Effect of Grain Size on Phase Transformation and Photoluminescence Property of the Nanocrystalline ZrO2 Powders Prepared by Sol-Gel Method

Nanocrystalline zirconia (ZrO2) powders were prepared by a solegel process followed by annealing treatments from 500 to 1200 degrees C. Phase transformation, microstructural features and photoluminescence properties were characterized by X-ray diffraction, transmission election microscopy and photoluminescence spectra, respectively. The results show that both monoclinic phase and tetragonal phase exist in the nanocrystalline ZrO2 powders at annealing temperature in the range of 500-900 degrees C, and the concentration of monoclinic phase increases with increasing the annealing temperature. Tetragonal phase is totally transformed to monoclinic phase when annealing temperature is up to 900 degrees C. The average grain size of the powders also increases when annealing temperature increases. Two emission peaks centered at 390 nm (named as I-390) and 470 nm (named as I-470) exist in the photoluminescence spectra, and the intensity ratio of I-390 to I-470 decreases with increasing annealing temperature. The grain size is proposed to be responsible for the phase transformation in the nanocrystalline ZrO2 powders.