Optical and electrochemical properties of cerium-zirconium mixed oxide thin films deposited by sol-gel and r.f. sputtering

Films of Ce-Zr mixed oxide were produced by sol-gel and r.f. sputtering. Th ese films can be used as 'passive' counter-electrodes in electrochromic sma rt windows because they retain their full transparency in both the oxidised and reduced state. Li intercalation was accomplished electrochemically usi ng a liquid electrolyte. Electrochemical behaviour of the samples was found to be dependent on the heat treatment (sol-gel deposited film) and crystal lite orientation (sputter deposited films). XRD analysis on sputter deposit ed films showed that the films are crystalline and grow following the orien tation of the underlying tin doped indium oxide (ITO) film. Films of Ce-Zr mixed oxide lacking in (111) crystallite orientation show continuous evolut ion of the voltammograms and reach a maximum value for the cycled charge on ly after a large number of cycles. The lithium diffusion coefficient, calcu lated from GITT measurements. is in the range 10(-12)-10(-14) cm(2) s(-1) f or sputter deposited films and becomes as low as 10(-15) cm(2) s(-1) for so l-gel deposited films. Optical constants of the thin films were calculated from reflectance and tr ansmittance spectra, Refractive index values are in the range of 2.15-2.30 at lambda = 633 mn depending on the deposition method. A sharp absorption e dge at about 320 nm is seen in accordance with CeO2 optical properties. (C) 1999 Elsevier Science Ltd. All rights reserved.