Preparation of transparent Y2O3 ceramic via gel casting: Realization of high solid volume via surface modification

In this article, isocyanate was adopted to modify Y₂O₃ powder for the purpose of preparing transparent Y₂O₃ ceramics via gel casting. The modification could enhance the hydration resistance of Y₂O₃ powder through the steric hindrance effect. The coating mechanism can be proved by the infrared spectrum of the surface-modified Y₂O₃ powder. Modification could not only prevent Y₂O₃ particles from reacting with water, but also prevents agglomeration between particles. The viscosity of the slurry with a solid content of 52.7 vol% is only 0.48 Pa·s at the shear rate of 100 s^?1, which is suitable for preparing high-density compacts by gel casting. The transmittance of the sample (1840°C × 8 h, 1 mm thickness) at 1100 nm reaches 75%. The microstructure of the sintered body is dense with the average grain size of 6.5 μm without obvious impurities nor pores. Five mol% ZrO₂-doped Y₂O₃ transparent ceramic fairing with the diameter of 5 cm without defects was successfully fabricated by gel casting (52.7 vol% solid volume) and vacuum sintering (1840°C × 8 h).