Effects of Particle Size on Densification Behavior of Si_3N_4 Ceramics

摘要

Silicon nitride (Si_3N_4) ceramics with Y_2O_3-Al_2O_3 as sintering additives were prepared by pressureless sintering technology using two kinds of Si_3N_4 powders as raw materials. The particle size of Si_3N_4 powders ball-milled with various times were characterized and the effects of particle size on the densification behavior of Si_3N_4 ceramics were investigated. The relative density and microstructure of the sintered bodies at different sintering temperatures were determined. The experimental results show that the powders with longer milling time have finer particle size and the samples with fine particle display higher shrinkage-rate at lower sintering temperature than the one with coarse particle. By extending milling time, the density gap between the sintered ceramics using different Si_3N_4 powder become narrower. The main factor resulting in the difference of sintering densification behavior is the particle size of Si_3N_4 powders rather than metallic oxide impurity of raw powders.