Use of XPS for the study of cerium–vanadium (electrochromic) mixed oxides

Abstract

Research 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 (CeVO 4 ) 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 WO 3 , which is the colouring electrode in electrochromic devices.In this work, cerium-vanadium stoichiometric oxides (CeO 2 -V 2 O 5 , 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 papers.

Nucleation and Growth of Nanophasic CeO2 Thin Films by Plasma‐Enhanced CVD

“…The intense satellite structure observed for the Ce 3d peak of sample 4 was characterized by three main 3d 5/2 features centered at 883.0 eV (v), 889.5 eV (v²), and 899.0 eV (v-), and three main 3d 3/2 peaks centered at 901.4 eV (u), 908.1 eV (u²), and 917.1 eV (u-). The origin of this band shape, typical of cerium(IV) oxide, [9,13,14,17,32,59,60] has been ascribed to the hy- u bands (18.4 eV), together with the peak positions and the separation between the O 1s signal and the v Ce 3d band (»353.4 eV), provided unambiguous confirmation of the presence of cerium(IV) oxide. [9,30] On the other hand, the Ce 3d photopeak for sample 1 (Fig.…”

“…Finally, the Ce 3d photopeak for film 9 closely resembled that observed for Ce IV . [9,13,14,17,32,59,60] Altogether, such phenomena indicate that, under the adopted conditions, nanosized defective ceria (CeO 2±x ) films, the defect content of which can be tailored as a function of the processing conditions, have been obtained. [62±65] The relative amounts of Ce IV and Ce III were estimated by the ratio of the u-satellite to the total Ce 3d integral area, [7] since the u-intensity is directly related to the Ce IV concentration.…”

Li+ distribution into V2O5 films resulting from electrochemical intercalation reactions

“…SSCV was used in order to visualize clearly the phase transformation processes of the oxide host matrix, while keeping a quasi-equilibrium condition during the reaction. Data from PITT experiments were treated, as shown in our previous work, 3,10 in order to calculate the ionic Li diffusion coefficient inside the solid electrode. After Li insertion the samples were packaged in an argon atmosphere and transferred from the laboratory in Rome to that in Guildford for SIMS analysis.…”

XPS and TOF‐SIMS study of the distribution of Li ions in thin films of vanadium pentoxide after electrochemical intercalation

“…The lithium ions were introduced by the widely used technique of electrochemical insertion from a non-aqueous electrolyte and continues an investigation of the Li-V 2 O 5 system by electrochemical and XPS characterisation. [5] Li + insertion is accompanied by the reversible reduction of V 5+ to V 4+ : oxidation states which are readily distinguished by XPS. Thus XPS enables correlation of the film composition with the electrochemical insertion of charge.…”