Tungsten trioxide

Names
IUPAC name

Tungsten trioxide

Other names

Tungstic anhydride
Tungsten(VI) oxide
Tungstic oxide

Identifiers

CAS Number

* 1314-35-8 Y

3D model (JSmol)

* Interactive image

ChemSpider |

* 14127

EC Number |

* 215-231-4

PubChem CID

* 14811

RTECS number |

* YO7760000

UNII |

* 940E10M08M Y

InChI

* InChI=1S/3O.W

Key: ZNOKGRXACCSDPY-UHFFFAOYSA-N

SMILES

* O=[W](=O)=O

Properties

Chemical formula

| WO3
Molar mass | 231.84 g/mol
Appearance  | Canary yellow powder
Density | 7.16 g/cm3
Melting point |  1,473 °C (2,683 °F; 1,746 K)
Boiling point |  1,700 °C (3,090 °F; 1,970 K) approximation

Solubility in water

| insoluble
Solubility | slightly soluble in HF

Magnetic susceptibility (χ)

| −15.8·10−6 cm3/mol
Structure

Crystal structure

| Monoclinic, mP32

Space group

| P121/n1, No. 14

Coordination geometry

| Octahedral (WVI)
Trigonal planar (O2– )
Hazards
Main hazards | Irritant
Safety data sheet | External MSDS
Flash point | Non-flammable
Related compounds

Other anions

| Tungsten trisulfide

Other cations

| Chromium trioxide
Molybdenum trioxide

Related tungsten oxides

| Tungsten(III) oxide
Tungsten(IV) oxide

Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

N verify (what is YN ?)
Infobox references

Tracking categories (test):

* SizeSet

Tungsten(VI) oxide, also known as tungsten trioxide is a chemical compound of oxygen and the transition metal tungsten, with formula WO3. The compound is also called tungstic anhydride, reflecting its relation to tungstic acid H
2WO
4. It is a light yellow crystalline solid.[1]

Tungsten(VI) oxide occurs naturally in the form of hydrates, which include minerals: tungstite WO3·H2O, meymacite WO3·2H2O and hydrotungstite (of the same composition as meymacite, however sometimes written as H2WO4). These minerals are rare to very rare secondary tungsten minerals.

## Contents

* 1 History
* 2 Structure and properties
* 2.1 Crystallography
* 2.1.1 Tetragonal WO3
* 2.1.2 Orthorhombic WO3
* 2.1.3 Monoclinic WO3
* 2.1.4 Triclinic WO3
* 2.1.5 Hexagonal WO3
* 3 Preparation
* 3.1 Industrial
* 3.2 Laboratory
* 4 Reactions
* 5 Uses
* 6 References
* 7 External links

## History

In 1841, a chemist named Robert Oxland gave the first procedures for preparing tungsten trioxide and sodium tungstate.[2] He was granted patents for his work soon after, and is considered to be the founder of systematic tungsten chemistry.[2]

## Structure and properties

The crystal structure of tungsten trioxide is temperature dependent. It is tetragonal at temperatures above 740 °C, orthorhombic from 330 to 740 °C, monoclinic from 17 to 330 °C, triclinic from −50 to 17 °C, and monoclinic again at temperatures below −50 °C.[3] The most common structure of WO3 is monoclinic with space group P21/n.[2]

The pure compound is an electric insulator, but oxygen-deficient varieties, such as WO
2.90 = W
20O
58, are dark blue to purple in color and conduct electricity. They can be prepared by combining the trioxide and the dioxide WO
2 at 1000 °C in vacuum.[1][4]

Possible signs of superconductivity with critical temperatures Tc = 80–90 K were claimed in sodium-doped and oxygen-deficient WO3 crystals. If confirmed, these would be the first superconducting materials containing no copper, with Tc higher than the boiling point of liquid nitrogen at normal pressure.[4][5]

### Crystallography

Tungsten trioxide exists in multiple polymorphs whose structures have been precisely determined using X-ray crystallography and neutron diffraction. Each phase exhibits a distinct arrangement of distorted WO6 octahedra, which affect its electronic and optical behavior.

