Progress in sintering technology of transparent polycrystalline alumina ceramics

As an important optical material, transparent polycrystalline alumina (PCA) ceramic is widely used in aerospace, high-temperature windows, medical due to its high strength, corrosion resistance, high hardness, and excellent stability at high temperatures. Since Al 2 O 3 belongs to the crystal structure of the trigonal crystal system ([Formula: see text]), light is prone to birefringence when passing through the interior of the ceramic, and its transmittance is difficult to reach that of cubic crystal materials such as Y 2 O 3 even under almost fully dense conditions. Using a special sintering process to decrease the sintering temperature and improve the real in-line transmittance of PCA ceramics has always been a research hotspot in related fields. In this work, a comprehensive review is made from the point of view of the sintering process based on the research status of transparent PCA ceramics in decades.