PHASE FORMATION IN MIXED TiO<sub>2</sub>-ZrO<sub>2</sub> OXIDES PREPARED BY SOL-GEL METHOD
Pure titania, zirconia, and mixed oxides (3-37 mol.% of ZrO<sub>2</sub>) are prepared using the sol-gel method and calcined at different temperatures. The calcined samples are characterized by Raman spectroscopy, X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption porosimetry. Measurements reveal a thermal stability of the titania anatase phase that slightly increases in the presence of 3-13 mol.% of zirconia. Practically, the titania anatase-rutile phase transformation is hindered during the temperature increase above 700 °C. The mixed oxide with 37 mol.% of ZrO<sub>2</sub> treated at 550 °C shows a new single amorphous phase with a surface area of the nanoparticles double with respect to the other crystalline samples and the formed srilankite structure (at 700 °C). The anatase phase is not observed in the sample containing 37 mol.% of ZrO<sub>2</sub>. The treatment at 700 °C causes the formation of the srilankite (Ti<sub>0.63</sub>Zr<sub>0.37</sub>O<sub><i>x</i></sub>) phase.