Si_3N_4セラミックスの焼結過程における固相-気相反応(第4報) : Si_3N_4の重量減少反応及びその形態

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The mass loss reaction during sintering of Si_3N_4 ceramics with 5 mass% Y_2O_3 and 3 mass% Al_2O_3, which was reported in the former paper, was discussed in greater detail, including the observation of cross-sectional morphology and the analysis of the distributions of crystal phases and elements. Differences in the conditions of the powder bed and N_2 gas pressure (0.1 and 1 MPa) during sintering caused significant differences in cross-sectional structures. A porous layer was formed in the surface of samples sintered under 0.1 MPa N_2 at more than 4h of soaking, while a pore-free densified layer was formed at the surface of samples sintered under 1 MPa N_2 at more than 4h of soaking. It was found that the packing powder not only suppressed mass loss reaction, but also drew Y-Si-Al-O-N glass from the grain boundary phase via capillary force. With increasing mass loss with longer soaking times, the oxygen content in specimens decreased and α-SiAlON, melilite and other crystals including Y, Si, O and N were formed. As a result, we concluded that mass loss reaction during sintering of Si_3N_4 ceramics occurred mainly through the following reaction: Si_3N_4(s)+3SiO_2(l)→6SiO(g)+2N_2(g).
社団法人日本セラミックス協会の論文
2000-04-01