| Summary: | 碩士 === 國立交通大學 === 材料科學與工程學系所 === 106 === A procedure is Ferroelectric materials have been widely used in many applications of sensors, actuators and memory devices in recent decades. These materials have strong electrical, thermal, or mechanical coupling, giving an opportunity for crystals to sense the change of external loading or boundary conditions. The microstructure is the most important factor to determining the crystal properties. However, there are some limitations of typical microstructural modeling. For example, certain patterns of microstructure are assumed for sharp interface models, and the small calculation regions for phase field methods. Thus, the aim of this study is to develop a multiscale analysis scheme combining the merits of sharp interface and phase field models.
Firstly, the microstructure pattern can be obtained by sharp interface model based on compatibility equations. Wherein the pattern is determined with the assumption of flat interfaces. Then, the pattern is set as the initial state of the phase field model, for further energy minimization to eliminate the flat interface assumption. The phase field algorithm is implemented by a commercial software COMSOL Multiphysics. Microstructures of the tetragonal and rhombohedral ferroelectrics crystal are both examined in order to demonstrate the validity of the current work. Interesting laminate structures, such as herringbone patterns and stripe patterns, are generated. Also the effect of depolarization energy, applied load and applied electric field will be examined. The current multiscale model eliminates the assumption of flat interfaces, and at the same time, has better efficiency for engineering purposes.
Keywords: phase-field method, ferroelectric, compatible pattern, interfacial energy
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