Ultra-fast High-temperature Sintering (UHS) of translucent alumina

Pressure-less consolidation of transparent alumina requires several hours dwelling at high temperature (1600 °C) under a strongly reducing atmosphere (hydrogen). Here, we report on the ultrafast consolidation of translucent alumina ceramics at 1360 °C. Transparency was promoted by synergistic effects of high initial green density (62.7%) and rapid sintering using Ultra-fast High-temperature Sintering (UHS) technique. The proposed approach, using a heating rate of 430 °C/min and dwelling time of 15 min, resulted in ultra-fine-grained translucent alumina ceramics with a grain size of 0.39 μm, and an in-line transmittance of 28.7% at a wavelength of 700 nm. For comparison, conventionally fired counterparts were opaque due to their incomplete densification and pore coalescence.