{
  "spore": "profile",
  "id": "tungsten-trioxide",
  "spore_version": "0.2",
  "family": "oxide-ceramics",
  "name": "Tungsten trioxide",
  "abbreviation": "WO3",
  "role": "electrochromic and gas-sensing oxide",
  "category": "ceramics",
  "type": "oxides",
  "summary": "Tungsten trioxide (WO3, tungsten(VI) oxide) is a yellow oxide that melts at 1472 °C. Supplier and chemical-database data give a density of 7.16 to 7.2 g/cm3. Laboratory films of WO3 switch colour in a few seconds: a Fe-doped mesoporous film reached a coloration efficiency of 71.1 cm2/C, and WO3 with about 5 wt% reduced graphene oxide reached about 386 cm2/C. A review reports WO3 gas sensors that detect NO2 at 10 ppb. No flight or space-environment test of WO3 was found in the sources opened for this profile. Tungsten is on both the USGS and the EU critical lists, and China produced 67000 of the 85000 t of tungsten mined in 2025.\n",
  "best_for": "Electrochromic films that switch in seconds, and resistive gas sensors for NO2 and NH3 at ppb levels (laboratory results)",
  "weakest_at": "Cycling stability and humidity tolerance: a bare WO3 film lost about 25% of its optical transparency over cycling in one study, and the sensor review lists humidity tolerance as a limit",
  "identity": {
    "formula": "WO3",
    "cas": "1314-35-8",
    "crystal_system": "monoclinic",
    "designations": [],
    "source": "pmc-gas-review",
    "where": "Monoclinic phase: the phases paragraph of the sensing section of the review, which compares monoclinic and hexagonal WO3. Formula O3W and CAS 1314-35-8: PubChem CID 14811 (Names and Identifiers)"
  },
  "tags": {
    "environments": [],
    "stresses": [],
    "applications": [
      "optics-and-cameras",
      "habitats-and-suits"
    ]
  },
  "properties": [
    {
      "benchmark": "molar_mass",
      "label": "Molar mass",
      "value": 231.84,
      "bound": "exact",
      "unit": "g/mol",
      "scope": "material",
      "conditions": {
        "basis": "molecular weight computed in the PubChem record for WO3"
      },
      "method": "Molecular weight printed in a chemical database (the Materion SDS prints 231.85 g/mol)",
      "status": "calculated",
      "source": "pubchem-wo3",
      "where": "Chemical and Physical Properties, Molecular Weight (CID 14811)",
      "source_detail": {
        "title": "PubChem compound record, Tungsten oxide (WO3), CID 14811",
        "id": "CID 14811; CAS 1314-35-8; molecular formula O3W",
        "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/14811/JSON",
        "year": 2026,
        "kind": "database",
        "license": "public domain (NCBI)"
      }
    },
    {
      "benchmark": "density",
      "label": "Density, estimated (Materion SDS)",
      "value": 7.2,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "grade": "tungsten oxide powder, Materion product, SDS revision 07-27-2015",
        "basis": "estimated, as printed"
      },
      "method": "Value printed in a supplier safety data sheet and marked as an estimate",
      "status": "ground",
      "note": "The SDS marks this as an estimate. The nano-powder SDS below gives 7.160 g/cm3.",
      "source": "materion-sds",
      "where": "Section 9, Other information, Density",
      "source_detail": {
        "title": "Materion Advanced Chemicals safety data sheet: Tungsten oxide (SDS T-MSDS0050)",
        "id": "revision 07-27-2015; issue 10-14-2013",
        "url": "https://www.physics.purdue.edu/primelab/safety/MSDS/SDS/tungsten%20(VI)%20oxide%20%20-%20Materion.pdf",
        "year": 2015,
        "kind": "datasheet",
        "license": "supplier document, linked not reproduced"
      }
    },
    {
      "benchmark": "density",
      "label": "Relative density, nano powder (Stanford Advanced Materials SDS)",
      "value": 7.16,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "grade": "Nano Tungsten Trioxide Powder, SDS version 3.0",
        "temperature": "not stated"
      },
      "method": "Value printed in a supplier safety data sheet",
      "status": "ground",
      "source": "sam-sds",
      "where": "Section 9.1, item m, Relative density",
      "source_detail": {
        "title": "Stanford Advanced Materials safety data sheet: Nano Tungsten Trioxide Powder",
        "id": "version 3.0, revision 09/04/2017; CAS 1314-35-8",
        "url": "https://samaterials.com/tds/sc/1727405467-NN1589.pdf",
        "year": 2017,
        "kind": "datasheet",
        "license": "supplier document, linked not reproduced"
      }
    },
    {
      "benchmark": "melting_point",
      "label": "Melting point (PubChem experimental record)",
      "value": 1472,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "basis": "experimental value in the PubChem record; sample and grade not stated"
      },
      "method": "Experimental property quoted in a chemical database",
      "status": "ground",
      "note": "PubChem also prints 1473 °C as a second experimental entry. The first is used here.",
      "source": "pubchem-wo3",
      "where": "Chemical and Physical Properties, Experimental Properties, Melting Point (first entry)",
      "source_detail": {
        "title": "PubChem compound record, Tungsten oxide (WO3), CID 14811",
        "id": "CID 14811; CAS 1314-35-8; molecular formula O3W",
