Diffusion of Li, Na, and K in fluorinated Ti dioxide films: Applicability of the Anderson–Stuart model

• Published in: Journal of applied physics 1997-03, Vol.81 (5), p.2167-2172
• Main Authors: Mattsson, M. Stro/mme, Niklasson, G. A., Granqvist, C. G.
• Format: Article
• Language: English
• ISSN: 0021-8979; 1089-7550; 1089-7550
• DOI: 10.1063/1.364232

Fluorinated Ti dioxide films were made by reactive sputtering. The mobility of Li, Na, and K in this host was studied by electrochemical techniques. Chronopotentiometry suggested that the cations occupy one type of site for cation/Ti ratios below 0.5, and that other sites are populated at higher ratios. Li and Na intercalation appeared to progress without major structural changes, whereas the intercalation of the larger K ions caused structural rearrangement. Impedance spectra were interpreted within a Randles circuit with a finite length Warburg element from which chemical diffusion coefficients were obtained at different intercalation levels and temperatures. The ion diffusion could be understood in detail from the classical Anderson–Stuart model [O. L. Anderson and D. A. Stuart, J. Am. Ceram. Soc. 37, 573 (1954)] as long as the structure remained unchanged, i.e., for the Li and Na intercalation, whereas K intercalation, expectedly, could not be reconciled with this model.