Preparation of transparent CeO2-TiO2 coatings for electrochromic devices

Thin films of mixed oxides of CeO2-TiO2 with a molar ratio of Ce/Ti of 0.5 have been obtained by the sonocatalytic sol-gel method. The precursor sols consist of a mixture of Cr(NH4)(2)(NO3)(6), titanium alkoxide (Ti((OPr)-Pr-i)(4)) and isopropanol, The films were deposited using the dip-coating technique and calcined at 450 degrees C in an oxygen atmosphere. Xerogels were characterized by thermal analysis (DTA-TG) and X-ray diffraction. The films prepared from the precursor sols were subjected to electrochemical measurements (cyclic voltammetry and chronoamperometry), SEM and AFM. Films of CeO2-TiO2 approx. 100 nm thick present a good electrochemical response under Li+ ions insertion. The cathodic and anodic charges at a scan velocity of 50 mV/s were about 16 mC/cm(2) and the process was fully reversible. The values measured up to 4500 cycles were constant indicating a good electrochemical stability of the films. The stability test and optical measurements confirm that the films can be used as ion storage (counter-electrode) in electrochromic devices. (C) 1998 Elsevier Science S.A. All rights reserved.