CRYSTALLIZATION AND SINTERING CHARACTERISTICS OF CHEMICALLY VAPOR-DEPOSITED SILICON-NITRIDE POWDERS

High purity silicon nitride powders have been obtained by Chemical Vapor Deposition (CVD), through the reaction of SiH4 and NH3 gas mixtures at 1000-degrees-C in a quartz reactor. The crystallization characteristics of the powder have been followed by infrared and x-ray diffraction analysis. The material shows a transition from amorphous to the alpha-phase after a thermal treatment at about 1300-degrees-C for 1 h, while the beta-phase starts to appear at 1725-degrees-C. The sintering properties of the amorphous and crystalline phases were evaluated by measuring the dilatometric curves of compacted powders.