Synthesis of β-Si3N4 particles from α-Si3N4 particles

This report describes an investigation of the synthesis of beta-Si3N4 particles from alpha-Si3N4 particles. The beta 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 alpha-Si3N4 particles converted to beta-Si3N4 after heating at 2000 degrees C for 90 min in an atmosphere of N-2 of 9 kgf/cm(2). The morphology of the resulting beta-Si3N4 particles appeared as a whisker shape. When Si3N4 particles were heated in a crucible made of boron nitride, most alpha-Si3N4 particles converted to beta-Si3N4 after heating at 2000 degrees 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. (C) 2000 Elsevier Science Ltd. All rights reserved.