X-ray diffraction, and Raman scattering study of nanostructured ZrO ₂-TiO₂ oxides prepared by sol-gel

In the present work, we study the phase composition of ZrO ₂-TiO₂ system by means of XRD and Raman spectroscopy, using also TG-ATD, and N₂ adsorption isotherms as complementary characterization techniques. TiO₂-ZrO₂ samples of selected compositions (0, 10, 90, 50 and 100% in weight of TiO₂) were prepared by sol-gel method and annealed at three different temperatures (400, 600 and 800 °C). Structural characterization reveals that only the pure oxides are crystalline at 400 °C: TiO₂ as anatasa with a minor brookite component, and ZrO₂ as a mixture of tetragonal (majority) and monoclinic phases. Following the 600 °C calcination, the TiO ₂-ZrO₂ 50-50% sample forms the ZrTiO₄ mixed oxide, although this materials remains partly amorphous. In contrast, samples with higher and lower TiO₂ content form solid solutions with, respectively, anatasa and tetragonal ZrO₂ structures. Zirconium incorporation into the TiO₂ lattice leads to the expansion of the unit cell parameters, and it stabilizes the anatase phase, hindering its transformation into rutile. Similarly, dissolving titanium atoms into the ZrO₂ structure delays the transformation from the tetragonal to the monoclinic polymorph.