Blue tungsten oxide (BTO) is also called tungsten blue oxide (TBO),from which reduction reaction of ATP by hydrogen come, is an common raw material for tungsten powder,it have certain advantage in high specific surface area,easy reduction.

The tungsten-oxygen system is rather complex which could be stable stoichiometric binary oxides(WO3, WO2.9, WO2.72 and WO2).TBO is an mixture of different compounds, mainly WO2.90 and ammonium tungsten bronze(ATB).TBO have been used to produced tungsten powder from 1970s, and now is the most important precursor in the line from oxide to W and WC powder. 

 

The main blue tungsten oxide preparation methods are pyrometallurgical process and hydrometallurgical process.The former is widely applied in industry,commonly using reduction reaction of ATP by hydrogen in rotary furnace.The chemical equations of TBO's preparation as shown follows:

 

5(NH4)2•O•12WO3•5H2O→5(NH4)2•O•12WO3+ 5H2O

5(NH4)2•O•12WO3→12 WO3+10NH3+5H2O

2NH3→N2+3H2

WO3+H2→WO2.9+H2O

 

The factors affecting  properties of TBO in preparation process are temperature,heating rate and heating time, etc.