12-Tungstosilicic Acid (12-TSA) as a Tungsten Precursor in Alcoholic Solution for Deposition of xWO3(1 − x)SiO2 Thin Films (x ≤ 0.7) Exhibiting Electrochromic Coloration Ability

The preparation of stable alcoholic solution of tungstosilicic acid and silicon alkoxide, which can be used for xWO3 (1 − x)SiO2 thin film deposition by dipping, is described. After thermal treatment at temperatures 440 to 500°C in nitrogen films with x higher than 0.6 exhibit electrochromic coloration ability. After coloring the film by H+ imtercalation (by contact with an indium wire trough a drop of aqueous solution of H2SO4) the luminous transmittance (illuminant D65, wavelength range from 380 to 780 nm, summation at 10 nm intervals) of glass coated with 90 nm thick xWO3(1 − x)SiO2 thin film decreases from 71.7 to 28.6% and the IR reflection increases to over 30%. At the same time the surface resistance decreases from a few MΩ/□ to about 400Ω/□. The thermal decomposition of tungstosilic acid embedded in alkoxy-hydroxy-oxy-silicon matrix is investigated with DTA, TGA, XRD and FTIR spectroscopy.