Tin(IV) oxide and indium tin oxide SnO2, ITO

spore: profile
id: tin-oxide
spore_version: 0.2
family: oxide-ceramics
name: Tin(IV) oxide and indium tin oxide
abbreviation: SnO2, ITO
role: transparent conductor and gas-sensing oxide
category: ceramics
type: oxides
summary: |
  Tin(IV) oxide (SnO2) is a white, water-insoluble oxide with a bulk band gap of 3.6 eV. Its safety data sheet gives a density of 6.95 g/mL and a melting point of 1630 degC. Indium tin oxide (ITO) is mostly indium oxide with 10 wt% SnO2 in the standard sputtering target, and it is used as a transparent conductive film. On the MISSE-9 flight, ITO on Kapton kept usable sheet resistance after about 0.77 years in low Earth orbit, although the ram-facing sample's sheet resistance doubled from 5230 to 10820 Ohm/square. Its solar absorptance stayed near 0.42.
best_for: Transparent conductive ITO films for displays and thin-film solar cells, and SnO2 as the active layer in gas sensors
weakest_at: 'Indium supply for ITO: China produced 70% of world indium, and USGS reports new Chinese export restrictions on indium from February 2025'
identity:
  formula: SnO2 (tin(IV) oxide); ITO is In2O3 with 10 wt% SnO2 in the standard 90/10 target
  cas: 18282-10-5
  source: isoflex-sno2-sds
  where: Section 3 (CAS 18282-10-5, formula SnO2, molecular weight 150.71 g/mol); composition from sputtertargets-ito, Standard Composition row
tags:
  environments:
    - low-earth-orbit
  stresses:
    - atomic-oxygen
    - uv
  applications:
    - electronics-and-chips
    - thermal-control
    - solar-arrays
properties:
  - benchmark: density
    label: Density, tin(IV) oxide (SDS)
    value: 6.95
    unit: g/mL
    scope: material
    conditions:
      form: tin(IV) oxide powder, CAS 18282-10-5
      temperature: 25 °C
    method: Value printed in the physical and chemical properties section of the supplier SDS
    status: ground
    source: isoflex-sno2-sds
    where: Section 9, Density row
  - benchmark: density
    label: Density, tin(IV) oxide (PubChem record)
    value: 6.95
    unit: g/cm3
    scope: material
    conditions:
      form: tin(IV) oxide, PubChem record; no temperature printed
    method: Value printed in the Density entry of the PubChem chemical and physical properties
    status: ground
    source: pubchem-sno2
    where: Chemical and Physical Properties, Density entry (reference 25)
  - benchmark: melting_point
    label: Melting point, tin(IV) oxide
    value: 1630
    unit: °C
    scope: material
    conditions:
      form: tin(IV) oxide powder
    method: Value printed in the SDS physical and chemical properties section (printed as 1630 °C (2966 °F))
    status: ground
    note: The PubChem physical description prints mp 1127 °C with sublimation at 1800 to 1900 °C; the 1127 value conflicts with the SDS and PubChem melting entries and is not used.
    source: isoflex-sno2-sds
    where: Section 9, Melting Point row
  - benchmark: band_gap
    label: Band gap of bulk SnO2
    value: 3.6
    unit: eV
    scope: material
    conditions:
      basis: expected value for bulk SnO2 from low-temperature valence-band photoemission, with the Fermi edge taken at the conduction band minimum
      form: single-crystal SnO2 surfaces
    method: Value quoted in an open-access review of SnO2 surface science, described as close to the expected bulk value
    status: ground
    note: This is the expected bulk gap quoted in the review, not an optical measurement of a film. band_gap is not in the property canon.
    source: batzill-sno2-review
    where: Section on valence-band spectroscopy of the (110) and (101) surfaces, paragraph with the 3.6 eV value
  - benchmark: oral_ld50
    label: Acute oral LD50, rat, tin(IV) oxide
    value: 20000
    bound: lower
    unit: mg/kg
    scope: material
    conditions:
      species: rat
      route: oral
      form: tin(IV) oxide
    method: Value printed in the SDS toxicological information section (printed as greater than 20,000 mg/kg)
    status: ground
    note: oral_ld50 is not in the property canon. The SDS gives no LD50 for the other routes.
