First-Principles Study on Crystal Structure Design and Fabrication of Implantable Lead-Free Piezoelectric Materials

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It is necessary for new medical electro-mechanical devices to develop implantable piezoelectric materials with biocompatibility. The purpose of this study is to improve material properties and to search the optimum fabrication condition of novel lead-free piezoelectric materials. Complex crystal structure of novel perovskite compounds, which can exhibit a giant piezoelectricity on morphotropic phase boundary, was designed through first-principles calculations. Substitution elements were specified with consideration of biocompatibility and structural phase transition process was predicted from phonon properties. Additionally a practical numerical simulation scheme based on Landau’s phenomenological theory was developed to support fabrication of piezoelectric materials. Formulation of energy and coefficient identification were carried out through first-principles calculations and phase diagram of novel materials was provided to find some optimum fabrication conditions of morphotropic phase boundary.