Si_3N_4-MgO-CeO_2陶瓷烧结过程中的致密化与相变

Densification and phase transfor mation during the sintering of Si 3N 4 MgO CeO 2 ceramics

氮化硅陶瓷有极大的应用潜力，但由于其强共价键，很难烧结致密化。采用了一种新的ＭｇＯ－ＣｅＯ２复合烧结助剂，利用Ｘ射线衍射、透射电镜等手段研究了ＭｇＯ－ＣｅＯ２复合烧结助剂对氮化硅陶瓷致密化和相变过程的影响，结果发现对Ｓｉ３Ｎ４－ＭｇＯ－ＣｅＯ２陶瓷，在１４５０℃就会有大量液相出现，１５００～１５５０℃为快速致密化阶段，而α－Ｓｉ３Ｎ４→β－Ｓｉ３Ｎ４相变主要发生在１５５０～１６００℃，相变过程滞后于致密化过程。常压烧结Ｓｉ３Ｎ４－ＭｇＯ－ＣｅＯ２陶瓷，强度达９４８ＭＰａ，因此，ＭｇＯ－ＣｅＯ２是一种非常有效的氮化硅的烧结助剂。

Silicon nitride ceramics show great potential for wide applications. It is difficult to densify silicon nitride due to its covalent nature of bonding. A new sintering aid with combination of MgO and CeO 2 was used in the present study. The effects of MgO CeO 2 on densification and phase transformation during sintering of Si 3N 4 were discussed. For Si 3N 4 MgO CeO 2 ceramics, a lot of liquid phase existed at 1450℃, and densification process took place rapidly from 1550℃ to 150℃; the phase transformation from α Si 3N 4 to β Si 3N 4 took place rapidly from 1550℃ to 1660℃, the phase transformation process lags behind the densification process. The nonpressure sintered Si 3N 4 MgO CeO 2 ceramics achieved a bending strength of 948MPa. MgO CeO 2 can be considered as an effective sintering aid for Si 3N 4.