Abstract: Substituted silicon aluminum oxynitrides are made electrically conductive by inclusion of titanium nitride at low levels, e.g. 15-38 vol %, by inclusion of titanium dioxide and in situ conversion thereof to titanium nitride which is contained in an intergranular phase. Further improvements in conductivity can be achieved by converting the intergranular phase from a glassy state to a crystalline state.

Abstract: A cutting tool tip is formed at least at a cutting edge of the tip from a ceramic product consisting essentially of at least 75% by volume of a single phase compound having an expanded .beta.-phase silicon nitride lattice and having the general formula Si.sub.6-z Al.sub.z N.sub.8-z O.sub.z, where O<z.ltoreq.5, together with a second phase containing a metal from the list yttrium, lanthanum, cerium and scandium, or other rare earth metal.

Abstract: A method of producing a ceramic product which comprises the step of forming a powder mixture consisting essentially of a first component consisting of compounds containing the elements silicon, aluminum, oxygen and nitrogen in proportion such that the ratio of the total number of silicon and aluminum atoms to the total number of oxygen and nitrogen atoms lies in the range 0.735 to 0.77 and such that said compounds react together during the subsequent sintering process to produce a single phase ceramic material obeying the general formula:Si.sub.6-z Al.sub.z O.sub.z N.sub.8-zwhere z is between 0.38 and 1.5, and between 0.1 and 10% by weight of a second component in the form of an oxide of at least one of the further elements yttrium, scandium, cerium, lanthanum and the metals of the lanthanide series. The mixture is then sintered in a protective environment at a temperature between 1600.degree. C and 2000.degree.