Effect of Nano-Sized SiC and Micro-Sized YAG Dispersion on the Microstructure of Alumina

Abstract

Alumina-based ceramic composites prepared by particulate dispersion using SiC and Y2O3 as additives were studied under hot-pressing at 1400 to 1600°C for 0 to 20h. An yttrium aluminum garnet (YAG, Y3Al5O12) phase was formed by the reaction between Al2O3 and Y2O3 above at 1400°C after 10min of hot-pressing, and dense Al2O3/5vol% SiC/20vol% YAG composites resulted. The YAG phase was dispersed at the grain boundary of the Al2O3 matrix with equiaxed grains. Fine SiC was dispersed uniformly within the Al2O3 matrix, whereas coarse SiC particulates, which showed stacking faults, were located in the grain boundaries between the Al2O3 and YAG. The YAG phase was bonded directly to the Al2O3. An impurity phase, which apparently was amorphous, could be detected at the interface between the Al2O3 and SiC. The grain size of the monolithic Al2O3 increased remarkably with increases in hot-pressing temperature and time; grain growth in the Al2O3/SiC/YAG composites were effectively restrained, and those samples exhibited a narrower grain size distribution. This uniformly fine microstructure could be attributed to the incorporation of the YAG and SiC particulates, because of grain boundary pinning by the particulates.