Pressureless sintering and fabrication of highly transparent MgAlON ceramic from the carbothermal powder

Abstract MgAlON transparent ceramics are fabricated by pressureless sintering using the carbothermal raw powder. The obtained MgAlON powder is well crystallined and exhibits a spinel structure. It shows a bimodal particle size distribution (PSD) at 0.3 μm and 0.9 μm. An investigation on the microstructural sintering evolution indicates the stages of significant densification at the intermediate temperature regions (1600–1700 °C) and rapid grain growth at higher temperature (1750–1850 °C). Additional holds at the intermediate temperature are effective to controlling the microstructure with reduced porosity, which in turns, improving the transmittance. The sample with hold at 1700 °C for 2 h followed by 1850 °C for 20 h exhibits excellent transmittance from the visible to middle infrared (IR) regions, achieving 86.59% at 3.70 μm and 82.37% at 0.60 μm.