• Title/Summary/Keyword: Piezoelectric Materials

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A study on temperature dependent acoustic receiving characteristics of underwater acoustic sensors (수중음향센서 수온 변화에 따른 음향 수신 특성 변화 연구)

  • Je, Yub;Cho, Yohan;Kim, Kyungseop;Kim, Yong-Woon;Park, Saeyong;Lee, Jeong-Min
    • The Journal of the Acoustical Society of Korea
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    • v.38 no.2
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    • pp.214-221
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    • 2019
  • In this paper, a temperature dependent acoustic receiving characteristics of underwater acoustic sensor is studied by theoretical and experimental investigations. Two different types (low mid frequency sensor and high frequency sensor) of underwater acoustic sensors are designed with different configuration of baffle and conditioning plate. The temperature dependent characteristics of the acoustic sensors are investigated within the temperature range from $-2^{\circ}C$ to $35^{\circ}C$. The material properties of the piezoelectric ceramics, molding and baffle, which are the primary materials of the acoustic sensors, are measured with temperature change. The temperature dependent RVS (Receiving Voltage Sensitivity) characteristics of the acoustic sensors are simulated by using the measured material properties. The RVS changes of the acoustic sensors are measured by changing temperature in the watertank where the acoustic sensors are installed. The measured and the simulated data show that the temperature dependent characteristics of the acoustic sensors are mainly dependent for the sound speed changes of the molding material.

Crystallization and Electrical Properties of SBM Thin Films by IBSD Process (IBSD법에 의한 SBN60 강유전체 박막의 배향 및 전기적 특성)

  • Jeong, Seong-Won;Jang, Jae-Hoon;Lee, Hee-Young
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2004.07b
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    • pp.869-873
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    • 2004
  • [ $Sr_xBa_{1-x}Nb_2O_6$ ] (SBN, $0.25{\leq}x{\leq}0.75$) ceramic is a ferroelectric material with tetragonal tungsten bronze (TTB) type structure, which has a high pyroelectric coefficient, piezoelectric, and a photo refractive properties. In this study, SBN60(x=0.6) thin film was manufactured by ion beam sputtering technique. Using the prepared SBN60 target in $Ar/O_2$ atmosphere as-deposited SBN60 thin film on Pt(100)/$TiO_2/SiO_2/Si$ substrate crystallization and orientation behavior as well as electric properties of SBN60 thin film were examined. SBN60 deposition up to $3000{\AA}$ in thickness, SBN60 thin film was heat-treated at $650^{\circ}C{\sim}800^{\circ}C$. The orientation was shown primarily along (001) plane from XRD pattern where working pressure was $4.3{\times}10^{-4}$ torr. The deposited layer was uniform, preferred orientatin and crystallization behavior resulted in the change of $O_2$ ratio was observed. In electric propertie of Pt/SBN60/Pt thin film capacitor remnant polarization (2Pr) value was $10{\mu}C/cm^2$, the coercive filed (Ec) 50 kV/cm, and the dielectric constant 615, respectively.

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Characterization of PMW-PZT Thick Films Prepared by Screen Printing Method (스크린 인쇄법에 의해 제조한 PMW-PZT 후막의 특성)

  • Son, Jin-Ho;Kim, Yong-Bum;Cheon, Chae-Il;Yoo, Kwang-Soo;Kim, Tae-Song
    • Journal of the Korean Ceramic Society
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    • v.41 no.1
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    • pp.30-35
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    • 2004
  • PMW-PZT thick films of about $30{\mu}m$ thickness were fabricated on Pt/$TiO_2$/$SiN_x$Si substrate by the hybrid method of screen printing and PZT sol application. With the increase of the number of the sol application times, the sintered density and electrical properties of PMW-PZT thick films were evidently increased. For the PMW-PZT thick film with PZT sol application of 10-times, the dielectric constant ($\varepsilon_r$) was 745 at the frequency of 100 KHz and thepiezoelectric coefficient ($d_33$) was 155 pC/N at the applied pressure of 1 atm.

