Silicon nitride sintered body, silicon nitride ball, silicon nitride bearing ball, ball bearing, motor having bearing, hard disk drive, and polygon scanner

摘要

A silicon nitride sintered body, e.g., a ball, exhibiting excellent machinability is disclosed, having an X-ray diffraction profile measured on a cross section of the silicon nitride sintered body by means of a diffractometer such that X/(XX) is 0.91, wherein X is the highest peak intensity associated with a silicon nitride phase and X is the highest peak intensity associated with silicon nitride phase, and silicon nitride grains of said body have an average grain size dav of 0.5-5.0 m and a grain aspect ratio of 1-5, and are present in an average number of not less than 210⁴ per square millimeter in a predominant crystalline phase observed on the cross section.