Abstract: A SiAlON material that includes a two phase composite of an alpha prime SiAlON phase and a beta prime SiAlON phase. The alpha prime phase contains ytterbium. The alpha prime SiAlON phase being present in an amount between about 25 weight percent and about 85 weight percent of the two phase composite. The SiAlON material further includes an intergranular phase.

Abstract: 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 ytterbium to the SiAlON ceramic. The SiAlON ceramic body includes a two phase composite comprising alpha prime SiAlON phase, which is present in an amount greater than or equal to about 20 weight percent of the two phase composite, and a beta prime SiAlON phase wherein the alpha prime SiAlON phase containing ytterbium therein. The starting silicon nitride powder contains less than or equal to about 1.6 weight percent beta-silicon nitride. The ceramic body further includes an intergranular phase that includes an intergranular crystalline phase comprising at least one of YbAG and J-phase. The overall composition of the ceramic body is YbaSibAlcOdNe, wherein when a is less than 0.05, The relative intensity of the peak associated with either one or both intergranular crystalline phases of YbAG and J-phase is greater than about 2.

Abstract: A SiAlON material that includes a two phase composite of an alpha prime SiAlON phase and a beta prime SiAlON phase. The alpha prime phase contains ytterbium. The alpha prime SiAlON phase being present in an amount between about 25 weight percent and about 85 weight percent of the two phase composite. The SiAlON material further includes an intergranular phase.

Abstract: A continuous process for the manufacture of a ceramic sintered compact wherein the process comprises the steps of: forming a green compact from a powder mixture comprising a first component comprising compounds which contain elements of silicon, aluminum, oxygen and nitrogen; and the powder mixture further comprising a second component comprising a compound of at least one element selected from the group consisting of yttrium, scandium, cerium, lanthanum and the metals of the lanthanide series, and the second component comprising between 0.1 and 10 weight percent of the powder mixture; heat treating the green compact wherein the heat treatment comprises continuously passing the green compact through at least one heating zone so as to produce a sintered compact.

Abstract: A ceramic body comprising at least about 80 w/o silicon nitride and having a mean tensile strength of at least about 800 MPa.

Abstract: A silicon nitride ceramic comprising:a) inclusions no greater than 25 microns in length,b) agglomerates no greater than 20 microns in diameter, andc) a surface finish of less than about 8 microinches, said ceramic having a four-point flexural strength of at least about 900 MPa.

Abstract: A sintered silicon nitride ceramic comprising between about 0.6 mol % and about 3.2 mol % rare earth as rare earth oxide, and between about 85 w/o and about 95 w/o beta silicon nitride grains, wherein at least about 20% of the beta silicon nitride grains have a thickness of greater than about 1 micron.

Abstract: A sintered silicon nitride ceramic comprising between about 0.6 mol % and about 3.2 mol % rare earth as rare earth oxide, and between about 85 w/o and about 95 w/o beta silicon nitride grains, wherein at least about 20% of the beta silicon nitride grains have a thickness of greater than about 1 micron.

Abstract: This invention relates to a sintered silicon nitride ceramic comprising samaria and ytterbia for enhanced toughness.

Abstract: A sintered silicon nitride ceramic having an L10 value of at least 50 million stress cycles in ASTM test STP 771 under 6.9 GPa applied contact stress.

Abstract: The flexural strength and stress rupture life of isostatically hot pressed silicon nitride containing between 1 and 12 weight percent of rare earth oxide and not more than 0.5 weight percent alumina is substantially increased by treating green bodies in flowing nitrogen at a temperature between 1000.degree. and 1500.degree. C. before degassing for the isostatic hot pressing. The iron content of the bodies is also reduced by this heat treatment, and this is believed to eliminate sources of fracture failure. Silicon nitride bodies with a flexural strength in excess of 525 MPa at 1370.degree. C. and with stress rupture lives reliably in excess of 200 hours at 300 MPa stress at 1370.degree. C. can be prepared in this way. The strain rates of silicon nitride under high temperature stress can also be reduced.

Abstract: A dual phase silicon aluminum oxynitride material comprising a first phase Si-Al-O-N, commonly referred to as .beta.-Si-Al-O-N, and a second phase Si-Al-O-N referred to as .alpha.-Si-Al-O-N. In addition to the double phase Si-Al-O-Ns, there is included a glassy type material which can formulate up to ten percent by weight of the total composition. The material may be manufactured by forming a polytype material made from reacted alumina, aluminum nitride and silicon nitride. The polytype material may be mixed with further powders of silicon nitride and an oxide of yttrium, lithium or calcium and finally reacted to a double phase Si-Al-O-N material where hardness is increased as the additional .alpha.-Si-Al-O-N is increased without significantly affecting its strength.The material may be formed in situ by mixing aluminum nitride, alumina, silicon nitride, together with an oxide of yttrium, lithium or calcium. These materials can then be sintered to a final product containing a double phase Si-Al-O-N.