Material and Ion Beam Application Division, Nuclear Research Center, P. O. Box 31485-498, Karaj, I.R. IRAN
Tungsten trioxide (WO3) films have been coated on indium thin oxide (ITO) conductive glass substrate, using aqueous solution of peroxotungstic acid (PTA) by the sol-gel dip coating method. X-ray diffractometery (XRD) analysis confirmed monoclinic and triclinic structure for the film and powdered WO3 respectively. Fourier transforms infrared spectroscopy (FT-IR) exhibited the structure of peroxotungstic acid. The SEM micrograph of annealed species revealed micro cracks due to decrease of density and contraction of layers. Energy- dispersive X-ray (EDX) study determined 1:3 ratios of oxygen and tungsten atoms in the prepared films at heat treatment temperature higher than 200ºC. The electrochromical behavior was investigated in 1M HCL solution employing cyclic voltammetry. It was found that WO3 films demonstrated good reversibility at 200 ºC.
 Sharma, N., Deepa, M., Varshney, P. and Agni-hotory, S. A., Influence of organic additives on the morphological, electrical, and electrochromic properties of sol-gel derived WO3 coatings, J. Sol-Gel Sci. &Technol., 18,167-173 (2000).
 Varshney, P.K., Nidhi, Ramachandran, R. and Agnihotory, S. A., Colloidal tungstic oxide films for electrochromic applications: preliminary studies Ind. J. Pure &Appl. Phys., 37, 262-265 (1999).
 Nishide, T., Mizkani, F., Crystal structures and optical properties of tungsten oxide films prepared by a complexing-agent-assisted sol-gel process, Thin Solid Films, 259, 212-217 (1995).
 Renard, Y.V., Leveque, G., Abdellaoui, A. and D Donnadieu, A., Optical constants of electrochromic polycrystalline WO3 thin films prepared by chemical vapor deposition, Thin Solid Films, 203, 33-39 (1991).
 Keneko, H., and Miyake, K., Estimation of the composition parameter of electrochemically colored amorphous hydrogen tungsten oxide films, J. Appl. Phys., 66, 845-850 (1989).
 Lrftheriotis, G., Papaefthimiou, S., Yianoulis P. and Siokou A., Effect of tungsten oxidation states in the thermal coloration and bleaching of amorphous WO3 films, Thin Solid Films, 384, 298-306 (2001).
 Lee, K. D., Preparation and electrochromic properties of WO3 coating deposition by the sol-gel method, Sol. Energy Mater., 57, 21-30, (1999).
 Ramachandran, R., Nidhi, Paradeep, S. A. and Agnihotory, S. A., Sol-gel deposition of EC-WO3 films using a precursor with enhanced stability, Ind. J. Pure & Appl.Phys., 37, 353-355 (1999).
 Yamanaka, K., Oakamoto, H., Kidou, H., Peroxo-tungstic acid coated films for electrochromic display devises, Jpn. J. Appl. Phys., 25 (9), 1420-1426, (1986).