Formation and Microstructure of Mg‐Si‐O–N Glasses

Bulk oxynitride glasses in the Mg‐Si‐O–N system were prepared by melting mixtures of SiO2, MgO, and Si3N4 powders and the microstructures and compositions of the glasses were analyzed by electron microscopy, energy and wavelength dispersive X‐ray analysis, and energy loss spectrometry. The melting experiments indicate the presence of a limited glass‐forming region in the system. For the melting conditions used, nitrogen was found to be a necessary constituent of the melts to prevent crystallization on cooling. Extension of the miscibility gap in the binary MgO‐SiO2 system into the Mg‐Si‐O–N system results in phase separation in most of the glasses. A partial plot of the miscibility gap in the Mg–Si‐O–N system is established from analysis of the composition of the phases formed during phase separation of the glasses. Copyright © 1984, Wiley Blackwell. All rights reserved