Electrochromic and structural investigation of InVO4 and some other vanadia-based oxide films

We extended our previous studies of M-3+VO4 orthovanadate (M3 + = Ce, Fe) a nd M-2(3+) V4O13 (Fe2V4O13) films to include InVO4 films because their phot opic transmittance T-vis(initial) is above 0.885. Structural studies (TEM a nd XRD) revealed that films prepared from In(NO3)(3)5H(2)O and V-oxoisoprop oxide sols annealed at 500 degreesC consist of the mixed monoclinic (InVO4- I) and orthorhombic (InVO4-III) phases, while the addition of acetylacetone (acac) to the sol results in amorphisation. The charge capacity of InVO4/a cac films is between - 30 and - 40 mC cm(-2) (single dipped films) and thei r electrochemical stability is more than 1000 cycles. In situ UV-visible sp ectroelectrochemical measurements show that charging to - 35 mC cm (-2) dec reases the photopic transmittance from T-vis(initial) = 0.885 to T-vis(ins) = 0.722, which contrasts the higher optical passiveness of previously inve stigated CeVO4 films (T-vis(ins) = 0.90). The increase in the broad absorption below 600 cm (-1) in IR spectra of cha rged/discharged InVO4 films shows that films irreversibly uptake lithium io ns. Charging up to - 20 mC cm(-2) does not affect the IR spectra, while cha rging up to - 40 mC cm-2 results in the transformation of the film structur e, which becomes similar to that of the amorphous InVO4 films obtained at 3 00 degreesC and to certain transition vanadate glasses. IR spectra of other vanadia-based films, i.e. FeVO4, Fe2V4O13, CeVO4, and V2O5 films in differ ent state of lithiation are discussed. (C) 2001 Elsevier Science Ltd. All r ights reserved.