Effect of α-Si₃N₄ initial powder size on the microstructural evolution and phase transformation during sintering of Si₃N₄ ceramics

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• 作者：Rhee ; Sang-Hoon ; Lee ; Jae Do ; Kim ; Doh-Yeon
• 关键词：Grain growth ; Microstructure ; Si₃N₄ ; Structural applications ; Toughness and toughening
• 刊名：Journal of the European Ceramic Society
• 出版年：2000
• 期刊代码：53_09552219
• 类别：ms
• 出版时间：October, 2000
• 卷：20
• 期：11
• 页码：1787-1794
• 文件大小：1.55 M

摘要

By using the Si₃N₄ ceramic specimens prepared with fine and coarse α-Si₃N₄ powders, respectively, the phase transformation from α- to β-Si₃N₄ and concurrent microstructural evolution during sintering were monitored. For the compact prepared with fine powder, the α/β transformation was completed much earlier than the coarse powder. The higher fraction of pre-existing β-grains in fine powder and its higher reactivity compared to those of coarse one are likely to cause a rapid phase transformation. The growth rate of β-Si₃N₄ grains at the expense of α-Si₃N₄ during phase transformation stage was quite significant while that after they impinge each other was very limited. As a result, the specimens prepared with coarse and fine initial α-Si₃N₄ powders resulted in coarse and fine grained β-Si₃N₄ ceramics, respectively. The specimen prepared with mixture of fine and coarse α-Si₃N₄ powders exhibited the microstructure containing a few elongated large grains and showed an increased value of fracture toughness.