Properties of some high Al content glasses in various lanthanide-Si-Al-O-N systems

A review of some behaviour diagrams in the Y-Si-Al-O-N system indicate that the liquid region, and hence the glass forming region, could be more extensive than previously documented. Apart from the glass-forming region of Drew et al. [Special Ceramics 7, Brit. Ceram. Proc., vol. 31, The British Ceramic Society, Stoke-on-Trent, UK, 1981, p. 119] at 1700 °C, the solid-liquid reactions in the β-SiAlON-Y₃Al₅O₁₂ seen as liquid isotherms at 1550, 1650 and 1750 °C are indicated by Tien [Silicon Nitride Ceramics Scientific and Technological Advances, Materials Research Society Symposium Proceedings, vol. 287, MRS Pittsburgh, 1993, p. 51]. Other researchers [J. Eur. Ceram. Soc. 17 (1997) 789] have studied the nitrogen-rich liquid phase regions in the Ln-Si-Al-O-N systems (40 e/o N). In the current work, selected compositions with high Al/Si ratio in the aluminium-rich part of these systems (52-62 e/o) were fired at 1700 °C. Properties have been investigated and compared with 'standard' glass compositions (i.e. 28M:56Si:16Al:83O:17N e/o) [J. Eur. Ceram. Soc. 17 (1997) 1933] where M = La, Nd, Sm, Dy, Er, Yb, Y.