Production of tungsten oxide coatings, via sol–gel processing of tungsten anion solutions

An investigation has been carried out into the production of tungsten oxide coatings from tungstic chloride and tungstic acid precursors, via a sol–gel type process, using various combinations of ethanediol and block co-polymers as stabilising additives to achieve microstructural control. The products were characterised by scanning electron microscopy, X-ray diffraction, FTIR spectroscopy and thermal analysis, with colour changes investigated by UV/Vis spectroscopy. Strongly photochromic transparent coatings were successfully prepared by the reaction of tungstic acid under basic conditions in the presence of ethanediol.