PZT is widely used for actuators and sensors of electromechanical devices and it has multiple crystal systems. Although PZT outputs large piezoelectricity, it shows a complicated hysteresis behavior caused by domain switching and structural phase transition at morphotropic phase boundary (MPB). It is important for development and improvement of lead-free piezoelectric materials to understand the mechanism of huge piezoelectricity in PZT. In this study, a multiscale nonlinear finite element method was developed to estimate ferroelectric material properties. The homogenization theory was employed for scale-bridging between macrostructure and microstructure. We utilized an incremental form of fundamental constitutive law in consideration with physical property change caused by domain switching and structural phase transition. Crystal morphologies, which are characterized as an inhomogeneous structure composed of many grains and domains with individual orientations, are modeled at a micro scale. Then the homogenized physical properties of macrostructure can be estimated with perfect correlation to microstructural changes such as domain switching and structural phase transition. The proposed multiscale finite element method was applied to a polycrystalline PZT, and the relation between the macroscopic properties and microscopic domain switching and structural phase transition were investigated. Especially the difference among tetragonal single phase, rhombohedral single phase and their dual phases were discussed.