Tungsten trioxide (WO3) is a polymorphic compound whose crystal structure changes depending on temperature. It adopts several forms, including:

* Tetragonal above 740 °C
* Orthorhombic from 330 to 740 °C
* Monoclinic from 17 to 330 °C
* Triclinic from −50 to 17 °C
* A second monoclinic phase below −50 °C
* A hexagonal form synthesized under specific conditions

The most common ambient phase is monoclinic with space group P21/n, featuring distorted WO6 octahedra linked at their corners. Each polymorph exhibits variations in symmetry, lattice parameters, and atomic positions, making structural determination important for understanding the material's physical and electronic properties.

#### Tetragonal WO3

This high-temperature phase is observed above 740 °C, but specific crystallographic data are often not tabulated separately in modern studies. It exhibits relatively symmetric WO6 octahedra.

#### Orthorhombic WO3

* Space group: Pmnb (No. 62)
* Lattice parameters (Å): a = 7.341(4), b = 7.570(4), c = 7.754(4)
* Angles (°): α = β = γ = 90°
* Cell volume: 430.90 Å3
* Z: 8
* Temperature: 873 K
* Pressure: Atmospheric
* R-value: 0.061
* Reference: Salje, E. (1977). Acta Crystallographica Section B, 33(2), 574–577.[6]

#### Monoclinic WO3

* Space group: P1/c1 (No. 7)
* Lattice parameters (Å): a = 5.27710(1), b = 5.15541(1), c = 7.66297(1)
* Angles (°): α = γ = 90°, β = 91.7590(2)
* Cell volume: 208.38 Å3
* Z: 4
* Temperature: 5 K
* Pressure: Atmospheric
* R-value: 0.09
* Reference: Salje, E.K.H. et al. (1997). Journal of Physics: Condensed Matter, 9, 6563–6577.[6]

WO3 triclinic structure

#### Triclinic WO3

* Space group: P−1 (No. 2)
* Lattice parameters (Å): a = 7.309(2), b = 7.522(2), c = 7.678(2)
* Angles (°): α = 88.81(2), β = 90.92(2), γ = 90.93(2)
* Cell volume: 421.92 Å3
* Z: 8
* Temperature: Room temperature
* Pressure: Atmospheric
* R-value: 0.05
* Reference: Diehl, R. et al. (1978). Acta Crystallographica Section B, 34, 1105–1111.[6]

#### Hexagonal WO3

A less common hexagonal polymorph of WO3 has been reported and characterized using powder X-ray diffraction. It exhibits higher symmetry and potentially distinct electronic properties.

* Space group: P6/mmm (No. 191)
* Lattice parameters (Å): a = 7.298(2), c = 3.899(2)
* Angles (°): α = β = 90°, γ = 120°
* Cell volume: 179.84 Å3
* Z: 3
* Temperature: Room temperature
* Pressure: Atmospheric
* R-value: 0.055
* Reference: Gérand, B. et al. (1979). Journal of Solid State Chemistry, 29, 429–434.[6]

## Preparation

### Industrial

Tungsten trioxide is obtained as an intermediate in the recovery of tungsten from its minerals.[7] Tungsten ores can be treated with alkalis to produce soluble tungstates. Alternatively, CaWO4, or scheelite, is allowed to react with HCl to produce tungstic acid, which decomposes to WO3 and water at high temperatures.[7]

CaWO4 \+ 2 HCl → CaCl2 \+ H2WO4
H2WO4 → H
2O \+ WO3

### Laboratory

Another common way to synthesize WO3 is by calcination of ammonium paratungstate (APT) under oxidizing conditions:[2]

(NH4)10[H2W12O42] • 4H2O → 12 WO3 \+ 10 NH3 \+ 10 H

## Reactions

Tungsten trioxide can be reduced with carbon or hydrogen gas yielding the pure metal.

