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Sputter-deposited cerium vanadium mixed oxide as counter-electrode for electrochromic devices
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Caratterizzazione spettroscopica (XPS e XAES) di ossidi misti di Cerio e Vanadio utilizzati in forma di film sottili per dispositivi elettrocromici
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Use of XPS for the study of cerium-vanadium (electrochromic) mixed oxides
No full textResearch studies on new materials have shown that cerium-vanadium mixed oxides have potential for use as counter-electrodes in electrochromic devices owing to the combination of the excellent stability and transparency of cerium oxides and the high ion-storage capacity of the vanadium oxides.
Among them, cerium orthovanadate (CeVO4) has shown its potentiality as an intercalation electrode of suitable structure into which ions can be inserted reversibly, thus balancing the ion-charge capacity required by WO3, which is the colouring electrode in electrochromic devices.
In this work, cerium-vanadium stoichiometric oxides (CeO2-V2O5, 1:1 molar ratio) have been used as a target material for r.f.-sputtering thin-film deposition onto suitable substrates. The films obtained have been characterized before and after electrochemical lithium intercalation. Their XPS and x-ray-induced Auger electron spectroscopy spectra have been compared with those obtained with the standard precursor oxides and the results discussed also on the basis of literature data.
In order to be able to observe the changes in chemical state and composition expected on film formation, a careful curve-fitting procedure has been used that allows the determination of the background structure and intrinsic satellites for each peak, as reported already in previous paper
Sputter deposited cerium-vanadium oxide: optical characterization and electrochromic behavior
No full textLithium diffusion in cerium-vanadium mixed oxide thin films: a systematic study
No full textThree electroanalytical techniques have been used to study the solid-state ionic diffusion of lithium into cerium-vanadium mixed oxide thin films, i.e. potentiostatic intermittent titration technique, galvanostatic intermittent titration technique and electrochemical impedance spectroscopy. Diffusion coefficients measured with the above mentioned techniques show a non-monotonic decay between 8 x 10(-12) and g x 10(-14) cm(2) s(-1). In particular, lithium diffusion coefficient drops by mon than one order of magnitude at lithium intercalation degree x = 0.6. This abrupt change seems to be related to a dramatic increase of the material resistance suggesting that the limiting factor in atomic lithium diffusion may be the low electronic conductivity. (C) 2001 Elsevier Science Ltd. All rights reserved
Optical and electrochemical properties of cerium-zirconium mixed oxide thin films deposited by sol-gel and r.f. sputtering
Full text linkFilms of Ce-Zr mixed oxide were produced by sol-gel and r.f. sputtering. These films can be used as 'passive' counter-electrodes in electrochromic smart windows because they retain their full transparency in both the oxidised and reduced state. Li intercalation was accomplished electrochemically using a liquid electrolyte. Electrochemical behaviour of the samples was found to be dependent on the heat treatment (sol-gel deposited film) and crystallite orientation (sputter deposited films). XRD analysis on sputter deposited films showed that the films are crystalline and grow following the orientation of the underlying tin doped indium oxide (ITO) film. Films of Ce-Zr mixed oxide lacking in (111) crystallite orientation show continuous evolution of the voltammograms and reach a maximum value for the cycled charge only after a large number of cycles. The lithium diffusion coefficient, calculated from GITT measurements, is in the range 10-12-10-14 cm2 s-1 for sputter deposited films and becomes as low as 10-15 cm2 s-1 for sol-gel deposited films. Optical constants of the thin films were calculated from reflectance and transmittance spectra. Refractive index values are in the range of 2.15-2.30 at λ = 633 mn depending on the deposition method. A sharp absorption edge at about 320 nm is seen in accordance with CeO2 optical properties
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