Nano tungsten trioxide is the most used photochromic material currently, which may be applied for preparing nano-ceramic dispersion solution. Thus, this type of ceramic dispersion will have the characteristics of high thermal insulation and excellent weather resistance. Also, it does not interfere with radio communications. The reason why tungsten trioxide has excellent photochromic properties is that tungsten trioxide is a type of semiconductor material, which has symmetrical structure, and therefore it can generate electron hole pair under light excitation.
Photochromism is the reversible transformation of a chemical species between two forms by the absorption of electromagnetic radiation, where the two forms have different absorption spectra. Trivially, this can be described as a reversible change of color upon exposure to light.
In other words, a substance reacts to get another substance under the action of light, and then turns into a previous reactant under a certain condition. This condition may be light, thermal effect, or the combination of light and thermal effect. This phenomenon is photochromism.
More details, please visit:
http://www.tungsten-powder.com/Tungsten-Trioxide.html