2 WO3 \+ 3 C → 2 W + 3 CO2 (high temperature)
WO3 \+ 3 H2 → W + 3 H2O (550–850 °C)[8]

## Uses

Tungsten trioxide is a starting material for the synthesis of tungstates. Barium tungstate BaWO
4 is used as a x-ray screen phosphors. Alkali metal tungstates, such as lithium tungstate Li
2WO
4 and cesium tungstate Cs
2WO
4, give dense solutions that can be used to separate minerals.[1] Other applications, actual or potential, include:

* Fireproofing fabrics[9]
* Gas and humidity sensors.[10][1]
* Ceramic glazes where it gives a rich yellow color.[7][1]
* Electrochromic glass, such as in smart windows, whose transparency can be changed by an applied voltage.[11][12][1]
* Photocatalytic water splitting.[13][14][15][16]
* Substrate for surface-enhanced Raman spectroscopy replacing noble metals.[17][18][19][20]

## References

1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 J. Christian, R.P. Singh Gaur, T. Wolfe and J. R. L. Trasorras (2011): Tungsten Chemicals and their Applications. Brochure by International Tungsten Industry Association.
2. ↑ 2.0 2.1 2.2 2.3 Lassner, Erik and Wolf-Dieter Schubert (1999). Tungsten: Properties, Chemistry, Technology of the Element, Alloys, and Chemical Compounds. New York: Kluwer Academic. ISBN 978-0-306-45053-2.
3. ↑ H. A. Wriedt (1898): "The O-W (oxygen-tungsten) system". Bulletin of Alloy Phase Diagrams., volume 10, pages 368–384. doi:10.1007/BF02877593
4. ↑ 4.0 4.1 A. Shengelaya, K. Conder, and K. A. Müller (2020): "Signatures of Filamentary Superconductivity up to 94 K in Tungsten Oxide WO2.90". Journal of Superconductivity and Novel Magnetism, volume 33, pages 301–306. doi:10.1007/s10948-019-05329-9
5. ↑ S. Reich and Y. Tsabba (1999): "Possible nucleation of a 2D superconducting phase on WO single crystals surface doped with Na". European Physical Journal B, volume 9, pages = 1–4. doi:10.1007/s100510050735 S2CID:121476634
6. ↑ 6.0 6.1 6.2 6.3 Sundberg, M. (1976-07-15). "The crystal and defect structures of W25O73, a member of the homologous series WnO3n−2" (in en). Acta Crystallographica Section B: Structural Crystallography and Crystal Chemistry 32 (7): 2144–2149. doi:10.1107/S0567740876007280. ISSN 0567-7408. Bibcode: 1976AcCrB..32.2144S. https://journals.iucr.org/paper?S0567740876007280.
7. ↑ 7.0 7.1 7.2 Patnaik, Pradyot (2003). Handbook of Inorganic Chemical Compounds. McGraw-Hill. ISBN 978-0-07-049439-8. https://books.google.com/books?id=Xqj-TTzkvTEC. Retrieved 2009-06-06.
8. ↑ "How to Make Tungsten: From Ore to Finished Metal" (in en-US). 2025-08-28. https://biologyinsights.com/how-to-make-tungsten-from-ore-to-finished-metal/.
9. ↑ Merck (2006): "Tungsten trioxide." The Merck Index, volume 14.
10. ↑ David E Williams, Simon R Aliwell, Keith F. E. Pratt, Daren J. Caruana, Roderic L. Jones, R. Anthony Cox, Graeme M. Hansford. and John Halsall (2002): "Modelling the response of a tungsten oxide semiconductor as a gas sensor for the measurement of ozone". Measurement Science and Technology. volume 13. pages 923–931. doi:10.1088/0957-0233/13/6/314