        "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/14811/JSON",
        "year": 2026,
        "kind": "database",
        "license": "public domain (NCBI)"
      }
    },
    {
      "benchmark": "melting_point",
      "label": "Melting point (nano powder SDS)",
      "value": 1472,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "grade": "Nano Tungsten Trioxide Powder, Stanford Advanced Materials"
      },
      "method": "Value printed in a supplier safety data sheet",
      "status": "ground",
      "source": "sam-sds",
      "where": "Section 9.1, item e, Melting point/freezing point",
      "source_detail": {
        "title": "Stanford Advanced Materials safety data sheet: Nano Tungsten Trioxide Powder",
        "id": "version 3.0, revision 09/04/2017; CAS 1314-35-8",
        "url": "https://samaterials.com/tds/sc/1727405467-NN1589.pdf",
        "year": 2017,
        "kind": "datasheet",
        "license": "supplier document, linked not reproduced"
      }
    },
    {
      "benchmark": "boiling_point",
      "label": "Boiling point at 1013 hPa (nano powder SDS)",
      "value": 1837,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "pressure": "1013 hPa (760 mmHg)",
        "grade": "Nano Tungsten Trioxide Powder, Stanford Advanced Materials"
      },
      "method": "Value printed in a supplier safety data sheet",
      "status": "ground",
      "note": "Printed in the SDS only; no second source for this boiling value was opened.",
      "source": "sam-sds",
      "where": "Section 9.1, item f, Initial boiling point and boiling range",
      "source_detail": {
        "title": "Stanford Advanced Materials safety data sheet: Nano Tungsten Trioxide Powder",
        "id": "version 3.0, revision 09/04/2017; CAS 1314-35-8",
        "url": "https://samaterials.com/tds/sc/1727405467-NN1589.pdf",
        "year": 2017,
        "kind": "datasheet",
        "license": "supplier document, linked not reproduced"
      }
    },
    {
      "benchmark": "coloration_efficiency",
      "label": "Coloration efficiency, Fe-doped mesoporous WO3 film",
      "value": 71.1,
      "bound": "exact",
      "unit": "cm2/C",
      "scope": "material",
      "conditions": {
        "film": "Fe-doped WO3 film with mesopores and oxygen vacancy defects",
        "device": "electrochromic device, as described in the abstract",
        "paper": "Switching electrochromic performance improvement enabled by highly developed mesopores and oxygen vacancy defects of Fe-doped WO3 films, Applied Surface Science 453 (2018)"
      },
      "method": "Value printed in the paper's abstract",
      "status": "ground",
      "source": "ass-2018-fe",
      "where": "Abstract, high CE (71.1 cm2/C)",
      "source_detail": {
        "title": "Switching electrochromic performance improvement enabled by highly developed mesopores and oxygen vacancy defects of Fe-doped WO3 films",
        "id": "Applied Surface Science 453, 238-244 (2018)",
        "url": "https://pure.seoultech.ac.kr/en/publications/switching-electrochromic-performance-improvement-enabled-by-highl/",
        "year": 2018,
        "kind": "paper",
        "license": "publisher abstract, linked not reproduced"
      }
    },
    {
      "benchmark": "coloration_time",
      "label": "Coloration time, Fe-doped mesoporous WO3 film",
      "value": 2.8,
      "bound": "exact",
      "unit": "s",
      "scope": "material",
      "conditions": {
        "film": "Fe-doped WO3 film with mesopores and oxygen vacancy defects",
        "device": "electrochromic device, as described in the abstract"
      },
      "method": "Value printed in the paper's abstract as the coloration speed",
      "status": "ground",
      "source": "ass-2018-fe",
      "where": "Abstract, 2.8 s for the coloration speed",
      "source_detail": {
        "title": "Switching electrochromic performance improvement enabled by highly developed mesopores and oxygen vacancy defects of Fe-doped WO3 films",
        "id": "Applied Surface Science 453, 238-244 (2018)",
        "url": "https://pure.seoultech.ac.kr/en/publications/switching-electrochromic-performance-improvement-enabled-by-highl/",
        "year": 2018,
        "kind": "paper",
        "license": "publisher abstract, linked not reproduced"
      }
    },
    {
      "benchmark": "bleaching_time",
      "label": "Bleaching time, Fe-doped mesoporous WO3 film",
      "value": 0.3,
      "bound": "exact",
      "unit": "s",
      "scope": "material",
      "conditions": {
        "film": "Fe-doped WO3 film with mesopores and oxygen vacancy defects",
        "device": "electrochromic device, as described in the abstract"
      },
      "method": "Value printed in the paper's abstract as the bleaching speed",
      "status": "ground",
      "source": "ass-2018-fe",
      "where": "Abstract, 0.3 s for the bleaching speed",
      "source_detail": {
        "title": "Switching electrochromic performance improvement enabled by highly developed mesopores and oxygen vacancy defects of Fe-doped WO3 films",
        "id": "Applied Surface Science 453, 238-244 (2018)",
        "url": "https://pure.seoultech.ac.kr/en/publications/switching-electrochromic-performance-improvement-enabled-by-highl/",
