Phase and microstructural evolution during the heat treatment of Sm–Ca–α-sialon ceramics

• Published in: Journal of the European Ceramic Society 2002-09, Vol.22 (9), p.1609-1620
• Main Authors: Seeber, A.J, Cheng, Y.-B, Harrowfield, I
• Format: Article
• Language: English
• Subjects: Applied sciences; Building materials. Ceramics. Glasses; Ceramic industries; Chemical industry and chemicals; Exact sciences and technology; Microstructure-final; Phase development; Sialon; Structural ceramics; Technical ceramics; X-ray methods
• ISSN: 0955-2219; 1873-619X
• DOI: 10.1016/S0955-2219(01)00482-4

The phase and microstructural evolution of multi-cation Sm–Ca–α-sialon ceramics was investigated. Six samples were prepared, ranging from a pure Sm-sialon to a pure Ca-sialon, with calcium replacing samarium in 20 eq% increments, thus maintaining an equivalent design composition in all samples. After pressureless sintering at 1820 °C for 2 h, all samples were subsequently heat treated up to 192 h at 1450 and 1300 °C. The amount of grain boundary glass in the samples after sintering was observed to decrease with increasing calcium levels. A M′ ss or M′ ss-gehlenite solid solution was observed to form during the 1450 °C heat treatment of all Sm-containing samples, and this phase forms in clusters in the high-Sm samples. The thermal stability of the α-sialon phase was improved in the multi-cation systems. Heat treatment at 1300 °C produces SmAlO 3 in the high-Sm samples, a M′ ss-gehlenite solid solution in the high-Ca samples, and a Sm–Ca–apatite phase in some intermediate samples.