Tungsten Bronze Preparation Strategy

The band gap of tungsten bronze (MxWO₃) is about 2.7 eV, and it has free-migrating electrons. It is one of the most suitable materials for transparent and thermal insulation. Research shows that tungsten bronze materials have better transparency and heat insulation than ITO, ATO, AZO and GZO. It is one of the effective means of saving energy for building or automobile glass. It is a kind of high quality filter for infrared light, and it can be coated on the surface of glass or plastic film to form a transparent insulation coating.

In the tungsten bronze lattice, the valence of oxygen atoms is - 2, that is, each oxygen atom is bound to 2 electrons. By introducing - 1 valent anion nM instead of - 2 valent oxygen ion in the lattice of tungsten bronze, 1 electrons bound to the original oxygen atom at the lattice point can be converted into free electrons, and the two kinds of semiconductors with different band width are dissolved, and the lattice point of a semiconductor material is replaced by the atoms of another conductor. On the other hand, the band gap of the solid solution formed is between two kinds of semiconductor band gap, and can be controlled by adjusting the molar ratio of two kinds of semiconductors. Therefore, in the existing technology, the preparation conditions of tungsten bronze are more stringent, which will inevitably increase the technical requirements of the hydrothermal equipment and the preparation cost of tungsten bronze powder, and affect its popularization and application.

In order to improve the production capacity of tungsten bronze, a kind of tungsten bronze powder, dispersing solution and preparation method of W and O lattice sites with substituted hetero atoms and their preparation methods are used in order to reduce the manufacturing cost of tungsten bronze. The experiment process is as follows:

0.2g ammonium tungstate was dissolved in 20ml deionized water and added with 1g oxalic acid and stirred evenly, the pH value of the solution was adjusted to 1.5 with concentrated hydrochloric acid. The above solution was aged for 2 hours at normal temperature, then 0.05g ammonium fluoride (NH₄F) was added to 0.05g, then 0.05g was added to the sodium borohydride (NaBH₄), and then it was poured into the 50ml water heat kettle, and the water heat treatment was 3 at 150. Tungsten bronze powders were obtained by centrifugal drying with a general formula of (NH₄) _0.33WO_2.75F0.2 and a yield of 78% and a diameter of 30-50nm.

The main point of this method is that the substitutional heteroatom guide band introduced into the lattice site is injected into the free electrons, thus improving the conductivity and transparent insulation properties of the tungsten bronze powder, and effectively regulating the band gap of the tungsten bronze powder and the morphology of the tungsten bronze powder during the hydrothermal preparation. At the same time, by introducing the alternative hetero atoms, it is expected to influence the growth of tungsten bronze in the hydrothermal environment, thus greatly reducing the preparation difficulty and preparation cost. The preparation of the tungsten bronze powder system is mild and the cost is low, and it is very widely used in the application of the corresponding system.

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