Optimization of pH and dispersant amount of Y-TZP suspension for colloidal stability

In this article, the amount of dispersant agent [i.e., polyethyleneimine (PEI)] and pH was optimized to achieve high colloidal stability in yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) suspension. Rheological properties of aqueous Y-TZP suspension in the presence of different amounts of PEI were evaluated via viscosity tests to identify the optimal amount of dispersant agent. Zeta potential and particle size measurements were employed to determine the suitable pH that can establish good colloidal stability. Mechanical properties (e.g., density and hardness) and morphological properties were also considered in determining the optimal pH. Rheological tests showed that Y-TZP suspension with 0.4 wt% PEI had the lowest viscosity, which is suitable for colloidal processing. pH 2 and 4 were recorded to have the lowest particle size and highest zeta potential, respectively. Characterization tests and morphological analysis showed that pH 2 had the highest density (92.5%), highest hardness (10.36 GPa), and homogeneous microstructure with fine average grain size (486 nm). Thus, the dispersant amount of 0.4 wt% PEI and pH 2 were selected as the optimal parameters for colloidal processing of aqueous Y-TZP suspension. Y-TZP suspension with excellent colloidal stability and reliable final products was produced under these parameters.