Dense β-Si4Al2O2N6 ceramics were obtained from α-Si3N4, α-Al 2O3, AlN, and Y2O3 upon sintering (for 4 h at 1675°C) green bodies consolidated by an aqueous gelcasting and a conventional dry-powder processing route. The as-purchased AlN powder was treated with H3PO4 and Al(H2PO 4)3 and dispersed in aqueous-organic premix solution along with α-Si3N4, α-Al2O3, and Y2O3 powder with the help of a commercial amino alcohol-based cationic (Dolapix A88) dispersing agent to obtain suspensions with 45-50 vol% solids loading for gelcasting purpose. The gelcat β-Si 4Al2O2N6 exhibited superior hardness (1423±6 Hv), fracture toughness (3.95±0.3 MPa·m 1/2), and coefficient of thermal expansion (3.798 × 10 -6/°C between 30° and 1000°C) in comparison with the ceramic consolidated by conventional dry-powder pressing route, which exhibited only 1317±5 Hv, 3.30±0.2 MPa·m1/2 and 3.532 × 10-6/°C between 30° and 700°C. © 2008 The American Ceramic Society.