Three phase Al 2 O 3 –A1ON–SiC composites can be obtained by hot-pressing Al 2 O 3 –AlN–SiC mixtures under 40 MPa at temperatures around 1700°C. Silicon carbide can be added in the form of powders or platelets. In the case of powder, densification and aluminum oxynitride formation occur at higher temperatures than in the case of platelets, because of a steric and chemical hindrance by SiC on both Al 2 O 3 densification and the Al 2 O 3 –AlN reaction. Composites containing powders present the highest values for rupture moduli of up to 800MPa and toughnesses close to those of alumina (4 MPa m). For platelets, a composite containing 20 vol.% SiC with a size of d 50 =8 μm produces a reinforcement effect (K 1C =6–7 MPa m).