Ceramics: Microstructural Toughening (Excluding Transformation Toughening, Whisker Toughening, and Continuous Fiber Toughening)

The enhancement of fracture toughness in ceramic materials can occur over a broad range of length scales. The length scale that has received the greatest attention in structural ceramic materials is the microstructural scale, that of the grain dimensions that normally vary from 1 µm to 20 µm. In single-phase materials, weak grain boundaries or residual stresses resulting from thermal expansion anisotropy perturb the propagation of a crack. The same is true for grain boundary phases or particulate reinforcements in multiphase materials