Cerium oxide and cerium (Ce)-vanadium (V) oxide films were synthesized on an ITO electrode by electrolysis in NH4HSO4-Ce2O3 and NH4HSO4-Ce2O3-NH4VO3 melts at a temperature of about 300 degreesC. The films obtained were characterized by X-ray diffraction, spectroscopic measurements and electrochemical measurement. In addition, the electrochromic (EC) reactions of the oxide films in a solution of propylene carbonate were investigated. The absorption spectra of Ce-V mixed oxide films obtained by electrodeposition in the NH4HSO4-Ce2O3-NH4VO3 melt showed peaks at 680 and 451 nm, due to a mixed valence of V4+ and V5+ in the orthovanadates (CeVO4), and these absorption peaks increased with Li+ insertion and disappeared with Li+ extraction in EC reactions. The Ce-V mixed oxide films showed a lower absorbance than vanadium oxide and cerium oxide films, respectively in the visible region. (C) 2003 Elsevier Science B.V. All rights reserved.