        "year": 2018,
        "kind": "paper",
        "license": "publisher abstract, linked not reproduced"
      }
    },
    {
      "benchmark": "coloration_efficiency",
      "label": "Coloration efficiency, WO3 with reduced graphene oxide",
      "value": 386,
      "bound": "exact",
      "unit": "cm2/C",
      "scope": "material",
      "conditions": {
        "film": "WO3 film with 5 wt% reduced graphene oxide",
        "comparison": "pristine WO3 about 81 cm2/C in the same abstract",
        "paper": "Study on the role of rGO in enhancing the electrochromic performance of WO3 film, Electrochimica Acta 427 (2022)"
      },
      "method": "Value printed in the paper's abstract as similar to 386 cm(2)/C",
      "status": "ground",
      "note": "The abstract gives about 81 for the pristine film and about 386 for the 5 wt% rGO film.",
      "source": "rgo-2022",
      "where": "Abstract, coloration efficiency rising from similar to 81 to similar to 386 cm(2)/C",
      "source_detail": {
        "title": "Study on the role of rGO in enhancing the electrochromic performance of WO3 film",
        "id": "Electrochimica Acta 427, 140820 (2022)",
        "url": "https://cgcri.csircentral.net/5420/",
        "year": 2022,
        "kind": "paper",
        "license": "publisher abstract, linked not reproduced"
      }
    },
    {
      "benchmark": "coloration_time",
      "label": "Coloration time, WO3 with reduced graphene oxide",
      "value": 5.3,
      "bound": "exact",
      "unit": "s",
      "scope": "material",
      "conditions": {
        "film": "WO3 film with 5 wt% reduced graphene oxide",
        "comparison": "pristine film about 9.6 s in the same abstract"
      },
      "method": "Value printed in the paper's abstract as similar to 5.3 s",
      "status": "ground",
      "source": "rgo-2022",
      "where": "Abstract, coloration time tc",
      "source_detail": {
        "title": "Study on the role of rGO in enhancing the electrochromic performance of WO3 film",
        "id": "Electrochimica Acta 427, 140820 (2022)",
        "url": "https://cgcri.csircentral.net/5420/",
        "year": 2022,
        "kind": "paper",
        "license": "publisher abstract, linked not reproduced"
      }
    },
    {
      "benchmark": "bleaching_time",
      "label": "Bleaching time, WO3 with reduced graphene oxide",
      "value": 6.2,
      "bound": "exact",
      "unit": "s",
      "scope": "material",
      "conditions": {
        "film": "WO3 film with 5 wt% reduced graphene oxide",
        "comparison": "pristine film about 10.4 s in the same abstract"
      },
      "method": "Value printed in the paper's abstract as similar to 6.2 s",
      "status": "ground",
      "source": "rgo-2022",
      "where": "Abstract, bleaching time tb",
      "source_detail": {
        "title": "Study on the role of rGO in enhancing the electrochromic performance of WO3 film",
        "id": "Electrochimica Acta 427, 140820 (2022)",
        "url": "https://cgcri.csircentral.net/5420/",
        "year": 2022,
        "kind": "paper",
        "license": "publisher abstract, linked not reproduced"
      }
    },
    {
      "benchmark": "optical_modulation",
      "label": "Optical modulation, WO3 with reduced graphene oxide",
      "value": 50,
      "bound": "exact",
      "unit": "%",
      "scope": "material",
      "conditions": {
        "film": "WO3 film with 5 wt% reduced graphene oxide",
        "basis": "printed as similar to 50%"
      },
      "method": "Value printed in the paper's abstract",
      "status": "ground",
      "source": "rgo-2022",
      "where": "Abstract, optical modulation",
      "source_detail": {
        "title": "Study on the role of rGO in enhancing the electrochromic performance of WO3 film",
        "id": "Electrochimica Acta 427, 140820 (2022)",
        "url": "https://cgcri.csircentral.net/5420/",
        "year": 2022,
        "kind": "paper",
        "license": "publisher abstract, linked not reproduced"
      }
    },
    {
      "benchmark": "detection_limit",
      "label": "NO2 detection limit, doped WO3 hollow nanosphere sensor (cited in the review)",
      "value": 10,
      "bound": "exact",
      "unit": "ppb",
      "scope": "material",
      "conditions": {
        "gas": "NO2",
        "detection_range": "10 to 1000 ppb",
        "material": "mesoporous WO3 hollow nanospheres with a dopant, reference 95 in the review",
        "temperature": "not stated in the sentence"
      },
      "method": "Value stated in a review of WO3 gas sensors; the primary paper was not opened",
      "status": "ground",
      "note": "Taken from the review, so the test conditions are not confirmed.",
      "source": "pmc-gas-review",
      "where": "Doping section, sentence beginning 'Enabling the detection of NO2 at concentrations as low as 10 ppb', citing reference 95",
      "source_detail": {
        "title": "Innovations in WO3 gas sensors: Nanostructure engineering, functionalization, and future perspectives",
        "id": "doi:10.1016/j.heliyon.2024.e27740 (Heliyon 10(6), PMC10955316)",
        "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC10955316/",
        "year": 2024,
        "kind": "paper",
        "license": "open access (PMC)"
      }
    },
    {
