spore: profile
id: gallium
spore_version: 0.2
family: gallium
name: Gallium
abbreviation: Ga
role: semiconductor feedstock
category: metals
type: heavy-metals
summary: |
  Gallium (Ga) is a metal that melts near room temperature: the Netzsch safety data sheet gives 29.8 °C and the Periodic Table page gives 29.76 °C. The solid has a density of 5.904 g/cm3 at 20 °C (Netzsch). Most primary low-purity gallium is made in China, and the element matters mainly as feedstock for gallium arsenide and gallium nitride chips, LEDs and solar cells.
best_for: Feedstock for gallium arsenide and gallium nitride chips, LEDs and laser diodes, where the metal is converted into compound wafers (USGS)
weakest_at: 'Corrosion and handling: liquid gallium attacks aluminium, the metal melts near 29.8 °C, and the toxicology is only partly investigated'
identity:
  formula: Ga (elemental gallium, a metal)
  cas: 7440-55-3
  source: pubchem-gallium
  where: Names and Identifiers, Other Identifiers (CAS)
tags:
  environments: []
  stresses: []
  applications:
    - electronics-and-chips
    - optics-and-cameras
    - solar-arrays
properties:
  - benchmark: density
    label: Density of the solid
    value: 5.904
    unit: g/cm3
    scope: material
    conditions:
      temperature: 20 °C
      state: solid
    method: Value printed in the SDS physical properties table
    status: ground
    source: sds-netzsch
    where: Section 9 (Physical and chemical properties), row Density at 20°C
  - benchmark: density
    label: Density of the liquid
    value: 6.095
    unit: g/cm3
    scope: material
    conditions:
      state: liquid
      temperature: not stated on the page
    method: Value printed in the Bulk physical properties table
    status: ground
    source: periodictable
    where: Bulk physical properties, row Density (Liquid)
  - benchmark: melting_point
    label: Melting point (Periodic Table)
    value: 29.76
    unit: °C
    scope: material
    conditions:
      pressure: not stated on the page
    method: Value printed in the Thermal properties table
    status: ground
    source: periodictable
    where: Thermal properties, row Melting Point
  - benchmark: melting_point
    label: Melting point (PubChem)
    value: 29.78
    unit: °C
    scope: material
    conditions:
      basis: PubChem experimental property, value as printed
    method: Value printed in the PubChem experimental properties record
    status: ground
    note: Differs from the Periodic Table value (29.76 °C) in the second decimal place; both are kept.
    source: pubchem-gallium
    where: Experimental Properties, Melting Point
  - benchmark: melting_point
    label: Melting point (Netzsch SDS)
    value: 29.8
    unit: °C
    scope: material
    conditions:
      pressure: not stated on the page
    method: Value printed in the SDS physical properties table
    status: ground
    note: The SDS prints 29.8°C with no space; the same SDS also notes a low melting point in its hazards section.
