THE STRUCTURE OF GRAIN BOUNDARIES IN SILICON NITRIDE BASED ALLOYS

Grain boundaries in silicon-based ceramics have been characterized by high resolution electron microscopy including the technique of lattice fringe imaging, and this work is illustrated with examples from both hot-pressed silicon nitrides (MgO and Y{sub 2}O{sub 3} fluxed) and a magnesium-sialon (Mg{sub 1.86} Si{sub 1.67} Al{sub 2.47} O{sub 3.19} N{sub 3.81}). Room temperature observations of the glassy phase are consistent with it being only a partially wetting phase, indicating that it cannot form a continuous film. The atomic configuration of the grain boundaries in both materials is presented together with lattice fringe observations of segregation at grain boundaries in the magnesium-sialon