A synthetic method of doped tungsten bronze powder having the high infrared shielding property by use of a hydrothermal-thermal reduction method and aims at solving the technical problem of improving the infrared shielding property of the single-phase tungsten  bronze having the molecular formula of M_xWO₃. According to the method, a tungstate containing molybdenum is synthesized firstly by use of a hydrothermal method, and then the molybdenum doped bronze powder having the diameter within the range of 10-200nm can be obtained by use of a hydrogen reduction method. The raw materials include a tungstate, a sulfate and a molybdate; the doping element is molybdenum; the molar ratio of molybdenum to tungsten ranges from 0.005 to 0.05.

Tungsten bronze is a typical non-stoichiometric compounds having the formula can be written as M_xWO₃, M is typically an alkali metal, X values ranged between 0 to 1. Tungsten bronzes typically have a metallic sheen and a special color. Changes in species and X values of M, and allow it to have a conductor or semiconductor properties. In recent years, this compound has a mixed valence ions, as a new infrared shielding material, caused some study based on those concerns.

 

For the infrared shielding properties of bronze, most study based on the object of this stage is mainly tungsten bronze of the formula with single system. With the in-depth study based on tungsten bronze complex system could gradually become the focus. Complex systems can be constructed by doping, or a method for preparing a cation M contains many pores of the composite tungsten bronze. Tungsten bronzes compared to a single system, complex system will bring about changes in the crystal structure, it is possible to produce more crystal defects. S weakness will destroy the continuity of the surface of the particle, so that localized surface plasmon enhancement, surface plasmon resonance and infrared absorption is one reason to produce tungsten bronze. On the other hand, it may also change the size and structure of the tungsten bronze bore from within, such as shear caused a kind of lattice distortion phenomenon. Changes in the pore structure may introduce more M cation, thereby increasing the free carrier concentration, and the free carrier concentration will affect the infrared shielding properties of tungsten bronze.

 

The hydrothermal process under certain temperature and pressure, in water, aqueous fluid, such as steam or related to general chemical reaction. Hydrothermal reaction depending on the type of reaction can be divided into hydrothermal oxidation, hydrothermal reduction, hydrothermal precipitation, hydrothermal synthesis, water, thermal hydrolysis, hydrothermal crystallization.

 

Hydrogen reduction at high temperature with hydrogen in the metal oxide reduction method of preparation of metal. Compared with other methods (such as carbon reduction, zinc reduction method, etc.), nature of the product easier to control, purity is higher.

 

A kind of doped tungsten bronze powder with high infrared shielding performance, characterized in that: the doped tungsten bronze powder is sodium tungsten bronze powder or potassium tungsten bronze powder .

 

A synthetic method of doped tungsten bronze powder with high infrared shielding performance,  including two steps of the hydrothermal reaction and the hydrogen reduction. The first step: the hydrothermal reaction, prepare a mixture solution; weighed a mount of tungstate, molybdate and sulfate, dissolved in deionized water to give a mixed solution; dosage: mixed solution of tungstate at a concentration of 0.05mol / L~0.2mol / L sulfate concentration of 0.05mol / L~0.5mol / Lo press 0.005~0.05 molybdenum/  tungsten molar ratio of added molybdate; the tungstate compound was prepared containing molybdenum; first with dilute sulfuric acid to adjust 1vol% the pH of the mixed solution to 1.4~1.7 and then poured into a stainless steel reactor has a Teflon liner Arthraxon; then, the reactor was placed in an electric oven at a rate of 2~5 ° C / min heating to the reaction temperature is 200 ° C~240 ° C, the reactor vessel temperature is 200 ° C~240 ° C, under a pressure of I~5MPa conditions, the reaction 20h~40h, after the reactor was cooled, the precipitate was removed; and then deionized water and ethanol precipitate was washed sequentially and 50 ° C~80 ° C dried 1h~24h, give tungstate compound containing molybdenum; Step two: hydrogen reduction reaction of molybdenum doped tungsten bronze powder the molybdenum-containing compound into a tube furnace, to 2~5 ° C / min heating rate of heating to the reaction temperature of 450 ° C~5500C; heating process required to continuously purged with nitrogen; when the reaction temperature reaches 450 ° C~ 550 ° C, the continuous flow of hydrogen at atmospheric conditions H₂ / N₂ were sufficiently reduced 0.5h~2h, the end of the reaction, this time still nitrogen gas to prevent oxidation of the product; the furnace temperature to be cooled to room temperature, remove the product was doped molybdenum tungsten bronze powder.

 

In the hydrogen reduction of this synthetic method, in order to make the reduction reaction sufficiently, tungsten valence and the reaction temperature is closely related to strictly control the reaction temperature to ensure that the product is a tungsten bronze mixed valence structure in line with its formula M_xWO₃, The doped tungsten bronze rod powder obtained by this preparation method with a simple preparation process, have regular shape products, uniform size, with good infrared shielding performance. Before and after the doping, infrared shielding performance is more evident.