    source: isoflex-sno2-sds
    where: Section 11, Acute Toxicity, Oral LD50 row
  - benchmark: occupational_exposure_limit
    label: Occupational exposure limit, time-weighted average, tin(IV) oxide
    value: 2
    unit: mg/m3
    scope: material
    conditions:
      basis: time-weighted average as printed for tin(IV) oxide; the SDS adds that tin(II) oxide has its own listing as Sn
      agencies: NIOSH REL, OSHA PEL and ACGIH TLV rows in the SDS
    method: Limit printed in the SDS exposure controls table
    status: ground
    note: occupational_exposure_limit is not in the property canon. The SDS does not state whether the 2 mg/m3 figure is as tin.
    source: isoflex-sno2-sds
    where: Section 8, exposure limits table, Tin (IV) oxide rows
  - benchmark: density
    label: Target density, standard 90/10 rotary ITO target
    value: 7.13
    bound: lower
    unit: g/cm3
    scope: material
    conditions:
      composition: 90 wt% In2O3 and 10 wt% SnO2 standard target
      form: rotary (tubular) sputtering target, SKU ST11192
      purity: 99.99% on oxide basis
    method: Specification value printed on a vendor product page (the page also gives relative density of 95% or more)
    status: ground
    note: Vendor specification for the target, not a measured density for the tested batch.
    source: sputtertargets-ito
    where: Complete Technical Specifications table, Density row
  - benchmark: purity
    label: Purity of the standard ITO target
    value: 99.99
    bound: lower
    unit: '%'
    scope: material
    conditions:
      basis: on oxide basis
      composition: 90 wt% In2O3 and 10 wt% SnO2
    method: Specification printed on a vendor product page
    status: ground
    source: sputtertargets-ito
    where: Complete Technical Specifications table, Purity row
  - benchmark: density
    label: Density of the ITO film used in the MISSE-9 erosion calculation
    value: 6.8
    unit: g/cm3
    scope: material
    conditions:
      form: ITO thin film about 10 nm thick on Kapton HN/Al and FEP/Ag/Inconel sheets
      basis: value used for the mass-loss and erosion-yield calculation
    method: Value printed in the atomic-oxygen mass-loss table as the ITO density
    status: ground
    note: A film density used for a calculation, not measured by the authors on a bulk part.
    source: nasa-misse9
    where: Section 5.4, Table 6, ITO Density column
  - benchmark: film_thickness
    label: ITO coating thickness on the MISSE-9 sheets
    value: 10
    unit: nm
    scope: material
    conditions:
      form: ITO coating on Kapton HN/Al and FEP/Ag/Inconel sheets
      basis: approximately, as printed
    method: Stated in the description of the ITO test articles
    status: ground
    note: film_thickness is not in the property canon.
    source: nasa-misse9
    where: Section 2, description of the ITO coatings
  - benchmark: sheet_resistance
    label: Sheet resistance, ITO on Kapton HN/Al, ram flight sample, average
    value: 10820
    unit: Ohm/square
    scope: material
    conditions:
      sample: M9R-S5 Flight, ITO/Kapton HN/Al, ram orientation
      exposure: ram position, about 0.77 years in low Earth orbit
      measurement: four-point probe
    method: Average of the measured values printed in Table 4 (printed as 10,820 Ohm/square)
    status: flight
    note: sheet_resistance is not in the property canon. The report says the value is still low enough to dissipate electrostatic charge.
    source: nasa-misse9
    where: Table 4, M9R-S5 Flight row, Average column; Section 5.2
  - benchmark: sheet_resistance
    label: Sheet resistance, ITO on Kapton HN/Al, unexposed material
    value: 5230
    unit: Ohm/square
    scope: material
    conditions:
      sample: unexposed backup sheets of ITO/Kapton HN/Al
      basis: overall average for unexposed material
    method: Overall average printed in Table 4 for the unexposed Kapton material
    status: ground
    note: The unexposed value used as the reference for the doubling reported in Section 5.2.
    source: nasa-misse9
    where: Table 4, ITO/Kapton HN/Al backup rows, Overall Average for Unexposed Material column
  - benchmark: solar_absorptance
    label: Solar absorptance, ITO/Kapton HN/Al, ram flight sample
    value: 0.42
    unit: '-'
    scope: material
    conditions:
      sample: M9R-S5 Flight, ram orientation
      control: control sample 0.423 in the same figure
      exposure: about 0.77 years in low Earth orbit
      spectrum: AM0
    method: Integrated AM0 solar absorptance printed in the figure caption (printed as 0.420)
    status: flight
    source: nasa-misse9
    where: Figure 9 caption; Table 5
  - benchmark: solar_absorptance_change
    label: Largest solar absorptance change, zenith flight sample
    value: 0.002
    unit: '-'
    scope: material
    conditions:
      sample: M9Z-S5 F, ITO/FEP/Ag/Inconel, zenith orientation
      exposure: about 0.54 years in low Earth orbit
    method: Change stated in the text of the optical properties section, described as within error of the Cary data
    status: flight
    note: solar_absorptance_change is not in the property canon. The report states the change is within instrument error.