    source: sds-netzsch
    where: Section 9, row Melting point / Melting range
  - benchmark: boiling_point
    value: 2204
    unit: °C
    scope: material
    conditions:
      pressure: 760 mm Hg
    method: Value printed in the PubChem experimental properties record
    status: ground
    source: pubchem-gallium
    where: Experimental Properties, Boiling Point (printed as 2204 °C @760 [mm Hg])
  - benchmark: thermal_conductivity
    value: 29
    unit: W/(m K)
    scope: material
    conditions:
      temperature: not stated on the page
    method: Value printed in the Thermal properties table
    status: ground
    source: periodictable
    where: Thermal properties, row Thermal Conductivity (also under Bulk physical properties)
  - benchmark: specific_heat
    value: 371
    unit: J/(kg K)
    scope: material
    conditions:
      phase: solid (the page notes that the value is given for the solid phase)
    method: Value printed in the Thermal properties table
    status: ground
    source: periodictable
    where: Thermal properties, row Specific Heat and its note
  - benchmark: cte
    label: Coefficient of linear thermal expansion (page label Thermal Expansion)
    value: 0.00012
    unit: K-1
    scope: material
    conditions:
      temperature: not stated on the page
    method: Value printed as 0.00012 K -1 in the Thermal properties table
    status: ground
    source: periodictable
    where: Thermal properties, row Thermal Expansion
  - benchmark: heat_of_fusion
    label: Heat of fusion (not in the canonical list)
    value: 5.59
    unit: kJ/mol
    scope: material
    conditions:
      state_change: solid to liquid at the melting point
    method: Value printed in the Thermal properties table
    status: ground
    source: periodictable
    where: Thermal properties, row Heat of Fusion
  - benchmark: brinell_hardness
    label: Brinell hardness (not in the canonical list)
    value: 60
    unit: MPa
    scope: material
    conditions:
      test: Brinell; test load and ball size not stated on the page
    method: Value printed in the Bulk physical properties table
    status: ground
    source: periodictable
    where: Bulk physical properties, row Brinell Hardness
  - benchmark: mohs_hardness
    label: Mineral (Mohs) hardness (printed with no unit)
    value: 1.5
    unit: '-'
    scope: material
    conditions:
      scale: Mohs mineral hardness, as printed
    method: Value printed in the Hardnesses section; the page gives no unit
    status: ground
    source: webelements
    where: Hardnesses, row Mineral hardness (printed as 1.5 (no units))
  - benchmark: speed_of_sound
    label: Speed of sound (not in the canonical list)
    value: 2740
    unit: m/s
    scope: material
    conditions:
      temperature: not stated on the page
    method: Value printed in the Bulk physical properties table
    status: ground
    source: periodictable
    where: Bulk physical properties, row Speed of Sound
  - benchmark: electronegativity
    label: Electronegativity (not in the canonical list; printed with no unit)
    value: 1.81
    unit: '-'
    scope: material
    conditions:
      scale: not stated on the page
    method: Value printed in the Reactivity table; the page gives no unit
    status: ground
    source: periodictable
    where: Reactivity, row Electronegativity
  - benchmark: atomic_weight
    label: Standard atomic weight (not in the canonical list; printed with no unit)
    value: 69.723
    unit: '-'
    scope: material
    uncertainty: (1)
    conditions:
      basis: standard atomic weight of natural gallium
    method: Value printed in the NIST table of atomic weights for gallium
    status: ground
    source: nist
    where: Table for gallium, Standard Atomic Weight column (printed as 69.723(1))
  - benchmark: atomic_radius
    label: Atomic radius (not in the canonical list)
    value: 136
    unit: pm
    scope: material
    conditions:
      basis: atomic radius as printed by the Periodic Table page
    method: Value printed in the Atomic dimensions and structure table
    status: ground
    source: periodictable
    where: Atomic dimensions and structure, row Atomic Radius
  - benchmark: vapor_pressure
    label: Vapour pressure (not in the canonical list)
    value: 1
    unit: Pa
    scope: material
    conditions:
      temperature: 1037 °C
    method: Value printed in the PubChem experimental properties record (printed as 1 Pa @ 1037 °C; the record gives further pairs at higher temperatures)
    status: ground
    source: pubchem-gallium
    where: Experimental Properties, Vapor Pressure
  - benchmark: crustal_abundance
    label: Abundance in Earth's crust (not in the canonical list)
    value: 0.0019
    unit: '%'
    scope: material
    conditions:
      basis: percent by mass in the Earth's crust, as printed
    method: Value printed in the Abundances table
    status: ground
    source: periodictable
    where: Abundances, row % in Earth's Crust
  - benchmark: isotopic_abundance
    label: Natural abundance of gallium-69 (not in the canonical list)
    value: 60.108
    unit: '%'
    scope: material
    conditions:
      isotope: 69Ga
      basis: natural isotopic composition
    method: Value printed in the Isotopic Abundances table
    status: ground
    source: periodictable
    where: Isotopic Abundances, row 69 Ga
  - benchmark: isotopic_abundance
    label: Natural abundance of gallium-71 (not in the canonical list)
    value: 39.892
    unit: '%'
    scope: material
    conditions:
      isotope: 71Ga
      basis: natural isotopic composition
    method: Value printed in the Isotopic Abundances table
    status: ground
    source: periodictable
    where: Isotopic Abundances, row 71 Ga
  - benchmark: ld50_oral
    label: Acute oral LD50 of gallium (not in the canonical list; a range as printed)
    value: 50
    value_high: 300
    bound: range
    unit: mg/kg
    scope: material
    conditions:
      component: Gallium
      species: not stated in the SDS
      route: oral
    method: Range printed in the SDS acute toxicity table
    status: ground
    note: The SDS gives no species or test method, so treat the range as a rough screening figure.
