical section in this run.'
  - 'Boiling point: sources disagree (1897 C in ATSDR and the Waterloo page citing CRC 91st ed.; 1640 C in the supplier sheet). Not resolved here.'
  - 'Density: 3.51 g/cm3 (supplier) and 3.62 g/cm3 (ATSDR) disagree. Both are kept and no value is chosen.'
  - Enthalpy of fusion, first ionization energy and Pauling electronegativity are not names in the canonical property file. The snake_case names are used as stated above, and enthalpy_of_fusion is already used in the lithium profile.
  - 'Alloying of barium into lead, bearing or aluminium-barium alloys for structural use: no source with compositions was read. Only ATSDR getter alloys with aluminium and magnesium are cited.'
  - 'Recycled share of barium supply: not read.'
  - 'Designations (UNS, EN, ASTM and similar codes) for barium metal: none printed by the sources read, so none are listed.'
  - No image with a checked licence was read in this run, so no media entries are included.
sources:
  aci-ba-sds:
    title: 'Barium safety data sheet, ACI Alloys (Material Name: Barium)'
    url: https://www.acialloys.com/wp-content/uploads/msds/ba.html
    kind: datasheet
    license: supplier document
  atsdr-2007:
    title: Toxicological Profile for Barium and Barium Compounds, ATSDR (Table 4-2, physical and chemical properties)
    url: https://www.atsdr.cdc.gov/ToxProfiles/tp24-c4.pdf
    year: 2007
    kind: report
    license: public domain (US government)
  webelements-physics:
    title: 'WebElements: Barium, physical properties'
    url: https://www.webelements.com/barium/physics.html
    kind: database
    license: web database
  webelements-chemistry:
    title: 'WebElements: Barium, chemistry (reaction with air and water)'
    url: https://www.webelements.com/barium/chemistry.html
    kind: database
    license: web database
  uwaterloo-barium:
    title: University of Waterloo chemistry page on barium (values cite CRC Handbook of Chemistry and Physics, 91st edition)
    url: https://uwaterloo.ca/chemistry/node/700
    kind: database
    license: web page
  knowledgedoor-barium:
    title: 'Elements handbook: barium (aggregator, cites CRC 88th edition in its references without per-value attribution)'
    url: https://www.knowledgedoor.com/2/elements_handbook/barium.html
    kind: database
    license: web page
  usgs-barite-2026:
    title: 'Mineral Commodity Summaries 2026: Barite (USGS)'
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-barite.pdf
    year: 2026
    kind: report
    license: public domain (US government)
  usgs-critical-2025:
    title: 'USGS: Interior Department releases final 2025 list of critical minerals'
    url: https://www.usgs.gov/news/science-snippet/interior-department-releases-final-2025-list-critical-minerals
    year: 2025
    kind: web
    license: public domain (US government)
  nasa-kovaleski:
    title: Life model of hollow cathodes using a barium calcium aluminate impregnated emitter (NASA Glenn, NTRS 20020013325)
    url: https://ntrs.nasa.gov/api/citations/20020013325/downloads/20020013325.pdf
    kind: report
    license: public domain (US government)
  nasa-reservoir:
    title: Miniature Reservoir Cathode, an update (Vancil and Wintucky, FDE Inc. and NASA Glenn, NTRS 20020072844)
    url: https://ntrs.nasa.gov/api/citations/20020072844/downloads/20020072844.pdf
    kind: report
    license: public domain (US government)