    source: nasa-misse9
    where: Section 5.3 (Optical Properties), text
  - benchmark: optical_transmittance
    label: Average optical transmittance, 400 to 800 nm, ITO film at 50 W
    value: 80.88
    unit: '%'
    scope: material
    conditions:
      wavelength_range: 400 to 800 nm
      sputtering_power: 50 W
      thickness: about 200 nm
      substrate: glass
    method: Average printed in Table 1 of the paper
    status: ground
    note: optical_transmittance is not in the property canon. The same table gives 77.06 at 200 W.
    source: sm-ito-2016
    where: Table 1, 400 to 800 nm row, 50 W column
corrosion:
  - environment: Reducing gas atmosphere during metal-oxide gas sensing
    headline: Reducing gases raise the conductance of SnO2, which is the sensing signal and not a damage mechanism.
    effect: The review explains the gas response as a change in charge carriers at the oxide surface, and the conductance increases in a reducing atmosphere. It argues that removal of lattice oxygen is unlikely to be the main cause of the increase.
    rating: unknown
    conditions:
      basis: sensing use; the review does not rate damage
      form: single-crystal and sensing SnO2 surfaces
    source: batzill-sno2-review
    where: Sections on gas response and surface reduction
  - environment: Potassium, sodium, magnesium and chlorine trifluoride
    headline: Reactive metals and chlorine trifluoride react violently with tin(IV) oxide.
    effect: The PubChem incompatibility notes say that potassium or sodium reduce stannic oxide at gentle heat with incandescence, that heating with magnesium makes it explode, and that chlorine trifluoride reacts violently without flame.
    rating: severe
    conditions:
      basis: laboratory incompatibility notes, not a corrosion test
      form: stannic oxide
    source: pubchem-sno2
    where: Hazardous Reactivities and Incompatibilities (reference 24)
  - environment: Recommended storage in a closed container
    headline: The SDS lists tin(IV) oxide as stable under recommended storage conditions.
    effect: The SDS calls the material stable under recommended storage, and it is insoluble in water. It gives no degradation rate for the powder.
    rating: none
    conditions:
      storage: tightly closed container in a dry, well-ventilated place (SDS Section 7)
      form: tin(IV) oxide powder
    source: isoflex-sno2-sds
    where: Section 10, Chemical Stability row; Section 9, Solubility row
  - environment: Low Earth orbit atomic oxygen, ram and wake positions (MISSE-9 PCE-1)
    headline: Atomic oxygen doubled the sheet resistance of the ram-facing ITO on Kapton, while the erosion yields were very low.
    effect: After about 0.77 years in low Earth orbit, the ram ITO/Kapton HN/Al sheet resistance rose from 5230 to 10820 Ohm/square. The report still calls this low enough to dissipate static charge. The erosion yields were very low, and the wake Kapton sample stayed at 5000 Ohm/square before and after flight.
    rating: low
    conditions:
      exposure: ram, wake and zenith positions, 0.54 to 0.77 years in low Earth orbit
      mission: MISSE-9 PCE-1
    source: nasa-misse9
    where: Section 5.2 (Sheet Resistance), Section 5.4 (Erosion Yield), Table 4, Table 6, Section 6 (Conclusions)
  - environment: Solar ultraviolet in low Earth orbit (MISSE-9 flight samples)
    headline: UV did not change the ITO sheets on Kapton, but it caused a small fluorescence on the FEP/Ag/Inconel sheets.
    effect: Post-flight UV luminescence images showed that space exposure did not affect the response of the ITO-coated Kapton/Al sheets to UV. The UV caused a small amount of fluorescence in the ITO-coated FEP/Ag/Inconel material.
    rating: low
    conditions:
      basis: UV luminescence imaging, not a solar absorptance test
      mission: MISSE-9 PCE-1
    source: nasa-misse9
    where: UV luminescence section, Figures 6 to 8
  - environment: Strong oxidizers, strong acids, aluminium, magnesium and alkali metals (PubChem record)
    headline: PubChem lists these materials as incompatible with the indium tin oxide record.
