Silicon nitride sintered body, method of preparing the same and nitrided compact

摘要

Provided is a silicon nitride sintered body prepared through nitriding reaction of Si. The silicon nitride sintered body consists of crystal grains mainly composed of silicon nitride and/or SIALON and a grain phase, components forming the grain boundary phase consist of a first component including at least one element selected from a group of Na, K, Mg, Ca and Sr and a second component including at least one element selected from a group of Y and lanthanoid series elements, the molar ratio of the first component to the second component is in the range of 1:1 to 6:1 in terms of oxides, the mean breadth and the mean length of the crystal grains are not more than 0.1 mu m and not more than 3 mu m respectively, and the standard deviation of the mean length in the sintered body is within 1.5 mu m. <IMAGE>