Preparation and optical characterization of thick-film zirconia and titania ormosils

Crack-free films with thicknesses of up to 30 mu m were prepared by the sol -gel process using the dip-coating technique. Thick films were obtained fro m various starting solutions based on two, three or four components, with p articular emphasis on ternary systems. The ternary systems were composed of two tetraalkoxy precursors (a silicon tetraalkoxide and a zirconium or a t itanium tetralkoxide) and a trialkoxysilane with a non-hydrolyzable group. By using these trialkoxysilanes, the tendency of the films to crack during the drying process is reduced because of the stress absorption by the netwo rk structure. The use of zirconia or titania allows for control of the refr active index of the films. Optical parameters of the films including refrac tive index, thickness, surface roughness and UV-Vis and IR transmission spe ctra were determined for each composition and the structural characteristic s of the films were inferred from the IR spectra. UV cut-off and antireflec tive properties were also studied for some compositions.