11. ↑ Lee, W. J.; Fang, Y. K.; Ho, Jyh-Jier; Hsieh, W. T.; Ting, S. F.; Huang, Daoyang; Ho, Fang C. (2000). "Effects of surface porosity on tungsten trioxide(WO3) films' electrochromic performance". Journal of Electronic Materials 29 (2): 183–187. doi:10.1007/s11664-000-0139-8. Bibcode: 2000JEMat..29..183L.
12. ↑ K. J. Patel, M. S. Desai, C. J. Panchal, H. N. Deota, and U. B. Trivedi (2013): "All-Solid-Thin Film Electrochromic Devices Consisting of Layers ITO / NiO / ZrO2 / WO3 / ITO". Journal of Nano-Electronics and Physics, volume 5, issue 2, article 02023.
13. ↑ Yugo Miseki, Hitoshi Kusama, Hideki Sugihara, and Kazuhiro Sayama (2010): "Cs-Modified WO3 Photocatalyst Showing Efficient Solar Energy Conversion for O2 Production and Fe (III) Ion Reduction under Visible Light". Journal of Physical Chemistry Letters, volume 1, issue 8, pages 1196–1200. doi:10.1021/jz100233w
14. ↑ É. Karácsonyi, L. Baia, A. Dombi, V. Danciu, K. Mogyorósi, L. C. Pop, G. Kovács, V. Coşoveanu, A. Vulpoi, S. Simon, Zs. Pap (2013): "The photocatalytic activity of TiO2/WO3/noble metal (Au or Pt) nanoarchitectures obtained by selective photodeposition". Catalysis Today, volume 208, pages 19-27. doi:10.1016/j.cattod.2012.09.038
15. ↑ István Székely, Gábor Kovács, Lucian Baia, Virginia Danciu, Zsolt Pap (2016): "Synthesis of Shape-Tailored WO3 Micro-/Nanocrystals and the Photocatalytic Activity of WO3/TiO2 Composites". Materials, volume 9, issue 4, pages 258-271. doi:10.3390/ma9040258
16. ↑ Lucian Baia, Eszter Orbán, Szilvia Fodor, Boglárka Hampel, Endre Zsolt Kedves, Kata Saszet, István Székely, Éva Karácsonyi, Balázs Réti, Péter Berki, Adriana Vulpoi, Klára Magyari, Alexandra Csavdári, Csaba Bolla, Veronica Coșoveanu, Klára Hernádi, Monica Baia, András Dombi, Virginia Danciu, Gábor Kovácz, Zsolt Pap (2016): "Preparation of TiO2/WO3 composite photocatalysts by the adjustment of the semiconductors' surface charge". Materials Science in Semiconductor Processing, volume 42, part 1, pages 66-71. doi:10.1016/j.mssp.2015.08.042
17. ↑ G. Ou (2018). "Tuning Defects in Oxides at Room Temperature by Lithium Reduction". Nature Communications 9 (1302). doi:10.1038/s41467-018-03765-0. PMID 29615620. Bibcode: 2018NatCo...9.1302O.
18. ↑ S. Hurst (2011). "Utilizing Chemical Raman Enhancement: A Route for Metal Oxide Support Based Biodetection". The Journal of Physical Chemistry C 115 (3): 620–630. doi:10.1021/jp1096162.
19. ↑ W. Liu (2018). "Improved Surface-Enhanced Raman Spectroscopy Sensitivity on Metallic Tungsten Oxide by the Synergistic Effect of Surface Plasmon Resonance Coupling and Charge Transfer". The Journal of Physical Chemistry Letters 9 (14): 4096–4100. doi:10.1021/acs.jpclett.8b01624. PMID 29979872. https://www.nature.com/articles/s41467-018-03765-0.
20. ↑ C. Zhou (2019). "Electrical tuning of the SERS enhancement by precise defect density control". ACS Applied Materials & Interfaces 11 (37): 34091–34099. doi:10.1021/acsami.9b10856. PMID 31433618. http://www.unilim.fr/pages_perso/zeng/a196.pdf.

