Si_3N_4セラミックスの焼結時における固相-気相反応(第1報) : 高温下でのSiO_2, Y_2O_3及びAl_2O_3の安定性

概要

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The stability during sintering of SiO_2, Y_2O_3 and Al_2O_3, well known as sintering aids of Si_3N_4 ceramics, was examined from both thermodynamical and experimental aspects. Both the heat treatment of SiO_2-Y_2O_3-Al_2O_3 glass and the sintering of Si_3N_4 ceramics were carried out. In the thermodynamical considerations, the stability of the glass composition was discussed on the basis of known volatility diagrams for SiO_2, Al_2O_3 and MgO and the thermodynamic data of Y_2O_3 available in the literature. The results suggest that Y_2O_3 is the most stable among all materials in the sintering temperature range usually selected for Si_3N_4 ceramics. SiO_2-Y_2O_3-Al_2O_3 (equi-mass%) glass was heat-treated in a BN sagger at 2023 K for 2 h in N_2 gas of 0.1 MPa. Si_3N_4 with addition of 5 mass% Y_2O_3 and 3 mass% Al_2O_3 was sintered in the BN sagger at 2023 K for 0 to 16 h in N_2 gas of 0.1 MPa. The elemental contents in the glass and ceramics before and after heat treatment and sintering were determined by chemical analysis. As a result, it was found that only SiO_2 in the glass and SiO_2 and Si_3N_4 in the Si_3N_4 ceramics vaporized. On the other hand, the Y_2O_3 and Al_2O_3 contents in both the glass and Si_3N_4 ceramics did not decrease under the selected temperature.
社団法人日本セラミックス協会の論文
2000-01-01