• Title/Summary/Keyword: Piezoelectric Method

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Microstructures and Electrical Properties of Thick PZT Films with Thickness Variation Fabricated by Multi-coating Method (Multi-coating법으로 제조된 두꺼운 PZT막의 두께 변화에 따른 미세구조 및 전기적 특성)

  • Park, Jun-Sik;Jang, Yeon-Tae;Park, Hyo-Deok;Choe, Seung-Cheol;Gang, Seong-Gun
    • Korean Journal of Materials Research
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    • v.12 no.3
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    • pp.211-214
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    • 2002
  • Properties of 52/48 PZT films with various thicknesses for piezoelectric micro-electro mechanical systems (MEMS) devices fabricated by multi-coating method on $Pt(3500{\AA})/Ti(400{\AA})/SiO_2(3000{\AA})/Si$(525$\mu\textrm{m}$) substrates were investigated. PZT films were deposited by spin-coating process at 3500 rpm for 30 sec, followed by pyrolysis at 45$0^{\circ}C$ for 10 min producing the thickness of about 120nm. These processes were repeated 4, 8, 12, 16 and 20 times in order to have various thicknesses, respectively. Finally, they were crystallized at $650^{\circ}C$ for 30 min. All thick PZT films showed dense and homogeneous surface microstructures. Thick PZT films showed crystalline structures of random orientations with increasing thickness. Dielectric constants of thick PZT films were increased with increasing film thickness and reached 800 at 100kHz for 2.3$\mu\textrm{m}$ thick PZT film. $P_r\; and\; E_c$ of 2.3$\mu\textrm{m}$ thick PZT films were about 20$\mu$C/$\textrm{cm}^2$ and 63kV/cm. Depth profile analysis by Auger Electron Spectroscopy (AES) of 4800 $\AA$ thick PZT film showed the formation of the perovskite phase on Pt layer by Pb diffusion behavior. It was considered that Pb-Pt intermediate layer promoted PZT (111) columnar structures.

Fabrication and Evaluation of Sensor for Measuring Pulse Wave Velocity using Piezo Film and Conductive Textile (압전 필름과 전도성 섬유를 이용한 맥파 전달 속도 측정을 위한 센서의 제작 및 성능평가)

  • Kim, Jung-Chae;Jee, Sun-Ha;Yoo, Sun-Kook
    • Journal of Sensor Science and Technology
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    • v.21 no.2
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    • pp.135-143
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    • 2012
  • Arterial stiffness is causing the serious problems for human who is suffered from hypertension and metabolic syndrome. So it is important that measure the arterial stiffness for early prevention. Many researches point out that pulse wave velocity(PWV) is the reliable and simple method to predict arterial stiffness. In this paper, we developed the sensing parts that detect the pulse wave and ECG by using piezoelectric film and conductive textile with elastic band. Our system could detect 3ch pulse wave and ECG. Simultaneously, our algorithm extracts the features for calculating the delays among pulse waves. The delays are the significant parameter to estimate PWV, thus we design the experiment for evaluating the performance of our sensing parts. The reference is PP-1000(HanByul Meditech, Korea) that is good for performance evaluation. As a result, the start point of the pulse wave was the most reliable feature for comparing with PP-1000(r=0.691, P=0.00). The results between two operators showed that there is only a slight difference in the reproducibility of the devices. In conclusion, we assume that the suggested sensor could be more comfortable and faithful method for arterial stiffness.

Spectral Element Formulation for Analysis of Lamb Wave Propagation on a Plate Induced by Surface Bonded PZT Transducers (표면 부착형 PZT소자에 의해 유발된 판 구조물의 램파 전달 해석을 위한 스펙트럼 요소 정식화)