## External links

* International Tungsten Industry Association
* Preparation of tungsten trioxide electrochromic films
* Sigma Aldrich (supplier)

* v
* t
* e

Tungsten compounds

Tungsten(0)|

* W(CO)6

Tungsten(II)|

* WSi2
* WCl2
* W(OH)2

Tungsten(III)|

* W2O3

Tungsten(IV)|

* WC
* WO2
* WS2
* WSe2
* WTe2
* WF4
* WCl4

Tungsten(V)|

* W2O5
* WBr5
* W2Cl10

Tungsten(VI)|

* H3PW12O40
* (NH4)10(H2W12O42)
* WO2Cl2
* WCl6
* WF6
* WN2
* WO3
* WS3
* WOBr4
* WOCl4
* WOF4
* H2WO4

| Organotungsten(VI) compounds|

* W(CH3)6

|

* v
* t
* e

Oxides

Mixed oxidation states|

* Antimony tetroxide (Sb2O4)
* Cobalt(II,III) oxide (Co3O4)
* Europium(II,III) oxide (Eu3O4)
* Iron(II,III) oxide (Fe<sub>3O4)
* Lead(II,IV) oxide (Pb3O4)
* Manganese(II,III) oxide (Mn3O4)
* Silver(I,III) oxide (Ag2O2)
* Triuranium octoxide (U3O8)
* Carbon suboxide (C3O2)
* Mellitic anhydride (C12O9)
* [[Chemistry:Praseodymium(III,IV) Praseodymium(III,IV) oxide]] (Pr6O11)
* Terbium(III,IV) oxide (Tb4O7)

+1 oxidation state|

* Copper(I) oxide (Cu<sub>2O)
* Caesium oxide (Cs2O)
* Dicarbon monoxide (C2O)
* Dichlorine monoxide (Cl2O)
* Gallium(I) oxide (Ga2O)
* Lithium oxide (Li2O)
* Potassium oxide (K2O)
* Rubidium oxide (Rb2O)
* Silver oxide (Ag2O)
* Thallium(I) oxide (Tl2O)
* Sodium oxide (Na2O)
* Water (hydrogen oxide) (H2O)

+2 oxidation state|

* Aluminium(II) oxide (AlO)
* Barium oxide (BaO)
* Beryllium oxide (BeO)
* Cadmium oxide (CdO)
* Calcium oxide (CaO)
* Carbon monoxide (CO)
* Chromium(II) oxide (CrO)
* Cobalt(II) oxide (CoO)
* Copper(II) oxide (CuO)
* Europium(II) oxide (EuO)
* Germanium monoxide (GeO))
* Iron(II) oxide (FeO)
* Lead(II) oxide (PbO)
* Magnesium oxide (MgO)
* Manganese(II) oxide (MnO)
* Mercury(II) oxide (HgO)
* Nickel(II) oxide (NiO)
* Nitric oxide (NO)
* Palladium(II) oxide (PdO)
* Silicon monoxide (SiO)
* Strontium oxide (SrO)
* Sulfur monoxide (SO)
* Disulfur dioxide (S2O2)
* Thorium monoxide (ThO)
* Tin(II) oxide (SnO)
* Titanium(II) oxide (TiO)
* Vanadium(II) oxide (VO)
* Zinc oxide (ZnO)

+3 oxidation state|

* Aluminium oxide (Al<sub>2O3)
* Antimony trioxide (Sb2O3)
* Arsenic trioxide (As2O3)
* Bismuth(III) oxide (Bi2O3)
* Boron trioxide (B2O3)
* Cerium(III) oxide (Ce2O3)
* Dibromine trioxide (Br2O3)
* Chromium(III) oxide (Cr2O3)
* Dinitrogen trioxide (N2O3)
* Dysprosium(III) oxide (Dy2O3)
* Erbium(III) oxide (Er2O3)
* Europium(III) oxide (Eu2O3)
* Gadolinium(III) oxide (Gd2O3)
* Gallium(III) oxide (Ga2O3)
* Holmium(III) oxide (Ho2O3)
* Indium(III) oxide (In<sub>2O3)
* Iron(III) oxide (Fe2O3)
* Lanthanum oxide (La2O3)
* Lutetium(III) oxide (Lu2O3)
* Manganese(III) oxide (Mn2O3)
* Neodymium(III) oxide (Nd2O3)
* Nickel(III) oxide (Ni2O3)
* Phosphorus trioxide (P4O6)
* Praseodymium(III) oxide (Pr2O3)
* Promethium(III) oxide (Pm2O3)
* Rhodium(III) oxide (Rh2O3)
* [[Chemistry:Samarium(III) Samarium(III) oxide]] (Sm2O3)
* Scandium oxide (Sc2O3)
* Terbium(III) oxide (Tb2O3)
* Thallium(III) oxide (Tl2O3)
* Thulium(III) oxide (Tm2O3)
* Titanium(III) oxide (Ti2O3)
* Tungsten(III) oxide (W2O3)
* Vanadium(III) oxide (V2O3)
* Ytterbium(III) oxide (Yb2O3)
* Yttrium(III) oxide (Y2O3)

