窒化ケイ素焼結体の模擬粒界相としてのY_2O_3-Al_2O_3-SiO_2ガラスの特性(第1報) : 機械的性質

概要

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Glasses in the system Y_2O_3-Al_2O_3-SiO_2 were employed as a model of grain boundary phase of Si_3N_4-Y_2O_3/Al_2O_3 ceramics and examined their physical properties and structure by means of IR spectroscopy. The glass compositions studied were xY_2O_3・(60-x) Al_2O_3・40SiO_2 in wt%, where x=30, 40 and 45. It was found that the substitution of Y_2O_3 for Al_2O_3 increases the density, glass transition temperature, elastic constants and Vickers hardness, but decreases fracture toughness. These results were explained from a proposed structure that Y^<3+> ions act as network modifiers in contrast to Al^<3+> ions which - are supposed to be a network former. On the basis of measurements of the properties of the glasses, some properties of Si_3N_4- Y_2O_3/Al_2O_3 ceramics were discussed. The Vickers hardness of Si_3N_4-Y_2O_3/Al_2O_3 ceramics had similar dependence on Y_2O_3/Al_2O_3 molar ratio with that of the model glasses. The flexural strength of the ceramics was related to the microstructure, more specifically to the aspect ratio of the Si_3N_4 grains and phase composition, rather than that of grain boundary phase.
社団法人日本セラミックス協会の論文
1989-12-01