High‐Temperature Mechanical Properties and Microstructures for Hot‐Pressed Silicon Nitrides with Amorphous and Crystalline Intergranular Phases

Abstract

Four‐point flexure tests were performed at 1100° to 1350°C on two hot‐pressed silicon nitrides, one in which the grain‐boundary phase was amorphous and one in which it was largely crystalline. Fracture stress and relative K 1c were plotted vs temperature. Fracture regions were analyzed by scanning and transmission electron microscopy. Grain‐boundary phases affected high‐temperature fracture significantly.