      "benchmark": "operating_temperature",
      "label": "Typical operating temperature range for WO3 gas response",
      "value": 100,
      "value_high": 400,
      "bound": "range",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "basis": "statement that the optimal temperature for WO3 gas sensors is typically in this range"
      },
      "method": "Range stated in a review",
      "status": "ground",
      "source": "pmc-gas-review",
      "where": "Operating temperature paragraph, sentence on the optimal temperature for WO3, citing reference 37",
      "source_detail": {
        "title": "Innovations in WO3 gas sensors: Nanostructure engineering, functionalization, and future perspectives",
        "id": "doi:10.1016/j.heliyon.2024.e27740 (Heliyon 10(6), PMC10955316)",
        "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC10955316/",
        "year": 2024,
        "kind": "paper",
        "license": "open access (PMC)"
      }
    },
    {
      "benchmark": "visible_absorption_limit",
      "label": "Visible-light absorption, upper wavelength",
      "value": 480,
      "bound": "exact",
      "unit": "nm",
      "scope": "material",
      "conditions": {
        "basis": "statement about WO3 as a visible-light-driven photocatalyst"
      },
      "method": "Value stated in a review abstract",
      "status": "ground",
      "note": "Only the wavelength is printed in the abstract. No band gap in eV was read in a fetched source.",
      "source": "dutta-2021",
      "where": "Abstract, high absorption of visible light (up to 480nm)",
      "source_detail": {
        "title": "An Overview on WO3 based photocatalyst for environmental remediation",
        "id": "Journal of Environmental Chemical Engineering 9(1), 105018 (2021)",
        "url": "https://pure.sruc.ac.uk/en/publications/an-overview-on-wo3-based-photocatalyst-for-environmental-remediat/",
        "year": 2021,
        "kind": "paper",
        "license": "publisher abstract, linked not reproduced"
      }
    }
  ],
  "corrosion": [
    {
      "environment": "Caustic alkali solutions and hydrofluoric acid",
      "headline": "WO3 is soluble in caustic alkalies and slightly soluble in hydrofluoric acid.",
      "effect": "PubChem's experimental solubility entries say insoluble in water, soluble in caustic alkalies, very slightly soluble in acids, and slightly soluble in hydrofluoric acid. No dissolution rate or test duration is given.",
      "rating": "moderate",
      "conditions": {
        "basis": "qualitative solubility statements in a chemical database; the rating is assigned from those words",
        "temperature": "not stated"
      },
      "source": "pubchem-wo3",
      "where": "Chemical and Physical Properties, Solubility (two entries)"
    },
    {
      "environment": "Repeated electrochromic switching in an electrolyte cell",
      "headline": "A bare WO3 film lost about 25% of its optical transparency over cycling, and the rGO composite lost under 10%.",
      "effect": "The abstract says the bare WO3 film showed a deterioration in optical transparency similar to 25%, while the film with reduced graphene oxide showed a deterioration of under 10%.",
      "rating": "moderate",
      "conditions": {
        "film": "bare WO3 and WO3 with 5 wt% reduced graphene oxide",
        "cycles": "not stated in the abstract",
        "electrolyte": "not stated in the abstract"
      },
      "source": "rgo-2022",
      "where": "Abstract, cyclic stability"
    },
    {
      "environment": "Gas-sensing operation over time, in humid air",
      "headline": "The sensor review lists stability, humidity tolerance and baseline drift as intrinsic limits of WO3 gas sensors.",
      "effect": "The review names these limits and mitigation strategies in its critical assessment. The passage read does not quantify drift or humidity effects.",
      "rating": "unknown",
      "conditions": {
        "basis": "review text only; no quantified test was read"
      },
      "source": "pmc-gas-review",
      "where": "Introduction, list of review aims, item iv"
    }
  ],
  "risks": {
    "hazards": [
      {
        "text": "PubChem's aggregated record says the substance does not meet GHS hazard criteria in 41.5% (333 of 803) of company reports. The other reports use the signal word Warning and give H302 (58.5%), H315 (57.3%), H319 (57.3%) and H335 (57.3%).",
        "ghs": [
          "H302",
          "H315",
          "H319",
          "H335"
        ],
        "source": "pubchem-wo3",
        "where": "GHS Classification, aggregated notifications (CID 14811)"
      },
      {
        "text": "The Materion SDS (product T-MSDS0050, revision 07-27-2015) states that the substance does not meet the criteria for classification and has no signal word.",
        "ghs": [],
        "source": "materion-sds",
        "where": "Section 2, Hazard(s) identification"
      },
      {
        "text": "The Stanford Advanced Materials SDS for a nano powder states that the product is not a hazardous substance or mixture.",
        "ghs": [],
        "source": "sam-sds",
        "where": "Sections 2.1 and 2.2"
      }
    ],
    "failure_risks": [
      {
        "mode": "Loss of optical transparency after cycling",
