IEEE Standard on Piezoelectricity has been utilized for decades though it has shown significant issues that prevent researchers from obtaining accurate materials coefficients. To resolve these issues, our research group recently proposed partial electrode (PE) method. PE method utilizes samples that consist of the center part covered with electrode, and the side part either covered or not covered with electrode for obtaining both intensive and extensive elastic parameters. In this review, we introduce our PE method, along with physical phenomenology and background, such as issues of IEEE standard, to bolster readers understanding of needs for developing new measurement method that can compensate the standard method. It is shown that development of the PE method not only provides technological benefits, but also gives scientific importance for the piezoelectric research community from its extremely high data accuracy.

Lead zirconate titanate/poly-vinylidene fluoride (PZT/PVDF) piezoelectric devices were fabricated by incorporating carbon nanotubes (CNTs), for use as flexible energy harvesting devices. CNTs were added to maximize the formation of the β phase of PVDF to enhance the piezoelectricity of the devices. The phase transition of PVDF induced by the addition of CNTs was confirmed by analyzing the X-ray diffraction patterns, scanning electron microscopy images, and atomic force microscopy images. The enhanced output efficiency of the PZT/PVDF piezoelectric devices was confirmed by measuring the output current and voltage of the fabricated devices. The maximum output current and voltage of the PZT/PVDF piezoelectric devices was 200 nA and 350 mV, respectively, upon incorporation of 0.06 wt% CNTs.

In this study, in order to develop coupled vibration mode piezoelectric devices for Acoustic Emission(abbreviated as AE) sensor application with outstanding displacement and piezoelectric properties have been simulatedby ATILA FEM program. And, From the results of ATILA simulation, the AE sensor specimen, obtained superiorelectromechanical coupling factor and displacement, when the size of specimen is 3.45 mmΦ×3.45 mm with ratio ofdiameter/thickness(Φ/T)= 1.0. Therefore, AE sensor was fabricated by (Na,K,Li)(Nb,Ta) O3(abbreviated as NKL-NT)system piezoelectric ceramics using coupled vibration mode. The piezoelectric properties of NKL-NT ceramics wasexhibited that piezoelectric constant(d33), piezoelectric voltage constant(g33) and electro mechanical coupling factor(kp)have the excellent values of 261[pC/N], 40.10[10-3Vm/N], and 0.44, respectively. The manufactured piezoelectric devicewith ratio of Φ/T= 1.0 indicated the optimum values of resonant frequency(fr)= 556.5[kHz], antiresonant frequency(fa)=631.1[kHz], and effective electromechanical coupling factor(keff)= 0.473. The maximum sensitivity of the coupledvibration mode AE sensor was 55[dB] at the resonant frequency of 75[kHz]. The results show that the coupledvibration mode piezoelectric device is a promising candidate for the application AE sensor piezoelectric device.

In this study, coupled mode piezoelectric devices for AE sensor application with excellent displacement and piezoelectric characteristics were simulated using ATILA FEM program, and then fabricated. Displacements and electromechanical coupling factors of the piezoelectric devices were investigated. The simulation results showed that excellent displacement and electromechanical coupling factor were obtained when the ratio of diameter/thickness was 1.0. The piezoelectric device of ф/T= 1.0 exhibited the optimum values of fr= 406 kHz, displacement= 6.11 × 10^-8[m], k_eff= 0.648. The results show that the coupled vibration mode piezoelectric device is a promising candidate for the application of AE sensor piezoelectric device.

In this study, thickness vibration mode piezoelectric devices for AE sensor application were simulated using ATILA FEM program, and then fabricated. Trajectory resonant displacement and electro mechanical coupling factors of the piezoelectric devices were investigated. The simulation results showed that excellent displacement and electro mechanical coupling factor was obtained when the ratio of diameter/thickness(Ф/T) was 0.75. The piezoelectric device of Ф/T=0.75 exhibited the optimum values of fr=183 kHz, displacement=4.44×10(-7)[m], k33=0.69, which were suitable for the application of AE sensor piezoelectric device.