The microscopic bridging stress distribution developed behind the crack tip of a highly anisotropic silicon nitride has been measured along the crack profile using Raman microprobe spectroscopy with a micrometer spatial resolution. The near‐tip rising R‐curve behavior and the crack‐opening displacement (COD) profile of the material were also determined and discussed in comparison with the Raman microstress data. A comparison with the fracture behavior of a previously investigated silicon nitride material with a three‐dimensional random microstructure is also proposed. According to this set of micro/macroscopic fracture characterizations, a self‐consistent view of toughening behavior in silicon nitride ceramics is obtained, and the role on toughness of anisotropically oriented acicular grains clarified. In agreement with previous studies, it is confirmed that crack‐face bridging is the most effective mechanism for toughening silicon nitride ceramics.
