Fabrication and characterization of highly transparent Y2O3 ceramics by hybrid sintering: A combination of hot pressing and a subsequent HIP treatment

We succeeded in the optimization of highly transparent Y2O3 ceramics with a submicrometer grain size approximately 0.6 μm by hot pressing (1300-1550 °C) and a subsequent HIP (1450 °C) treatment using commercial Y2O3 powders as starting powders and ZrO2 as a sintering additive. The optimum microstructure for the HIP treatment was prepared by hot pressing at a temperature as low as 1400 °C for 3 h with a relative density of 99.3%. The thus HIP-treated specimen showed the best transmittance (2 mm thick) ever reported of 83.4% and 78.3% at 1100 and 400 nm, respectively. Specifically, the transmittance using this hybrid sintering method improved substantially in the visible range compared to that of the counterpart using hot pressing only. A simulation of the transmittance based on the Beer-Lambert law and Mie scattering theory has proved that this improvement is mainly due to the elimination of nanopores below 15 nm in size.