Defect Mechanics of Flexoelectric Material

Flexoelectricity was theoretically proposed more than 50 years ago and was discovered experimentally four years later by Scott and Bursian. The flexoelectric effect was overlooked owing to its relatively weak effects. Recently, it has attracted increasing attention due to much higher flexoelectric response observed in bending measurements, which is three orders larger than previous theoretical estimations. The change coupling of polarization from strain to strain gradient causes huge difference between piezoelectricity and flexoelectricity: Flexoelectricity can exist in all insulators due to strain gradient breaking the inversion symmetry of the materials. This provides us much more candidate materials from simple silicon to complex perovskites for electromechanical applications. In addition, flexoelectric effect will be more pronounced with size reducing as the strain gradient can increase by 6-7 orders of magnitude at nanoscale compared with bulk materials.