    source: sds-labally
    where: Section 11, Acute toxicity table, LD50 Oral for Gallium
corrosion:
  - environment: Dry air at room temperature
    headline: Gallium is stable in dry air.
    effect: The Isoflex SDS says gallium is stable in dry air and tarnishes in moist air or oxygen. The PubChem record says the same for moist air.
    rating: none
    conditions:
      temperature: room temperature
      exposure: not stated
    source: sds-isoflex
    where: Section 10, Chemical Stability
  - environment: Moist air or oxygen
    headline: Gallium tarnishes in moist air.
    effect: The Isoflex SDS says gallium 'tarnishes in moist air or oxygen', and PubChem says 'in moist air it tarnishes'. Tarnish is a surface change; the sources give no depth or rate.
    rating: low
    conditions:
      exposure: moist air or oxygen; time not stated
    source: sds-isoflex
    where: Section 10, Chemical Stability; the same point appears in the PubChem Air and Water Reactions entry
  - environment: Aluminium and aluminium alloys
    headline: Gallium forms an amalgam with aluminium alloys and corrodes aluminium.
    effect: PubChem records gallium as corrosive to aluminum and says it forms an amalgam with aluminum alloys. The rating is our reading of that wording; the record gives no exposure time, temperature or rate.
    rating: severe
    conditions:
      temperature: not stated
      exposure: not stated
    source: pubchem-gallium
    where: Hazards Summary; Stability and Reactivity, Hazardous Reactivities and Incompatibilities
  - environment: Most metals, including at elevated temperature
    headline: The Isoflex SDS says gallium is corrosive to most metals.
    effect: The Isoflex SDS says gallium 'will dissolve the metal' and is 'corrosive to most metals'. PubChem says gallium is very corrosive to most metals at elevated temperature, but the temperature range printed in that record is garbled, so no temperature is used here.
    rating: moderate
    conditions:
      temperature: elevated, not given as a number
      exposure: not stated
    source: sds-isoflex
    where: Section 6, Methods for cleaning up
risks:
  hazards:
    - text: 'PubChem''s aggregated GHS record for gallium lists H290, H302, H314 and H412 across company notifications, with the signal word Danger. The record says: ''This chemical does not meet GHS hazard criteria for 2.3% (9 of 388) of reports.'''
      ghs:
        - H290
        - H302
        - H314
        - H412
      source: pubchem-gallium
      where: Hazards Identification, GHS Classification
    - text: The Netzsch safety data sheet classifies gallium as H290 (may be corrosive to metals), H302 (harmful if swallowed) and H412 (harmful to aquatic life with long lasting effects), with the signal word Warning.
      ghs:
        - H290
        - H302
        - H412
      source: sds-netzsch
      where: Sections 2.1 and 2.2 (Classification and Label elements)
    - text: The Lab Alley safety data sheet lists corrosive to metals and acute oral toxicity classes, the signal word Warning, and the statements 'May be corrosive to metals. Harmful if swallowed.'
      ghs: []
      source: sds-labally
      where: Section 2.1 and 2.2 (Classification and Label elements)
    - text: The Isoflex safety data sheet describes gallium as irritating to the eyes, respiratory system and skin, and says its toxicological properties have not been fully investigated. The Netzsch sheet describes a caustic effect on skin and mucous membranes, so the two sheets disagree.
