2.1. Materials

The positive piezoelectric effect is the basis of piezoelectric power generation or sensing. When the physical pressure is applied to the piezoelectric material, the electric dipole moment in the material will become shorter due to compression. At this time, in order to resist this change, the piezoelectric material will generate equal positive and negative charges on the opposite surface of the material to maintain its original state. The positive piezoelectric effect is essentially a process in which mechanical energy is converted into electrical energy. In this study, we selected cylindrical piezoelectric ceramics, which were polarized along the axial direction. The piezoelectric element has a large piezoelectric coefficient of d₃₃ and a high electromechanical coupling coefficient of k₃₃ under the action of axial force.

The material used in this study was lead zirconate titanate piezoelectric (PZT) ceramics. The type of piezoelectric ceramics was PZT-5H, which was fabricated by Baoding Hongsheng Acoustic Equipment Co., Ltd. in Baoding, China. The main parameters of the material are shown in Table 1.

Typical material properties of PZT-5H.