Synthesis of β-Si3N4 particles from α-Si3N4 particles

This report describes an investigation of the synthesis of β-Si3N4 particles from α-Si3N4 particles. The β fraction of Si3N4 particles was found to depend on temperature, heating time, and the type of crucibles in which the Si3N4 particles were heated. When Si3N4 particles were heated in a crucible made of carbon, most α-Si3N4 particles converted to β-Si3N4 after heating at 2000°C for 90 min in an atmosphere of N2 of 9 kgf/cm2. The morphology of the resulting β-Si3N4 particles appeared as a whisker shape. When Si3N4 particles were heated in a crucible made of boron nitride, most α-Si3N4 particles converted to β-Si3N4 after heating at 2000°C for 480min in an atmosphere of N2 of 9kgf/cm2. 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.