    effect: The PubChem incompatibility entry names strong oxidizing agents, potassium, strong acids, aluminum, sodium or sodium oxides and magnesium. The Angstrom Sciences SDS prints no incompatible conditions.
    rating: unknown
    conditions:
      basis: compound record CID 57350325, which has a generic composition
      form: indium tin oxide powder
    source: pubchem-ito
    where: Hazardous Reactivities and Incompatibilities
risks:
  hazards:
    - text: PubChem reports that tin(IV) oxide does not meet GHS hazard criteria in 44.7% (356 of 796) of company reports. The other reports carry H335 (35.1%, may cause respiratory irritation) and H413 (17.3%, may cause long-lasting harmful effects to aquatic life).
      ghs:
        - H335
        - H413
      source: pubchem-sno2
      where: Safety and Hazards, GHS Classification (CID 16747781)
    - text: The ISOFLEX SDS (version 1.4, revised 10/18/2024) says the powder may be harmful if inhaled and may cause respiratory tract irritation, skin irritation and eye irritation, and lists it as not a dangerous substance under GHS.
      ghs: []
      source: isoflex-sno2-sds
      where: Section 2, Potential Health Effects and GHS rows
    - text: The Angstrom Sciences SDS for indium tin oxide lists H335 (may cause respiratory irritation) with the signal word Warning.
      ghs:
        - H335
      source: angstrom-ito-sds
      where: Section 2, Signal Word and Hazard Statements
    - text: PubChem's indium tin oxide record (CID 57350325) lists H315 and H319 (skin and eye irritation) in aggregated notifications, and H372 (causes damage to organs through prolonged or repeated exposure, Danger) in one notification.
      ghs:
        - H315
        - H319
        - H372
      source: pubchem-ito
      where: GHS Classification, notification blocks (references 5, 8 and 12)
    - text: PubChem's summary notes interstitial lung disease, called indium lung disease, in workers exposed to airborne ITO dust in production.
      ghs: []
      source: pubchem-ito
      where: Hazards Summary (reference 9)
  failure_risks:
    - mode: Sheet resistance rise under atomic oxygen
      trigger: Ram-facing ITO on Kapton HN/Al in low Earth orbit for about 0.77 years
      consequence: Sheet resistance doubled from 5230 to 10820 Ohm/square. The report still considers the value low enough to dissipate static charge.
      severity: moderate
      source: nasa-misse9
      where: Section 5.2 and Table 4; Section 6 (Conclusions)
    - mode: Unreliable sheet resistance on FEP/Ag/Inconel sheets
      trigger: Post-flight four-point probe measurements on ITO-coated FEP/Ag/Inconel
      consequence: Readings were very scattered, and a few were above 370000 Ohm/square. The report recommends measuring all samples again with calibrated equipment.
      severity: moderate
      source: nasa-misse9
      where: Section 5.2 and Section 6 (Conclusions)
  side_effects: []
  handling:
    - text: Keep the container tightly closed in a dry, well-ventilated place, and provide exhaust ventilation where dust forms (SDS Section 7).
      source: isoflex-sno2-sds
      where: Section 7, Handling and Storage rows
    - text: Store the indium tin oxide in a cool, dry place in a tightly sealed container. Wash thoroughly after handling and do not blow dust off clothing or skin with compressed air.
      source: angstrom-ito-sds
      where: Section 7, Handling and Storage
    - text: Tin(IV) oxide is not combustible (PubChem fire hazards entry); its decomposition products under fire conditions are tin and tin oxides (SDS Section 5).
      source: pubchem-sno2
      where: Fire Hazards entry; ISOFLEX SDS Section 5 for decomposition products
  mitigations:
    - text: For spills, use a HEPA air filter to collect the dust and place it in a closed container, taking care not to raise dust.
      source: angstrom-ito-sds
      where: Section 6, Accidental Release Measures
uses:
  - application: electronics-and-chips
    device: Metal-oxide gas sensors
    example: A surface-science review uses tin dioxide as the model system for metal-oxide gas sensing materials, and explains the gas response as a change in charge carriers at the oxide surface.
    source: batzill-sno2-review
    where: Abstract and introduction to the gas-sensing discussion
  - application: electronics-and-chips
    device: Dopant in indium tin oxide transparent electrodes
    example: The standard ITO sputtering target is 90 wt% In2O3 and 10 wt% SnO2, so SnO2 is the dopant in the transparent conductor used for flat displays and touch sensors.