  • Lim, Ki-Lyong;Kim, Eun-Jin;Kang, Joo-Sung;Park, Hyun-Woo
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.18 no.11
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    • pp.1157-1169
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    • 2008
  • This paper presents spectral element formulation which approximates Lamb wave propagation by PZT transducers bonded on a thin plate. A two layer beam model under 2-D plane strain condition is introduced to simulate high-frequency dynamic responses induced by a piezoelectric (PZT) layer rigidly bonded on a base plate. Mindlin-Herrmann and Timoshenko beam theories are employed to represent the first symmetric and anti-symmetric Lamb wave modes on a base plate, respectively. The Euler-Bernoulli beam theory and 1-D linear piezoelectricity are used to model the electro-mechanical behavior of a PZT layer. The equations of motions of a two layer beam model are derived through Hamilton's principle. The necessary boundary conditions associated with the electro-mechanical properties of a PZT layer are formulated in the context of dual functions of a PZT layer as an actuator and a sensor. General spectral shape functions of response field and the associated boundary conditions are obtained through equations of motions converted into frequency domain. Detailed spectrum element formulation for composing the dynamic stiffness matrix of a two layer beam model is presented as well. The validity of the proposed spectral element is demonstrated through numerical examples.

Sparse reconstruction of guided wavefield from limited measurements using compressed sensing

  • Qiao, Baijie;Mao, Zhu;Sun, Hao;Chen, Songmao;Chen, Xuefeng
    • Smart Structures and Systems
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    • v.25 no.3
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    • pp.369-384
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    • 2020
  • A wavefield sparse reconstruction technique based on compressed sensing is developed in this work to dramatically reduce the number of measurements. Firstly, a severely underdetermined representation of guided wavefield at a snapshot is established in the spatial domain. Secondly, an optimal compressed sensing model of guided wavefield sparse reconstruction is established based on l1-norm penalty, where a suite of discrete cosine functions is selected as the dictionary to promote the sparsity. The regular, random and jittered undersampling schemes are compared and selected as the undersampling matrix of compressed sensing. Thirdly, a gradient projection method is employed to solve the compressed sensing model of wavefield sparse reconstruction from highly incomplete measurements. Finally, experiments with different excitation frequencies are conducted on an aluminum plate to verify the effectiveness of the proposed sparse reconstruction method, where a scanning laser Doppler vibrometer as the true benchmark is used to measure the original wavefield in a given inspection region. Experiments demonstrate that the missing wavefield data can be accurately reconstructed from less than 12% of the original measurements; The reconstruction accuracy of the jittered undersampling scheme is slightly higher than that of the random undersampling scheme in high probability, but the regular undersampling scheme fails to reconstruct the wavefield image; A quantified mapping relationship between the sparsity ratio and the recovery error over a special interval is established with respect to statistical modeling and analysis.

Corrosion visualization under organic coating using laser ultrasonic propagation imaging

  • Shi, Anseob;Park, Jinhwan;Lee, Heesoo;Choi, Yunshil;Lee, Jung-Ryul
    • Smart Structures and Systems
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    • v.29 no.2
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    • pp.301-309
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    • 2022
  • Protective coatings are most widely used anticorrosive structures for steel structures. The corrosion under the coating damages the host material, but this damage is completely hidden. Therefore, a field-applicable under-coating-corrosion visualization method has been desired for a long time. Laser ultrasonic technology has been studied in various fields as an in situ nondestructive inspection method. In this study, a comparative analysis was carried out between a guided-wave ultrasonic propagation imager (UPI) and pulse-echo UPI, which have the potential to be used in the field of under-coating-corrosion management. Both guided-wave UPI and pulse-echo UPI were able to successfully visualize the corrosion. Regarding the field application, the guided-wave UPI performing Q-switch laser scanning and piezoelectric sensing by magnetic attachment exhibited advantages owing to the larger distance and incident angle in the laser measurement than those of the pulse-echo UPI. Regarding the corrosion visualization methods, the combination of adjacent wave subtraction and variable time window amplitude mapping (VTWAM) provided acceptable results for the guided-wave UPI, while VTWAM was sufficient for the pule-echo UPI. In addition, the capability of multiple sensing in a single channel of the guided-wave UPI could improve the field applicability as well as the relatively smaller size of the system. Thus, we propose a guided-wave UPI as a tool for under-coating-corrosion management.

