WO3 airtight calcination producing violet tungsten oxide is by mixing tungsten powder and tungsten trioxide(WO3) under a certain ratio, caocinating under airtight or argon gas atmosphere. Tungsten powder as reducing agent, it is oxidized first. Tungsten trioxide as reducing material, tungsten valence decreases which generates violet tungsten oxide.
Violet tungsten oxide crystalline has needle shape or slender prismatic, its dimension is usually smaller than 1um. Use it as precursor can easily obtain tungsten powder with finer grain size. Violet tungsten oxide is used as raw material to produce super fine crystalline tungsten carbide in recent years.