A Pilot Study of Implementing Bender Element to In-situ Civil Engineering Measurement (현장 토목 계측을 위한 벤더 엘리멘트의 적용성 연구)

  • Jung Jae-Woo;Jang In-Sung;Mok Young-Jin
    • Journal of the Korean Geotechnical Society
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    • v.21 no.5
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    • pp.215-223
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    • 2005
  • Piezo-ceramics are special materials which transform energy from mechanical to electrical forms and vice versa. Bender elements are composite materials consisting of thin piezo-ceramics and elastic shims, and are widely used as actuators and transducers in the field of electronics, robotics, autos and mechatronics utilizing the effectiveness of energy transformation capability. In geotechnical engineering, commercial bender elements are used in laboratory as source and receiver in the measurements of soil stiffness. The elements were built by using various metal shims sandwiched between piezo-ceramics and coating over the composite in the research. A pair of elements were buried in a concrete block and used as source and receiver to measure the stiffness of the concrete. The test results were verified by comparing with the resonant column testing results. In a preliminary stage of the development of an in-situ seismic testing equipment using bender elements for soft clay materials, shear waves were generated and measured by burying the elements in the barrel of kaolinite and water mixture. The measured shear wave signals were so distinct for the first-arrival pick that applicability of the elements in the field measurements could be very promising.

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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Effect of Initial Particle Size Distribution of (K0.5Na0.5)NbO3 Powders on Microstructure of Their Sintered Ceramics ((K0.5Na0.5)NbO3 세라믹스의 초기 분말 입도 분포가 소결체의 미세구조에 미치는 영향)

  • Yoo, Il-Ryeol;Choi, Seong-Hui;Cho, Kyung-Hoon
    • Journal of the Korean Society for Heat Treatment
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    • v.35 no.2
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    • pp.57-65
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    • 2022
  • In this study, the effect of the initial particle size distribution (PSD) of (K0.5Na0.5)NbO3 powders on the microstructure of sintered ceramics was investigated. (K0.5Na0.5)NbO3 powders with uni-, bi-, tri-, and quad-modal PSDs were obtained through a planetary ball-mill. For the specimens sintered at 1080℃, the growth of abnormal grains was promoted from the powders exhibiting quad- and tri-modal PSDs with a high content of large particles, resulting in a microstructure in which huge abnormal grains were predominant. However, as the number of peaks in PSD and the overall particle size decreased, the abnormal grain growth was suppressed and the grain growth of small particles started, resulting in a microstructure with a uniform grain size. For the specimens sintered at 1100℃, huge abnormal grains were not observed due to the decrease in the critical driving force for 2D nucleation even when powders with quad- and tri-modal PSDs were used. It was confirmed that when powder with unimodal PSD was used, a uniform microstructure that was not significantly affected by the sintering temperature could be obtained. The results of this study demonstrate that the microstructure of (K0.5Na0.5)NbO3-based ceramics can be controlled by controlling the particle size of the initial powder.

Studies on Fabrication and Characteristics of $Al_{0.3}Ga_0.7N/GaN$ Heterojunction Field Effect Transistors for High-Voltage and High-Power Applications (고전압과 고전력 응용을 위한 $Al_{0.3}Ga_0.7N/GaN$ 이종접합 전계효과 트랜지스터의 제작 및 특성에 관한 연구)

  • Kim, Jong-Wook;Lee, Jae-Seung;Kim, Chang-Suk;Jeong, Doo-Chan;Lee, Jae-Hak;Shin, Jin-Ho
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.38 no.8
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    • pp.13-19
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    • 2001
  • We report on the fabrication and characterization of $Al_{0.3}Ga_{0.7}N$ HFETs with different barrier layer thickness which were grown using plasma-assisted molecular beam epitaxy (PAMBE). The barrier thickness of $Al_{0.3}Ga_{0.7}N$/GaN HFETs could be optimized in order to maximize 2 dimensional electron gas induced by piezoelectric effect without the relaxation of $Al_{0.3}Ga_{0.7}N$ layer. $Al_{0.3}Ga_{0.7}N$/GaN (20 nm/2 mm) HFET with 0.6 ${\mu}m$-long and 34 ${\mu}m$-wide gate shows saturated current density ($V_{gs}=1\;V$) of 1.155 A/mm and transconductance of 250 ms/mm, respectively. From high frequency measurement, the fabricated $Al_{0.3}Ga_{0.7}N$/GaN HFETs showed $F_t=13$ GHz and $F_{max}=48$ GHz, respectively. The uniformity of less than 5% could be obtained over the 2 inch wafer. In addition to the optimization of epi-layer structure, the relation between breakdown voltage and high frequency characteristics has been examined.

