METHOD FOR SINTERING SILICON NITRIDE

摘要

The invention relates to the method of sintering silicon nitride for obtaining a silicon nitride sintered compact having advanced high temperature strength and high density, the method wherein silicon nitride powder mixed with at least one kind selected from among the metallic oxides except silicon oxide and/or at least one kind selected from among the nitrides and carbides of the IVa, Va, VIa metals is pressed and sintered being characterized in that the heating process is effected in atmospheres of different conditions varying by stages from the elevation of temperature to the completion of sintering, i.e. a vacuum below 10<-><3> atm for the first stage, a partial pressure atmopshere of 10<-><3>- 0.9 atm for the second stage, and a high pressure atmosphere above 1 atm for the third stage. The invention enables to impart the aforedescribed characteristics to a silicon nitride sintered compact, although it has been considered difficult to sinter due to its covalent bending, e.g. Si3N4 powder alone, and to produce a sintered compact of advanced high temperature strength and high density even when sintered in a vacuum, under normal pressure or under pressure at a high temperature by using a sintering additives such as metallic oxides, nitrides, carbides, etc.