X-RAY CHARACTERIZATION OF SOL-GEL TiO2 THIN FILMS

MIGUEL ANGEL ALTERACH; MARIO ROBERTO ROSENBERGER; DIEGO GERMAN LAMAS; CARLOS ENRIQUE SCHVEZOV; ALICIA ESTHER ARES

Madrid

Congreso; XXII IUCr CONGRESS; 2011

IUCr

TiO2 thin films deposited on a Ti-6Al-4V alloy by means of the sol–gel dip-coating technique were characterized using X-ray synchrotronradiation. The crystalline structure and thickness of the films wereobtained and related to the parameters of the sol-gel process.The process involves immersing the substrate (Ti-6Al-4V) in acolloidal dispersion (sol), withdrawing the substrate at constant lowvelocity, drying of the coating and heat treatment. For the dispersionpreparations, titanium butoxide, isopropanol, ethyl acetoacetate, HCland distilled H2O were used. Several withdrawing velocities andnumber of layer were used, these ranged from 1 to 3 cm/min and from1 to 3, respectively. Two values of titanium butoxide/isopropanol molarratio were used in the dispersions: 1/20 and 1/10. Dispersions withaging times ranged from 1 to 10 days were used. The samples receiveda heat treatment for 1 h at a fixed temperature of 500 C to each layerof coating and heated to 10 C/min and cooling inside the furnace. Themorphology of the coatings was observed by optical microscopy andSEM. The crystalline structure was determined by X-ray diffractionwith a glancing incidence angle of 1º and the thickness was determinedby the X-ray reflectometry technique. These experiments were carriedout at the D12A-XRD1 beamline of the LNLS (Campinas, Brazil).The coatings were homogeneous, compact and smooth to theoptical microscope, and of different colors according to their thickness.With increase of the withdrawing velocity, the number of layers, thetitanium butoxide/isopropanol ratio or the aging time of the dispersions,the thicknesses of the coatings increased, all in a range from 25 nm to142 nm. Cracks were observed on films with thicknesses thicker than100 nm. By X-ray diffraction of the monolayer and multilayer coatingswas determined the presence of anatase and rutile.The results show a relation between thickness and structure. In thethinnest films no crystal structure was detected, while for films withintermediate thickness rutile phase was detected, and for the thickestfilms both rutile and anatase phases were detected. The brookitestructure was not detected in any film.