α-Si_3N_4与γ-Si_3N_4超高压烧结体的性能对比

Characteristic Comparison of α-Si_3N_4 and γ-Si_3N_4 Sintered under Ultra-high Pressure

以Y2O3～Al2O3-LaO23体系作烧结助剂，在5．4～5．7GPa、1620-1770K的高温高压条件下进行了a-Si3N4与γ-Si3N4粉体的烧结，研究了烧结体的相对密度、韦氏硬度和物相组成。结果表明：a—Si3N、γ-Si3N4在烧结后完全转变为B—Si3N4；在相同烧结条件下，γ-SbN4烧结体的相对密度、维氏硬度比a—Si3N4的高γ-Si3N4与a—Si3N4烧结体的最高相对密度与维氏硬度分别为99．20%，23．42GPa和98．78％，21．87GPa；烧结体由相互交错的长柱状β-Si3N4晶粒组成，显微结构均匀。

Ultra-high pressure sintering of T-SiaN4 and a-Si3 N4 with Y2O3-Al2 O3-La2O3 as additives was studied under pressures of 5.4-5.7 GPa and at temperatures of 1 620--1 770 K. The relative density, Vichers hardness and phase composition of sintered compacts were investigated. The results show that both T-Sia N4 and a- Sia N4 transformed to β-Si3N4 completely after sintering. The relative densities and Viekers hardness of T-Si3 N4 sintered compacts were higher than those of a-Si3 N4 sintered compacts prepared under the same conditions. The highest relative density and Vickers hardness in all the as-sintered samples of 7-Si3 N4 and ccSia N4 were 99. 20% and 23. 42 GPa, 98. 78% and 21.87 GPa, respectively. The sintered compacts were composed of elongated β-Si3N4 rod crystals with disordered orientation and uniform microstructure.