Micromechanical modeling of PMN-32PT ceramic based on single crystal properties

摘要

The behavior of ferroelectric ceramic materials is governed by complex multiscale phenomena. At the macroscale, the constitutive behavior displays time dependent coupling between stress, electric field and temperature. This behavior is dependent on composition, microstructure and dopants. Plasticity based macroscale phenomenological models utilize the concept of internal state variables and their evolution to represent the volume average behavior. These models include many variables that must be determined through a combination of experiment and micromechanical modeling. At the mesoscale, the microstructure plays an important role in the material behavior. Grains form during the sintering process and porosity can occur at grain boundaries. Upon cooling, the material undergoes a phase transformation to a ferroelectric state. Domains form within grains to minimize intergranular stress and electric fields. Within a single domain, the material behavior is governed by the crystal structure and the local fields. Micromechanics approaches connect the mesoscale with the macroscale. Micromechanical models utilize single crystal behavior and a self consistent approach to handling intergranular stress and electric fields to simulate the macroscopic behavior. This approach considers average local fields and utilizes volume fractions of domain types to characterize the state. This work implements measured single crystal behavior in a micromechanics code to predict the macroscopic material behavior. Specimens of the same composition are characterized under combined stress and electric field loading and the results are discussed.