Blue tungsten oxide refers to a class of dark blue compound containing tungsten (Ⅵ) and tungsten (V) mixed valence state, usually formed in the solution. For example, suspension of tungsten oxide in hydrochloric acid can be reducted by zinc to produce tungsten blud. Besides that, wet tungsten oxide exposed under UV radiation and white gum tungstate in sunlight will turns into tungten blue. Tungsten blue is different with blue tungsten oxide.

Blue tungsten oxide is the product of reductant and the tungsten compound, commonly referred to as blue tungsten. The composition of blue tungsten oxide is very complicated, Among which there is also medium oxide like WO2 and WO4. If blue tungsten oxide composition is calculated by WO, then the content of Wolframate is 82.13%. But the content of Wolframate in WO3 is 79.30%. So Wolframate content in blue tungsten oxide is more than yellow tungsten oxide. According to the standard of blue tungsten oxide, its WO3 content is 99.95%, wolframate content should reach 80.00%-80.80%.

Preparation of blue tungsten oxide: Blue tungsten oxide is an important raw material for producing tungsten powder. Tungsten powder produced by blue tungsten oxide is easier to operate and control the particle size also particle distribution, it can help other elements mixing with tungsten powder during reduction process. As a result, blue tungsten oxide is gradually become raw material for producing tungsten powder instead of yellow tungsten powder. There are three methods can be used to produce blue tungsten oxide: APT calcination method, APT hydrogen reduction and internal reduction method. The first two methods are commonly used in the present industry area.