• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.302-302
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• 2010

The lead-free piezoelectric ceramics must have high piezoelectric properties and electrical properties for the applications of piezoelectric devices. Therefore, KNN ceramics were investigated as a function of the variation of Nb. The density was increased with the increase of Nb. The density was saturated above 0.8895 mol Nb. The maximum value of electromechanical coupling coefficient(kp) was obtained 0.428 at 0.8895mol Nb. This result can be attributed to the well sintered of specimens. Also, The maximum value of mechanical quality factor(Qm) showed 1554 at 0.8895mol Nb. Therefore, this composition can be used for application of piezoelectric device such as piezoelectric transformer and piezoelectric actuator.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.296-299
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• 2002

In this paper, a hexagon-type piezoelectric transformer was investigated to increase the output power. The length of its side was 14mm and 17.5mm, respectively. The piezoelectric ceramics was composed to PZT-PMN-PSN. This composition showed the characteristics which had an about 1500 of the mechanical Q-factor, 0.55 of the electromechanical coupling coefficient, $320{\times}10^{-12}C/N$ of the piezoelectric constant $d_{31}$, 0.3 % of the dissipation factor, etc. The voltage step-up ratio increased with increasing the load resistance, $R_{L}$, so it reached 80 with $R_{L}$ of $1M{\Omega}$ and was proportion to the length of side of the hexagon-type piezoelectric transformer. Also, the output power increased with increasing the size of the hexagon-type piezoelectric transformer.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.1
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• pp.105-111
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• 2009

Dielectric breakdown in piezoelectric ceramics is analyzed by using the three dimensional J integral. The J integral is shown to be a path-independent surface integral for a conductive tubular channel in a piezoelectric material. J integrals are also numerically calculated for conductive defects and tubular channels in piezoelectric ceramics through finite element analysis.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.331-331
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• 2010

본 연구에서는 차량 하중에 의해 압전체가 변형되어 전기에너지를 발생시키는 도로용 압전에너지 하베스터를 개발하기위한 설계 및 실험을 진행하였다. 최대의 전기에너지가 발생되도록 압전사각 시트를 닥터브레이드로 제작하여, 이를 강판에 부착하고 고유주파수를 낮추기 위해 끝단에 질량을 달아 캔틸레버형태의 구조로 제작하였으며 끝단 질량의 변화와 가진주파수에 따른 발전특성을 비교하였다. 이로써 도로용 센서 및 방향지시등의 전원으로 사용하기 위한 도로매설용 압전 에너지 하베스터의 타당성을 확인하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.697-700
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• 2003

This paper presents design and analysis of step-down piezoelectric transformer for application to AC-adapters. These transformers are consist of rectangular type and disk type multilayered piezoelectric ceramic plate. This piezoelectric transformer operated in third thickness resonance vibration mode. Finite element methode(FEM) was used for analysing transformer. Vibration mode and electric field of piezoelectric transformer were simulated at resonance frequency. As results, rectangular type transformer's output voltage was higher than the disk type. But disk type transformer's current was lagger than rectangular type. These results are assumed that disk type transformer's mixed vibration mode influence transformer's output characteristics. From these results, we expect that disk type piezoelectric transformer is more adoptable than rectangular plate type piezoelectric transformer for AC adapters.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.200-203
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• 2000

The application of the ultrasonic nozzle has been extended because it is possible atomization of liquid material. In this study, the characteristics of the ultrasonic nozzle and ceramic oscillator were investigated. The oscillator for the ultrasonic nozzle were made piezoelectric ceramic of Pb[($Sb_{1/2}$ $Nb_{1/2}$)$_{0.035}$-($Mn_{1/3}$$Nb_{2/3}$)$_{0.065}$-($Zr_{0.49}$$Ti_{0.51}$)$_{0.90}$]$O_3$. The electromechanical coupling factor($k_p$) and mechanical quality factor(Qm) showed the values of 0.555, 1, 214 respectively when the Zr/Ti ratio was 49/51. Moreover, this oscillator will have the temperature stability because it's curie temperature is 322[$^{\circ}C$]. The driving current of ultrasonic nozzle showed the value of 80[mA] when the driving time was lO[min.]. Also, The surface temperature of ceramic oscillator showed 80[$^{\circ}C$] at driving time lO[min.] We knew that the ultrasonic nozzle had stabile driving above 10[min.].

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.11
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• pp.963-968
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• 1998

The stress distribution in multilayer piezoelectric ceramic actuators was investigated by Finite element analysis. The y direction stress was concentrated at electrode tip. The y direction maximum stress was decreased to 4.9$\times10^ 7 N/m^2$ with internal electrode gap(a) until 0.4 mm and was not much difference with external electrode thickness(c). The stress distribution with internal layers was almost same and the stress distribution of load condition was higher than that of no load condition The y direction maximum stress increased with the number of layer and saturated at 260 layers. In the case of defective actuator, the stress distribution was disconnected around the defect and larger than that of normal actuator.

• Transactions on Electrical and Electronic Materials
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• v.14 no.5
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• pp.268-272
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• 2013

The aim of this study was to develop an ultrasonic tooth-whitening apparatus using piezoelectric transducers, which enhance bleaching efficiency by applying ultrasound, while performing a teeth whitening procedure. For this purpose, an ultrasonic transducer was designed and manufactured, and the effects of reduction in the whitening material's concentration and in the whitening treatment time through using the ultrasound cavitation phenomenon were confirmed. Also, the validity of this study was investigated by comparing the whitening performance with a commercialized optical whitener, through color comparison. The results revealed that the ultrasound whitener produced color values that were enhanced by as much as double that of the conventional LED light whitening method. Even when the operational time was reduced by half, the ultrasound method showed superior performance by over 54% compared to the conventional light whitener, revealing that the ultrasound method showed a remarkable treatment reduction effect.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.710-713
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• 2003

The PZT(KP12) powder was synthesized by sintering at $1250^{\circ}C$ for 2hrs and wet milling for 24 hrs. The PZT composite mixed with PVdF was fabricated into bulk, sheet, and plate type and the characteristics of three types were estimated. The bulk type which has PZT volume percent of 70 showed the best piezoelectric constant. Dielectric constant increased exponentially as an increase of PZT volume percent. The figure of merit of bulk and plate type was better than pure PZT over PZT volume percent of 50.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.12
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• pp.802-807
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• 2015

This paper describes the development of a piezoelectric level switch, which aims to effectively monitor the level status in high ambient temperatures. In order to adjust the impedance near the resonant frequency and temperature characteristics, the effect of the case and backing layer materials on its performance was analyzed using the finite element method (FEM). The suggested prototype new level switch has three heat-sink plates attached to SUS bar of 230 mm long, and case of PEEK which contains PZT sensing part. To illustrate the validity of this level switch, 10 samples are prepared and investigated the sensing performance through the high and low temperature ambient.