A Study on the single crystal growth of the optic-grade $LiTaO_3$ as a electro-optic materials

  • Kim, B.k.;J.K. Yoon
    • Proceedings of the Korea Association of Crystal Growth Conference
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    • 1996.06a
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    • pp.526-526
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    • 1996
  • The single crystal of LiTaO3 is well known eletro-optic material as well as the piezoelectric one applied to SAW filter. LiTaO3 has large electro-optic effects, so applied to optical switch, acosto-optic deflector, and optical memory device using photorefractive effects. The crystal growth of SAW-grade LiTaO3 has been studied many aspects, but there is no detail research about optic-grade crystal growth. The conditions of optic-grade LiTaO3 single crystal are as below. The optical transmittance must be over 75%, and axial and radial concentratiom uniformity below 1%. The variation of Curie temperature depending on Li/Ta ratio must be also below 2$^{\circ}C$ and no internal no internal cracks and defects. Because of the limitation of crystal quality, the growing of optic-grade LiTaO3 single crystal is very difficult compared with the growing of SAW-grade. In this research, upper conditions of optic-grade single crystal was investigated after growing of 1 inch diameter and 1.5 inch length LiTaO3 single crystal having no internal cracks and defects using Czochralski method. Curie temperature was determined with DSC and measuring capacitance and lattice parameter was calculated about the grown crystal and ceramic powder samples of various Li/Ta ratio. The result of Tc variation was below 1.2$^{\circ}C$ all over the grown crystal, so it is confirmed that LiTaO3 was grown under congruent melting composition having optical homogeniety. Also, the optical transmittance was about 78%, which was sufficient for optical device.

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Feasibility Study on Detection of Defective Elements in a Linear Phased Array Transducer through Ultrasonic Field Analysis and Visualization (초음파 음장해석 및 가시화를 통한 선형 위상차배열 트랜스듀서의 결함요소 검출 가능성 연구)

  • Choi, Kwang-Yoon;Yang, Jeong-Won;Ha, Kang-Lyeol;Kim, Moo-Joon;Kim, Jung-Soon;Lee, Chae-Bong
    • The Journal of the Acoustical Society of Korea
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    • v.28 no.5
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    • pp.416-423
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    • 2009
  • The ultrasonic pressure fields for the 3 MHz linear phased array transducer with sixteen piezoelectric elements of which one may not be operated by defect were simulated theoretically and measured experimentally using a visualization system of the Schlieren method. The simulation results for steering angles of $0^{\circ}$ and $30^{\circ}$ show that the side-lobe patterns of the transducer including a defective element is quite different from the transducer with all normal elements, and those patterns are in good agreement with the results of visualization. It is shown that the defective elements in a linear array transducer can be detected by comparison of the simulated and the visualized side-lobe patterns in two dimensional acoustic fields.

A Study on Property Distribution of [011] Poled Mn:PIN-PMN-PT Single Crystals Grown by Bridgeman Method (Bridgeman 성장 [011] 분극 Mn:PIN-PMN-PT 압전단결정의 물성 분포 연구)

  • Soohyun Lim;Yub Je;Yohan Cho;Sang-Goo Lee;Hee-Seon Seo
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.37 no.4
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    • pp.412-419
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    • 2024
  • Mn-doped Pb(In1/2Nb1/2)O3-Pb(Mg2/3Nb1/3)O3-PbTiO3 (Mn:PIN-PMN-PT) single crystals, which exhibit improved phase transition temperatures and coercive field properties compared to Pb(In1/2Nb1/2)O3-Pb(Mg2/3Nb1/3)O3-PbTiO3 (PIN-PMN-PT) single crystals, are expected to be utilized in high-power acoustic transducers. Bridgeman method, growing single crystals along the axial direction from melt, is most widely used method for single crystal growth with large size and high quality. However, single crystal boules grown by the Bridgeman method demonstrate a PT compositional variation, giving rise a distribution of crystal structure and material properties along the growing axis. To employ piezoelectric single crystals grown by the Bridgeman method for acoustic transducers, it is essential to investigate their overall property distribution. In this study, the compositional distribution and property variation of Mn:PIN-PMN-PT single crystals grown by the Bridgeman method was investigated. Measured compositional distribution of PT was from 29% to 32.5% in the Rhombohedral crystal region of the boule. Two types of specimen, [011]-poled Mn:PIN-PMN-29PT and Mn:PIN-PMN-32PT single crystals, were fabricated and tested to obtain full property variation at both ends of the Rhombohedral crystal region. The properties related to the 32 directional vibration mode and the properties related to high-power driving were measured to confirm the overall distribution of properties by composition.

