Preparation and Light Transmission Properties of AlON Ceramics by the Two-Step Method with Nanosized Al₂O₃ and AlN

The single-phase aluminum oxynitride (AlON) powder used in this experiment was obtained at relatively low temperature by the solid-state-reaction method with nanosized AlN powder and nanosized alumina powder. The obtained powder was ground by ball milling and doped with Y₂O₃; then, it was shaped into pellets. Transparent ceramics sintering was carried out at 2153 K (1880 °C) for 5, 10, and 20 hours. Obtained samples for three duration times are all are transparent, and the light transmittance of samples increases with increasing the holding time at the sintering temperature. The transmittance of the sample with 20 hours holding time is 55 pct at near 5 μm. X-ray diffraction (XRD) measurement shows that all samples were single-phase AlON. The fracture surfaces of samples from scanning electron microscopy (SEM) analysis shows that with increasing the holding time, the grain size grows slightly, while the pore size and porosity decrease apparently, which bring about the transmittance increase. The pore size and the porosity are the main factors affecting the light transmitting properties of samples.