Nickel oxide (NiOx) thin films were prepared by the chemical deposition method (solution growth) on two kinds of substrates: (1) glass and (2) glass/SnO2: F. Films were thermally treated at 200degreesC for 10 min in atmosphere, The texture, microstructure and composition were examined by optical microscopy, X-ray diffraction patterns (XRD) and X-ray photoelectron spectroscopy (XPS) analysis of the surface layer. The films exhibited anode electrochromism. The optical properties of the bleached and colored state were examined with transmittance spectroscopy in the visible region and reflectance FTIR spectroscopy. An electrochromic test device (ECTD), consisting of SnO2/NiOx/NaOH-H2O/SnO2, was assembled and tested by cyclic voltammetry combined with a simultaneous recording of the change of transparency at lambda = 670 nm. The coloration efficiency was evaluated to be 24.3 cm (2)/C. The spontaneous ex-situ change of coloration with time of the colored and bleached NiOx/SnO2/glass was also examined. (C) 2002 Elsevier Science B.V. All rights reserved.