1. Chemical properties of cesium tungsten bronze
Cesium tungsten bronze is a kind of blue black powder, which is a kind of non stoichiometric compound. Its English name is Cesium Tungsten Bronze, and its chemical formula is CsxWO3. The purity is generally higher than 99.9%. The particle size is uniform, the primary particle size is about 30nm, the loose density is 1.5g/ml, and the specific surface area is 50m2/g. The crystal structure is oxygen Octahedron structure with high crystallinity and good dispersion.

Because of the special structure of oxygen Octahedron, cesium tungsten bronze has better near-infrared absorption characteristics, better weather resistance, higher physical and chemical adsorption capacity, lower resistivity and excellent low-temperature superconductivity. Network data shows that cesium tungsten bronze has a blocking rate of up to 90% in the near-infrared region. Usually, adding 2g CsxWO3 per square meter of coating can achieve a transmittance of less than 10% at 950nm, while achieving a transmittance of over 70% at 550nm (a 70% indicator is the basic indicator for most highly transparent films).

2. Characteristics of nano cesium tungsten bronze
Nano tungsten bronze materials have potential applications in transparent insulation coatings, electronic devices, humidity sensors, gas sensors, and photocatalysis due to their unique chemical, electrochemical, and optical properties.
1) Transparent insulation coating
Nano cesium tungsten bronze has excellent near-infrared light shielding performance and good visible light transmittance. CsxWO3 solution and Polyvinylpyrrolidone solution are mixed evenly to prepare mixed slurry, which is coated on the clean glass surface by scraping method, and dried in an oven at 60 ℃ to obtain the glass with tungsten bronze nano coating.
2) The Use of Cs0.33WO3 in Glass
Cs0.33WO3 nano powder has good visible light transmittance and near-infrared light shielding performance, which can make the prepared glass products have better light transmittance and heat insulation effect, so it is suitable for building glass windows and car windows, which can effectively save the consumption of air conditioning power, and effectively prevent indoor items from aging.
3. Application technology of nano cesium tungsten bronze in the field of solar energy storage
The nano cesium tungsten bronze coating has high near-infrared (NIR) absorption ability, which can effectively reduce the solar thermal gain and air conditioning energy consumption of buildings. However, according to research, nano tungsten bronze materials can quickly convert absorbed infrared light into heat, exhibiting significant photothermal conversion properties. Due to the high photothermal conversion efficiency of Cs0.33WO3 coating, the absorbed solar energy may cause the surface of building glass windows to overheat, generating secondary thermal radiation, thereby affecting their transparent insulation performance.
Due to the high photothermal conversion efficiency (73%) of nano cesium tungsten bronze, the absorbed solar energy is efficiently converted into thermal energy (after 360 seconds of illumination, the surface temperature of the material increases by 56 ℃). When cesium tungsten bronze is used as a coating, it will cause strong secondary thermal radiation. Therefore, in order to solve the overheating problem of nano cesium tungsten bronze coatings, we have designed a new type of energy-saving composite window by combining nano cesium tungsten bronze with phase change energy storage materials (PCMs, such as paraffin) with near-infrared light shielding function. In the preparation process of this composite window, hexagonal nano cesium tungsten bronze nanoparticles were prepared by solid phase method, and nano cesium tungsten bronze/SiO2 composite sol was prepared by sol-gel method. Then, the blank glass and the glass coated with Cs0.33WO3/SiO2 coating are combined to form a glass groove, and the melted paraffin is poured into the glass groove to form a composite window. When the sunlight is strong, the composite window can absorb infrared light through the Cs0.33WO3/SiO2 coating, reducing infrared light entering the building. At the same time, the melting phase transition process of paraffin suppresses the increase in temperature of Cs0.33WO3 layer and secondary thermal radiation. When the ambient temperature is low enough, paraffin can gradually release the thermal energy stored in phase change energy storage materials to the indoor environment through the solidification phase change process. Therefore, this Cs0.33WO3 paraffin composite window can effectively maintain stable and comfortable indoor temperature in buildings. The specific experimental data shows that in the self-made temperature measurement building model, the nano cesium tungsten bronze paraffin composite window can reduce the indoor temperature change and maintain the indoor temperature change within 7.3 ℃, while the indoor temperature change of the blank glass window is within 24.2 ℃. This composite window is expected to improve the energy efficiency of buildings, and is more suitable for areas with significant temperature fluctuations during the day and night or between seasons.
4. Innovative ideas in the field of solar energy storage
Cs0.33WO3/SiO2 coating with high visible light transmittance, excellent infrared obscuration, and high photothermal conversion efficiency. And by utilizing the transparent insulation properties of the coating and the phase change energy storage characteristics of paraffin, a composite window that effectively regulates indoor temperature is obtained. In composite materials, nano cesium tungsten bronze can convert infrared light absorbed during the day into thermal energy, coexisting in phase change materials; When the temperature is low, phase change materials will release thermal energy. The synergy of two functional materials can not only solve the overheating problem of nano cesium tungsten bronze, but also efficiently capture and utilize solar energy. It can prevent the indoor temperature from being too high and also prevent the indoor temperature from being too low, which not only reduces the cooling energy consumption of the building, but also reduces the heating energy consumption. The nano cesium tungsten bronze paraffin composite material is not limited to windows, but can be more widely used in indoor furniture, flooring and other building materials to achieve the goal of effectively regulating indoor temperature.