Y2O3-Al2O3含量对Si3N4陶瓷相组成、致密化、显微结构和力学性能的影响

以α-Si3N4粉为原料,通过添加不同含量的Y2O3-Al2O3烧结助剂(6wt;、8wt;和10wt;),在1800℃下采用热压烧结制备了Si3 N4陶瓷,研究了Y2 O3-Al2 O3含量对Si3 N4陶瓷的物相、致密度、显微结构与力学性能的影响,结果表明:添加6wt;的Y2 O3-Al2 O3助剂即可获得高致密的Si3 N4陶瓷,继续增加助剂含量对Si3 N4陶瓷的致密度影响不大,但是显著影响 α-Si3 N4相和β-Si3 N4相的含量,较高的Y2 O3-Al2 O3助剂含量有利于α-Si3 N4转化为β-Si3 N4.不依赖于Y2 O3-Al2 O3助剂含量,Si3 N4陶瓷均包含细小的等轴晶粒和大尺寸的棒状晶粒,呈现双峰结构,但是Y2 O3-Al2 O3助剂含量增加到10wt;时,可以显著增加棒状晶粒的数量,形成更显著的双峰结构.基于当前研究,发现加入低含量的Y2O3-Al2O3助剂(6wt;),可以获得高硬度高强度的Si3N4陶瓷,而引入高含量的Y2O3-Al2O3助剂(10wt;),则可以获得高韧性高强度的Si3N4陶瓷.

Effect of Y2O3-Al2O3 Contents on Phase Composition,Densification, Microstructure and Mechanical Properties of Si3N4 Ceramics

The Si3N4 ceramics were prepared by hot-pressing at 1800℃using different amounts of Y2O3-Al2O3 as sintering additives and α-Si3N4 as raw powder.The effects of Y2O3-Al2O3 content on phase composition , densification , microstructure and mechanical properties were studied .The results show that dense Si3N4 ceramics could be hot-pressed by the addition of 6wt;Y2O3-Al2O3 at 1800 ℃.The densification of Si3N4 ceramics was not affected by the further increase of Y2O3-Al2O3 content, whereas the amounts of α-Si3N4 and β-Si3N4 phases in the ceramics were influenced by the Y2O3-Al2O3 content. The higher Y2O3-Al2O3 content could promote the α-βphase transformation .Regardless of the Y2O3-Al2O3 content , the Si3N4 ceramics had bimodal microstructures composed of fine equiaxedgrains and large elongated grains.When the Y2O3-Al2O3 content increased to 10wt;, the Si3N4 ceramics with higher content of elongated grains show more bimodal microstructure .Based on the present study , it was found that the Si3N4 ceramics with high hardness and high strength could be prepared by the addition of low Y2O3-Al2O3 content(6wt;), and the Si3N4 ceramics with high toughness and high strength could be obtained by the addition of high Y2O3-Al2O3 content(10wt;).