| 摘要 |
PURPOSE:To produce the sintered body having high toughness and a uniform structure even when beta-type silicon nitride is used by using beta-type silicon nitride powder having high-temp. stability and having a specified small grain diameter and sintering the powder under specified conditions by gas pressure. CONSTITUTION:The silicon nitride powder consisting essentially of a beta-type and having <=1.5mu average grain size is mixed with a sintering assistant, and the mixture is formed and then sintered at 1800-2100 deg.C in N2 at 2-200atm. In this case, when the average grain size is larger than 1.5mu, the grain of the sintered body is enlarged, large pores remain in the body, and hence the fracture toughness and strength are lowered. In addition, N2 has to be used to prevent the thermal decomposition of silicon nitride, and the pressure is increased as the temp. is elevated. |
