Cation intercalation and surface fractality in metal oxide based films

Abstract: New methods have been developed for determining the fractal dimension df of asurface from cyclic voltammograms with the sample of interest serving as the workingelectrode in an electrochemical cell. The methods have been verified by applying them tovoltammograms recorded on gold samples with a well-defined fractal dimension.Agreement between the "voltammetry dimension" and the dimension obtained fromatomic force microscop on various metal oxide surfaces has been established.Cation insertion electrodes have been studied by different electrochemical and physical techniques, and it has been shown that a unique fractal dimension can be obtained for such electrodes from diffusion-limited voltammetry and from the capacitance dispersion observed in impedance spectroscopy.From temperature dependent impedance spectroscopy, it was found that diffusion ofLi, Na, and K ions in a Ti dioxide based host was thermally activated. The experimentalactivation energies were analysed using the classical Anderson-Stuart method as well as aquantum-chemical intermediate neglect of differential overlap method. The effect offluorine doping of Ti as well as Sn oxide films was also investigated.The electron density of states in mixed Ti-Ce and mixed Zr-Ce oxide films werestudied by electrochemical techniques, and the Ce4f states were found to account for thedecreasing electrochromism in the Ti-Ce oxide films, as well as for the increased chargecapacity in the Zr-Ce oxide films in comparison with the pure transition metal oxides.