Production of ultrafine particles of high-temperature tetragonal WO3 by dc arc discharge in Ar-O2 gases

Ultrafine particles of WO3 are successfully produced by dc arc discharge in Ar-O2 gases. Particle sizes are distributed from 10 nm to 1 μm depending on production conditions: gas pressure, collection position and discharge current. Observations of the cooled particles by electron microscopy indicate that the WO3 particles are tetragonal, a phase that is usually only stable above 725 deg. C. The octahedral crystals are bounded by eight {1 0 1} faces and occasionally truncated by {1 0 0} and/or {0 0 1} faces. This method of producing WO3 by dc arc discharge therefore affords a high-temperature phase that is preserved upon cooling to room temperature