Wynette Redington

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

Abstract 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-Y 3 Al 5 O 12 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.

Effect of Cooling Rate on Glass Formation for Some Oxynitride Glasses

Rapid cooling rates and quenching have traditionally been associated with glass formation. Hampshire et al. [1] investigated oxynitride glasses cooled in a tungsten resistance furnace at approximately 200oC/min and found that fast cooling rates were only important near the limits of the glass-forming region. In the current work on various M-Si-Al-O-N (M=Y, La, Yb, Nd) systems, it was found that even at a relatively slow cooling rate glass formation was still possible for a wide range of compositions. Different cooling rates were investigated to determine the minimum cooling rate at which a glass will form. Quantitative X-ray analysis of melted compositions indicated the relative amounts of amorphous phase and crystalline phase.

Extension and Representation of the Glass forming Region in the Nd-Si-Al-O-N System

Recent work has indicated that the glass-forming region in the Y-Si-Al-O-N system could be more extensive than originally reported, particularly in the Al-rich part of the system. With knowledge gained from the Y-Si-Al-O-N system and bringing together published behaviour diagrams for the Nd-Si-Al-O-N system, a further study of the latter system was undertaken. The present work outlines the extension of the glass-forming region to Al-rich glasses compositions in the Nd-Si-Al-O-N system.

High Aluminium Content Glasses and their Properties in Y- and Ln-SiAlON Systems

A review of some behaviour diagrams in the Y-Si-Al-O-N system indicated that the liquid region, and hence the glass forming region, could be more extensive than previousl y d cumented. Apart from the glass-forming region of Drew et al [1] at 1700 C, the solid liquid reactions in the βSiAlONY3Al 5O12 system, seen as liquid isotherms at 1550 C, 1650C and 1750 C, are indicated by Tien [2]. The representation of these is shown on the Jänecke pri sm. Various compositions were fired at 1700 C to determine the extent of the region in which glass formed. The areas of glass formation are indicated for the different M-Si-Al-ON systems investigated, (M= Y, Nd, Sm, Dy, Yb). Mechanical properties have been investigated and compared with low er Al content glass compositions in these system (i.e. 28M:56Si:16Al:83O:17N e/o) [3].