| 摘要 |
PURPOSE:To obtain a calcined compact having a high tensile strength at ambient temperature and 1400 deg.C at a low temperature under a low pressure by using Si3N4 powder having specified alpha content and particle diameter and a group IIIa element compound and SiO2 as a calcining assistant and calcining the resultant powder in pressurized N2 atmosphere under specific conditions. CONSTITUTION:Si3N4 powder having >=98% alpha content and <=0.5mu average particle diameter and a group IIIa element compound and SiO2 as a calcining assistant without containing Al2O3 and MgO are used and formed. The resultant compact is then calcined at a low temperature of 1600-1800 deg.C under <=1.5 atm N2 gas pressure. Thereby, a calcined compact consisting of the Si3N4 and Si, group IIIa element, O and N as the second phase and Si3N4 crystal grains, having <=0.5mu grain diameter and present in a part at >=40area% on specular surfaces with a bulk density of >=95% based on the theoretical density and >=600MPa four-point flexural strength at 1400 deg.C is obtained. |
