Cesium tungsten bronze (Cs_xWO₃, x=-0.1、0.2、0.3) powders were synthesized with different cesium content by the low temperature hydrothermal method in citric acid solution. Citric acid is a weak organic tribasic acid. It occurs naturally in citrus fruits. In biochemistry, it is an intermediate in the citric acid cycle, which occurs in the metabolism of all aerobic organisms. More than a million tons of citric acid are manufactured every year. It is used widely as an acidifier, as a flavoring, and as a chelating agent. A citrate is a derivative of citric acid; that is, the salts, esters, and the polyatomic anion found in solution. An example of the former, a salt is trisodium citrate; an ester is triethyl citrate. When part of a salt, the formula of the citrate ion is written as C₆H₅O₇³⁻ or C₃H₅O(COO)₃³⁻.

 

Hydrothermal synthesis includes the various techniques of crystallizing substances from high-temperature aqueous solutions at high vapor pressures; also termed "hydrothermal method". Temperature-difference method is the most extensively used method in hydrothermal synthesis and crystal growing. Supersaturation is achieved by reducing the temperature in the crystal growth zone. The nutrient is placed in the lower part of the autoclave filled with a specific amount of solvent. The autoclave is heated in order to create two temperature zones. The nutrient dissolves in the hotter zone and the saturated aqueous solution in the lower part is transported to the upper part by convective motion of the solution. The cooler and denser solution in the upper part of the autoclave descends while the counterflow of solution ascends. The solution becomes supersaturated in the upper part as the result of the reduction in temperature and crystallization sets in.

 

The Cs_xWO₃ film was prepared with PVA as film forming agent by roller coating method. The near-infrared shielding and heat insulation performance of the glass coated with Cs_xWO₃ film with different cesium content were mainly investigated. The results indicate that the near-infrared shielding and insulation of the glass coated with Cs_xWO₃ film is improved with the increasing of the cesium content. By comparison with the blank glass, the glass coated with Cs_0.3WO₃ film has best near-infrared shielding and heat insulation, and the temperature difference of heat insulation can attain to 13.5℃.