Dehydration and crystallization process in sol-gel zirconia -: Thermal and spectroscopic study

Sol-gel zirconia was characterized using high-resolution thermogravimetry (Hi-Res TG) and differential scanning calorimetry (DSC) and compared with X-ray diffraction, Raman scattering, and UV-Vis spectroscopy. ZrO2-x(OH)(2x).yH(2)O annealed below 400degreesC show typical behavior of amorphous material. As the annealing temperature is increased, the tetragonal and monoclinic phases crystallize. Typical Hi-Res TG curve shows that the samples are continuously dehydrated in a long temperature range, between room temperature and 600degreesC. The total mass loss relative to the initial mass is of about 29%. The DSC analysis coupled with TG and structural information, indicate that the exothermic processes about 355 and 447degreesC can be related to the nucleation process of the formation of tetragonal zirconia, with bulk crystallization at 447degreesC.