Crystal defects often lead to an intriguing variety of catastrophic failures of materials and determine the mechanical properties. Here we discover that a dislocation, which was believed to be a source of plasticity, leads to brittle fracture in SrTiO3. The fracture mechanism, i.e., bond breaking at the dislocation core triggers crack initiation and subsequent fracture, is elucidated from an atomic view by hybrid quantum and molecular simulations and in situ nanomechanical experiments. The fracture strength of the dislocation-included SrTiO3 was theoretically evaluated to be 8.8-10.7 GPa, which was eminently lower than that of the pristine one (21.7 GPa). The experimental results agree well with the simulated ones. Moreover, the fracture toughness of the ultrasmall crack initiating from the dislocation is quantitatively evaluated. This study reveals not only the role of dislocations in brittle fracture but also provides an in-depth understanding of the fracture mechanism of dislocations at the atomic scale.
Keywords: Brittle fracture; Dislocation; Fracture criterion; SrTiO3; Ultrasmall-scale.