Multilayers coatings were obtained by inmersion with 13.5 cm/s velocity on soda-lime glasses as substrates from solutions of FeO - SiO 2 in stoichiometric relations 1:3:6, using methiltrietoxilano (ME 3 S) and iron chloride like initial precursors. The layers were prepared by the sol-gel technique and then thermally treated in oven at 60ºC per 12 hours and 500ºC per 60 minutes. Coatings thickness was calculated from transmission spectra in 400 nm - 800 nm range using interference measurements. Results were compared with Gugliemi and Zenezini´s method which uses the viscosity and density of sol. The thickness from interference measurements for two layers was 510.85 nm, four layers 1008.55 nm and six layers 1532.85 nm given a monolayer valued approximately equal to 255 nm, as obtained from the other method.
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