Grain Boundary Phases in a Hot‐Pressed MgO Fluxed Silicon Nitride

Abstract

Although high‐temperature strength loss in ceramics such as silicon nitride has been attributed to the presence of intergranular amorphous phases, until now no direct proof has been offered. The present paper describes high resolution electron microscopy lattice imaging studies of an MgO fluxed hot‐pressed silicon nitride. These studies indicate that intergranular second phases do indeed exist, but they are heterogeneously distributed, appearing especially at multiple grain junctions. These room temperature observations are compatible with the microstructures expected at elevated temperatures.