        "trigger": "Repeated colour switching of a bare WO3 film",
        "consequence": "In the rGO study the bare film lost about 25% of its optical transparency, against under 10% for the rGO composite, so the cycling loss depends on the film.",
        "severity": "moderate",
        "source": "rgo-2022",
        "where": "Abstract, cyclic stability"
      },
      {
        "mode": "Drift and loss of stability in gas sensors",
        "trigger": "Long operation at the sensing temperature, including humid air",
        "consequence": "The review lists stability, humidity tolerance, baseline drift and power consumption as intrinsic limits of WO3 gas sensors.",
        "severity": "moderate",
        "source": "pmc-gas-review",
        "where": "Introduction, list of review aims, item iv"
      },
      {
        "mode": "Dissolution in strong alkali",
        "trigger": "Contact with caustic alkali solutions",
        "consequence": "WO3 is soluble in caustic alkalies, so a part or film left in an alkaline solution can lose material.",
        "severity": "moderate",
        "source": "pubchem-wo3",
        "where": "Chemical and Physical Properties, Solubility"
      }
    ],
    "side_effects": [],
    "handling": [
      {
        "text": "Minimize dust generation and accumulation, provide exhaust ventilation where dust is formed, and practice good housekeeping. Store in a tightly closed container in a well-ventilated place, away from incompatible materials.",
        "source": "materion-sds",
        "where": "Section 7, Precautions for safe handling and Conditions for safe storage"
      },
      {
        "text": "The ACGIH threshold limit values for tungsten oxide are 10 mg/m3 as a short-term limit (STEL) and 5 mg/m3 as a time-weighted average (TWA).",
        "source": "materion-sds",
        "where": "Section 8, US ACGIH Threshold Limit Values"
      },
      {
        "text": "The SDS says that gases hazardous to health may form in a fire, and asks users to wash hands after handling.",
        "source": "materion-sds",
        "where": "Section 5, Specific hazards arising from the chemical; Section 2, Response"
      }
    ],
    "mitigations": [
      {
        "text": "Wear safety glasses with side shields, or goggles, as the SDS specifies for eye protection.",
        "source": "materion-sds",
        "where": "Section 8, Eye/face protection"
      }
    ]
  },
  "uses": [
    {
      "application": "optics-and-cameras",
      "device": "Electrochromic smart-window film (laboratory device)",
      "example": "A Fe-doped mesoporous WO3 film in an electrochromic device switched to colour in 2.8 s and bleached in 0.3 s, with a coloration efficiency of 71.1 cm2/C.",
      "source": "ass-2018-fe",
      "where": "Abstract"
    },
    {
      "application": "optics-and-cameras",
      "device": "Electrochromic film with reduced graphene oxide (laboratory device)",
      "example": "Adding about 5 wt% reduced graphene oxide raised coloration efficiency from about 81 to about 386 cm2/C, with optical modulation of about 50%.",
      "source": "rgo-2022",
      "where": "Abstract"
    },
    {
      "application": "habitats-and-suits",
      "device": "Resistive gas sensors for NO2, NH3 and VOCs (air monitoring)",
      "example": "The review reports WO3 sensors that detect NO2 at concentrations as low as 10 ppb, and describes WO3 as used for environmental monitoring of NO2, SO2 and VOCs.",
      "source": "pmc-gas-review",
      "where": "Introduction (applications paragraph) and doping section"
    },
    {
      "application": "habitats-and-suits",
      "device": "Visible-light photocatalyst for environmental remediation",
      "example": "The review describes WO3 as a visible-light-driven photocatalyst for environmental remediation, absorbing visible light up to 480 nm.",
      "source": "dutta-2021",
      "where": "Abstract"
    }
  ],
  "supply": [
    {
      "subject": "Tungsten (feedstock for WO3)",
      "producers": [
        {
          "country": "China",
          "share_percent": 78.8,
          "year": 2025
        },
        {
          "country": "Vietnam",
          "share_percent": 4,
          "year": 2025
        },
        {
          "country": "Kazakhstan",
          "share_percent": 2.8,
          "year": 2025
        },
        {
          "country": "Russia",
          "share_percent": 2.4,
          "year": 2025
        },
        {
          "country": "Korea, North",
          "share_percent": 2.4,
          "year": 2025
        }
      ],
      "critical_lists": [
        {
          "list": "USGS 2025 List of Critical Minerals (tungsten listed)",
          "listed": true
        },
        {
          "list": "EU critical raw materials list (fifth list of 34 critical raw materials, as shown on the European Commission page)",
          "listed": true
        }
      ],
      "recycling": "USGS: the quantity of secondary tungsten produced and consumed from secondary sources in 2025 was withheld to avoid disclosing company proprietary data.",
      "substitutes": [
        "USGS: potential substitutes for cemented tungsten carbides include molybdenum, niobium or titanium carbides, ceramics and cermets. No substitute is named for WO3 itself."
