SINTERED SILICON NITRIDE COMPACT, SILICON NITRIDE BALL, SILICON NITRIDE BEARING BALL, BALL BEARING, MOTOR WITH BEARING, HARD DISK DEVICE AND POLYGON SCANNER

摘要

PROBLEM TO BE SOLVED: To provide a sintered silicon nitride compact having excellent workability. SOLUTION: The strongest peak intensity resulting to the αsilicon nitride phase when the X-ray diffraction profile by a diffractometer method is measured at the section of the sintered compact is defined as Xα and the strongest peak intensity resulting to the β silicon nitride phase as Xβ and the value of Xβ/(Xα+Xβ) is regulated to a range from 0.9 to 1, and the silicon nitride particles in a main crystal phase which have grain size average dimensions dav of 0.5 to 5.0 μm and have particle aspect ratios α of >=1 <=5 are made to exist at >=2×104 pieces in average in each 1 mm2 in the sintered compact, by which workability of the sintered compact may be improved.