• Advances in materials Research
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• v.5 no.2
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• pp.93-105
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• 2016

KNN-based ceramics modified with small amounts of $Bi_4Zr_3O_{12}$ (BiZ) has been synthesized using high-throughput experimentation (HTE). The results from X-ray diffraction show that for samples with base composition $(K_{0.5}Na_{0.5})NbO_3$ (KNN), the phase present changes from orthorhombic to pseudo-cubic with more than 0.2 mol% BiZ addition; for samples with base composition $(K_{0.48}Na_{0.48}Li_{0.04})(Nb_{0.9}Ta_{0.1})O_3$ (KNNLT), the phase present changes from a mixture of orthorhombic and tetragonal symmetry to pseudo-cubic with more than 0.4 mol % while for samples with base composition $(K_{0.48}Na_{0.48}Li_{0.04})(Nb_{0.86}Ta_{0.1}Sb_{0.04})O_3$ (KNNLST), the phase present is tetragonal with <0.3 mol% BiZ addition and transforms to pseudo-cubic with more dopant addition. The microstructures of the samples show that addition of BiZ decreases the average grain size and increases the volume of pores at the grain boundaries. The values of dielectric constant for KNN and KNNLT compositions increase slightly with BiZ addition while that for KNNLST decreases gradually with BiZ addition. The dielectric loss values are between 0.02 and 0.04 for KNNLT and KNNLST compositions while they are ~ 0.05 for KNN samples. The resistivity values increases with BiZ addition and values in the range of $10^{10}{\Omega}cm$ and $10^{12}{\Omega}cm$ are obtained. The piezoelectric charge coefficient ($d{^*}_{33}$) is highest for KNNLST samples and decreases gradually from ~400 pm/V to ~100 pm/V with BiZ addition.

• Electrical & Electronic Materials
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• v.3 no.3
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• pp.233-241
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• 1990

본 연구에서는 xPb(Zn$_{1}$3/Nb$_{2}$3/)O$_{3}$-yBa(Zn$_{1}$3/Nb$_{2}$3/)O$_{3}$-zPbTiO(0.50.leq.x.leq.0.60, 0.10.leq.y.leq.0.20, 0.20.leq.z.leq.0.40)세라믹을 1050.deg.C에서 2시간동안 유지시켜 일반소성법으로 제작하였다. 시편 제작시 조성은 조성변태 상경계부근을 선택하였으며 Ba(Zn$_{1}$3/ Nb$_{2}$3/)O$_{3}$ 고용량에 따른 purochlore상의 억제 및 그 영향을 조사하고 구조적, 유전적 및 압전적 특성을 측정하였다. X-선 회절분석 및 미세구조의 관찰 결과, Ba(Zn$_{1}$3/Nb$_{2}$3/)O$_{3}$의 고용량에 따라 pyrochlore상 및 미반응 물질등은 억제되어 0.20mol 고용된 시편에서는 균질한 perovskite상이 형성되었다. Ba(Zn$_{1}$3/Nb$_{2}$3/)O$_{3}$의 고용량이 증가함에 따라 유전상수는 증가하여 0.50PZN-0.20BZN-0.30PT시편의 경우 6880.9의 높은 값을 나타내었으며 정전용량의 온도계수는 감소하여 0.383[%/.deg.C]의 양호한 값을 나타내었다. 큐리온도는 PbTiO$_{3}$의 고용량이 0.20mol에서 0.40mol로 증가함에 따라 30.deg.C에서 170.deg.C로 증가하였다. 전기기계 결합계수 (K$_{p}$), 기계적 품질계수(Qm) 및 압전전하 계수 (d$_{33}$)는 조성변태 상경계 부근의 조성에서 크게 나타났으며 0.60PZN-0.15BZN-0.25PT 시편의 경우 각각 58.5%, 120.5, 150x$10^{-12}$[C/N]의 값을 나타내었다.다.다.

• Electrical & Electronic Materials
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• v.5 no.2
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• pp.198-206
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• 1992

(P $b_{1-x}$L $a_{x}$)[(S $b_{1}$2/S $n_{1}$2/) $Ti_{y}$ Z $r_{1-y}$] $O_{3}$(0.leq.x.leq.0.04, 0.25.leq.y.leq.0.40) 세라믹을 1250[.deg.C]에서 2시간동안 유지시켜 일반 소성법으로 제작하였으며 조성 및 L $a_{2}$ $O_{3}$첨가량에 따른 구조적, 압전적 특성을 관찰하였다. L $a_{2}$ $O_{3}$의 첨가량이 3-4[mol%]인 경우 La-rich의 pyrochlore상이 형성되었다. 시편의 평균결정립 크기는 1-2[.mu.n]의 크기를 나타내었으며 PbTi $O_{3}$조성이 증가함에 따라 다소 감소하는 경향을 나타내었다. 각 조성의 시편에 대해 PbTi $O_{3}$ 및 L $a_{2}$ $O_{3}$의 첨가량이 증가할수록 유전상수는 증가하는 경향을 나타내었으며 상전이 온도인 큐리온도는 PbTi $O_{3}$조성이 감소할수록 L $a_{2}$ $O_{3}$첨가량이 증가할수록 감소하는 경향을 나타내었다. 압전 전하계수 및 전기기계 결합계수는 L $a_{2}$ $O_{3}$첨가량 및 PbTi $O_{3}$조성에 따라 증가하였으며 L $a_{2}$ $O_{3}$가 4[mol%]첨가된 0.10PSS-0.40PT-0.50PZ 시편에서 각각 250x$10^{-12}$[C/N], 29.7[%]의 최대값을 나타내었다. 기계적 품질계수는 L $a_{2}$ $O_{3}$첨가량 및 PbTi $O_{3}$조성이 증가할수록 감소하는 경향을 나타내었으며 0.10PSS-0.25PT-0.65PZ 시편에서 138의 최대값을 나타내었다.다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.307-307
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• 2007

