Prediction and fabrication of textured Si3N4 ceramics via grain rotation model

The grain preferential orientation has a significant influence on the mechanical properties of silicon nitride (Si3N4) ceramics. Based on the Jeffery's theory, a grain rotation model under uniaxial compression is created to predict the texture evolution mechanism during sintering of Si3N4 ceramics. With deformation, the grain orientation was predicted to rotate towards the plane perpendicular to the pressure direction, and large strain was favorable for the formation of strong texture. According to guidance of the model, the weakly textured microstructure prepared by normal hot pressing is attributed to the limited strain, due to the constrains of graphite die. Therefore, a new PHIP (pseudo-hot isostatic pressing) process with the large deformation is guided to fabricate the strongly textured ceramics by promoting the grain rotation and dynamic grain growth. Generally, the experimental results are well accordance with the model prediction. Furthermore, this model could be applied to guide the design and fabrication of other isotropic and anisotropic ceramic materials.