    source: sputtertargets-ito
    where: Standard Composition row; Typical Applications
  - application: electronics-and-chips
    device: Transparent electrodes in flat-panel displays (ITO)
    example: USGS reports that ITO thin-film coatings are used mainly for electrically conductive purposes in flat-panel displays, most commonly liquid crystal displays.
    source: usgs-indium-2026
    where: Domestic Production and Use paragraph
  - application: thermal-control
    device: ITO-coated thermal control sheets (Kapton HN/Al and FEP/Ag/Inconel) on an external ISS tray
    example: The MISSE-9 report concludes that all ITO-coated sheets performed well and were not noticeably damaged in low Earth orbit, implying they are suitable as thermal control sheet materials.
    source: nasa-misse9
    where: Section 6 (Conclusions)
  - application: thermal-control
    device: Charge-dissipating ITO coating on thermal control sheets
    example: The report says the ITO-coated Kapton sheet's final resistance of 10820 Ohm/square is believed to be low enough to dissipate electrostatic charges.
    source: nasa-misse9
    where: Section 6 (Conclusions)
  - application: solar-arrays
    device: Transparent electrodes in thin-film solar cells (supplier application)
    example: The vendor lists thin-film solar cells, including heterojunction and perovskite cells, among the typical applications of its standard ITO rotary target.
    source: sputtertargets-ito
    where: Typical Applications paragraph
supply:
  - subject: Tin (for SnO2 and ITO)
    producers:
      - country: China
        share_percent: 24.5
        year: 2025
      - country: Indonesia
        share_percent: 21
        year: 2025
      - country: Peru
        share_percent: 11.4
        year: 2025
      - country: Brazil
        share_percent: 9.7
        year: 2025
      - country: Burma
        share_percent: 4.1
        year: 2025
    critical_lists:
      - list: USGS 2025 List of Critical Minerals (tin is on the final list)
        listed: true
    recycling: 'USGS: about 17,000 tons of tin from old and new scrap was estimated to have been recycled in 2025, 22% of apparent consumption in the United States.'
    substitutes:
      - 'USGS: aluminum, glass, paper, plastic or tin-free steel substitute for tin in cans and containers, and epoxy resins can replace tin in solder.'
    source: usgs-tin-2026
    where: World Mine Production and Reserves table, 2025e (shares calculated by Space Mushroom against the 290000 t world total; China 71000, Indonesia 61000, Peru 33000, Brazil 28000, Burma 12000); Recycling; Substitutes; critical list from usgs-crit-2025
  - subject: Indium (for ITO)
    producers:
      - country: China
        share_percent: 70
        year: 2025
    critical_lists:
      - list: USGS 2025 List of Critical Minerals (indium is on the final list, used in flat-panel displays and touchscreens)
        listed: true
    recycling: 'USGS: indium is most commonly recovered from ITO scrap in Japan and the Republic of Korea; quantities recovered are not reported.'
    substitutes:
      - 'USGS: antimony tin oxide, carbon nanotube coatings, PEDOT, copper or silver nanowires and graphene have been developed as alternatives to ITO in some uses.'
    source: usgs-indium-2026
    where: Domestic Production and Use; World Resources; Recycling; Substitutes. The 70% share is printed in the text as China accounting for 70% of the world total (year assumed to be the 2025 data year of the report)
documents:
  - title: 'ISOFLEX safety data sheet: Tin(IV) oxide, CAS 18282-10-5 (version 1.4, revision date 10/18/2024)'
    type: sds
    url: https://isoflex.com/cn/docman-all-categories/sds/614-tin-oxide-rev-3/file
    year: 2024
  - title: 'PubChem: Tin(IV) oxide (CID 16747781), GHS classification and physical properties'
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/compound/16747781
    year: 2026
  - title: 'Surface Science Studies of Gas Sensing Materials: SnO2 (open access, Sensors 2006)'
    type: paper
    url: https://pmc.ncbi.nlm.nih.gov/articles/PMC3909400/
    year: 2006
  - title: Effect of Sputtering Power on Optical and Electrical Properties of Indium Tin Oxide Films (Sensors and Materials, open access)
    type: paper
    url: https://sensors.myu-group.co.jp/sm_pdf/SM1259.pdf
    year: 2016
  - title: Space Exposure of Indium Tin Oxide Coatings (NASA/TM-20240002413)
    type: report
    url: https://ntrs.nasa.gov/api/citations/20240002413/downloads/TM-20240002413.pdf
    year: 2024
  - title: 'Sputter Targets: ITO rotary sputtering target specification (ST11192)'
    type: datasheet
    url: https://www.sputtertargets.net/st11192-indium-tin-oxide-ito-rotary-sputtering-target/
    year: 2026
  - title: 'Angstrom Sciences safety data sheet: Indium Tin Oxide'
    type: sds
    url: https://angstromsciences.com/wp-content/uploads/files/SDS/Indium%20Tin%20Oxide.pdf
    year: 2015
  - title: 'PubChem: Indium tin oxide record (CID 57350325), GHS classification and reactivity'
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/compound/57350325
    year: 2026
  - title: 'USGS Mineral Commodity Summaries 2026: Tin'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-tin.pdf
    year: 2026
  - title: 'USGS Mineral Commodity Summaries 2026: Indium'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-indium.pdf
    year: 2026
  - title: 'USGS: About the 2025 List of Critical Minerals (final list)'
    type: report
    url: https://www.usgs.gov/programs/mineral-resources-program/science/about-2025-list-critical-minerals
    year: 2025
gaps:
  - A Japanese government GHS listing (NITE) that classifies ITO as carcinogenic (H350) appeared in a search result, but both NITE pages returned 404 in this run. It is not used. Check it before any work that involves repeated inhalation of ITO powder.
