Al_2O_3-Y_2O_3 AlN を助剤としたSi_3N_4焼結体における異常組織

概要

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When AlN polylype (21R) powder is used as an addi tive to sinter Si_3N_4 ceramics together with Al_2O_3 and Y_2O_3 additives, anomalous black spots are found. These black spots contain β-Si_3N_4 and YAG-phase, i.e., garnet type crystal structure consisting of 5Al_2O_3・3Y_2O_3. The matrix contains also β-Si_3N_4 with addition of YAP-phase, i.e., perovskite type crystal structure with equal molar anrount of Al_2O_3 and Y_2O_3・ The differ ent precipitated crystals in the black spots and in the matrix cause the dissimilarity of the appearance of the two regions. The YAG-phase nucleates at Fe inclusions which play a role as an embryo, and forms black spots. YAP-phase simply precipitates in the matrix by cooling the Si_3N_4 cerumics. To reduce the amount of the black spots, it is necessary to eliminate the Fe contamination which normally origins frorn raw powder production or miniug processes.
社団法人日本セラミックス協会の論文
1994-04-01