Transparent cubic-ZrO2 ceramics for application as optical lenses

Optical transparent polycrystalline ZrO2 ceramics were fabricated by solid-state sintering process using first vacuum sintering followed by hot isostatic pressing. In the visible wavelength range (400–800 nm), the in-line transmittance of 5.6-mm thick samples reaches 68% at exemplary wavelength 600 nm (corresponding to an in-line absorbance based on 10 of A10 = 0.08 cm−1), which is approximately 90% of theoretical limit. The refractive indices of the ZrO2 optoceramics at 630 nm (nd) are varying between 2.10 and 2.20, depending on TiO2 contents, the latter being used as sintering aid. The appearance of birefringence is strongly correlated to the addition of TiO2 as sintering additive in the ceramic samples, whereas addition of TiO2 and simultaneous increase in Y2O3 content resulted in a decrease of birefringence.