• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.224-225
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• 2009

Aluminium nitride thin film was deposited on Au electrode and Si substrate by radio frequency sputtering system. X-ray diffraction (XRD) was utilized to identify the AlN phase, and Atomic Force Microscope (AFM) was used to obtain the images of surface morphology and roughness value of AlN thin film. The result of XRD and AFM measurement showed that the AlN thin film has strong c-axs orientation and smooth surface. In order to investigate piezoelectric response and polarization properties along to the direction of electric field, PFM (Piezoresponse Force Microscope) system was used, and the images of piezoelectric response due to switching of polarization was observed by PFM.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.776-778
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• 2003

In the paper, the novel linear ultrasonic motor for precision position control was designed and fabricated. It was composed of two piezoelectric actuators with longitudinal ultrasonic fluctuations and shaking beam. When two AC electric fields ($Usin{\omega}t$, $Ucos{\omega}t$) were applied in two piezoelectric actuators respectively, the middle part of shaking beam had an elliptical trajectory. According to experimental results, good symmetrical characteristic of two piezoelectric actuators were obtained.

• International Journal of Internet, Broadcasting and Communication
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• v.4 no.1
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• pp.1-2
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• 2012

A speaker is a system which produces sound through electromechanical operations. It transforms electronic signals into audible sound signals. Almost all speakers are three dimensional. These days, many mobile electronic devices such as mobile electronic devices have become smaller and thinner. A problem with this miniaturization, however, is that the volume of speakers has also decreased. In contrast to conventional three dimensional speakers, we have invented a new type of two dimensional flexible speaker by utilizing the reverse piezoelectric effect.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.62-63
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• 2005

Recently, a tiny piezoelectric linear motor using a vibration made of the transducer has been invented. The motor consists of a shaft, mobile element, and piezoelectric transducer using a piezoelectric radial mode bimorph disk. The fringe of the bimorph disk is fixed firmly which means this area has no degree of freedom. Therefore, the radial mode of the tranducer transfers to the flexurd mode. The mobile elements move along the shaft by the impact force generated by the flexurd mode of the piezoelectric transducer. The piezoelectric ceramic disks have thickness of 0.1 mm and diameter of 3.5 mm. The elastic disk is introduced between two disks of the ceramic, which has thickness of 0.1 mm and diameter of 3.8 mm. The fringe of the elastic disk is fixed by a brass cylinder which height is 1.2 mm. The Pyrex shaft is used which has diameter of 1 mm and height of 10 mm. The motors are operated at their resonant frequencies. The dynamic properties of the motor have been intensively measured and analyzed according to the applied voltage wave forms at the resonant frequencies. As the sawtooth and rectangular voltage waves are applied, the velocity, the thrust force, and the velocity dependence of the mobile position are measured. The dynamic characteristics are also analyzed within a period of each wave using laser vibrometer. The velocity of the mobile is moderately constant along the shaft. The better dynamic characteristics are obtained in the case of applying the rectangular wave.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.10a
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• pp.174-178
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• 2001

The piezoelectric thin film sensor can be used to interpret variations in structural and material properties, e.g. for structural integrity monitoring and assessment. To illustrate one of this potential benefit, PVDF film sensors are used for monitoring impact damage initiation in Gr/Ep composite panel. Both PVDF film sensors and strain gages are surface mounted to the Gr/Ep specimens. A series of impact test at various impact energy by changing impact mass and height is performed on the instrumented drop weight impact tester. The sensor responses are carefully examined to predict the onset of impact damage such as matrix cracking, delamination, and fiber breakage, etc. Test results show that the particular waveforms of sensor signals implying the damage initiation and development are detected above the damage initiation impact energy. As expected, the PVDF film sensor is found to be more sensitive to impact damage initiation event than the strain gage.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1240_1241
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• 2009

In this paper, sol-gel-spin coated $Pb(ZrTi)O_3$ thin film with $ZrO_2$ buffer-layer and $PbTiO_3$ seed-layer was investigated for vibration MEMS energy harvester to scavenge power from ambient vibration via d33 piezoelectric mode. Piezoelectric thin film deposition techniques on insulating layer is the important key for $d_{33}$ mode of piezoelectric vibration energy harvester. $ZrO_2$ buff-layer was utilized as an insulating layer. $PbTIO_3$ seed-layer was applied as an inter-layer between PZT and $ZrO_2$ layer to improve the crystalline of PZT thin film. The fabricated PZT thin film had a remanent polarization of 5.3uC/$cm^2$ and the coercive field of 60kV/cm. The fabricated energy harvester using PZT thin film with PTO seed-layer generated 1.1uW of electrical power to $2.2M{\Omega}$ of load with $4.4V_{pvp}$ from vibration of 0.39g at 528Hz.

• Journal of Sensor Science and Technology
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• v.17 no.4
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• pp.267-272
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• 2008

Energy harvesting from the vibration through the piezoelectric effect has been studied for powering the small wireless sensor nodes. As piezoelectric uni-morph cantilever structure can transfer low vibration to large displacement, this structure was commonly deployed to harvest electric energy from vibrations. Through our previous results, when stress was applied on the cantilever, stress was concentrated on the certain point of the ceramic of the cantilever. In this study, for miniaturing the energy harvester, we investigated how the size of ceramics and the stress distribution in ceramic affects energy harvester characteristics. Even though the area of ceramic was 28.6 % decreased from $10{\times}35{\times}0.5mm^3$ to $10{\times}25{\times}0.5mm^3$, both samples showed almost same maximum power of 0.45 mW and the electro-mechanical coupling factor ($K_{31}$) of 14 % as well. This result indicated that should be preferentially considered to generate high power with small size energy harvester.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.68-69
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• 2005

Low temperature ($\leq900^{\circ}C$) sintering piezoelectric ceramics $0.01Pb(Mg_{1/2}W_{1/2})O_3$-0.41Pb$(Ni_{1/3}Nb_{2/3})O_3-0.35PbTiO_3-0.23PbZrO_3+0.1wt%Y_2O_3+xwt%ZnO$ $(0{\leq}x{\leq}2.5)$ have been developed and investigated. The electromechanical coupling coefficient ($k_p$), piezoelectric constant ($d_{33}$), and mechanical quality factor ($Q_m$) have been measured to characterize the piezoelectric materials system. When 2.0 wt% ZnO is added, the properties of the system, $d_{33}$ = 559 pC/N, $k_p$ = 55.0 % and $Q_m$ = 73.4 are obtained which are very suitable for piezoelectric actuators. A bending mode multilayer actuator has been also developed using the materials which size is $27(L)\times9(W)\times1.07(t)mm^3$. The actuators are fabricated by multilayer ceramic (MLC) process and consist of24 layers and each layer thickness is $35{\mu}m$. At this time, the displacement of actuator was $100{\mu}m$ at 28V.

• 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 IEEK Conference
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• 2000.06b
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• pp.5-8
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• 2000

This paper proposes GaN film as a piezoelectric material for SAW(surface acoustic wave) filters. The fabricated GaN SAW filter exhibited a very high velocity of 5800 ㎧and relatively low insertion loss of -9.9 dB without matching circuit. From Smith's equivalent circuit model, the calculated electromechanical coupling factor (K$^2$) was about 4.$\pm$03％. which is larger than those obtained from other thin film piezoelectric materials and allows the realization of wider filter fractional bandwidths.