Abstract: The polymerization process of hydrolysis products in ZrOCl₂ solutions under boiling condition has been investigated by tha electron microscopic tachnique. The results show that there exists a palymarization process in ZrOCl₂ solutions with different concentrations. First a number of crystal nuclei are formal which grow gradually to definite-sized, definite-shaped multimorphous particles through the process of polymerization. Tha urea additive has been proved to promote the polymerization process. The synthesized particle size mostly depends on the concentrations of the initial ZrOCl₂ solution and the boiling time. The higher the concentration and the longer the boiling time, the larger the obtained particle size. So the particle size can be controlled by selecting the suitable initial concentration and boiling time.

Key words: ultrafine particle, hydrolysis, polymerization, ZrOCl₂ܮH₂O, ZrO₂