Abstract
Thin layers of tungsten trioxide have been prepared from an aqueous solution of peroxotungstic acid (PTA) using the sol-gel method. Compositional, structural and optical characteristics of WO3 coated on indium tin oxide (ITO) conductive glass substrates were studied using X-ray diffractometery (XRD), cyclic voltammetery (CV), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). Monoclinic and triclinic crystalline structures for thin film and powdered WO3 were confirmed by XRD analysis. SEM micrograph of annealed samples revealed micro cracks due to a decrease in density and a contraction of layers. EDX analysis showed that 1∶2 ratio of oxygen and tungsten atoms in the prepared films is obtained at heat treatment temperatures higher than 200 °C. Furthermore, the annealed samples showed very good electrochromic behavior in cyclic voltammetery studies. Refractive index “n” and extinction coefficient “k” values were found to be reduced by increasing the wavelength and decreasing the temperature.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
N. Sharma, M. Deepa, P. Varshney and S.A. Agnihotory: “Influence of organic additives on the morphological, electrical, and electrochromic properties of sol-gel derived WO3 coatings”, J. Sol-Gel Sci. & Technol., Vol. 18, (2000), pp. 167–173.
P.K. Varshney, Nidhi, R. Ramachandran and S.A. Agnihotory: “Colloidal tungstic oxide films for electrochromic applications: preliminary studies”, Ind. J. Pure & Appl. Phys., Vol. 37, (1999), pp. 262–265.
T. Nishide and F. Mizkani: “Crystal structures and optical properties of tungsten oxide films prepared by a complexing-agent-assisted sol-gel process”, Thin Solid Films, Vol. 259, (1995), pp. 212–217.
Y.V. Renard, G. Leveque, A. Abdellaoui and A. Donnadieu: “Optical constants of electrochromic polycrystalline WO3 thin films prepared by chemical vapor deposition”, Thin Solid Films, Vol. 203, (1991), pp. 33–39.
H. Keneko and K. Miyake: “Estimation of the composition parameter of electrochemically colored amorphous hydrogen tungsten oxide films”, J. Appl. Phys., Vol. 66, (1989), pp. 845–850.
G. Lrftheriotis, S. Papaefthimiou, P. Yianoulis and A. Siokou: “Effect of tungsten oxidation states in the thermal coloration and bleaching of amorphous WO3 films”, Thin Solid Films, Vol. 384, (2001), pp. 298–306.
K.D. Lee: “Preparation and electrochromic properties of WO3 coating deposition by the sol-gel method”, Sol. Energy Mater & Sol. Cells, Vol. 57, (1999), pp. 21–30.
R.R. Amachandran, Nidhi, S.A. Paradeep and S.A. Agnihotory: “Sol-gel deposition of EC-WO3 films using a precursor with enhanced stability”, Ind. J. Pure & Appl. Phys., Vol. 37, (1999), pp. 353–355.
K. Yamanaka, H. Oakamoto and H. Kidou: “Peroxotungstic acid coated films for electrochromic display devises”, Jpn. J. Appl. Phys., Vol. 25, (1986), pp. 1420–1426.
Joint Committee on Powder Diffraction Standard: Powder Diffraction File, PA. Swarthmore, 1972, Card Nos. 2-310, 5-363.
K.D. Lee: “Deposition of WO3 thin films by the sol-gel method”, Thin Solid Films, Vol. 302, (1997), pp. 84–88.
H.L. Hartnagel, A.L. Dawar, A.K. Jain and C. Jagadish: “Semi conducting Transparent Thin Films,” IOP, London, 1995.
N. Ozer: “Optical and electrochemical characteristics of sol-gel deposition tungsten oxide films: a comparison”, Thin Solid Films, Vol. 304, (1997), pp. 310–314.
I. Shimizu, M. Shizukuishi and E. Inoue: “Solid state electrochromic devices consisting of amorphous WO3 and Cr2O3”, J. Appl. Phys., Vol. 50, (1979), pp. 4027–4032.
T. S. Moss: Optical Properties of Semiconductors, Bother Worth, London, 1961.
H. Demiryont and K. Nietering: “Tungsten oxide films by reactive and conventional evaporation techniqes”, Appl. Opt., Vol. 28, (1989), pp. 1494–1498.
A. Dannadieu, D. Davazoglou and A. Abdellaui: “Structure, optical and electro-optical properties of polycrystalline WO3 and MoO3 thin film prepared by chemical vapor deposition”, Thin Solid Films, Vol. 164, (1988), pp. 333–338.
P.R. Patil and P.S. Patil: “Preparation of mixed oxide MoO3−WO3 thin films by spray pyrolysis techniques and their characterization”, Thin Solid Films, Vol. 382, (2001), pp. 13–22.
Author information
Authors and Affiliations
About this article
Cite this article
Novinrooz, A., Sharbatdaran, M. & Noorkojouri, H. Structural and optical properties of WO3 electrochromic layers prepared by the sol-gel method. centr.eur.j.phys. 3, 456–466 (2005). https://doi.org/10.2478/BF02475650
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.2478/BF02475650