The deformation behavior and fracture toughness of single crystal YSZ(111) by indentation

The nano-scale deformation behaviors and indentation-induced fracture features of the (111)-oriented yttrium-stabilized zirconia single crystal (YSZ(111)) were investigated by Berkovich and micro-Vicker indentations, respectively. The load-displacement curves in the Berkovich nano-indentation experiments evidently exhibited indentation-induced single “pop-in” phenomenon during loading, indicating that the nano-scale deformation in the YSZ(111) crystals is due primarily to the activities of dislocation nucleation and propagation. Based on this scenario, the number of nanoindentation-induced dislocation loops giving rise to the pop-in event was estimated to be around 2 × 10⁵ with a critical radius of ∼2 nm. The hardness and Young's modulus of YSZ(111) single crystal obtained by the continuous contact stiffness measurements (CSM) mode were 22.3 ± 1.1 GPa and 270.6 ± 8.5 GPa, consistent with those reported previously in the literature. In addition, the fracture toughness of YSZ(111) single crystal was estimated to be about 1.4–1.6 MPa m^1/2.