Melilite Formation in a Samarium-Stabilized α-Sialon Ceramic during Postsintering Heat Treatments |
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| Authors: | Zhijian Shen Daniel Ashkin Oleg Babushkin Thommy Ekstrm |
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| Affiliation: | Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, People's Republic of China;Department of Engineering Materials, LuleåUniversity of Technology, S-971 87 Luleå, Sweden;Department of Inorganic Chemistry, Arrhenius Laboratory, Stockholm University, S-106 91 Stockholm, Sweden |
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| Abstract: | The formation of the melilite solid solution phase (M'), Sm2Si3?xAlxO3+xN4?x, in an α-sialon sample of overall composition Sm0.6Si9.28Al2.69O1.36N14.76, was studied as a function of time in the temperature interval 1375–1525°C. The alpha-sialon ceramic contained only minor amounts of the 21R sialon polytype and some residual grain-boundary glass before heat treatment. In situ studies by high-temperature X-ray diffraction were combined with postsintering heat treatment followed by quenching. The M'-phase was found to be formed by two different mechanisms: either crystallization of the residual grain-boundary liquid or a direct decomposition of the α-sialon phase. The liquid crystallized during the first 10–15 min of heat treatment, yielding a rapid M'-phase formation, and further formation of M'-phase continued at a much slower rate, related to the decomposition of α-sialon. |
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