The topic of this thesis was to study the influence of thermal treatment on the phase development of ZrO2-SiO2 system. ZrO2-SiO2 amorphous precursors were obtained by the evaporation of Zr-propoxide and silicon tetraethoxysilane (TEOS) solutions, with different molar fraction of silicon (from 0 to 100%). Crystallization of the obtained powder samples was carried out by annealing in the air for 2 h at temperatures of 400 °C, 600 °C, 800 °C, 1000 °C, 1200 °C and 1400 °C. Structural analysis of crystallization products was performed by X-ray powder diffraction and Raman spectroscopy. The DTA/TGA analysis determined the crystallization temperature of zirconium dioxide and the loss of samples mass during annealing and the SEM analysis provided data on morphology and the size of the crystalline grain. Quantitative analysis of the ZrO2 polymorph was carried out by Rietveld refinements on powder diffraction patterns. The obtained results show that the increase in SiO2 content significantly increases the crystallization temperature of zirconium dioxide, from 420 °C (sample with 0 mol% SiO2) to 928 °C (sample with 70 mol% SiO2). Although under the applied thermal processing conditions there was no significant incorporation of Si cations into the ZrO2 lattice, the results of the structural analysis showed that the presence of SiO2 significantly increases the resistance of metastable tetragonal ZrO2 to the influence of temperature. The influence of pressure on the phase transitions of ZrO2 was also investigated, and the obtained results showed that the stability of the tetragonal ZrO2 significantly increased with the decrease of the crystal grain size. SiO2 increases the resistance of the tetragonal ZrO2 to the impact of pressure only when present in very large proportions (80 mol%). SEM analysis has shown that zirconia crystalline particles are embedded in the amorphous silica gel which affects the nucleation rate and crystal growth. By increasing the silica content and reducing the treatment temperature, the crystalline grain size decreases.