• Journal of the Korean Ceramic Society
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• v.53 no.2
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• pp.171-177
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• 2016

Rhombohedral $Ba(Ti_{0.92}Zr_{0.08})O_3$ single crystals are fabricated using the cost-effective solid-state single crystal growth (SSCG) method; their dielectric and piezoelectric properties are also characterized. Measurements show that (001) $Ba(Ti_{0.92}Zr_{0.08})O_3$ single crystals have an electromechanical coupling factor ($k_{33}$) higher than 0.85, piezoelectric charge constant ($d_{33}$) of about 950 [pC/N], and piezoelectric voltage constant ($g_{33}$) higher than 40 [${\times}10^{-3}Vm/N$]. Especially the $d_{33}$ of (001) $Ba(Ti_{0.92}Zr_{0.08})O_3$ single crystals was by about six times higher than that of their ceramics. Because their electromechanical coupling factor ($k_{33}$) and piezoelectric voltage constant ($d_{33}$, $g_{33}$) are higher than those of soft PZT ceramics, it is expected that rhombohedral (001) $Ba(Ti_{0.92}Zr_{0.08})O_3$ single crystals can be used as "lead-free" piezoelectric materials in many piezoelectric applications such as actuator, sensor, and transducer.

• Journal of the Korean Ceramic Society
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• v.50 no.6
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• pp.545-550
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• 2013

Piezoelectric PMN-29PT single crystal multilayer actuators [100 $mm^2$ in cross section and 22 mm in length] are designed and fabricated by stacking square plates [$10{\times}10{\times}0.5(t)\;mm^3$] of PMN-29PT single crystals having a $d_{33}$ of about 1,500 pC/N. The characteristics of PMN-29PT multilayer actuators are compared with those of P-025.40P multilayer PZT ceramic actuators [490 $mm^2$ in cross section and 60 mm in length] produced by PI in Germany. Even though the total volume of the PMN-29PT single crystal multilayer actuator is only about 7.5% of that of the P-025.40P ceramic multilayer actuator, PMN-29PT single crystal multilayer actuators are expected to show very similar properties to P-025.40P ceramic actuators in terms of static stroke and blocking force. Therefore, on the basis of their smaller mass and volume compared to the conventional PZT ceramic multilayer actuators, piezoelectric PMN-29PT single crystal multilayer actuators have significant potential regarding the development of various high performance actuators for aerospace subsystems.

• Journal of Sensor Science and Technology
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• v.22 no.6
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• pp.400-403
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• 2013

The piezoelectric composite film of ferroelectric PZT ceramic ($PbZr_xTi_{1-x}O_3$) and polymer (PDMS, Polydimethylsiloxane) was prepared to improve the flexibility of piezoelectric material. The bar coating method was applied to fabricate flexible nanocomposite film with large surface area by low cost process. In the case of using metal electrode on the composite film, although there is no problem by bending process, the electrode is usually broken away from the film by stretching process. However, the well-attached, flexible CNT electrode on PZT/PDMS film improved flexibility, especially stretchability. PZT particles was usually settled down into polymer matrix due to gravity of the weighty particle, so to improve the dispersion of PZT powder in polymer matrix, small amount of additives (CNT powder, Carbon nanotube powder) was physically mixed with the matrix. By stretching the film, an output voltage of PZT(70 wt%)/PDMS with CNT (0.5 wt%) was measured.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.10
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• pp.966-970
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• 2006

We reported on characteristics of the piezoelectric ceramic-polymer composite for the application of the thick-film speaker. The PVDF-PZT composites were fabricated to incorporate the advantages of both ceramic and polymer with various mixing ratios by 3-roll mill mixer. The composite solutions were coated by the conventional screen-printing method on ITO electrode coated PET (Polyethylene terephthalate) polymer film. After depositing the top-electrode of silver-paste, 4 kV/mm of DC field was applied at $120^{\circ}C$ for 30 min to poling the composite films. The value of $d_{33}$ (piezoelectric charge constant) was increased when the PZT weight percent was increased. The maximum value of the $d_{33}$ was 24 pC/N at 70 wt% PZT. But the $g{33}$ (piezoelectric voltage constant) showed the maximum value of $32mV{\cdot}m/N$ at 65 wt% of PZT powder. The SPL (sound pressure level) of the speaker fabricated with the 65:35 composite film was about 68 dB at 1 kHz.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.8
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• pp.870-879
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• 2007

In this study, various damage modes in bending unimorph piezoelectric composite actuators with a thin sandwiched PZT plate during bending fracture tests have been evaluated by monitoring acoustic emission (AE) signals in terms of waveform and peak frequency as well as AE parameters. Three kinds of actuator specimens consisting of woven fabric fiber skin layers and a PZT ceramic core layer are loaded with a roller and an AE activity from the specimen is monitored during the entire loading using an AE transducer mounted on the specimen. AE characteristics from a monolithic PZT ceramic with a thickness of $250{\mu}m$ are examined first in order to distinguish different AE signals from various possible damage modes in piezoelectric composite actuators. Post-failure observations and stress analyses in the respective layers of the specimens are conducted to identify particular features in the acoustic emission signal that correspond to specific types of damage modes. As a result, the signal classification based on waveform and peak frequency analyses successfully describes the failure process of the bending piezoelectric composite actuator exhibiting diverse failure mechanisms. Furthermore, it is elucidated that when the PZT ceramic embedded actuators are loaded mechanical bending loads, the failure process of actuator specimens with different lay-up configurations is almost same irrespective of their lay-up configurations.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.27-28
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• 2005