      ],
      "source": "usgs-mcs2026-tungsten",
      "where": "World Mine Production and Reserves, 2025 column. World total 85000 t (rounded). Shares calculated by Space Mushroom by dividing each 2025 figure by 85000 t: China 67000 t, Vietnam 3400 t, Kazakhstan 2400 t, Russia 2000 t, Korea, North 2000 t. Salient Statistics: net import reliance above 50% (2025e). Price, Rotterdam, tungsten trioxide, 380 dollars per dry metric ton unit (2025e). Critical lists: usgs-crit2025 page and ec-crm page."
    }
  ],
  "media": [],
  "documents": [
    {
      "title": "PubChem: Tungsten oxide (WO3), CID 14811, GHS classification and experimental properties",
      "type": "database",
      "url": "https://pubchem.ncbi.nlm.nih.gov/compound/14811",
      "year": 2026
    },
    {
      "title": "Materion Advanced Chemicals safety data sheet: Tungsten oxide, SDS T-MSDS0050 (revision 07-27-2015)",
      "type": "sds",
      "url": "https://www.physics.purdue.edu/primelab/safety/MSDS/SDS/tungsten%20(VI)%20oxide%20%20-%20Materion.pdf",
      "year": 2015
    },
    {
      "title": "Stanford Advanced Materials safety data sheet: Nano Tungsten Trioxide Powder (version 3.0)",
      "type": "sds",
      "url": "https://samaterials.com/tds/sc/1727405467-NN1589.pdf",
      "year": 2017
    },
    {
      "title": "USGS Mineral Commodity Summaries 2026: Tungsten",
      "type": "report",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-tungsten.pdf",
      "year": 2026
    },
    {
      "title": "Innovations in WO3 gas sensors: Nanostructure engineering, functionalization, and future perspectives (Heliyon 2024, open access)",
      "type": "paper",
      "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC10955316/",
      "year": 2024
    },
    {
      "title": "Switching electrochromic performance improvement enabled by highly developed mesopores and oxygen vacancy defects of Fe-doped WO3 films (Applied Surface Science 453, 2018)",
      "type": "paper",
      "url": "https://pure.seoultech.ac.kr/en/publications/switching-electrochromic-performance-improvement-enabled-by-highl/",
      "year": 2018
    },
    {
      "title": "Study on the role of rGO in enhancing the electrochromic performance of WO3 film (Electrochimica Acta 427, 2022)",
      "type": "paper",
      "url": "https://cgcri.csircentral.net/5420/",
      "year": 2022
    },
    {
      "title": "An Overview on WO3 based photocatalyst for environmental remediation (Journal of Environmental Chemical Engineering 9, 2021)",
      "type": "paper",
      "url": "https://pure.sruc.ac.uk/en/publications/an-overview-on-wo3-based-photocatalyst-for-environmental-remediat/",
      "year": 2021
    },
    {
      "title": "USGS: About the 2025 List of Critical Minerals",
      "type": "report",
      "url": "https://www.usgs.gov/programs/mineral-resources-program/science/about-2025-list-critical-minerals",
      "year": 2025
    },
    {
      "title": "European Commission: Critical raw materials",
      "type": "report",
      "url": "https://single-market-economy.ec.europa.eu/sectors/raw-materials/areas-specific-interest/critical-raw-materials_en",
      "year": 2024
    }
  ],
  "gaps": [
    "No vacuum, radiation, thermal-vacuum or flight result for WO3 was found in any source opened for this profile.",
    "Band gap in eV was not read in a fetched source. Search snippets gave a range of about 2.4 to 2.8 eV, which was not used because the snippets were not opened.",
    "Density in PubChem (7.2 at 25 °C) is printed without a unit, so it is left out. The Materion SDS value of 7.2 g/cm3 is used instead.",
    "Crustal abundance of tungsten was not found. The USGS PP 1802-A Table A1 we opened has no tungsten row.",
    "Space group is not read in a fetched primary source. Wikipedia gives P121/n1 (No. 14) in the infobox and P21/n in the text, and the page conflicts with itself, so it is not used.",
    "The electrochromic values come from single films with different electrolytes, thicknesses and dopants, so they are not directly comparable. The MDPI Coatings 2025 review and the RSC Materials Advances 2021 review returned HTTP 403 and were not read.",
    "The NO2 detection limit is taken from a review and the primary paper was not opened, so its test temperature is not confirmed.",
    "Hazard classifications conflict: PubChem's aggregate reports H302, H315, H319 and H335 in most notifications, while the Materion SDS and the Stanford nano-powder SDS do not classify the material. The Stanford SDS is for a nano powder.",
    "Atomic weights were not read in a fetched source, so the recipe parts carry no atoms or atomic_weight.",
    "Corrosion ratings are qualitative assignments made by the author from the wording of the sources.",
    "Coloration, bleaching, modulation and cycling values use the wording of the abstracts (similar to, under) and are not checked against the full papers.",
    "Properties not in the property canon use short snake_case names: molar_mass, coloration_efficiency, coloration_time, bleaching_time, optical_modulation, detection_limit, operating_temperature and visible_absorption_limit."