Fabrication and Electrical Properties of High Tc $A_{2}B_{2}O_{7}$ Piezoelectric Ceramics Using the Powders Prepared by the Chemical Coprecipitation Method (화학적공침법에 의한 $A_{2}B_{2}O_{7}$ 고온압전세라믹스의 제작과 전기적 특성)

  • Son, Chang-Heon;Jeon, Sang-Jae;Nam, Hyo-Duk
    • Journal of Sensor Science and Technology
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    • v.6 no.4
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    • pp.316-327
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    • 1997
  • Polycrystalline $Sr_{2}Nb_{2}O_{7}$ and $La_{2}Ti_{2}O_{7}$ ceramics with very high Curie temperatures were synthesized by the chemical coprecipitation method (CCP). The powders synthesized were identified by XRD and their sintering behavior and physical properties were studied. The grain-orientation and electrical properties of sintered ceramics were investigated as a function of firing temperature. Single phase could be obtained by CCP method at temperature lower than that of the conventional method by 100 - $150^{\circ}C$. Strontium niobate, $Sr_{2}Nb_{2}O_{7}$, powder was Prepared by CCP method at temperatures as low as $800^{\circ}C$ via intermediate phase of $Sr_{5}Nb_{4}O_{15}$ formed at $700^{\circ}C$. The resulting CCP-derived powder was observed to have finer and more uniform particle size distribution than those obtained through the conventional or the molten salt synthesis method. Sintering of CCP-derived $Sr_{2}Nb_{2}O_{7}$ powder at $1500^{\circ}C$ yielded a highly dense ceramics with 97% theoretical density. Very high grain-orientation developed along the (0k0) direction was observed by SEM, which resulted in anisotropic dielectric properties of the sintered samples, with the dielectric constant values approaching those for single crystal.

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PIEZOELECTRIC VERTICAL BONE AUGMENTATION USING SANDWICH TECHNIQUE IN ATROPHIC MANDIBLE: TWO CASES REPORT (Sandwich technique을 이용한 하악골 증대술의 치험 보고)

  • Lee, Ji-Soo;Lee, Jung-Kwang;Lee, Hyun-Jin;Ahn, Mi-Ra;Sohn, Dong-Seok
    • Maxillofacial Plastic and Reconstructive Surgery
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    • v.30 no.3
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    • pp.276-282
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    • 2008
  • Objective: This is to report the efficacy of the sandwich technique for bone augmentation in a moderate atrophic posterior mandible through clinical and histological results in two cases. Subjects and Method: Two patients selected had moderate bone resorption in left lower edentulous area. Sandwich osteotomy using the piezosurgery was performed and the osteomized alveolar segments were elevated by 6mm in each two patients. The interpositional mineral allograft materials were inserted in the atrophic posterior mandibles. After four months healing period, bone biopsies in the grafted areas and placement of dental implants were performed. In both cases, panoramic views were taken preoperatively to measure the alveolar bone height for diagnosis, to monitor patient healing, and to evaluate bone healing and bone gain. Results: Sufficient vertical bone height was gained by using the sandwich technique and implants were placed successfully. In radiological evaluation, there was minimal resorption of bone height after the second operation and in histomorphometric evaluation, they showed favorable new bone formation without inflammation in the grafted areas. Conclusion: The sandwich technique can be an effective choice for augmenting vertical bone height in the atrophic mandible. More of cases and long term follow-up are needed to evaluate bone resorption and implant prognosis.