Effect of milling ball size on the densification and optical properties of transparent Y2O3 ceramics

In this study, we report highly transparent Y2O3 ceramics fabricated by hot-pressing only at 1500 °C without a HIP treatment, featuring in-line transmittance levels of 77% and 84% at a wavelength of 400 and 1100 nm, respectively with the grain size suppressed to 710 nm. The effect of the ball size during the grinding of Y2O3 powders on the correlation between the thus-prepared Y2O3 powders and the optical properties of the hot-pressed samples is demonstrated for the first time. With a decrease in the diameter of the ZrO2 balls from 5 mm to 1 mm, the milling efficiency was enhanced and admirable transparency of Y2O3 was attained at a short milling time. However, several micron-sized pores remained in the transparent specimens prepared with 1 mm balls, originating from the inhomogeneously packed region of the green body. Finally, the 2 mm was found to be optimum for obtaining a fine-grained and pore-free microstructure with the best in-line transmittance of Y2O3 ceramics.