Texture development and phase transformation in liquid-phase-sintered SiC ceramics

By using Y2O3 and Al2O3 as sintering aids, the effect of additive amount on the texture was investigated during the liquid-phase sintering of fine SiC powders, and the resulting microstructure and phase transformation of the hot-pressed and subsequently annealed materials were investigated. In this investigation quantitative texture measurements, including the pole figures and X-ray diffraction patterns, are used in conjunction with scanning electron microscopy to demonstrate the degree of preferred orientation and texture development mechanisms in these materials. The results show that annealing can produce textures and the degree of preferred orientation of hot-pressed and annealed SiC enhances with increasing amount of additives. The strong effect of additive amounts on texture was due to the anisotropic grain growth by the beta-->alpha phase transformation during annealing. The presence of a large amount of sintering aids accelerated the grain growth of elongated large grains during annealing and increased the texture intensity.