Characterization of TiO2 and ZrO2 coatings on silica slabs and fibres

Titanium and zirconium dioxide coatings were deposited on optical fibres by the sol-gel procedure. The thickness of the layers on fibres was established by measurement of the intensity of characteristic X-rays by an electron microprobe analyser. The accuracy of the measurements was verified on broken layers by scanning electron microscopy. Also determined were the thicknesses of similar layers deposited on flat silica substrates with an ellipsometer and stylus surfometer as well as from reflectivity spectra and from specular total reflection of X-rays. The densities of TiO₂ and ZrO₂ layers on silica glass slabs were determined by X-ray total reflection. Values of 3.16 ± 0.02 and 4.69 ± 0.03 gm cm^–2 were found for titania and zirconia, respectively. The crystallinity of layers on silica plates was investigated by Raman spectroscopy. The thicknesses of coatings prepared by the dipping technique were related to the withdrawal speed. Equations for Newtonian and non-Newtonian fluids were tested and compared. A pseudo-plastic behaviour was suggested for all the solutions used in the experiments.