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Preparation and Electrical Properties of Piezoelectric Glass-Ceramics for Application in Hydrophones (하이드로폰용 결정화 유리의 제조 및 전기적 특성)

  • Park, S.S.;Lee, C.H.;Lee, H.;Lee, H.S.;Shon, M.M.;Park, H.C.
    • Korean Journal of Materials Research
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    • v.8 no.12
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    • pp.1146-1151
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    • 1998
  • The crystallization behaviour of perovskite $PbTiO_3$ for the samples heat- treated at various temperatures for various times in the $PbO-TiO_2-A1_2O_3-SiO_2$, glass system has been investigated by the means of X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses. Higher crystallinity obtained in the sample heat-treated at higher temperature for longer time. With increasing heat-treatment time, dielectric constant of the samples heat-treated at $610^{\circ}C$ and $650^{\circ}C$ increased, but that of the sample heat- treated at $800^{\circ}C$ decreased. Loss tangent of the heat-treated samples was not much influenced by heat-treatment conditions. Piezodielectric charge constant was approximately $1.0\times10^{-12}~8.0$\times$10^{-12}C/N$ in the samples heat-treated at $800^{\circ}C$ for 1h, 2h, and 8h.

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Fabrication of a FBAR device using a novel process and the effect of bottom electrode on the frequency response (신 공정을 이용한 멤브레인형 체적탄성파 공진기의 제작 및 하부전극이 주파수 응답특성에 미치는 영향)

  • Kim, Bo-Hyun;Kim, Do-Young;Cho, Dong-Hyun;Lee, Jin-Bock;Park, Jin-Seok
    • Proceedings of the KIEE Conference
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    • 2004.07c
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    • pp.1594-1596
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    • 2004
  • Film bulk acoustic resonator (FBAR) devices which adopt a membrane-type configuration are fabricated by a novel process. In contrast to the conventional FBAR structure, the newly fabricated resonator doesn't employ any supporting layer below or above it, so that the properties of piezoelectric layer are not influenced by the bottom electrode material. FBAR devices with Mo/AlN/Metal configuration are also fabricated. The frequency response characteristics ($S_{11}$) of the devices fabricated using the proposed process are compared with those of the conventional devices. The return losses are also estimated, in terms of the kind and thickness of bottom electrode materials.

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Electrical/Optical Characterization of PZT Thin Films Deposited through Sol-Gel Processing

  • Hwang, Hee-Soo;Kwon, Kyoeng-Woo;Choi, Jeong-Wan;Do, Woo-Ri;Hwang, Jin-Ha
    • Proceedings of the Korean Vacuum Society Conference
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    • 2012.08a
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    • pp.361-361
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    • 2012
  • PZT (Pb(Zr,Ti)O3) thin films have been used widely in the MEMS application, due to their inherent ferroelectric and piezoelectric properties. Such ferroelectricity induces much higher dielectric constants compared to those of the nonperovskite materials. In this work, the PZT thin films were deposited onto Indium-Tin-oxide (ITO) substrates through the spin-coating of PZT sols. The deposited PZT thin films were characterized in terms of the electrical and optical properties with special emphases on conductivity and optical constants. The detailed analysis techniques incorporate the dc-based current-voltage characteristics for the electrical properties, spectroscopic ellipsometry for optical characterization, atomic force microscopy for surface morphology, X-ray Photoelectron Spectroscopy for chemical bonding, Energy-dispersive X-ray Spectrometry for chemical analyses and X-ray diffraction for crystallinity. The ferroelectric phenomena were confirmed using capacitance-voltage measurements. The integrated physical/chemical features are attempted towards energy-oriented applications applicable to next-generation high-efficiency power generation systems.

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