      ghs: []
      source: sds-isoflex
      where: Section 2, Emergency Overview and Potential Health Effects; Netzsch Section 11
  failure_risks:
    - mode: Melting in a warm environment
      trigger: Temperature rising above the melting point of 29.8 °C given in the Netzsch SDS
      consequence: The solid turns liquid and can flow. The Netzsch SDS warns that gallium has a low melting point and that melted gallium has to be handled with appropriate care.
      severity: moderate
      source: sds-netzsch
      where: Section 2.3 (Other hazards) and Section 9
    - mode: Attack on aluminium parts and tools
      trigger: Contact with aluminium or aluminium alloy parts, or with aluminium tools
      consequence: Amalgam formation and corrosion of the aluminium, as recorded by PubChem
      severity: high
      source: pubchem-gallium
      where: Hazardous Reactivities and Incompatibilities; Accidental Release Measures
    - mode: Violent reaction with halogens and strong oxidisers
      trigger: Contact with halogens such as chlorine, or with hydrogen peroxide
      consequence: PubChem reports a violent or vigorous reaction with halogens, and a potentially explosive reaction with hydrogen peroxide plus hydrochloric acid.
      severity: high
      source: pubchem-gallium
      where: Stability and Reactivity, Reactivity Profile; Hazardous Reactivities and Incompatibilities
  side_effects: []
  handling:
    - text: Keep the container tightly closed, under an inert atmosphere, in a dry and well-ventilated place, and refrigerated to maintain quality.
      source: sds-labally
      where: Section 7.2 (Conditions for safe storage)
    - text: Do not use steel or aluminium tools or equipment with gallium, and cover spills with non-combustible material, as PubChem's safety record advises.
      source: pubchem-gallium
      where: Accidental Release Measures, Preventive Measures
    - text: Avoid generating dust and provide ventilation where the metal is cleaned up or handled.
      source: sds-isoflex
      where: Section 6 (Methods for cleaning up) and Section 7 (Handling and storage)
  mitigations: []
uses:
  - application: electronics-and-chips
    device: Integrated circuits and optoelectronic devices made from gallium arsenide and gallium nitride
    example: USGS reports that integrated circuits are the largest domestic use of gallium, ahead of optoelectronic devices.
    source: usgs-mcs2026-gallium
    where: Domestic Production and Use
  - application: optics-and-cameras
    device: Laser diodes, light-emitting diodes and photodetectors made from gallium arsenide or gallium nitride
    example: USGS says optoelectronic devices were used in aerospace applications, consumer goods, industrial equipment, medical equipment and telecommunications equipment.
    source: usgs-mcs2026-gallium
    where: Domestic Production and Use
  - application: solar-arrays
    device: Gallium arsenide solar cells
    example: USGS says silicon is the principal competitor with GaAs in solar-cell applications.
    source: usgs-mcs2026-gallium
    where: Substitutes
supply:
  - subject: Gallium
    abundance: 'Earth''s crust 0.0019 % by mass (Periodic Table). USGS: ''The average gallium content of bauxite is 50 parts per million.'''
    producers:
      - country: China
        share_percent: 99
        year: 2025
      - country: Japan
        year: 2025
      - country: Russia
        year: 2025
    critical_lists:
      - list: 'USGS 2025 List of Critical Minerals (entry: Gallium, used in semiconductors)'
        listed: true
      - list: EU critical raw materials list (Regulation (EU) 2024/1252)
        listed: true
    recycling: 'USGS: ''Old scrap, none.'' New scrap from the manufacture of GaAs-based devices is reprocessed to recover high-purity gallium at one facility in New York.'
    substitutes:
      - 'USGS: silicon is the principal competitor with GaAs in solar-cell applications.'
