Polymerization of Zr (IV) in an oxynitrate solution: effects on the nucleation and aggregation of hydrated ZrO2

In this study, the effect of the Zr(IV) polymerization degree in a nitric acid solution on the characteristics of hydrated zirconia particles and zirconia powders was investigated. Samples of hydrated zirconia were produced via the controlled double-jet precipitation (CDJP) method. The degree of Zr (IV) polymerization in the solution was varied by modifying the NO ₃ /ZrO ²⁺ ratio. The properties of the hydrated zirconia particles and zirconia powders formed after calcination were investigated via laser diffraction, optical and scanning electron microscopy, X-ray phase analysis, thermogravimetry and BET. The polymerization of Zr (IV) involves the formation and elongation of polymer chains consisting of tetramers of Zr ₄ (OH) ₈ (NO ₃ ) ₈ . An increase in the degree of Zr (IV) polymerization leads to a decrease in the size of the crystallites and an increase in the diameter of the primary particles. This facilitated the formation of dense aggregates with significantly reduced macroporosity. The mechanism of particle aggregation obtained by the CDJP method from a zirconium oxynitrate solution with different degrees of Zr(IV) polymerization was established and discussed in detail.