Coating Y2O3 nano-particles with ZrO2-additive via precipitation method for colloidal processing of highly transparent Y2O3 ceramics

In the present work, transparent Y2O3 ceramics were prepared via colloidal processing method using ZrO2 coated nano-sized Y2O3 powders. The chemical precipitation method was adopted for the coating of Y2O3 raw powder. The evolution of the coated-ZrO2 layer upon calcination was studied. The rheological behaviors of the slurries of Y2O3 powders coated with different content of ZrO2-additive were investigated. The pH(IEP), of ZrO2 coated Y2O3 powders shows intermediate values between that of raw Y2O3 and ZrO2 powders. As the ZrO2 coating concentration increased from 0 to 5.0 at%, the magnitude of the negative zeta potential at pH > pH(IEP) shows a general trend of increment, whereas it decreased at pH < pH(IEP). The viscosity decreases pronouncedly with the increase of ZrO2 content from 0.5 at% to 3.0 at%. The suspensions with low viscosity and high stability was achieved for a solid loading of 35.0 vol% using Y2O3 powders coated with 5.0 at% ZrO2. The dispersed suspensions were consolidated by centrifugal casting method and the green bodies shown improved homogeneity. Transparent Y2O3 ceramics were fabricated by vacuum sintering at 1800 degrees C for 5 h. Transmittance at wavelength 800 nm (1.0 mm thick) reached 80.8%, close to the theoretical value of Y2O3.