Simulation of the polarization currents of ferroelectric ceramics, arising from the simultaneous application of an electric field and mechanical stresses
Abstract
Simulation of the polarization currents of ferroelectric ceramics, arising from the simultaneous application of an electric field and mechanical stresses
Incoming article date: 16.02.2022The operating conditions of polycrystalline dielectrics in external mechanical and electric fields make it relevant to study the properties of such materials and their resistance to extreme loads, which depends on the processes of polarization reversal and the dynamics of the domain structure. Based on the model of motion of domain walls and the rheological model, equations are obtained for the dependence of polarization on the applied mechanical, electrical, or simultaneous electromechanical load. It is shown that the nonlinearity of the current in the ferroelectric ceramic is due to the dependence of the coefficients of the model on the through conduction current and the current associated with the emission of charges from traps. The physical meaning of the coefficients makes it possible to use their well-known dependences on the electric field and external mechanical stresses both in the range of the linear piezoelectric effect and in the region of external loads, when linearity ceases to exist. The obtained coefficients make it possible to pass from polarization (macroscopic parameter) to domain walls (mesoscopic scale). The parameters of the model depend on the change in the domain structure and its interaction with defects; therefore, the current relaxation time in the ferroceramic is described by changing the corresponding times for 180°-domains and non-180°-domains. The model considers two polarization components: elastic and irreversible. Changes in polarization after the external action of the electric field can be explained by the movement of domain and interphase boundaries. When a critical mechanical load is applied, the domain boundaries are detached from the defects and the crack grows abruptly, and as a result, destruction occurs. The relaxation motion of domain walls with constant friction leads to the growth of cracks due to the creation of mechanical stresses. The chosen rheological model and approach, taking into account the mechanisms of motion of domain walls, will make it possible to describe the rate of polarization change using the behavior of defects (dislocations, domain walls). The model will allow from a unified point of view to describe the experimental patterns of the behavior of currents under electromechanical action.
Keywords: ferroelectric ceramics, computer simulation, rheological model, polarization current, polarization current density, domain wall, 1800-domains, not 1800-domains, mechanical load, electrical load, relaxation time