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对于重烧结以及重烧结后再进行热处理的Si_3N_4样品分别进行了透射电子显微镜和能量色散谱EDS分析。在重烧结但未经热处理样品中发现,无论是三晶粒晶界还是两晶粒晶界相,主要是含钇的玻璃相。在重烧结又经热处理样品中,发现三晶粒的晶界相大部已转为YAG晶体。二晶粒晶界仍有极少量的玻璃相。我们的结果指出,正是晶界玻璃相结晶化,提高了材料的高温强度。本工作还发现,经热处理的样品中Si_3N_4晶界处的YAG相具有区域性择优取向。这可能是影响力学性能的重要因素。
The Si3N4 samples that were re-sintered and re-sintered after heat treatment were analyzed by transmission electron microscopy (SEM) and energy dispersive spectroscopy (EDS). In the heavy sintered but not heat-treated samples were found, whether it is three grain boundaries or two grain boundary phase, mainly containing yttrium glass phase. In the heavy sintering and heat treatment of the sample, we found that most of the grain boundary phase of the three grains have been converted to YAG crystals. Two grain boundaries are still a very small amount of glassy phase. Our results indicate that it is the crystallization of the glassy phase in the grain boundary that increases the high temperature strength of the material. The work also found that the YAG phase at the Si_3N_4 grain boundaries in the heat-treated sample has a regionally preferred orientation. This may be an important factor affecting the mechanical properties.