The method of preparing purple tungsten oxide is similar to that of preparing blue tungsten oxide, but different chemicals need to be introduced in the preparation process to control the color of tungsten oxide. The following is a common method to prepare purple tungsten oxide from ammonium paratungstate:
Material Science:
Ammonium paratungstate
Sodium hydroxide (NaOH)
Ammonium chloride (NH4Cl)
Calcium chloride (CaCl2)
Ammonia water (NH3 • H2O)
Sodium nitrate (NaNO3)
distilled water
Step:
At room temperature, dissolve sodium tungstate chloride in distilled water until the concentration reaches 10%.
Add NH4Cl to the solution until the pH value is 3-4.
Add appropriate amount of CaCl2 and stir to dissolve.
Adjust the pH value to 9-10 with NH3 • H2O and keep it for 2 hours under stirring to fully precipitate tungsten oxide (WO3).
Filter out the sediment and wash it to neutral.
Mix NH4) 2W2O7 with NaOH at room temperature, stir and dissolve.
Transfer the mixture to distilled water and add appropriate amount of CaCl2 and NaNO3.
Adjust the pH value to 9-10 and stir for 2 hours to fully precipitate purple tungsten oxide (WO3).
Filter out the precipitate, wash it to neutral, and dry it at 50 ℃.
The final product is purple tungsten oxide, whose chemical formula is WO3. The function of adding NaNO3 is to control the color of tungsten oxide and adjust it to purple.
