Ngk Insulators, Inc.

Kouichi Imao

Shinichi Miwa

Seiichi Asami

Takehiro Kajihara

Masakazu Adachi

A process for degreasing ceramic molded bodies containing a large quantity of paraffin wax includes a constant-temperature heating conducted for a certain period of time appropriately determined according to the size and shape of the ceramic molded bodies, at a temperature immediately below the temperature for the ceramic molded bodies to begin contraction, essentially in a low temperature region wherein the contraction occurs due to liquefaction of the paraffin wax and optionally in a high temperature region wherein the contraction occurs due to thermal decomposition of the paraffin wax. According to the process of the invention, build-up of stress in the ceramic molded bodies by heating is prevented and a temperature gradient between the surface and the inside of the molded bodies is leveled, so that crack-free molded bodies are obtained with a shortened degreasing schedule.

Process for degreasing ceramic molded bodies

Silicon nitride sintered bodies including Si.sub.3 N.sub.4 and at least one element selected from Y.sub.2 O.sub.3, MgO, ZrO.sub.2. In the silicon nitride bodies, a J phase solid solution is present in an intergranular phase, which satisfies a relation of 0.65x.ltoreq.y.ltoreq.x+2 wherein y is an amount of J phase solid solution and x is an amount of Y.sub.2 O.sub.3 as an additive.

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Kagamihara, Japan

Kouichi Imao