Synthesis of DL-alanine-based piezoelectric materials and characterization of their piezoelectric characteristics

Abstract

Due to the recent serious environmental problems, piezoelectric materials with biodegradability and biocompatibility are in the spotlight in the field of piezoelectric energy harvesting. Therefore, in this dissertation, we propose PVA/DL-alanine polycrystals in which DL-alanine amino acids are mixed with poly(vinyl alcohol) (PVA), a water-soluble polymer, as such piezoelectric materials. The piezoelectric characteristics of the PVA/DL-alanine polycrystals were investigated by measuring the piezoelectric strain coefficient $\mathit{d}_{33}$, and the development mechanism of the piezoelectricity was studied in terms of the crystal structure and surface. In addition, we discuss the correlation between the bonds within in the DL-alanine-based materials and their resultant piezoelectric properties by measuring and analyzing the piezoelectric characteristics and the crystal structures of the DL-alanine-based materials combined with several materials. As ways to improve the piezoelectric performance of the PVA/DL-alanine polycrystals, we have suggested the deposition of a zinc oxide (ZnO) thin film and the formation of a thin-film p-n junction using RF and DC magnetron sputtering and have confirmed these methods experimentally. This dissertation proposes the PVA/DL-alanine polycrystals as piezoelectric materials and discusses their piezoelectric characteristics and the piezoelectricity development mechanism together with the methods for improving the piezoelectric performance of the PVA/DL-alanine polycrystals employing conventional piezoelectric thin film deposition techniques.