Fast pressureless sintering of highly transparent AlON ceramics with broad optical transmission range

Abstract

In our recent work, AlON ceramics with transmittance ≥80% at 380–4150 nm were fabricated via pressureless sintering at 1880°C for 2.5 h by reducing Y enrichment. To further improve transparency and gain a deeper insight into the fast densification behavior, a new nano-sized Y₂O₃ powder prepared via the Pechini method (NGY-P), together with the Y₂O₃ powders used in the previous work, was employed to investigate the effects of Y distribution on densification process and transparency of AlON ceramics. In the entire densification process, diffusion through liquid phase at the grain boundaries dominates the mass transport mechanism when the nano-sized Y₂O₃ is doped. Moreover, by optimizing the Y distribution, rapid high densification sintering is achieved, and grain growth is effectively suppressed. As a result, highly transparent AlON ceramics were successfully fabricated by doping with NGY-P, achieving transmittance of ≥80% across the 350–4480 nm wavelength range after dwelling for 4.0 h, with the maximum transmittance of 87.2% and Vickers hardness of 17.05 ± 0.36 GPa.