Ultrahigh Electro-Bending Deformation in Lead-free Piezoelectric Ceramics via Defect Concentration Gradient Design.

Recent breakthroughs in defect-engineered lead-free piezoelectric ceramics have reported remarkable electro-strain values, surpassing the limit of lattice distortion. This has aroused wide concern on bending deformation and the associated underlying mechanism. Herein, via designing lead-free piezoelectric ceramics with varying volatilization characteristics, it is uncovered that the ultrahigh electro-bending deformation is primarily attributed to a large strain gradient induced by unevenly distributed defect dipoles. In 0.5mm-thick Sr/Sn co-doped potassium sodium niobate ceramics featuring volatile K/Na elements, the inherent bipolar electro-strain value can reach 0.3% at 20 kV cm -1 due to the existence of defect dipoles, while the gradient distribution of defect dipole generates significant bending displacement, amplifying apparent electro-strain value to 1.1%. Notably, non-volatile Ba 0.99 TiO 2.99 ceramic with homogeneous defect dipole distribution does not present electro-bending. Of particular interest is that the electro-bending phenomenon can be observed through introducing a defect dipole gradient into barium titanate ceramic. A monolayer ceramic with defect dipole gradient can generate large tip displacement (±1.5 mm) in cantilever structure, demonstrating its promising potential in precise positioning. This study delves into the underlying mechanism driving electro-bending deformation and its impact on the apparent electro-strain measurement in defect-engineered piezoelectric ceramics, providing fresh perspectives for the development of piezoelectric bending actuators. This article is protected by copyright. All rights reserved.