SILICON NITRIDE POWDER, SILICON NITRIDE SINTERED BODY AND CIRCUIT SUBSTRATE, AND PRODUCTION METHOD FOR SAID SILICON NITRIDE POWDER

摘要

The present invention addresses the problem of providing: a silicon nitride sintered body and a circuit substrate which exhibit both high mechanical strength and high thermal conductivity; a silicon nitride powder used as a starting material for these; and a production method for the silicon nitride powder. Provided is a silicon nitride powder which has a specific surface area of 4.0-9.0 m2/g, a β phase ratio of less than 40%, and an oxygen content of 0.20-0.95 mass%, said silicon nitride powder wherein: the frequency distribution curve obtained from a volume-based particle size distribution measurement performed using laser diffraction scattering has two peaks; the tops of the peaks are within the range of 0.4-0.7 µm, and within the range of 1.5-3.0 µm respectively; the ratio (the frequency of the top of the peak in the particle size range of 0.4-0.7 µm/the frequency of the top of the peak in the particle size range of 1.5-3.0 µm) of the frequencies of the tops of the peaks is 0.5-1.5; and the ratio (D50/DBET) (µm/µm) of the median diameter (D50) (µm) obtained from the particle size distribution measurement, to the specific surface area equivalent diameter (DBET) (µm) calculated from the specific surface area is at least 3.5. Also provided are: a silicon nitride sintered body and a circuit substrate which are obtained from the silicon nitride powder; and a production method for the silicon nitride powder.