Phase-field method explored ferroelectric vortex topologystructure and morphotropic phase boundaries br

The perovskite crystal structure determines the appearance of ferroelectricity and the polarization directionof ferroelectric ceramics. When the polarization direction has a certain order, different domain structures willcombine to form a multiparticle system with a specific morphology, i.e. the topological structure existing inferroelectrics. In this study, the domain structures of potassium sodium niobate () thin films underdifferent hysteresis electric fields and thickness are simulated and observed by the phase field method.According to the different switching paths of the domain structure under the electric field, the domain isdivided into fast and slow switching process. Based on this, a method is proposed to first determine the domainswitching state of the desired experiment and then conduct directional observation. Through the analysis of thedomain structures combined with the polarization vector, a clear multi-domain combined with vortex-antivortexpair topological structure is observed for the first time in film. The vortex structure is furtheranalyzed for its switching process, and it is observed that this vortex topological microstructure can make thedomain more likely to switch, so that more small-scale polarization vectors can be ordered, forming the desiredmultiparticle system topology. The mechanism of improving the dielectric properties of ferroelectric material bythis polarization vector ordering is similar to that of the microscopic phase boundary formed by the specificpolarization directions on both sides of the quasi morphotropic phase boundary