以冲击波合成的γ-Si3N4粉体为原料, Y2O3-Al2O3-La2O3体系作烧结助剂, 在5.7GPa、1370~1670K的高温高压条件下, 进行了γ-Si3N4粉体的烧结. 研究了不同烧结温度对γ-Si3N4稳定性、相对密度、力学性能及显微结构的影响. 结果表明: γ-Si3N4在 1420~1670K的条件下, 完全相变为β-Si3N4, 在1370K左右的条件下, 发生部分向β-Si3N4相变. 在5.7GPa, 1370K的条件下, 烧结样品的相对密度与维氏硬度分别为98.83%和21.09GPa.
Silicon nitride ceramics was prepared by super-high pressure using the γ-Si3N4 powders synthesized by the shock-wave technique as raw materials and with Y2O3-Al2O3-La2O3 mixtures as additives at 5.7GPa from 1370K to 1670K. The stability, relative density, mechanical properties and microstructure of the compacts synthesized at different temperatures were investigated. The results show that γ-Si3N4 is completely transformed to β-Si3N4 at temperature from 1420K to 1670K,
and partly transformed to β-Si3N4 at 1370K. Micro-analysis indicates that the typical microstructure of sintered Si3N4 is mainly composed of β-Si3N4 rod crystals with disordered orientation and uniform microstructures. The relative density
and Vickers hardness in the as-sintered (5.7GPa, 1370K) samples are 98.83% and 21.09GPa, respectively.
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