Tungsten trioxide (WO3) consists of one tungsten atom and three oxygen atoms. Tungsten is a d-block metal from group 6 and has an oxidation state +6 in the compound. Oxygen belongs to group 16 and each of three oxygen atoms have oxidation state -2 in WO3. The physical properties of WO3 have been presented in Table 1. From tungsten minerals, tungsten is recovered and WO3 is an intermediate of that process[1, p.954]. Tungstic acid, H2WO4, is known as related compounds of WO3 and while it decomposes at high temperatures, tungsten trioxide is formed [1]. Other ways to obtain WO3 are by heating metallic tungsten, its lower oxides or its carbides in air [1].

WO3's class of materials is metal ceramics[2]. Metallic tungsten and earth doped WO3 form together WO3 ceramics

[2]. Metal ceramics overall are studied and used for example in dentistry and to be more precise as a crown to retrofit an existing abutment tooth[3]

WO3 is a fascinating compound in many fields since it obtains fascinating physical and chemical properties. In the next chapter of this wiki page is presented some common synthesis methods of WO3 as WO3 is being used for example in thin films and in high-tech applications. After that is shown the typical structures of WO3. Temperature has a crucial affect on the structure of WO3. After structure of WO3 is presented, most common applications of WO3 is described. Finally, there is listed characterization methods that are used for WO3.

Table 1. Physical properties of tungsten trioxide [4]


Physical properties

Molar mass

231.84 g/mol
Density7.16 g/cm3
AppearanceCanary yellow powder
Melting point1472 °C


WO3 can be synthesized into nanoparticles or thin films and then used in various applications. There's several different ways to synthesize WO3. WO3 nanoparticles can by synthesized by a 2-stage method[5]. Firstly, ammonium tungstate pentahydrate was ball-milled and then it when through calcination process [5]. The ball-milling process took 8 hours and the calcination process was held in the electrical furnace where temperature was increased to 500 °C and held there for 30 minutes before cooling back to room-temperature [5].

In one study, WO3 thin films can be obtained for example by hydrothermal reaction [6]. Tungsten-source was an aqueous Na2WO4 and in acidic conditions, WO3 was synthesized by hydrothermal reaction at 180 °C [6]. Stainless steel was used as a substrate and it was found that when the Na2WO4 solution had pH value of 2.5, there was a hexagonal WO3 thin film formed while the sample was dried in an autoclave [6]. In other paper, a carbonized WO3 thin films were obtained by a 3-stage synthesis [7]. The 3-stage synthesis consisted of radio-frequency sputtering system, annealing and the carbonization process at high temperature



WO3 owns a triclinic structure and its space group and structure type differ depending on the surrounding temperature[8, p.1105-1106]

. Different WO3 phases can be observed in temperature range 900-0 °C. In Table 2., there's been presented four main forms of WO3 between temperatures 0 and 900 °C. The information for the table 2 was found by using ICSD. As seen in Table 2. structures of WO3 obtains 8 "formula units" per unit cell under 740 °C. However, above 740 °C the crystal structure of WO3 turns into tetragonal and the amount of "formula units" per unit cell drops down to 2. As WO3 is monoclinic at room temperature, that is the most common structure of WO3. 

Table 2. Different structures of tungsten trioxide depending on temperature.

Temperature (°C)-50 - 1717 - 330330 - 740740 - 900

Crystal system [8, p.1105-1106]


Space group [8, p.1105-1106]

Structure typeWO3(aP32)WO3(mP32)-WO3(tP8)
Coll. code on ICSD135341865483688367
Formula units, Z8882
Cell parameters a, b, c (Å)7.308, 7.525, 7.6867.343, 7.624, 7.7167.341, 7.570, 7.7545.303, 5.303, 3.935
Cell parameters α, β, γ (°)89.021, 90.865, 90.75390.000, 90.233, 90.00090.000, 90.000, 90.00090.000, 90.000, 90.000

In Figure 1. is presented the structure of WO3 in under 17 °C where its crystal system is triclinic. 

Figure 1. The structures of WO3(aP32) (Figure: Eino Kilpeläinen)

In Figure 2. is shown the most common structure of WO3 because monoclinic crystal system appears in room temperature.

Figure 2. The structures of WO3(mP32) (Figure: Eino Kilpeläinen)

When temperature is between 330 and 740 °C, WO3 have an orthorhombic crystal system as seen in Figure 3. 

Figure 3. The structures of orthorhombic WO3. (Figure: Eino Kilpeläinen)

When temperature is increased to 740-900 °C, the crystal system changes quite radically into tetragonal and its number of formula units drops form 8 to 2 as shown in Figure 4.

