日本金属学会誌

J. Japan Inst. Metals, Vol. 69, No. 8 (2005),
pp. 719-722

Grain Growth of β-Silicon Nitride in RE(RE=Y, Gd, Nd and La)-Mg-Si-O-N Melts

Daiji Nakata1,, Noritaka Saito1, Ayumu Umemoto2 and Kunihiko Nakashima1

1Department of Material Process Engineering, Graduate School of Engineering, Kyushu University, Fukuoka 812-8581
2Advanced Ceramics Division, TOTO Ltd., Kitakyushu 802-8601

Abstract:

Isothermal growth of β-Si3N4 crystals dispersed in rare-earth (RE=Y, Gd, Nd and La) oxynitride melts (RE-Mg-Si-O-N) was studied during heat treatment at 1773 K under 0.9 MPa of nitrogen pressure for 64 to 512 min. The microstructure of β-Si3N4 crystals was characterized by electron microscopy. It is found that the rate of α-β transformation increases with decreasing ionic radius of the rare-earth element. Likewise, the radii of rare-earth elements make significant differences in the morphology and mean aspect ratio of β-Si3N4. Especially, the aspect ratio of β-Si3N4 crystals with the additive of La2O3 was found to be much larger than that in oxynitride melts with additives of others.


(Received 2005/4/25)

Keywords:

silicon nitride, morphology, rare-earth, oxynitride melt, anisotropic ostwald ripening


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