Deformation behaviors and fracture strength of β$\ubeta$‐Si3N4 single crystals

Abstract

AbstractIn this study, the yield stress and fracture strength of ‐Si3N4 single crystals were directly measured by bending tests of microcantilever beam specimens that were prepared by a focused ion beam method. The ‐Si3N4 single crystals were plastically deformed at room temperature under high bending stress, and the yield stress depended on the crystal orientation. Transmission electron microscopy observation of the specimens after bending tests indicates that the plastic deformation resulted from dislocations in the primary slip system <0001>, and the critical resolved shear stress of this slip system determined from the yield stress was 1.34 GPa. The fracture strength of ‐Si3N4 single crystals ranged approximately up to 20 GPa, depending on the crystal orientation as with the yield stress. The fracture behavior of ‐Si3N4 single crystals was discussed in terms of the accumulation of dislocations.