SILICON NITRIDE CERAMIC-MADE VALVE

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PROBLEM TO BE SOLVED : To provide a silicon nitride ceramic-made valve having high dimensional accuracy after firing and high bending strength on a surface left after firing.SOLUTION : An umbrella part 12 and a columnar stem part 13 integrally formed on the center of the umbrella part 12 comprise the silicon nitride ceramic containing 80-92.5 wt.% silicon nitride, 2-10 wt.% rare earth element expressed in terms of oxide, 2-5 wt.% aluminum expressed in terms of aluminum oxide and 0.5-5 wt.% excess oxygen expressed in terms of silicon oxide, wherein the ratio by weight of rare earth element expressed in terms of oxide to aluminum expressed in terms of aluminum oxide and a ratio by weight of the rare earth element expressed in terms of oxide to the excess oxygen expressed in terms of silicon oxide are respectively 0.5-0.8 and the concentricity of the stem part 13 is ≤0.15 mm.COPYRIGHT : (C)2008, JPO&INPIT