High-transparency AlON ceramics fabricated by pressureless sintering method

Alumina nitride (AlON) ceramics have the advantages of wide transmission ranges, high-strength, and high-hardness, and these characteristics make it have potential applications in the fields of national defense and aerospace. However, the prolonged high-temperature (≥1900°C) sintering process severely reduces of its mechanical and optical properties far below the theoretical value in practice. In this work, we successfully fabricated AlON transparent ceramics exhibiting superior mechanical (bending strength of 293 MPa and hardness of 18 GPa) and optical properties (76.2% at 2100 nm), and the sintering temperature is approximately 50°C lower than that of conventional methods. Here, the first obtained high-activity and high-purity AlON powders through solid-state reaction method with secondary ball milling process, could effectively reduce both the sintering temperatures and durations. Subsequently, by optimizing the doping content of Y₂O₃, AlON ceramics were sintered at 1850°C, in which represent the minimal porosity at the grain boundaries and fine grains of uniform size, still keeping the superior mechanical and optical properties. The methods developed in this work are not only suitable for the large-scale production of high-activity and high-purity AlON powders but also for the preparation of large-scale AlON ceramics by using the casting process in future.