Tungsten trioxide (WO 3), also known as yellow tungsten oxide, is an oxide of tungsten and an N-type semiconductor as well. These two characteristics make tungsten trioxide not only have high density, high boiling point and high melting point, but also have catalytic, optical and electrical properties.

WO3 has extremely high sensitivity for NO2 detection, and has been an ideal material for gas sensor coatings. WO3 has received considerable attention on the potential applications as gas sensors, photocatalyst and electrochromic devices. And it is also reported that doping another kind of oxides into WO3 leads to the formation of semiconductor heterojunction, thus can effectively improve the gas sensitivity of the coatings.

Tungsten trioxide, also known as tungsten anhydride (WO₃), is a yellow powder, insoluble in water and alkali, and slightly soluble in acid. Because of its good optical, electrical and gas sensitive properties, it is widely used in life, chemical industry, medical treatment and military affairs.

Tungsten is a metal with the highest melting point of 3440 °C.  Its excellent physical properties, such as good thermal conductivity and low thermal expansion coefficient, make it widely used in high-temperature applications, including aerospace, nuclear, and the national defence industry. One of the significant applications of tungsten is plasma-facing material, which faces a harsh environment such as high temperature, high nuclear irradiation.