Texture Development in Silicon Nitride–Silicon Oxynitride In Situ Composites via Superplastic Deformation

Silicon nitride–silicon oxynitride (Si 3 N 4 –Si 2 N 2 O) in situ composites have been fabricated via either the annealing or the superplastic deformation of sintered Si 3 N 4 that has been doped with a silica‐containing additive. In this study, quantitative texture measurements, including pole figures and X‐ray diffraction patterns, are used in conjunction with scanning electron microscopy and transmission electron microscopy techniques to examine the degree of preferred orientation and texture‐development mechanisms in these materials. The results indicate that (i) only superplastic deformation can produce strong textures in the β‐Si 3 N 4 matrix, as well as Si 2 N 2 O grains that are formed in situ ; (ii) texture development in the β‐Si 3 N 4 matrix mainly results from grain rotation via grain‐boundary sliding; and (iii) for Si 2 N 2 O, a very strong strain‐dependent texture occurs in two stages, namely, preferred nucleation and anisotropic grain growth.