Basic Study of Elasticity Control of Soft and Hard Piezoelectric Materials Using Different Types of Negative-Capacitance Circuits

We studied a method of controlling the elastic modulus of lead zirconate titanate (PZT) using the negative-capacitance circuit (NCC). NCCs are of two types: soft NCC that softens the piezoelectric material and hard NCC that hardens the piezoelectric material. In this study, the piezoelectric materials PZT ceramics and poly(L-lactic acid) (PLLA) were prepared. The elastic moduli of these materials markedly differ. By connecting the materials to soft and hard NCCs, the control of the vibrations of PZT ceramics and PLLA was studied. It was found that only the vibration amplitude of PZT ceramics markedly changes with the connection to soft and hard NCCs. In other words, no complex vibration mode of the PZT ceramics, such as torsion, chattering and segmental vibrations, is induced. It was also shown that only the vibration amplitude of PLLA, which is a softer material than PZT ceramics, could be similarly controlled by connection to soft and hard NCCs.