METHOD OF PRODUCING HIGH THERMAL CONDUCTIVE SILICON NITRIDE SINTERED BODY

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PROBLEM TO BE SOLVED : To provide a method of producing a silicon nitride sintered body having high thermal conductivity and excellent heat-radiating property as well as inherent high strength characteristics.SOLUTION : The method of producing a high thermal conductive silicon nitride sintered body is characterized in that : the sintered body has at least 20% proportion of a crystal compound phase formed in a grain boundary phase to the entire grain boundary phase; and the sintered body is obtained by compacting a source mixture into a compact, the source mixture prepared by adding 2.0 to 17.5 wt% of rare earth elements in terms of oxides, and 0.3 to 3.0 wt% of Mg in terms of oxide to silicon nitride powder containing oxygen in an amount of at most 1.7 wt%, Al, Li, Na, K, Fe, Ba, Mn and B as impurity cation elements in total of at most 0.3 wt% and α-phase silicon nitride in an amount of at least 90 wt%, and having an average particle diameter of at most 1.0 μm, degreasing followed by sintering the compact at 1, 700 to 1, 900°C, and gradually cooling from the above sintering temperature down to 1, 500°C at a cooling rate of at most 100°C per hour.COPYRIGHT : (C)2009, JPO&INPIT