Abstract
Bio-compatible piezoelectric materials are becoming increasingly important for actuators and sensors in medical devices, that is Bio-MEMS such as health monitoring systems and drag delivery systems. In this study, we challenged to derive new piezoelectric materials with bio-compatibility by first principles calculation. Firstly, constituent elements of bio-compatible piezoelectric materials have been specified by HSAB method from the viewpoint of interaction energy with in-vivo molecules. Secondly, in order to create a perovskite-type crystal structure with good piezoelectric response, the combination of bio-compatible elements was selected to satisfy geometric stable condition defined by tolerance factor. As a result, we discovered 7 kinds of new piezoelectric materials. We focused on one of them, MgSiO3 that is known to be a mineral with perovskite-type crystal structure, and analyzed the stable cubic structure at paraelectric non-polar phase and the stable tetragonal structure at ferroelectric phase by first principles DFT. Additionally, structural phase transition of MgSiO3 has been investigated on the assumption of linear structural change from cubic structure to tetragonal one. DFT calculation indicated that MgSiO3 can change spontaneously to tetragonal structure with high tetragonality and polarization, and that MgSiO3 can present a good piezoelectricity.
