Synthesis of β-Si 3N 4 particles from α-Si 3N 4 particles

Abstract

This report describes an investigation of the synthesis of β-Si 3N 4 particles from α-Si 3N 4 particles. The β fraction of Si 3N 4 particles was found to depend on temperature, heating time, and the type of crucibles in which the Si 3N 4 particles were heated. When Si 3N 4 particles were heated in a crucible made of carbon, most α-Si 3N 4 particles converted to β-Si 3N 4 after heating at 2000°C for 90 min in an atmosphere of N 2 of 9 kgf/cm 2. The morphology of the resulting β-Si 3N 4 particles appeared as a whisker shape. When Si 3N 4 particles were heated in a crucible made of boron nitride, most α-Si 3N 4 particles converted to β-Si 3N 4 after heating at 2000°C for 480min in an atmosphere of N 2 of 9kgf/cm 2. The resulting morphology was equiaxed. It is suspected that the transformation occurs via the gas phase and is affected by the partial pressure of oxygen in the atmosphere.