      - 'USGS: no effective substitutes exist for GaAs and GaN in the defence-related applications where they are used.'
    source: usgs-mcs2026-gallium
    where: 'World Low-Purity Production table; Events, Trends, and Issues (the sentence ''China accounted for 99% of worldwide primary low-purity gallium production'' prints no year, so 2025 is the reporting year used here; Japan and Russia are named in the same paragraph); Recycling; Substitutes. Critical lists: USGS 2025 final list page and European Commission page (see sources).'
media: []
documents:
  - title: 'USGS Mineral Commodity Summaries 2026: Gallium'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-gallium.pdf
    year: 2026
  - title: PubChem compound record, Gallium (CID 5360835)
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/compound/5360835
    year: 2026
  - title: Lab Alley safety data sheet, Gallium Metal 99.99%
    type: sds
    url: https://media.laballey.com/docbuilder/gallium-metal-9999-safety-data-sheet-66a115cc271fd.pdf
    year: 2024
  - title: NETZSCH MSDS E Gallium, version 6.0
    type: sds
    url: https://analyzing-testing.netzsch.com/_Resources/Persistent/6/b/1/b/6b1b7407656ada04cf7ff8df6636921100b743d0/MSDS%20E%20Gallium%206.0.pdf
    year: 2022
  - title: ISOFLEX safety data sheet, Gallium, Enriched Gallium (version 1.3)
    type: sds
    url: https://www.isoflex.com/docman-all-categories/sds/527-gallium-rev-4/file
    year: 2024
  - title: NIST Atomic Weights and Isotopic Compositions for Gallium
    type: database
    url: https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=Ga&ascii=html&isotype=some
gaps:
  - Electrical resistivity and electrical conductivity are printed in exponent form on the pages read (WebElements and the Periodic Table), so no value is recorded for them.
  - Young's modulus, shear and bulk modulus and Vickers hardness have no data on the WebElements page; no tensile, creep or fatigue data for solid gallium were found in the sources read.
  - The WebElements coefficient of linear thermal expansion is printed in exponent form and is not used; the Periodic Table value is recorded instead, with its own page label.
  - The Lab Alley SDS gives its melting point in degrees Celsius and Fahrenheit and gives 'No information available' for density, so neither is used as a row from that sheet.
  - Liquid density has no stated temperature on the Periodic Table page, and PubChem gives a liquid value without a printed unit, so only the Periodic Table value is recorded for the liquid.
  - The electronegativity scale is not stated on the Periodic Table page.
  - No corrosion-rate, exposure-time or test data for gallium on aluminium or other metals were found in the sources read; the corrosion ratings are qualitative readings of the sources' wording.
  - No flight, vacuum, radiation or space-environment data for elemental gallium were found in the sources read. Its space use is through gallium arsenide and gallium nitride, which have their own profiles.
  - No UNS, EN or other grade designation applies to gallium metal in the sources read, so none is listed.
  - The USGS production table text is partly garbled in the PDF; the China share is taken from the sentence in the Events section, and no 2025 share is computed from the table.
  - The USGS 2025 critical-minerals and EU critical-raw-materials list entries were read from a web summary of each page and should be checked against the printed list before they are cited in a report.
  - The NIST table prints the isotope composition in a spaced form that does not parse cleanly, so the Periodic Table isotope values are used instead.
  - The PubChem record gives a single vapour-pressure pair (1 Pa at 1037 °C) in the text read, with other pairs at higher temperatures that were not used.
  - The heat of fusion value is from the Periodic Table only; no second source for it was opened.