  ],
  "story": {
    "why": "Tungsten trioxide (WO3) is a dense yellow oxide with a density of 7.2 g/cm3 and a melting point of 1472 °C. It is studied for two uses: electrochromic films that change colour when a small voltage is applied, and resistive gas sensors. Its laboratory films switch in a few seconds, and its sensors respond to ppb levels of NO2. Its limits are cycling loss, sensitivity to humidity, and hazard data that do not agree across suppliers.",
    "uses": [
      {
        "where": "Electrochromic smart windows",
        "line": "A Fe-doped WO3 film switched to colour in 2.8 s and bleached in 0.3 s in one laboratory device. Adding 5 wt% reduced graphene oxide raised coloration efficiency from about 81 to about 386 cm2/C."
      },
      {
        "where": "Gas sensors",
        "line": "A review reports WO3 sensors that detect NO2 at 10 ppb, and describes WO3 as used for monitoring NO2, SO2 and VOCs in air."
      },
      {
        "where": "Photocatalyst",
        "line": "WO3 absorbs visible light up to 480 nm, so it is studied for environmental cleanup under sunlight."
      }
    ],
    "can_do": [
      {
        "label": "Colour switching",
        "line": "The Fe-doped mesoporous film switched to colour in 2.8 s and bleached in 0.3 s, with a coloration efficiency of 71.1 cm2/C.",
        "scope": "material",
        "value": "2.8 s to colour"
      },
      {
        "label": "Coloration efficiency",
        "line": "Adding about 5 wt% reduced graphene oxide raised the coloration efficiency from about 81 to about 386 cm2/C.",
        "scope": "material",
        "value": "386 cm2/C"
      },
      {
        "label": "Gas detection",
        "line": "A doped WO3 sensor cited in the review detects NO2 at 10 ppb, within a range of 10 to 1000 ppb.",
        "scope": "material",
        "value": "10 ppb NO2"
      },
      {
        "label": "Visible light",
        "line": "WO3 absorbs visible light up to 480 nm, which is why it is studied as a photocatalyst.",
        "scope": "material",
        "value": "Up to 480 nm"
      }
    ],
    "compare": "WO3 is a powder-based oxide whose strengths lie in optics and sensing, not in structure. Its density is about 7.2 g/cm3 and its melting point is 1472 °C. Its films show coloration efficiencies from 71.1 to 386 cm2/C, which depend on the dopant and on whether a graphene additive is present.",
    "compare_rows": [
      {
        "label": "Melting point",
        "benchmark": "melting_point",
        "scope": "material"
      },
      {
        "label": "Density",
        "benchmark": "density",
        "scope": "material"
      },
      {
        "label": "Colour efficiency",
        "benchmark": "coloration_efficiency",
        "scope": "material"
      }
    ],
    "handling": [
      "Minimize dust, use exhaust ventilation where dust forms, and practice good housekeeping.",
      "Store in a tightly closed container, away from incompatible materials.",
      "Wear safety glasses with side shields or goggles.",
      "Keep it out of caustic alkali solutions, which dissolve WO3."
    ],
    "good_for": [
      "Fast electrochromic films. The Fe-doped film colours in 2.8 s and bleaches in 0.3 s in a laboratory device.",
      "Low-level gas sensing. The review cites detection of NO2 at 10 ppb."
    ],
    "watch_out": [
      "Cycling loss. A bare film lost about 25% of its transparency over cycling in one study.",
      "Humidity and drift. The sensor review lists humidity tolerance and baseline drift as limits.",
      "Conflicting hazard data. PubChem reports H302, H315, H319 and H335, while the Materion SDS does not classify the powder."
    ],
    "verdict": "WO3 is a promising laboratory material for fast electrochromic films and low-level gas sensors. Its hazard data conflict, its cycling and humidity stability are the main limits, and no space test was found.",
    "recipe": {
      "line": "WO3 is one tungsten and three oxygen. Tungsten(VI) oxide is a yellow powder that does not dissolve in water, and it is used as the starting material for making tungstates.",
      "parts": [
        {
          "name": "Tungsten",
          "symbol": "W",
          "role": "The metal in the oxide, in its highest oxidation state."
        },
        {
          "name": "Oxygen",
          "symbol": "O",
          "role": "Three oxygen per tungsten, bonded into the WO3 framework."
        }
      ]
    },
    "risk_groups": [
      {
        "title": "For people",
        "lead": "PubChem's aggregated record lists irritant and harmful-if-swallowed hazards, but the Materion SDS does not classify the powder, so the data conflict.",
        "points": [
          {
            "label": "Hazard data",
            "line": "PubChem reports H302, H315, H319 and H335 in 57.3 to 58.5 percent of its company reports. The Materion SDS and the Stanford nano-powder SDS do not classify the material."
          },
          {
            "label": "Exposure limit",
            "line": "The Materion SDS lists an ACGIH limit of 10 mg/m3 as a short-term limit and 5 mg/m3 as a time-weighted average for tungsten oxide."
          },
          {
            "label": "Dust",
            "line": "Minimize dust and provide exhaust ventilation where dust forms."
