Domain switching criteria for ferroelectrics

Domains, which exist in ferroelectric ceramics, on the application of external loads, such as electric fields and stress, undergo reorientation known as domain switching. This domain switching results in nonlinear behavior of ferroelectric ceramics. In this work, a domain switching criterion applicable to a generalized electromechanical loading is proposed based on an assessment of some of the existing microscopic energetically motivated domain switching criteria for ferroelectrics. The criterion is based on an instability condition of the current domain state determined by a critical value of the input energy calculated with respect to the state of switch-worthiness. The switch-worthiness is a state at which the Gibbs free energy of the current variant of the domain is no longer the lowest amongst that of all the variants. The criterion highlights the importance of the loading sequence in response evaluation, which has rarely been given any importance in literature so far. In obtaining the macroscopic response, it is assumed that the material is composed of several domains, each of which is defined by its local coordinate relative to a fixed global coordinate. For simplicity, Reuss average has been used to obtain macroscopic material response. The model is able to capture the essential features and trends of experimental results found in literature. The results obtained from the proposed model, other energetically motivated models and experiments have been compared, highlighting the important features of the proposed model.