本文对以Y203、La20，及A1203作为添加剂的Si3N4陶瓷气压烧结工艺进行了研究，探索了烧结温度、时间和相对密度三者的关系。采用二步气压烧结工艺，制备了致密的高性能Si3N4陶瓷材料。以Y203-A120，为添加剂，材料具有良好的室温抗弯强度(口RT=1015MPa)，而以Y203-La20，为添加剂，材料具有优异的高温力学性能， 其强度可保持到1300℃几乎不下降。(GRT=905MPa，G1300℃=885MPa)。 通过与无压烧结对比，研究了高压氮气对GPS过程中致密化、以—"相变和相组成的影响。结果发现，高压氮气溶人液相，改变液相的组成，降低了材料致密化和 相变的速率。此研究表明在气压烧结过程的前期应避免使用高压氮气。 利用XRD、EDAX定量分析及TEM显微形貌观察，研究了GPS SiaN，陶瓷的晶界玻璃相特性。由于气压烧结温度较高，将促进Si3N，进一步溶人液相，增加液相的含量。采用统计方法分析了GPS Si3N4陶瓷其晶粒直径和长径比的变化，结果表明，"-Si3N4晶粒的生长遵循立方法则，其生长活化能为352kJ／mol，高温长时间烧结，易产生晶粒的粗化致使晶粒长径比下降，材料中常见少数异常生长的晶粒，形成一种由少量大晶粒和多数小晶粒交织而成 的显微形貌。
The gas pressure sintering (GPS) process of Si3N4 ceramics with Y203 La203 and A1203 as additives was studied by means of establishing the relation between densification and sintering temperature and time. Dense and homo geneous high performance Si3N4 ceramic materials were obtained by using the two-step GPS process. The Si3N4 ceramics added Y203, A1203 had good room temperature bending strength (aRT=1015MPa), the Si3N4 ceramics with Y203, La203 as additives exhibited excellent high temperatune mechanical properties. (aRt = 905MPa, al300e = 885MPa). The effect of high pressure N2 on densification phase transformation and composition were investigated by compared with that of atmosphereN2. It was found that high pressure N2 dissolves in liquid phase andconsquently reduces the rate of densification and phasetransformation. The results indicated that high pressure N2 should be avoided during the early stage of GPS process. The characteristics of grain boundary glassy phase of GPS Si3N4 were examined by way of XRD, EDAX quantitative analysis and TEM micrograph observation. The results showed that higher sintering temperature could promote the dissolvtion of particles and increase the amount of liquid phase The microstructure of GPS Si3N4 ceramics was cval. uated in terms of diameter and aspect ratio of the grains. The statistical results indicated that the growth of grain follows a cubic law, the activation energy of grain growth is 352k J/mol and extending sintering time or increasing sintering temperature would lead to grain coalescence. The GPS Si3N4 ceramic materials had such a microstructure which composed of a small number of large and anisotropic grains and a large number of small grains.
