Ceramic material and method of manufacture

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 by the additional .alpha.-Si-Al-O-N is increased 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. Control of the alumina content in the polytype or in situ methods affects the percentage of .alpha.-Si-Al-O-N produced in the final product. The hardness of the material increases with the .alpha.-Si-Al-O-N content without significantly affecting its transverse rupture strength.