Dispersion of nano-sized yttria powder using triammonium citrate dispersant for the fabrication of transparent ceramics

In the present work, transparent Y2O3 ceramics were prepared via colloidal processing method from nano-sized Y2O3 powders. The effects of triammonium citrate (TAC) on the colloid stability of aqueous suspensions of nano-sized Y2O3 powders were studied. The surface properties of yttria powders were notably affected by the addition of TAC dispersant. The adsorption of TAC on the particle surface shifts the IEP to lower pH values and increases the absolute zeta potential in alkaline region. Rheological characterization of the investigated system revealed an optimal dispersant concentration of 1 wt%, which correlated well with the saturation adsorption of TAC on Y2O3 powder surfaces. The suspensions with solid loadings up to 35 vol% were achieved with further addition of Tetramethylammonium hydroxide (TMAH) into the dispersing system. The consolidated green bodies were treated by cold isostatic pressing to further increase the green density. Transparent Y2O3 ceramics were prepared after vacuum-sintering at 1700 °C for 5 h. The transmittances of the sample were 74.5% at 800 nm and 79.8% at 2000 nm, respectively.