Patent ID: 6964933

Claim:
A SiAlON ceramic body made from a starting powder mixture that includes silicon nitride powder and one or more powders that provide aluminum, oxygen, nitrogen, and a rare earth to the SiAlON ceramic body, the SiAlON ceramic body comprising: a two phase composite comprising an alpha prime SiAlON phase and a beta prime SiAlON phase, and the alpha prime SiAlON phase containing the rare earth therein; the alpha prime SiAlON phase being present in an amount greater than or equal to about 20 weight percent of the two phase composite; the starting silicon nitride powder comprises at least about 70 weight percent of the starting powder mixture, the silicon nitride powder in the starting powder mixture contains beta-silicon nitride powder wherein the beta-silicon nitride powder comprises less than or equal to about 1.6 weight percent of the starting silicon nitride powder; and the SiAlON ceramic body having a Vickers hardness (18.5 Kg load) equal to or greater than about 16.5 GPa, and a fracture toughness (K IC ) equal to or greater than about 5.5 MPam 1/2 .