Effect of Initial ZrOCl₂ Concentration on the Homogeneous Precipitation of Nanoscale 3Y-TZP Powder.

Nanoscale yttria-stabilized zirconia (Y-TZP) powder was synthesized by homogeneous precipitation via urea hydrolysis, and the influence of a dispersing agent and the initial ZrOCl2 concentration on the powder characteristics was investigated. A precipitated gel was obtained from the reaction of the precursor solution with zirconium oxychloride, yttrium chloride, and urea with heating at 110 °C for 5 h. The initial ZrOCl2 concentration was controlled from 0.25 to 1 M. To observe the effect of adding a dispersing agent on the agglomeration of primary particles, we used two starting compositions, one with and the other without a dispersing agent, ammonium polymethacrylate. Two crystalline powders were obtained after drying, calcination, and milling the gel, and we investigated the powder characteristics, such as particle agglomeration, the specific surface area, the microstructure, and phase composition. Two scales of agglomerates were observed in the particle size distribution, namely, 190 to 362 nm at the primary scale and 1.6-4.0 μm at the secondary scale. The amount of secondary agglomerate increased from 6 to 20 vol% with the increasing initial ZrOCl2 concentration. The size of both types of agglomerate and the amount of secondary agglomerates decreased due to the addition of the dispersing agent, especially the primary agglomerate size. The sintered density and microstructure of Y-TZP were affected by the agglomeration behavior, especially the amount of secondary agglomerates.