license: CC-BY-4.0
sources:
  webelements:
    title: 'WebElements Periodic Table: Gallium, physical properties'
    id: WebElements, Gallium - 31 Ga physical properties
    url: https://www.webelements.com/gallium/physics.html
    year: 2026
    kind: database
    license: WebElements (Mark Winter), all rights reserved; cited, not reproduced
  periodictable:
    title: 'Periodic Table (periodictable.com): Gallium technical data'
    id: Element 31 data page
    url: https://periodictable.com/Elements/031/data.html
    kind: database
    license: Web page, cited not reproduced; values from Mathematica ElementData per the page
  nist:
    title: NIST Atomic Weights and Isotopic Compositions for Gallium
    id: NIST Physical Measurement Laboratory, standard atomic weight
    url: https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=Ga&ascii=html&isotype=some
    kind: database
    license: US government data, public domain
  pubchem-gallium:
    title: PubChem compound record, Gallium (CID 5360835), JSON view
    id: CID 5360835; CAS 7440-55-3
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/5360835/JSON
    kind: database
    license: public domain (NCBI)
  usgs-mcs2026-gallium:
    title: Mineral Commodity Summaries 2026, Gallium
    id: USGS MCS 2026, February 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-gallium.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  sds-labally:
    title: Lab Alley safety data sheet, Gallium Metal 99.99%
    id: Issue date 07/22/2024, revision 0
    url: https://media.laballey.com/docbuilder/gallium-metal-9999-safety-data-sheet-66a115cc271fd.pdf
    year: 2024
    kind: datasheet
    license: supplier document, linked not reproduced
  sds-netzsch:
    title: NETZSCH safety data sheet, MSDS E Gallium 6.0 (EC 1907/2006 format)
    id: Version 6.0, revision date 02.08.2022
    url: https://analyzing-testing.netzsch.com/_Resources/Persistent/6/b/1/b/6b1b7407656ada04cf7ff8df6636921100b743d0/MSDS%20E%20Gallium%206.0.pdf
    year: 2022
    kind: datasheet
    license: supplier document, linked not reproduced
  sds-isoflex:
    title: ISOFLEX safety data sheet, Gallium, Enriched Gallium (version 1.3)
    id: Revision date 05/10/2024, revision number 3
    url: https://www.isoflex.com/docman-all-categories/sds/527-gallium-rev-4/file
    year: 2024
    kind: datasheet
    license: supplier document, linked not reproduced
  usgs-crit2025:
    title: About the 2025 List of Critical Minerals (USGS)
    id: Final 2025 List of Critical Minerals
    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), Regulation (EU) 2024/1252
    id: 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, cited not reproduced
updated: '2026-11-01'
review:
  status: draft
  method: assistant
  checked_values: 21
  unreachable: 0
  caveats: 3
  note: Written by an AI assistant on 2026-11-01 from pages read in this run. Three melting-point values and two density values differ or lack a printed unit; each is kept with its source. Values with exponent form are left out.
story:
  recipe:
    line: 'Gallium is a single element, symbol Ga. The USGS says primary gallium is recovered predominantly as a byproduct of processing bauxite ores, with some from zinc-processing residues. Natural gallium is a mix of two stable isotopes: 69Ga at 60.108% and 71Ga at 39.892% (Periodic Table).'
    parts:
      - name: Gallium
        symbol: Ga
        atoms: 1
        atomic_weight: 69.723
        role: The whole metal. It is a single element, so there is no alloying element in this profile; the atomic weight is the NIST standard value.
  risk_groups:
    - title: For people
      level: 1
      verdict: Harmful if swallowed; corrosive to metals
      lead: The safety data sheets read for this profile give a Warning label with H290 and H302. PubChem's aggregated reports add H314 (severe skin burns) with a Danger label.
      points:
        - label: Ingestion
          line: The Lab Alley sheet gives an oral LD50 range of 50 to 300 mg/kg for gallium, with no species or test named. The sheets classify it as harmful if swallowed (H302).
        - label: Skin and eyes
          line: The Isoflex sheet calls the metal irritating to the eyes, respiratory system and skin. The Netzsch sheet describes a caustic effect on skin and mucous membranes. The two sheets do not agree.
        - label: Dust and fire
          line: Avoid dust. In a fire, decomposition gives irritating and toxic fumes and gases, according to the Isoflex sheet.
    - title: If the metal melts or spills
      level: 2
      verdict: Liquid metal attacks aluminium
      lead: Above its melting point the metal is a liquid, and it can attack other metals.
      points:
        - label: Aluminium
          line: PubChem says gallium is corrosive to aluminum and forms an amalgam with aluminum alloys. It advises against steel and aluminum tools.
        - label: Cleanup
          line: The Isoflex sheet advises cooling spilled metal so that it solidifies before cleanup, and protecting metal construction from contact.
    - title: Handling and storage
      lead: Store the metal closed, dry and refrigerated, and keep it away from metals and oxidising agents.
      points:
        - label: Storage
          line: The Lab Alley sheet calls for a tightly closed container under an inert atmosphere and refrigeration.
