Tungsten Trioxide is a semiconductor material with great development potential. In recent years, scientific research achievements have been made in the fields of new energy batteries, electrochromic devices, photocatalysts and supercapacitors. Industry flexibly chooses preparation methods according to different needs, among which precipitation method is a popular preparation method of Tungsten Trioxide.
1.Principles
Precipitation method refers to adding a solvent which is miscible with the solution into the solution of mixed components, and changing the solubility of some components in the solution of mixed components by changing the polarity of the solvent, so as to precipitate them from the solution. Precipitation is divided into coprecipitation and chemical precipitation.
2.Preparing Tungsten Trioxide
Coprecipitation mainly refers to sol-coprecipitation method:
(1) Taking a mixture of WCl6 and TiCl4 as a raw material;
(2) Adding surfactant and ammonia water to form mixed colloid of W(OH)6 and Ti(OH)4;
(3) Tungsten Trioxide of 3-9nm was obtained by centrifugal separation and calcination.
Tungsten Trioxide prepared by sol-coprecipitation method is thin film, which is called WO3 electrochromic thin film because of its good electrochromic properties.
Chemical precipitation method:
(1) Taking a certain proportion of 1mol/L Na2WO4 solution and Na2SnO4 solution and mixing them evenly;
(2) Slowly drip that evenly mixed solution when dilute H2SO4 boil;
(3) Continuously stirring to generate precipitate, aging, washing, filtering, drying and calcining to obtain Tungsten Trioxide
With this method, it is found that the growth of WO3 grains is inhibited by the addition of SnO2, so that the sensitivity of Tungsten Trioxide gas is higher, and the best doping amount is 0.5%.
3.The advantages and disadvantages of precipitation method
Tungsten Trioxide powder prepared by precipitation method has small particle size and uniform distribution, and Tungsten Trioxide with uniform composition can be directly obtained by various chemical reactions in solution during the preparation. Therefore, the preparation method has the advantages of simple process, low calcination temperature, short time, good product performance and the like. Although this preparation method has many advantages, it also has some disadvantages, for example, Tungsten Trioxide powder is easy to agglomerate, which is unfavorable for detection.