  - Crystal system and lattice constants of SnO2 were not printed in any source opened for this profile. The review discusses rutile-type surfaces, but the body text gives no crystal system.
  - No refractive index of SnO2 with a stated wavelength was found. PubChem prints 1.997 and 2.093 with no wavelength or source, so they are not used.
  - No open paper with a measured SnO2 film resistivity or gas-sensor response value was opened. The review used for gas sensing is a surface-science review with no sensor response numbers.
  - The PubChem record CID 16747781 also carries one H372 notification (Danger, repeated exposure) whose substance is not named in the record. It is not used.
  - The PubChem ITO record (CID 57350325, formula InOSn) is a generic composition record. Its hazard and reactivity entries may describe indium compounds rather than ITO film, so they are flagged rather than treated as ITO-specific.
  - The indium tin oxide CAS number was not read in a source opened for this profile, so the identity block gives the SnO2 CAS only.
  - Crustal abundance of tin and indium was not read in a source opened for this profile (USGS PP 1802-A not fetched).
  - The EU critical raw materials list was not checked for tin or indium, so no EU list entry is given.
  - Mine shares for tin are calculated by Space Mushroom from the USGS 2025e table against the 290000 t world total. Indium producer share is the printed 70% statement, not a table.
  - Bulk ITO strength, fracture toughness and thermal conductivity were not read in any source opened. The ITO properties above describe thin films on polymer sheets and sputtered films, not dense ceramic parts.
  - The vendor page lists target resistivity only as High (Insulating), with no number, so it is not used.
  - The MISSE-9 atomic oxygen erosion yields are printed in exponent form, so the numeric values are left out of properties. The corrosion entry describes them qualitatively.
  - The sputtering paper (Sensors and Materials 2016) prints the 50 W film resistivity as 5.702 x 10 to the minus 4 Ohm cm with a Unicode minus sign, so the value check could not match it. The property is left out until it is checked by hand. The text (2.376) and Table 3 (23.76) also conflict at 200 W.
  - Vacuum outgassing (TML and CVCM) and radiation results for SnO2 or ITO were not found in a source opened for this profile.
