Correlation between Thermal Treatment and Tetragonal/MonoclinicNanostructured Zirconia Powder Obtained by Sol-Gel Process

摘要

The purpose of this paper was to investigate the correlation between thermal treatment and tetragonal/monoclinic nanostructured zirconia powders obtained by sol-gel process. The originality of this work is in the evaluation of the temperature influence on the preparation of nanostructured zirconia powders. The structure of the zirconia produced is amorphous when the samples are heated below 400 °C. The zirconia powders were prepared using zirconium n-propoxide diluted in n-propanol under stirring and refluxed under controlled temperature at pH=5. The resulting gel was air-dried and annealed under air atmosphere at temperatures up to 800 °C for 12 h. The zirconia powders were characterized by means of differential thermal analysis, thermogravimetric analysis, X-ray diffraction, size distribution by laser diffraction, Fourier transform infrared spectroscopy, and scanning and transmission electron microscopy. Crystallite size was calculated by single-line technique using the mathematical function Pearson VII. The presence of the tetragonal phase was observed at a temperature higher than 400 °C. The monoclinic phase was formed at 600 °C, which resulted in a lowering of the content of tetragonal phase. At 800 °C, the particle showed D₅₀=11.54 μm. The crystallite size was calculated using X-ray diffraction-single line and measured by TEM, both approximately 30 nm.