TEXTURE AND ANISOTROPY IN SILICON-NITRIDE

In this investigation quantitative texture analysis, including calculation of the orientation distribution function, is used to demonstrate the degree of preferred orientation in beta-Si3N4 which has been hot-pressed or hot-worked. The results indicate that plane strain compression can produce strong textures. The texture is decided by the processing parameters including temperature, sintering additives, and stress state. Grain rotation and preferred grain growth apparently both contribute to texture development in beta-Si3N4. Basal (00l) pole figures obtained from the orientation distribution function are consistent with microstructural observations and are reflected in indentation fracture toughness anisotropy. In plane strain the ratio of maximum to minimum fracture toughness is greater than 2.