QUANTITATIVE-ANALYSIS OF MICROSTRUCTURE O F SELF-REINFORCED SILICON-NITRIDE CERAMICS

Beta-Si3N4 powders containing 0.5 mol% Y2O3 and 0.5 mol% Nd2O3 were ga s-pressure sintered at 2000-degrees-C for 2, 4, and 8h. The obtained m aterials presented the microstructure of self-reinforced composites co nsisting of some large rod-like grains in a fine matrix, as it was obs erved by scanning electron microscopy of plasma-etched surfaces. Two-d imensional distributions of grain diameter, grain length, and cross-se ctional area were quantitatively analyzed using an image analyzer. The distribution curve of grain number and grain cross-sectional area did not reflect the presence of large grains, and therefore this method i s not suitable for evaluation of self-reinforced materials. The volume fractions of large grains and fine matrix grains were estimated from the relation between the grain size and the two-dimentional distributi on curve of grain cross-sectional area.