The structural evolution during the thermal treatment of $70SiO_2-3OTiO_2(mole%)$ sol-gel derived powders and films was investigated by FT-IR, Raman and XPS, and XRD. From these results, the $TiO_2-rich$ regions involving $Ti^{4+}$ ions in octahedral coordination were confirmed to be amorphous at $600^{circ}C$. However, Raman spectra along with XRD patterns indicated that at high temperature (above $700^{circ}C)$, the amorphous $TiO_2was$ segregating to form anatase crystal. Also, the effect of experimental variables such as thermal treatment, heating rate and exposure to water vapor on structural changes, refractive index and thickness of the film coated on sodalime-silicate glass were investigated.