Pressure filtration and sintering of ultra‐high‐density Al ₂ O ₃ green bodies

Abstract A high‐density green body is critical for producing fine‐grained ceramics at low sintering temperatures. However, achieving high density from submicron powders is challenging due to their high specific surface area. In this study, an alumina slurry using a super‐fine α‐Al 2 O 3 powder ( d 50 = 180 nm) and a low molecular weight dispersant (CE‐64) was prepared with a high solid loading of 55 vol% and a low viscosity of 0.40 Pa·s. The slurry was post‐treated by pressure filtration at 0.4 MPa. After de‐binding at 750°C, the resulting green bodies exhibited a relative density of 67.4%, 0.9% higher than that of the counterparts formed without pressure filtration. Pressureless sintering at 1300°C in air yielded ceramics with a relative density of 99.97%, an average grain size of 0.70 µm, a flexural strength of 631 MPa, and a hardness of 18.5 GPa. These findings demonstrate the feasibility of achieving high‐performance alumina ceramics with fine‐grained microstructures under simplified sintering conditions through the combined use of high solid loading slurry and low‐pressure filtration forming.