Giant electromechanical response in layered ferroelectrics enabled by asymmetric ferroelastic switching

Bismuth layer-structured ferroelectrics (BLSFs) are highly desired for high-temperature piezoelectric systems owing to their high Curie temperature and large spontaneous polarization. However, the inferior electromechanical response, which results from their unique layered crystal structure and inherently low piezoelectric activities, has restricted the practical application. Here, we report discovery of a large electric-field-induced strain in a simplest BLSF Bi2WO6, which is comparable to perovskite ferroelectrics and exhibits an intriguing asymmetric loop-like feature. Through comprehensive analysis on the displacement test configuration and polarization switching process, it is demonstrated that the exotic loop-like strain curve originates from the reversible bending deformation induced by asymmetric 90° ferroelastic switching in the upper and lower surfaces. Specifically, the textured Bi2WO6 ceramic exhibits a giant nominal strain value of ∼0.75% with excellent cycling stability. This discovery raises the possibility of utilizing the bending effect and ferroelastic switching to design piezoelectric actuators and may accelerate the development of high-performance lead-free ceramics.