Ceramic composition and a process for producing the same

A novel ceramic composition having high strength at high temperatures and needing no degreasing step before its sintering step, and a process for producing the same are provided, which composition is obtained by calcining a molded body composed of alumina powder and a polysilazane in an inert gas such as nitrogen, argon, etc. and/or ammonia, or under pressure and at 800 DEG -1950 DEG C. the polysilazane including the following: a polysilazane (i) having a core structure consisting of repetitive units of and comprising the residual groups of the precursor of (i) having and partly forming structural units of the structural units being bonded to each other, a polysilazane (ii) having the above core structure and comprising the residual groups of the precursor of (ii) consisting of repetitive units of being bonded by a structural unit of to each other, and the precursor being composed of units of wherein; and a polysilazane (iii) having the above core structure and comprising the residual groups of the precursor of (iii), partly forming structural units of these units being bonded to each other, and the precursor being composed of units of wherein R1, R2, R3, R4, R5 and R6 which may be the same or different, each represent a lower alkyl group of 1 to 6 carbon atoms, a substituted or unsubstituted vinyl group, a substituted or unsubstituted allyl group, a substituted or unsubstituted lower aryl group of 6 to 10 carbon atoms, a tri-lower alkyl- or di-lower alkylsily group, and R1, R2 and R3 each represent a hydrogen atom or a di-lower alkylamino group.