Direct coarse powder aqueous slip casting and pressureless sintering of highly transparent AlON ceramics

Abstract Direct coarse powder aqueous slip casting was proposed to prepare AlON green body for pressureless sintering of highly transparent AlON ceramics. It was reported that anti-hydrolysis treatment to AlON powder before aqueous slip casting was essential due to hydrolysis reaction between AlON and water. However, both XRD of hydrolyzed powder and pH value of aqueous slurry indicate that the hydrolyzate amount is positively correlating with hydrolysis reaction area, i.e., surface area of powder. Therefore, replacing fine particle with coarse one to reduce surface area of powder is an efficient hydrolyzates reduction scheme by lessening hydrolysis reaction sites. As a result, the hydrolyzate in green body of direct slip casting coarse AlON powder (91 vol% of particles have a size of >1.0 μm) was successfully reduced to an insignificant amount so that the sintered ceramics had a high transmittance (84.1% at ∼3750 nm), which also verified the effectiveness of the proposed hydrolyzate-reduction scheme.