+4 oxidation state|

* Americium dioxide (AmO2)
* Carbon dioxide (CO2)
* Carbon trioxide (CO3)
* Cerium(IV) oxide (CeO2)
* Chlorine dioxide (ClO2)
* Chromium(IV) oxide (CrO<sub>2)
* Dinitrogen tetroxide (N2O4)
* Germanium dioxide (GeO<sub>2)
* [[Chemistry:Hafnium(IV) Hafnium(IV) oxide]] (HfO2)
* Lead dioxide (PbO2)
* Manganese dioxide (MnO2)
* Neptunium(IV) oxide (NpO2)
* Nitrogen dioxide (NO2)
* Osmium dioxide (OsO2)
* Plutonium(IV) oxide (PuO2)
* Praseodymium(IV) oxide (PrO2)
* Protactinium(IV) oxide (PaO2)
* Rhodium(IV) oxide (RhO2)
* Ruthenium(IV) oxide (RuO<sub>2)
* Selenium dioxide (SeO2)
* Silicon dioxide (SiO2)
* Sulfur dioxide (SO2)
* Tellurium dioxide (TeO<sub>2)
* [[Chemistry:Terbium(IV) Terbium(IV) oxide]] (TbO2)
* Thorium dioxide (ThO2)
* Tin dioxide (SnO2)
* Titanium dioxide (TiO<sub>2)
* Tungsten(IV) oxide (WO2)
* Uranium dioxide (UO2)
* Vanadium(IV) oxide (VO2)
* Zirconium dioxide (ZrO2)

+5 oxidation state|

* Antimony pentoxide (Sb2O5)
* Arsenic pentoxide (As2O5)
* Dinitrogen pentoxide (N2O5)
* Niobium pentoxide (Nb2O5)
* Phosphorus pentoxide (P2O5)
* Protactinium(V) oxide (Pa2O5)
* Tantalum pentoxide (Ta2O5)
* Vanadium(V) oxide (V2O5)

+6 oxidation state|

* Chromium trioxide (CrO3)
* Molybdenum trioxide (MoO3)
* Rhenium trioxide (ReO3)
* Selenium trioxide (SeO3)
* Sulfur trioxide (SO3)
* Tellurium trioxide (TeO3)
* Tungsten trioxide (WO3)
* Uranium trioxide (UO3)
* Xenon trioxide (XeO3)
* Iridium trioxide (IrO3)

+7 oxidation state|

* Dichlorine heptoxide (Cl2O7)
* Manganese heptoxide (Mn2O7)
* [[Chemistry:Rhenium(VII) Rhenium(VII) oxide]] (Re2O7)
* Technetium(VII) oxide (Tc2O7)

+8 oxidation state|

* Osmium tetroxide (OsO4)
* Ruthenium tetroxide (RuO4)
* Xenon tetroxide (XeO4)
* Iridium tetroxide (IrO4)
* Hassium tetroxide (HsO4)

Related|

* Oxocarbon
* Suboxide
* Oxyanion
* Ozonide
* Peroxide
* Superoxide

Oxides are sorted by oxidation state. Category:Oxides

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