CsxWO3 Influence on NIR Shielding Property

Near-infrared(NIR, IR-A DIN), is defined by the water absorption, and commonly used in fiber optic telecommunication because of low attenuation losses in the SiO2 glass (silica) medium. Image intensifiers are sensitive to this area of the spectrum. Examples include night vision devices such as night vision goggles.

Recently, shielding not only ultraviolet rays but also infrared rays has been attracted attentions in terms of saving resource and energy and creating comfortable life space. Cs doped tungsten bronze (CsxWO3) which has suitable amounts of free electrons in crystal is one of the candidate materials of inorganic infrared rays shielding materials, since it can shield ultraviolet and infrared rays by interband transition and plasma oscillation of free electrons, respectively. Nanoparticles of CsxWO3 particles were synthesized by solvothermal reaction of WCl6 and CsOH・H2O in ethanol and ethanol aqueous solutions at 200 ℃ for 12-47 h. After that, CsxWO3 particles were heated in 500 ml/min NH3 gas flow at 400 ℃ for 1 h. Sheet-like and rod-like nanopartricles of CsxWO3 were synthesized in ethanol and 42.9 vol% ethanol aqueous solution at 200 ℃, respectively. The samples formed in 42.9 vol% ehanol aqueous showed higer crystallinity but lower Cs/W atomic ratio than those in ethanol. Sheet-like particles showed higher visible light transparency, while rod-like particles showed more excellent infrared shielding properties, indicating that rod-like particles were more suitable for shielding infrared rays. Moreover, the visible light transparency and infrared shielding properties could be improved by improving the dispersion state of the particles by agitating with ZrO2 beads. The electric conductivity of the pressed pellet of rod-like particles could be increased by heating in NH3 gas atmosphere at 400 ℃.

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