본 연구에서는$Cr_2O_3$ 와 $Nb_2O_5$ 를 첨가한 $Pb(Zr_{0.54}Ti_{0.48})O_3$ 세라믹스에서 $Nb_2O_5$ 첨가량에 따른 소결 및 압전, 유전특성을 조사하였다. $Pb(Zr_{0.54}Ti_{0.48})O_3$ + 0.2 wt% $Cr_2O_3$ + wt% $Nb_2O_5$ ($0.{\sim}2wt.%$)의 첨가량에 따른 압전, 유전특성 및 미세구조에 관해 연구하였다. 본조성에서 $Nb_2O_5$ 첨가량이 증가함에 따라 입경의 크기는 증가하였으며, 0.5 wt% $Nb_2O_5$ 첨가조성에서 $4\sim5\mu m$의 최대 평균입경을 보이다가 그 이상의 첨가 조성에서 급격히 감소하였다. 유전상수와 kp 는 $Nb_2O_5$ 첨가량이 1.0 wt% 조성까지 증가하였다가 그 이상 조성에서 감소하였다. $Nb_2O_5$ 첨가량이 증가함에 따라 삼방정(rhombohedral)구조에서 정방정(tetragonal)구조로 상전이 일어났으며, 본 조성의 상경계 영역인 0.5 wt% 조성에서 $\varepsilon_r$ = 730, $k_p$ = 0.72, $d_{33}$ = 450, $g_{33}$ = 70의 우수한 압전 특성을 나타내었다. 이러한 조성은 접촉센서용 복합압전소재의 실용가능성을 제시하였다.

• Journal of Powder Materials
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• v.26 no.5
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• pp.405-409
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• 2019

Piezoelectric ceramic specimens with the $Pb(Mg_{1/3}Nb_{2/3})_{0.65}Ti_{0.35}O_3$ (PMN-PT) composition are prepared by the solid state reaction method known as the "columbite precursor" method. Moreover, the effects of the $Li_2O-Bi_2O_3$ additive on the microstructure, crystal structure, and piezoelectric properties of sintered PMN-PT ceramic samples are investigated. The addition of $Li_2O-Bi_2O_3$ lowers the sintering temperature from $1,200^{\circ}C$ to $950^{\circ}C$. Moreover, with the addition of >5 wt.% additive, the crystal structure changes from tetragonal to rhombohedral. Notably, the sample with 3 wt.% additive exhibits excellent piezoelectric properties ($d_{33}=596pC/N$ and Kp = 57%) and a sintered density of $7.92g/cm^3$ after sintering at $950^{\circ}C$. In addition, the sample exhibits a curie temperature of $138.6^{\circ}C$ at 1 kHz. Finally, the compatibility of the sample with a Cu electrode is examined, because the energy-dispersive X-ray spectroscopy data indicate the absence of interdiffusion between Cu and the ceramic material.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.5
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• pp.274-278
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• 2016

A road energy harvester was designed and fabricated to convert mechanical energy from the vehicle load to electrical energy. The road energy harvester is composed of 20 piezoelectric materials. This study attempted to evaluate output depending on pavement materials when paving road piezoelectric energy harvester in the road. Harvester is the bender type and is the method of supporting the both ends of piezoelectric material and applying the load in the middle part. Harvester was paved in the type paved with asphalt, type paved with cement and in the exposed type not covering the top of harvester. The output characteristics were compared and evaluated depending on changes in vehicle load and vehicle speed changes. As vehicles, truck (11.9 ton), SUV(1.6 ton) and sedan (1.5 ton) were used and the output characteristics when driving at the interval of 10 km/h from 10 km/h to 100 km/h were evaluated.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.12
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• pp.769-775
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• 2016

Characteristics of a wireless sensor powered by the IDE (interdigitated electrode) embedded piezoelectric cantilever generator were analyzed in order to evaluate its potential for use in wireless sensor applications. The IDE embedded piezoelectric cantilever was designed and fabricated to have a self-resonance frequency of 126 Hz and acceleration of 1.57 G, respectively, for the mechanical resonance with a practical conveyor system in a thermal-power plant. It produced maximum output power of 2.81 mW under the resistive load of $160{\Omega}$ at 126 Hz. The wireless sensor module is electrically connected to a rectifier capacitor with capacity of 0.68 farad and 3.8 V for power supply by the piezoelectric cantilever generator. The unloaded capacitor could be charged as a rate of approximately $365{\mu}V/s$ while the capacitor exhibited that of 0.997 mV/min. during communication under low duty cycle of 0.2%. Therefore, it is considered that the fabricated IDE embedded piezoelectric cantilever generator can be used for wireless sensor applications.

• Journal of Sensor Science and Technology
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• v.28 no.5
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• pp.311-317
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• 2019

Rotating devices are commonly installed in power plants and factories. This study proposes a self-powered sensor node that is powered by converting the vibration energy of a rotating device into electrical energy. The self-powered sensor consists of a piezoelectric harvester for self-power generation, a rectifier circuit to rectify the AC signal, a sensor unit for measuring the vibration frequency, and a circuit to control the light emitting diode (LED) lighting. The frequency of the vibration source was measured using a piezoelectric-cantilever-type vibration frequency sensor. A green LED was illuminated when the measured frequency was within the normal range. The power generated by the piezoelectric harvester was determined, and the LED operation was assessed in terms of the vibration frequency. The piezoelectric harvester was found to generate a power of 3.061 mW or greater at a vibration acceleration of 1.2 g ($1g=9.8m/s^2$) and vibration frequencies between 117 and 123 Hz. Notably, the power generated was 4.099 mW at 122 Hz. As such, our self-powered sensor node can be used as a module for monitoring rotating devices, because it can convert vibration energy into electrical energy when installed on rotating devices such as air compressors.