Patent ID: 6139791
Filing Date: 2000-10-31
Classification: C04B

Abstract:
A method for making an alpha prime SiAlON-based ceramic article, comprising the steps of:a) providing an admixture of starting materials, including:i) beta silicon nitride.ii) a source of aluminum selected from the group consisting of aluminum nitride, alumina, and mixtures thereof;iii) at least one oxide compound selected from the group consisting of Li.sub.2 O, MgO, CaO, Y.sub.2 O.sub.3, Nd.sub.2 O.sub.3, Sm.sub.2 O.sub.3, Gd.sub.2 O.sub.3, Tb.sub.2 O.sub.3, Dy.sub.2 O.sub.3,Ho.sub.2 O.sub.3, Fr.sub.2 O.sub.3, Tm.sub.2 O.sub.3, Yb.sub.2 O.sub.3, Lu.sub.2 O.sub.3, and mixtures thereof; andiv) a plurality of alpha prime SiAlON seeds having a seed diameter ranging from about 0.2 micron to about 1 micron, said seeds being present in an amount of about 2 to about 10% by weight of the total starting materials;b) densifying said admixture for forming an article having a first phase of at least about 50% by weight of the final material of an alpha prime SiAlON phase;said ceramic article having an indentation toughness of at least about 5 MPa.multidot.m.sup.1/2 ;said first phase including a plurality of alpha prime SiAlON elongated rod shape grains, wherein said article has a hardness of at least about 19 GPa.