Photochromic Upgrade Scheme for Tungsten Trioxide

Tungsten trioxide is an important inorganic photochromic material, which has wide application prospects in large screen display and high density information storage. Compared with organic photochromic materials, WO₃ has good stability and low cost, but its photochromic efficiency is poor. In order to improve the discoloration efficiency of this kind of inorganic materials, scholars at home and abroad have proposed various solutions and achieved many results.

In recent years, the preparation of tungsten oxide ultrafine powders, especially pyrochlore and tungsten bronze phase metastable tungsten oxide materials, has attracted wide attention. Hydrothermal synthesis at medium and low temperatures is a good method to prepare metastable oxide nanomaterials, but its synthesis conditions are limited and are not conducive to industrial synthesis. In order to solve the technical problems, some scholars have synthesized doped tungsten oxide nanomaterials doped with gallium and zinc in tungsten oxide, which have achieved good results. The doping process involves the following steps:

(1)Raw material preparation: accurately weigh the corresponding weight of zinc oxide, zinc oxide, gallium trichloride GaCl₃ and ammonium tungstate in proportion;

(2)Preparation of precursor solution: ammonium tungstate, zinc oxide, zinc oxide and gallium trichloride GaCl₃ were dissolved in deionized water in turn, then HNO₃ solution was added while stirring, making the PH value of the prepared precursor solution 5;

(3)Hydrothermal reaction: the precursor solution is stirred at room temperature for 1 hour, then added to the reactor, and reacted at 250 ℃ for 6 hours, then cooled naturally to room temperature. The lower sediment is filtered, washed, dried and crushed to obtain the crushed sample.

(4)Powder sintering: The crushed sample is calcined at 400 ℃ in sintering furnace for 8 hours, and the target product is doped with tungsten oxide nano-material ZnxGayWO₃. The prepared ZnxGayWO₃ powder has small particle size, narrow distribution, difficult to agglomerate, good stability and high purity.

By doping gallium and zinc to synthesize doped tungsten oxide nanomaterials, it can effectively inhibit the electron recombination process after photoexcitation, thus greatly increasing the number of photogenerated carriers involved in the photochromic process, and further improving the photochromic efficiency of tungsten oxide. Compared with traditional WO₃, the photochromic efficiency of the newly synthesized nanomaterials can be increased by more than 200 times. The color changes from light blue to dark blue, and the powder color restores to the original color. It has a wide range of applications, including decorations and protective packaging materials, auto-developing holographic recording technology, computer memory storage elements, information display screen, radiometer, discolored glasses and so on.

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