SILICON NITRIDE CERAMIC HAVING RARE EARTH ALUMINATE-BASED HIGH TEMPERATURE CORROSION RESISTANT LAYER

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PROBLEM TO BE SOLVED : To provide a silicon nitride ceramic having a high temperature corrosion resistant coating film and its manufacturing method. SOLUTION : The silicon nitride ceramic having a corrosion resistant layer comprising a multiple oxide of a rare earth oxide and alumina and their multi-phase composition has a high temperature corrosion resistant layer having a composition between Ln4Al2O9 and Ln3Al5O12 (Ln expresses a rare earth) in which the atomic ratio Ln : Al is 1 : (0.5-5/3). The silicon nitride ceramic is manufactured by film-forming a dense rare earth aluminate layer having 0.1-10 μm film thickness on a base material by a vapor phase method or a liquid phase method and further forming the corrosion resistant layer having 0-200 μm film thickness and comprising a rare earth aluminate having the composition between Ln4Al2O9 and Ln3Al5O12 (Ln expresses rare earth) and their multi-phase composition.