COMPOSITION AND MICROSTRUCTURE OF NANOSIZED, AMORPHOUS AND CRYSTALLINE SILICON-NITRIDE POWDERS BEFORE, DURING AND AFTER DENSIFICATION

The composition, microstructure;and densification behaviour of two amo rphous and three crystalline silicon nitride powders containing an MgO -Y2O3 sintering aid have been investigated. The powders were character ised in terms of bulk and surface chemical compositions, crystallinity and morphology. The hot-pressing behaviours of the powders were asses sed by considering the mass losses on densification, relative densitie s and the chemical and phase compositions and microstructure of the de nse materials. Densification kinetics were analysed by the computer ev aluation of hot-pressing data.