以Y2O3-Al2O3-La2O3体系作烧结助剂,在5.4～5.7 GPa、1 620～1 770 K的高温高压条件下进行了α-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:α-Si3N4、γ-Si3N4在烧结后完全转变为β-Si3N4;在相同烧结条件下,γ-Si3N4烧结体的相对密度、维氏硬度比α-Si3N4的高γ-Si3N4与α-Si3N4烧结体的最高相对密度与维氏硬度分别为99.20%,23.42 GPa和98.78%,21.87 GPa;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 γ-Si3N4 and α-Si3N4 with Y2O3-Al2O3-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 γ-Si3N4 and α-Si3N4 transformed to β-Si3N4 completely after sintering. The relative densities and Vickers hardness of γ-Si3N4 sintered compacts were higher than those of α-Si3N4 sintered compacts prepared under the same conditions. The highest relative density and Vickers hardness in all the as-sintered samples of γ-Si3N4 and α-Si3N4 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.
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