| 摘要 |
PURPOSE:To provide a silicon nitride powder capable of producing a sintered compact having excellent sintering property and toughness by specifying the ratio of alpha phase and beta phase of crystal form and the amount of oxygen solid solution. CONSTITUTION:The objective silicon nitride has a crystal form consisting of <=70% alpha phase and >=30% beta phase and has <0.5wt.% oxygen solid solution. When the ratio of alpha phase exceeds 70%, an abnormal grain growth occurs in an alpha beta transfer accompanying crystallization of columnar crystal and the columnar crystal becomes irregular, and the material having a large aspect ratio is crystallized and the densification is inhibited. When the amount of oxygen solid solution is >=0.5%, alpha beta transfer occurs readily in low temperature and a grain boundary phase formed by sintering assistant is increased and the solubility of silicon nitride is changed and a beta-columnar crystal having small aspect ratio alone is produced. Therefore, through the sintering property is improved, toughness is not improved. Furthermore, a silicon halide method capable of controlling the characteristics of amount of oxygen solid solution, average grain size and specific surface area, etc., is most preferable for this production method of silicon nitride powder. |
