Influence of dislocations on domain walls in perovskite ferroelectrics: Phase-field simulation and driving force calculation

Abstract

Dislocations in ferroelectrics cause domain wall pinning and nucleation of ferroelectric domains, which significantly influence the electromechanical properties of ferroelectrics. To have an in-depth understanding of the role of dislocations in ferroelectrics, this work presents a finite element analysis of the driving force on domain walls and their interaction with dislocations. The phase-field model coupled with the non-singular continuum dislocation theory and the generalized configurational force theory are derived for dislocated ferroelectrics. In particular, by making use of the driving force on domain walls and dislocations, we propose a new approach to evaluate the critical electric field for domain walls to break through dislocations. It is shown to be computationally much more efficient than the brute force approach of scanning all electric fields. The influences of dislocations on the 180° and 90° domain walls are analyzed numerically. The dislocation-induced stress field causes fluctuation of the polarization, which results in multiple equilibrium positions of the domain wall. Increased polarization was observed on the tensile side of the dislocation, which is responsible for the strong pinning strength of the dislocation. The needle domain nucleated from the dislocation core also causes the pinning of domain walls, and the interaction between the domain wall and the needle domain results in nonlinear dependency of the critical electric field on the Burgers vector.