          }
        ],
        "level": 1,
        "verdict": "Hazard data conflict across sources"
      },
      {
        "title": "If it fails",
        "lead": "These results come from laboratory film and sensor tests, not from field failures.",
        "points": [
          {
            "label": "Cycling",
            "line": "In one study the bare WO3 film lost about 25% of its transparency over cycling, against under 10% for the rGO composite."
          },
          {
            "label": "Sensors",
            "line": "The review lists stability, humidity tolerance and baseline drift as the main limits of WO3 gas sensors."
          }
        ]
      },
      {
        "title": "Handling and storage",
        "points": [
          {
            "label": "Storage",
            "line": "Store in a tightly closed container, away from incompatible materials."
          },
          {
            "label": "Alkali",
            "line": "Keep it out of caustic alkali solutions, which dissolve WO3."
          }
        ]
      }
    ]
  },
  "updated": "2026-10-26",
  "review": {
    "status": "draft",
    "method": "assistant",
    "checked_values": 16,
    "unreachable": 2,
    "caveats": 5,
    "note": "Read by an AI assistant on 2026-10-26 from the PubChem JSON record, the USGS MCS 2026 tungsten PDF, two supplier SDS PDFs, the PMC gas-sensor review, and three paper abstracts. The MDPI and RSC full texts and the DOAJ page returned HTTP 403 and were not read. Caveats: the PubChem and SDS hazard data conflict; the electrochromic values come from different films; the NO2 limit and the abstract wording are second-hand; no space data was found."
  },
  "sources": {
    "pubchem-wo3": {
      "title": "PubChem compound record, Tungsten oxide (WO3), CID 14811",
      "id": "CID 14811; CAS 1314-35-8; molecular formula O3W",
      "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/14811/JSON",
      "year": 2026,
      "kind": "database",
      "license": "public domain (NCBI)"
    },
    "materion-sds": {
      "title": "Materion Advanced Chemicals safety data sheet: Tungsten oxide (SDS T-MSDS0050)",
      "id": "revision 07-27-2015; issue 10-14-2013",
      "url": "https://www.physics.purdue.edu/primelab/safety/MSDS/SDS/tungsten%20(VI)%20oxide%20%20-%20Materion.pdf",
      "year": 2015,
      "kind": "datasheet",
      "license": "supplier document, linked not reproduced"
    },
    "sam-sds": {
      "title": "Stanford Advanced Materials safety data sheet: Nano Tungsten Trioxide Powder",
      "id": "version 3.0, revision 09/04/2017; CAS 1314-35-8",
      "url": "https://samaterials.com/tds/sc/1727405467-NN1589.pdf",
      "year": 2017,
      "kind": "datasheet",
      "license": "supplier document, linked not reproduced"
    },
    "usgs-mcs2026-tungsten": {
      "title": "Mineral Commodity Summaries 2026, Tungsten",
      "id": "USGS MCS 2026, February 2026",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-tungsten.pdf",
      "year": 2026,
      "kind": "report",
      "license": "public domain (USGS)"
    },
    "usgs-crit2025": {
      "title": "About the 2025 List of Critical Minerals (USGS, final list)",
      "id": "Final 2025 List of Critical Minerals, November 2025",
      "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, fifth list of 34 critical raw materials)",
      "id": "EU critical raw materials list",
      "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"
    },
    "pmc-gas-review": {
      "title": "Innovations in WO3 gas sensors: Nanostructure engineering, functionalization, and future perspectives",
      "id": "doi:10.1016/j.heliyon.2024.e27740 (Heliyon 10(6), PMC10955316)",
      "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC10955316/",
      "year": 2024,
      "kind": "paper",
      "license": "open access (PMC)"
    },
    "ass-2018-fe": {
      "title": "Switching electrochromic performance improvement enabled by highly developed mesopores and oxygen vacancy defects of Fe-doped WO3 films",
      "id": "Applied Surface Science 453, 238-244 (2018)",
      "url": "https://pure.seoultech.ac.kr/en/publications/switching-electrochromic-performance-improvement-enabled-by-highl/",
      "year": 2018,
      "kind": "paper",
      "license": "publisher abstract, linked not reproduced"
    },
    "rgo-2022": {
      "title": "Study on the role of rGO in enhancing the electrochromic performance of WO3 film",
      "id": "Electrochimica Acta 427, 140820 (2022)",
      "url": "https://cgcri.csircentral.net/5420/",
      "year": 2022,
      "kind": "paper",
      "license": "publisher abstract, linked not reproduced"
    },
    "dutta-2021": {
      "title": "An Overview on WO3 based photocatalyst for environmental remediation",
      "id": "Journal of Environmental Chemical Engineering 9(1), 105018 (2021)",
      "url": "https://pure.sruc.ac.uk/en/publications/an-overview-on-wo3-based-photocatalyst-for-environmental-remediat/",
      "year": 2021,
      "kind": "paper",
      "license": "publisher abstract, linked not reproduced"
    }
  },
  "license": "CC-BY-4.0",
  "url": "https://spacemushroom.com/profiles/tungsten-trioxide/"
}