sources:
  isoflex-sno2-sds:
    title: 'ISOFLEX safety data sheet: Tin(IV) oxide, CAS 18282-10-5'
    id: Version 1.4, revision date 10/18/2024
    url: https://isoflex.com/cn/docman-all-categories/sds/614-tin-oxide-rev-3/file
    year: 2024
    kind: datasheet
    license: supplier document, linked not reproduced
  pubchem-sno2:
    title: PubChem compound record, Tin(IV) oxide (CID 16747781)
    id: CID 16747781; formula O2Sn
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/16747781/JSON
    year: 2026
    kind: database
    license: public domain (NCBI)
  batzill-sno2-review:
    title: 'Surface Science Studies of Gas Sensing Materials: SnO2'
    id: Sensors 6(10), 1345-1366 (2006), PMC3909400
    url: https://pmc.ncbi.nlm.nih.gov/articles/PMC3909400/
    year: 2006
    kind: paper
    license: open access (PMC)
  sm-ito-2016:
    title: Effect of Sputtering Power on Optical and Electrical Properties of Indium Tin Oxide Films (Her and Chang)
    id: Sensors and Materials 28(9), 975-981 (2016), S&M 1259
    url: https://sensors.myu-group.co.jp/sm_pdf/SM1259.pdf
    year: 2016
    kind: paper
    license: open access (MYU Research, Sensors and Materials)
  nasa-misse9:
    title: Space Exposure of Indium Tin Oxide Coatings (NASA MISSE-9 PCE-1)
    id: NASA/TM-20240002413; NTRS 20240002413
    url: https://ntrs.nasa.gov/api/citations/20240002413/downloads/TM-20240002413.pdf
    year: 2024
    kind: report
    license: public domain (NASA)
  sputtertargets-ito:
    title: 'Sputter Targets: Indium tin oxide (ITO) rotary sputtering target, standard 90/10'
    id: SKU ST11192 (page undated; retrieved 2026-10-26)
    url: https://www.sputtertargets.net/st11192-indium-tin-oxide-ito-rotary-sputtering-target/
    year: 2026
    kind: datasheet
    license: supplier page, linked not reproduced
  angstrom-ito-sds:
    title: 'Angstrom Sciences safety data sheet: Indium Tin Oxide'
    id: Revision date printed as 076/21/15 (garbled in the PDF)
    url: https://angstromsciences.com/wp-content/uploads/files/SDS/Indium%20Tin%20Oxide.pdf
    year: 2015
    kind: datasheet
    license: supplier document, linked not reproduced
  pubchem-ito:
    title: PubChem compound record, Indium tin oxide (CID 57350325)
    id: CID 57350325; formula InOSn (generic composition record)
    url: https://pubchem.ncbi.nlm.nih.gov/compound/57350325
    year: 2026
    kind: database
    license: public domain (NCBI)
  usgs-tin-2026:
    title: Mineral Commodity Summaries 2026, Tin
    id: USGS MCS 2026, February 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-tin.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  usgs-indium-2026:
    title: Mineral Commodity Summaries 2026, Indium
    id: USGS MCS 2026, February 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-indium.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  usgs-crit-2025:
    title: About the 2025 List of Critical Minerals (USGS, final list)
    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)
license: CC-BY-4.0
updated: '2026-10-26'
review:
  status: draft
  method: assistant
  checked_values: 15
  unreachable: 1
  caveats: 4
  note: 'Read by an AI assistant on 2026-10-26 from the pages and PDFs fetched in that run. The NITE page (ITO carcinogenicity listing) returned 404 and is not used. Caveats: the ITO values are thin-film or vendor-target values, not bulk ceramic; the SnO2 band gap is an expected bulk value from a review; the 200 W resistivity conflicts inside the sputtering paper.'
story:
  recipe:
    line: SnO2 is tin(IV) oxide, one tin and two oxygen per formula unit. Indium tin oxide (ITO) is mostly indium(III) oxide with 10 wt% SnO2 in the standard sputtering target, which is 90 wt% In2O3 and 10 wt% SnO2.
    parts:
      - name: Tin
        symbol: Sn
        role: The metal in SnO2. The review describes surface tin as changing between Sn(IV) and Sn(II) states, which matters for gas sensing.
      - name: Oxygen
        symbol: O
        role: Two oxygen per formula unit of SnO2.
      - name: Indium(III) oxide
        symbol: In2O3
        share_percent: 90
        role: The host oxide in the standard ITO target (90 wt%). Its film is sputtered as the transparent conductor.
      - name: Tin(IV) oxide
        symbol: SnO2
        share_percent: 10
        role: The dopant in the standard ITO target (10 wt%) and the active oxide in tin-oxide gas sensors.
  risk_groups:
    - title: For people, tin(IV) oxide powder
      level: 1
      verdict: Irritant dust; not a GHS hazard in most reports
      lead: The SDS calls the powder not a dangerous substance under GHS, but it may irritate the eyes, skin and airways, and PubChem reports an H335 classification in some company reports.
      points:
        - label: The powder
          line: The SDS says the powder may be harmful if inhaled and may irritate the respiratory tract, skin and eyes. PubChem reports that 44.7% of company reports do not meet GHS criteria.
        - label: Dust
          line: Use exhaust ventilation where dust forms. The stannosis entry in PubChem describes a benign lung change from breathing tin dust or fume.
    - title: For people, indium tin oxide
      level: 1
      verdict: Irritant; lung disease reported in ITO workers
      lead: The indium tin oxide supplier SDS classes the material as a respiratory irritant, and PubChem records lung disease in workers who breathed ITO dust.
      points:
        - label: Respiratory
          line: The Angstrom Sciences SDS lists H335 with the signal word Warning, and PubChem's record also lists H315, H319 and one H372 notification.
