Influence of YOF on the preparation and optical quality of MgAl₂O₄ transparent ceramics

In this paper, YOF was used as the sintering additive for obtaining MgAl2O4 transparent ceramics with excellent optical properties. It is found that YOF enhances the densification of MgAl2O4 ceramics. In addition, YOF can effectively suppress grain growth in the final stage because of the reduction of grain boundary energies and the pinning effect at the grain boundary region during the hot isostatic pressing (HIPing) process. Nevertheless, it is important to carefully control the content of YOF. Although the formation of a low amount of Y3Al5O12 (YAG) is advantageous because its grains are doing the pinning effect at the grain boundary, an excessive amount is not desired as it is likely to cause scattering. After optimizing the YOF content and sintering temperature, the final sample (4 mm thick after polishing) with 0.01 wt% YOF HIPed at 1550 C-degrees is obtained, showing the high in-line transmittance of 82.6% at 400 nm and high flexural strength of 271.6 MPa.