        - label: Moist air
          line: Gallium tarnishes in moist air, according to the Isoflex sheet and PubChem.
  why: Gallium (Ga) melts at 29.8 °C in the Netzsch safety data sheet, close to the 29.76 °C and 29.78 °C given by the other two sources, so the metal can turn liquid in a warm room. In electronics, the element matters as feedstock. The USGS says gallium is used through gallium arsenide and gallium nitride, for integrated circuits and optoelectronic devices such as LEDs, laser diodes and photodetectors. This profile covers the element only; the compounds have their own profiles (gallium arsenide, gallium nitride and gallium oxide).
  uses:
    - where: Chips and optoelectronics
      line: USGS reports that integrated circuits are the largest domestic use of gallium, with optoelectronic devices second. Gallium arsenide and gallium nitride are the two compound forms it names.
    - where: Light-emitting and laser devices
      line: USGS lists laser diodes, light-emitting diodes and photodetectors among the optoelectronic devices made from gallium compounds, and says optoelectronic devices were used in aerospace applications.
    - where: Solar cells
      line: USGS names silicon as the principal competitor with gallium arsenide in solar-cell applications.
  can_do:
    - label: Melting point
      line: Gallium melts at 29.76 °C (Periodic Table), 29.78 °C (PubChem) and 29.8 °C (Netzsch SDS). The three values agree to one decimal place, and the second decimal place differs between the sources.
    - label: Density
      line: The solid has a density of 5.904 g/cm3 at 20 °C (Netzsch SDS). The liquid has a density of 6.095 g/cm3 (Periodic Table), with no temperature stated.
    - label: Heat conduction
      line: The metal conducts heat at 29 W/(m K) (Periodic Table), with no temperature stated on the page.
    - label: Boiling point
      line: Gallium boils at 2204 °C at 760 mm Hg (PubChem).
  compare: 'Read together, the printed values show that solid gallium is less dense than liquid gallium: 5.904 g/cm3 for the solid at 20 °C (Netzsch SDS) against 6.095 g/cm3 for the liquid (Periodic Table, temperature not stated). A solid piece would therefore float on its own melt, though the two densities come from different sources and temperatures. The sources also disagree on the melting point in the second decimal place: 29.76 °C (Periodic Table), 29.78 °C (PubChem) and 29.8 °C (Netzsch SDS). The differences are small, but the value for a given grade should come from its supplier''s certificate.'
  compare_rows:
    - label: Melting point
      benchmark: melting_point
    - label: Density
      benchmark: density
    - label: Thermal conductivity
      benchmark: thermal_conductivity
  handling:
    - Store the metal tightly closed under an inert atmosphere and refrigerated, as the Lab Alley sheet directs.
    - Do not use steel or aluminium tools with it, because gallium attacks aluminium (PubChem).
    - Avoid dust and provide ventilation where the metal is handled or cleaned up (Isoflex sheet).
    - Take care with melted metal, which the Netzsch sheet says needs appropriate care.
  good_for:
    - Semiconductor feedstock. USGS describes gallium arsenide and gallium nitride as the forms used for chips and optoelectronic devices.
    - Light-emitting and laser devices. USGS lists LEDs and laser diodes among the optoelectronic devices made from gallium compounds.
  watch_out:
    - 'Melting point near room temperature: the solid turns liquid at 29.8 °C (Netzsch SDS), so a sample can change state in a warm room.'
    - 'Corrosion of aluminium: gallium forms an amalgam with aluminium alloys (PubChem).'
    - 'Conflicting hazard labels: PubChem''s aggregated reports show H314 and a Danger label, while the safety data sheets read here use Warning.'
    - 'Thin toxicity data: the Isoflex sheet says its toxicological properties have not been fully investigated.'
  verdict: Gallium is a low-melting metal whose main value is as feedstock for gallium arsenide and gallium nitride chips and LEDs. Handle the metal as corrosive to aluminium and to most metals, and check the supplier's safety sheet for the grade you buy.