        - label: Lung disease
          line: PubChem's summary reports indium lung disease in workers exposed to airborne ITO dust in production.
    - title: In orbit, ITO coatings
      points:
        - label: Sheet resistance
          line: On the MISSE-9 flight, the ram-facing ITO on Kapton doubled its sheet resistance, from 5230 to 10820 Ohm/square, after about 0.77 years in low Earth orbit.
        - label: Scatter
          line: The FEP/Ag/Inconel sheets gave very scattered readings, with some above 370000 Ohm/square, so the report asks for a repeat with calibrated equipment.
  why: Tin(IV) oxide is a white, water-insoluble oxide with a bulk band gap of 3.6 eV. Its gas-sensing behavior comes from charge carriers at the surface, which the surface-science review describes in detail. Indium tin oxide adds 10 wt% SnO2 to indium oxide to make a transparent conductive film. The MISSE-9 flight tested ITO sheets in low Earth orbit and the sheets kept usable sheet resistance and low solar absorptance, which makes the film a candidate for thermal control and charge dissipation.
  uses:
    - where: Metal-oxide gas sensors
      line: A surface-science review uses tin dioxide as the model system for metal-oxide gas sensing materials, and explains the gas response as a change in charge carriers at the oxide surface.
    - where: Transparent conductor for displays
      line: The standard ITO target is 90 wt% In2O3 and 10 wt% SnO2. USGS reports that ITO coatings are used mainly in flat-panel displays, most commonly liquid crystal displays.
    - where: Thermal control sheets in orbit
      line: In the MISSE-9 test, ITO-coated sheets were not noticeably damaged by about 0.54 to 0.77 years in low Earth orbit, and the authors judged them suitable as thermal control sheet materials.
  can_do:
    - label: Transparency
      value: '80.88'
      line: A DC-sputtered ITO film made at 50 W averaged 80.88% transmittance from 400 to 800 nm, on a glass substrate about 200 nm thick.
    - label: Heat
      value: 1630 °C
      line: Tin(IV) oxide melts at 1630 °C according to the SDS, and the SDS lists the powder as stable under recommended storage.
    - label: Low absorptance in orbit
      value: '0.42'
      line: The ram-facing ITO on Kapton reached a solar absorptance of 0.42 on the flight, against 0.423 for the control sample.
    - label: Charge dissipation
      value: 10820 Ohm/square
      line: The report says the flown ITO on Kapton kept a sheet resistance low enough to dissipate electrostatic charge.
  compare: SnO2 is an insoluble oxide with a melting point of 1630 °C and a density of 6.95 g/mL. Indium tin oxide shares this oxide base, but its sputtered films are used for electrical rather than structural properties, with a visible transmittance of 80.88% at 50 W. The table compares density, melting point and film transmittance across the two forms.
  compare_rows:
    - label: Density
      benchmark: density
    - label: Melting point
      benchmark: melting_point
    - label: Film transmittance
      benchmark: optical_transmittance
  handling:
    - Keep the powder in a tightly closed container in a dry, well-ventilated place, with exhaust ventilation where dust forms.
    - Do not blow dust off clothing or skin with compressed air. Wash thoroughly after handling.
    - Use a HEPA filter for spills, and place the collected dust in a closed container.
  good_for:
    - Transparent conductive films for displays and thin-film solar cells (ITO). The standard target has a density of 7.13 g/cm3 or more and 99.99% purity on an oxide basis.
    - Gas-sensing layers based on SnO2, which the review uses as the model metal-oxide sensing material.
    - Thermal control sheets with a low solar absorptance, shown in the MISSE-9 flight test.
  watch_out:
    - 'Indium supply: China produces 70% of world indium, and USGS reports new export restrictions on indium from February 2025.'
    - Sheet resistance can double under atomic oxygen on the ram side of the spacecraft, and some measured values scatter widely.
    - Irritation and lung disease in workers who breathe ITO dust. The NITE carcinogenicity listing could not be checked in this run.
    - Reducing gases change the conductance of SnO2, which is the sensing signal, so the material should not be used as a stable resistor without checking the atmosphere.
  verdict: SnO2 and ITO are useful oxide materials for transparent conductors, gas sensing and low-absorptance thermal coatings. The space record is limited to thin ITO films on polymer sheets for about 0.77 years in low Earth orbit, and the main supply and health risks are indium-related.