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Effect of Ti4+ ion incorporation on the phase development of ZrO2-type solid solutions obtained using low temperature sol-gel technique

Low temperature hydrolysis and polycondensation reaction of zirconium and titanium propoxide, given in different molar ratios, were used to obtain amorphous precursors of the ZrO2-TiO2 system at the ZrO2-rich side of the concentration range. In order to insure quantitative transition of Zr4+ and Ti4+ ions from liquid to solid phase, a small amount of ammonia was used as a catalyst. The obtained gels were washed, dried and calcinated at different temperatures up to 1100 °C. Structural and microstructural changes produced during the thermal treatment of the amorphous precursors were examined by differential scanning calorimetry, X-ray powder diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy and field emission scanning electron microscopy. The Zr/Ti molar ratio in the obtained products was determined by energy-dispersive X-ray spectrometry. The results of phase analyses indicated that maximum solubility of Ti4+ ions in the ZrO2 lattice occurred in the metastable products obtained after crystallization of the amorphous precursors. Precise unit-cell parameters of the ZrO2-type solid solutions were determined by using the Le Bail method (program GSAS) of whole-powder-pattern refinements. Effect of TiO2 content on the crystallization temperature of the amorphous precursors and phase development of ZrO2-type solid solutions during the thermal treatment were compared with the previously obtained results for ZrO2-SnO2 system. Differences in the thermal behaviour of these two systems will be discussed.

ZrO2; X-ray diffraction; Raman spectroscopy; Electron microscopy; DSC; FT-IR spectroscopy

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