Figure 4. The structures of WO3(tP8). (Figure: Eino Kilpeläinen)


As seen in Table 1. WO3 appears as a heavy yellow powder and it is also insoluble in water [1]. These properties makes WO3 as a great pigment used in ceramics [1]. WO3 has arose interest in various of fields due to its fascinating physical and chemical characteristics [5]. In Table 3. is shown some of the physical and chemical characteristics of WO3. WO3 is used as a ingredient to produce tungstates for x-ray screens [1]. WO3 owns suitable properties for different high-tech applications [5]. In one study about thin films, was described that tungsten oxides suit well as rechargeable lithium batteries in electrochemical devices [6]. With so fascinating properties, WO3 has been presented to fit for microelectronics, selective catalysis and environmental engineering [5]

Table 3. WO3 has a lot of interesting properties [5].

Physical and chemical characteristics of WO3
  • Innocuous
  • Mechanically strong 
  • Chemically and thermally stable
  • Good optical properties
  • Chemically inert
  • Extensive band gap
  • Inexpensive
  • Environmentally friendly 
  • Ability in adsorbing visible light

Metal-ceramics are used for example in dentistry because they meet the esthetic criteria and suit well under existing partial removable dental prosthesis [3] Metal-ceramics are so common in dentistry that they have 11 evaluation criteria to measure and compare their fit[9, p.168-170]

. Surface texture and color match are examples of these criteria [9, p.168-170]. WO3 ceramics has been under investigation about the origin of varistor properties of them by applying heat treatment in different atmospheres



In one study, SEM, X-ray diffraction and Fourier transform infrared were used to support the analysis of adsorption isotherm of densed monoclinic tungsten trioxide nanoparticles [5]. With the results of these characterization methods, the researchers could study how chemical and physical interactions occur during adsorption process [5]. In other research, a WO3 thin film and powder were characterized by SEM, XRD and TG measurements [6]. For example, with SEM the surface of WO3 thin film could be studied [6]


1. 1 2 3 4 5 6

Pradyot, P. (2003) Handbook of Inorganic Chemicals. New York: McGraw-Hill. p. 954.

2. 1 2

Ross, L. What is the Tungsten Trioxide Ceramic? Advanced Ceramic Materials. 28.2.2023.

3. 1 2

Seo, J.-M. & Ahn, S.-G. (2014) Fabrication of a metal-ceramic crown to fit an existing partial removable dental prosthesis using ceramic pressed to metal technique: a clinical report. The journal of advanced prosthodontics. [Online] 6 (3), 241–244. DOI: 10.4047/jap.2014.6.3.241.

4. 1
Tungsten trioxide. PubChem. National Library of Medicine. 23.2.
5. 1 2 3 4 5 6 7 8 9

Nandiyanto, A. B. D. et al. (2020) Adsorption Isotherm of Densed Monoclinic Tungsten Trioxide Nanoparticles. Sains Malaysiana. [Online] 49 (12), 2881–2890. DOI: 10.17576/jsm-2020-4912-01.

6. 1 2 3 4 5 6

Kumagai, N. Kozawa, K. Kumagai, N. Komaba, S. Derja, A. Synthesis of Hexagonal Tungsten Trioxide Thin Film and Electrochemical Lithium Intercalation, Denki Kagaku oyobi Kogyo Butsuri Kagaku, 1998, Volume 66, Issue 12, Pages 1223-1229, Released on J-STAGE September 10, 2019, Online ISSN 2434-2556, Print ISSN 0366-9297,

7. 1 2

Cho, H. et al. (2021) Highly carbonized tungsten trioxide thin films and their enhanced oxygen evolution related electrocatalytic functions. Journal of materials research and technology. [Online] 122216–2223.

8. 1 2 3

Diehl, R. Brandt, G. Salje, E. (1978) The Crystal Structure of Triclinic WO3. Acta Crystallographica Section B. 34. 1105-1111.

9. 1 2

Esquivel-Upshaw, J. Rose, W. Oliveira, E. Yang, M. Clark, A. Anusavice, K. (2013) Randomized, Controlled Clinical Trial of Bilayer Ceramic and Metal-Ceramic Crown Performance. Journal of prosthodontics. [Online] 22 (3), 166–173.

10. 1

Hongwang, Z. Zhongqiu, H. Tongye, L. Yu, W. Yong, Z. (2010) Origin of varistor properties of tungsten trioxide (WO 3 ) ceramics. Journal of semiconductors. [Online] 31 (2).

  • No labels