• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.9
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• pp.702-710
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• 2012

Eco-friendly $(Na,K)NbO_3$ (NKN)-based piezoelectric ceramic materials were fabricated by conventional ceramic method for shear mode piezoelectric energy harvesting application. $NKN-LiTaO_3$ (LT) based compositions were adopted for the high $d_{15}{\times}g_{15}$ which is proportional to harvested energy density. The composition $0.935(Na_{0.535}K_{0.485})NbO_3-0.065LiTaO_3$ was found to be lie on the boundary of tetragonal and orthorhombic phases. With reducing Ta content, the dielectric constant decreased gradually while maintaining high $d_{15}$, which resulted in increased $d_{15}{\times}g_{15}$. The composition $0.935(Na_{0.535}K_{0.485})NbO_3-0.065Li(Nb_{0.990}Ta_{0.010})O_3$ was found to possess excellent piezoelectric and electromechanical properties ($d_{15}{\times}g_{15}=29\;pm^2/N$, $d_{15}$ = 417 pC/N, $k_{15}$ = 0.55), and high curie temperature ($T_c=455^{\circ}C$).

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2005.05a
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• pp.35-39
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• 2005

This paper presents a method to reduce hysteresis in multilayer ceramic actuator by connecting the actuator with a capacitor in a series circuit. The change in hysteresis with respect to the capacitor was examined. $0.2Pb(Mg_{1/3}Nb_{2/3})O_3-0.8Pb(Zr_{0.475}Ti_{0.525})O_3$ ceramic material was used as a piezoelectric material for the actuator. Displacement of the actuator was measured in a capacitive gap sensor measuring system. In case of inserting a capacitor in a total circuit, hysteresis became dramatically decreased, and then finally the hysteresis value can be reduced below $0.2\%$. It was found in this present study that reducing the hysteresis in the actuator is dependent upon the characteristics of the capacitor in total circuit and also operating frequency.

• 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.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.156-156
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• 2009

우리 주변에서 쉽게 얻을 수 있는 에너지를 수확하여 전기에너지로 변환해서 전자기기의 전원으로 사용하고자 하는 에너지 하비스팅의 연구가 활발히 진행중이다. 본 연구에서는 일정장소에 설치된 압전발판을 사람이 보행시 밟았을 때 압전체가 변형되어 전기에너지를 발생시키는 자가발전 압전발판을 제작하였다. 발생된 전기에너지를 육안으로 확인하기 위해 발판 주변에 LED를 설치하여 점등되도록 하였다. 최대의 전기에너지가 발생되도록 압전발판을 제작하고자 디스크형태의 압전체를 아크릴판에 휨이 발하는 지점에서 일정거리를 두어 부착하고 인위적으로 일정 변위가 발생하도록 가진을 하였을 때 발생하는 전압을 비교하였다. 또한 압전체에 동판이 부착된 형태로 동판 두께에 따른 발전특성도 비교하였다. 이를 바탕으로 최대의 발전특성을 나타내는 형태로 제작하여 다수의 압전소자를 밀집시키고 그 위에 판을 대어서 보행시 밟은 부분 외의 압전체에도 하중이 인가되도록 제작하였다. 인도, 도로, 교량 등에 압전발판을 다수 설치하여 전기에너지를 축적하여 센서등의 전원으로 응용성을 검증하였다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.3
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• pp.188-193
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• 2011

The osseointegration of dental implant is influenced by many factors such as surface geometry, loading and the amount of bone. Thus, stability of the dental implant should be checked periodically. In order to test the stability of dental implant by using resonance frequency analysis, we designed a structure of transducers and fabricated a piezoelectric devices. Using finite element analysis, the thickness and length of piezoelectric device and transducers were tailorized and the optimized frequency of 10 kHz was obtained. The resonance frequency from simulation analysis and evaluation was estimated to be similar as 10 kHz. The osseointegration was further enhanced with increasing frequency from the evaluation result of the finite element analysis.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.7
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• pp.517-520
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• 2010

Lead-free $0.9(Na_{0.52}K_{0.48})NbO_3$ - $0.1LiTaO_3$ piezoelectric ceramics doped with $Ag_2O$ (0-4 mol%) have been prepared by the conventional mixed oxide method. The structural and electrical properties were analyzed in order to find its potential applications. The crystal structure of 1-4 mol% Ag doped $0.9(Na_{0.52}K_{0.48})NbO_3$-$0.1LiTaO_3$ lead free piezoelectric ceramics were investigated for several sintering temperatures ($1100^{\circ}C$) by the use of X-ray diffraction analysis. In order to analyze the effect of Ag dopants on the $0.9(Na_{0.52}K_{0.48})NbO_3$-$0.1LiTaO_3$ ceramic, the diffraction intensity ratio of the (002) to (200) planes were calculated from the X-ray diffraction patterns of the ceramic samples.

• Electrical & Electronic Materials
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• v.10 no.7
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• pp.727-731
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• 1997

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.418-421
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• 2001

The ceramic filters were developed using technology similar to that of quartz crystal and electro- mechanical filter. However, the key to this development involved the theoretical analysis of vibration modes and material improvements of piezoelectric ceramics. The primary application of ceramic filters has been for consumer-market use. Accordingly, a major emphasis has involved mass production technology, leading to low-priced devices. A typical ceramic filter includes monolithic resonators and capacitors packaged in unique configurations. Nakazawa developed a double-mode resonator as two acoustically coupled single resonators. And he developed 10.7MHz crystal filters using multi-energy trapping mode of thickness shear vibration. He succeeded in realizing a two-pole band pass filter response without external inductance by splitting a dot electrode to creak coupled symmetric and anti- symmetric vibration modes. Accordingly, the simulation for ceramic (inter were important. So that, this paper were investigated the pass frequency of filter on the electrode length and thickness of ceramic.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.578-580
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• 2002

In this thesis, specimens was manufactured in general method annexing PMB-PZT system ceramic, and the following conclusion has been deduced. In XRD, the crystal structure of ceramic has the tetragonal structure which is close to rombohedral structure, and consequently the specimen characterized by MPB was manufactured. According to dopping with xPMB, electromechanical factor(kp) little is changed. kp was maximum value 23.37[%] at xPMB 0.03[mol%]. mechanical quality factor(Qm) was maximum value 237,04 at xPMB 0.03[mol%].

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.223-224
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• 2006

This paper present a new disk-type piezoelectric transformer. The input side of the transformer has a crescent-shaped electrode and the output side has a focused poling direction. This transformer has multi-layered structure. The piezoelectric transformers operated m each transformer's resonance vibration mode. The electrodes and poling directions on commercialy available piezoelectric ceramic disks were designed so that the planar or shear mode coupling factor ($k_p,\;k_{15}$) becomes effective rather than the transverse mode coupling factor ($k_{31}$). The Resonance frequency is 65.22[kHz] and maximum voltage step-up ratio is 149. Multi-layered transformer has better efficiency and step-up ratio than the single-layered transformer.