Roles of Oxygen Vacancies and Surface Layers in Piezoceramic Electrobending

Abstract Electrobending—an electric‐field‐induced bending deformation observed in thinned piezoceramics—has emerged as a promising mechanism to achieve large electrobending strain in piezoelectrics. However, its underlying mechanisms remain insufficiently understood, particularly regarding the role of oxygen vacancies and surface‐layer defect structures. In this work, the correlation between oxygen vacancy concentration (OVC) and electrobending behavior in 0.70Bi 0.5 + x Na 0.5 TiO 3± δ ‐0.30SrTiO 3 (BNST) ceramics is systematically investigated with varying Bi non‐stoichiometry ( x = −0.02, 0, and 0.02). These results reveal that higher OVC, induced by Bi deficiency, significantly enhances the electrobending effect, leading to asymmetric strain‐electric field ( S‐E ) responses and electrostrain values exceeding 1.6% in 200 µm‐thick samples. Depth‐resolved cathodoluminescence spectroscopy (DRCLS) analyses demonstrate the higher defect concentration in the surface layer than in the ceramic interior, and thus the defect dipoles preferentially form in the surface layer rather than in the ceramic interior and tend to orient inward, which is responsible for the observed bending deformation. This study provides direct experimental evidence linking surface defect chemistry with macroscopic electromechanical behavior, offering new design principles for high‐performance lead‐free actuators based on defect dipole engineering.