Phase Field Simulation Of Microstructure Evolution Of Ferroelectric Materials Under Mechanical And Electric Fields

As is known to all, the electric domain structure of ferroelectric materials is vulnerable to be changed by external factors, such as the electric field, temperature, and mechanical constraints, which directly affect the macro ferroelectric device performance and working cycle. And at the same time, electromechanical coupling behaviors of ferroelectric materials are much more complex than other ordinary materials. Therefore, to carry out the research of ferroelectric materials’ performance under multi field coupled microstructure evolution as well as the macro mechanical and electrical properties is not only the indispensable way to improve the performance of macroscopic devices which are based of ferroelectric materials, but also the effective means to promote ferroelectric materials working in increasingly complex environment.Based on the basic principle of thermodynamics and kinetics, phase field method is established to predict the microstructure evolution during the process of phase transformation. In this paper, we select the time dependent Ginzburg Landau equation to establish a phase field model to describe the dynamic microstructure evolution characteristics of phase boundary, domain boundaries during the process of phase transition of ferroelectric materials under multi field coupling loading. We carry out the simulation of evolutionary process and transformation mechanism about ferroelectric materials under external electric field and mechanical stress field. The results showed that the formation of ferroelectric domains is a process of nucleation and growth with the energy reduction under the condition of no external electric field. The new domain grows through the expansion and devour circumjacent domain, after reaching the stable structure, domain structure is no longer changing with the time, domain wall regularization and domain structure satisfies certain regularity. However, when a constant electric field is applied to the system, equilibrium is broken, those ferroelectric domains who have the same direction with the electric field gradually grow up with 90 or 180 degrees of polarization reversal in different regions respectively. Domain structure is no longer changing with the time when the system energy reaches a minimum value. When a constant force field is applied to the system, after equilibrium is broken, we will find that only 90 degrees domain inversion occurred. This is because the forming process of 90 degrees along with the dropping of elastic energy, in turn, reduces the energy of the whole system; however 180 domain polarization reversals will not produce any strain changes. When the stable state is reached, the domain structure will not change with time.The established phase field model under electromechanical coupling reveals the meso and micro phase evolution mechanism of ferroelectric materials, providing the basic theory and analysis methods for the further study about the mechanical and physical behaviors of ferroelectric materials at the meso and micro scales. At the same time, it also provide some theoretical guidance for the prediction and evaluation of the electromechanical properties of those sensitive devices based on ferroelectric materials in practical engineering application.