Structural and spectroelectrochemical investigations of tetragonal CeVO4 and Ce/V-oxide sol-gel derived ion-storage films

U. Opara Krašovec, B. Orel*, A. Šurca, N. Bukovec, R. Reisfeld

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

102 Scopus citations

Abstract

Thin films of CeVO4 prepared via the sol-gel route, with a tetragonal (I41/amd) crystalline structure, show good ion-storage properties. The sol-gel route combined with the dip-coating deposition technique allowed thin solid films and powders with a specific Ce/V molar ratio (Ce/V=2:1, 1:1 (CeVO4), 1:2) to be made. The structure of films and powders prepared at 400°C, and at different times of heat-treatment, was determined using X-ray diffractometry (XRD). It is shown that films containing more ceria than vanadia (Ce/V>1) are nanocrystalline with a CeO2 grain size up to 100 Å, but a tetragonal CeVO4 (Wakefieldite) phase is formed when the Ce/V molar ratio is 1:1. By using cyclic voltammetry it was possible to observe the Ce4+/Ce3+ and V5+/V4+ redox changes occurring in the films, while in-situ UV-VIS spectroelectrochemical measurements confirmed the sole presence of V5+/V4+ redox changes in tetragonal CeVO4 films. The small (~0.1-0.5 cm2/C) coloration efficiency of CeVO4 films suggests their utilization as counter electrodes in electrochromic (EC) devices. Comparison of the IR transmission spectra of as-deposited CeVO4 with CeVO4 films charged to x≅0.9 revealed that besides A2u and Eu modes - attributed to the VO43- stretching vibrations predicted by factor group analysis, the Raman active Eg and B2g modes appear in IR spectra. This suggests that inserted Li+ ions occupy the accessible sites within the structure resulting in the loss of inversion symmetry and the consequent disappearance of the distinction between g and u modes. Charging to x≅2.3 causes instability of the film structure.

Original languageEnglish
Pages (from-to)195-214
Number of pages20
JournalSolid State Ionics
Volume118
Issue number3-4
DOIs
StatePublished - 2 Mar 1999

Keywords

  • CeVO
  • Electrochromism
  • In-situ UV-VIS spectroelectrochemistry
  • Infrared and Raman spectra
  • Li insertion
  • Sol-gel
  • Thin films
  • X-ray diffraction

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