Size-dependent electrobending in piezoceramics mediated by gradient defect dipoles

Electrobending in thin piezoceramics represents a promising route to achieving ultrahigh output range for precision actuators, yet its governing mechanical mechanism and predictable size dependence have remained elusive. Here, we demonstrate that the bending deformation originates from an electrostrain gradient caused by the non-uniform distribution of defect dipoles along the thickness direction, and propose a generalized model to describe its size-dependent behavior. Using Mn-doped PZT-based piezoceramics as an example, the initial bending of poled piezoceramics is observed and explained. Regarding the dynamic electrobending phenomenon, a mechanical mechanism is proposed, which supports the view that the electrobending effect originates from surface strain differences induced by the non-uniform distribution of defect dipoles and elucidates the entire bending evolution process under bipolar electric fields. Furthermore, a mechanical model considering the synergistic effect of electrobending and intrinsic electrostrain is developed. The size dependence is accurately described by the model, as rigorously validated by both finite element simulations and experimental measurements. These findings deepen the fundamental understanding of the electrobending mechanism and provide a valuable foundation for the design of devices utilizing this effect.