압전액츄에이터 및 초음파진동자는 전자제품의 소형화 및 경량화, 의료기기, 모바일기기 및 소형로붓의 발전에 힘입어 그 활용범위가 넓게 확장되고 있다. 1960년 Smolenski등에 의해 $A(B_1,B_2)O_3$형 복합 페로브스카이트 구조를 갖는 강유전성 세라믹스에 대한 연구가 시작된 이래 $Pb(Co,Nb)O_3-Pb(Zr,Ti)O_3$, $Pb(Zn,Nb)O_3-Pb(Zr,Ti)O_3$, $Pb(Mg,Nb)O_3-Pb(Zr,Ti)O_3$ 등 3성분계 세라믹스의 유전, 압전 및 강유전 특성에 대한 많은 연구가 진행되어 왔다. 그러나 압전성이 우수한 세라믹스들은 Pb가 포함되어 있기 때문에 $1000^{\circ}C$ 이상에서 PbO가 급격하게 휘발되는 성질에 따라서 조성의 변동이 생겨 재현성이 어려우며 이를 방지하기 위하여 과잉 PbO를 첨가시키기 때문에 환경오염뿐만 아니라, 경제적인 측면에서도 많은 문제점을 가지고 있다. 소결조제를 이용한 산화물 첨가법은 PbO의 휘발을 억제하는 저온소결 방법중 가장 효과적인 방법으로 알려져 있다. 따라서, 본 연구에서는 적층형 압전액츄에이터로 사용하기위한 저온소결 압전세라믹스를 개발하기 위하여 PZN-PZT세라믹스에 $Li_2CO_3$, $Bi_2O_3$, CuO 를 소결조제로 사용하여 $Li_2CO_3$의 첨가량 변화에 따른 압전 및 유전 특성을 관찰하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.260-260
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• 2007

강유전성 세라믹스 재료로써는 PZT계열의 세라믹재료가 널리 쓰이고 있다. 이는 우수한 유전 및 압전특성을 가지고 있으나, PbO을 다량 함유하고 있어 $1000^{\circ}C$이상에서 PbO가 급격하게 휘발되는 성질에 따라서 조성의 변동이 생겨 재현성이 어려우며 이를 방지하기 위하여 과잉 PbO를 첨가시키기 때문에 PbO휘발로 인한 강한 독성이 인체에 유해하다. 최근에는 Pb의 환경문제가 대두됨에 따라 이를 대체할 다른 물질의 개발이 활발하게 연구되고 있다. 대표적인 비납계 강유전 세라믹스인 $(Na_{0.5}K_{0.5})NbO_3$ ($d_{33}$ = 120 pC/N, Kp = 39%, Qm = 210, 이하 NKN라 표기) 조성은 $KNbO_3,\;NaNbO_3$ 상태도에 따라 순수한 NKN 세라믹스는 $1140^{\circ}C$에서 안정상을 가지나, 높은 온도로 인하여$Na_2O$와 $K_2O$가 쉽게 휘발됨에 따라 화학량 비의 변화가 생겨 이차 상을 형성하기도 한다. 따라서 본 연구에서는 $LiNbO_3$의 새로운 고용체를 추가시켜 기본 NKN조성에 압전성 및 고온에서의 상안정성을 향상시키고자 하였다. 최적 조성을 설계하기 위하여 (1-x)$(Na_{0.5}K_{0.5})NbO_3-xLiNbO_3$, x=(0,0.02,0.04,0.06,0.08)의 범위에서 조성을 변화시키면서 실험하였다. 시편 제작은 일반적인 세라믹스 소결 공정을 적용하였는데, $850^{\circ}C$에서 5시간 하소 후 $1080^{\circ}C$에서 2시간 소결하였다. 하소 및 소결 후에는 XRD분석을 통해 perovskite구조를 확인하였고, 미세구조 확인을 위해 주사전자현미경 (SEM)으로 관찰하였다. 압전특성을 평가하기 위해 압전 $d_{33}$-meter를 사용하였으며, impedance analyzer (HP 4194A)를 이용하여 전기적 특성을 측정하였다.

• Applied Science and Convergence Technology
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• v.25 no.5
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• pp.88-91
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• 2016

The $Pb[(Mg_{1/3}Ta_{2/3})_{0.7}Ti_{0.3}]O_3$+xwt%PbO systems at temperature of $1250^{\circ}C$ for 4 hours was successful synthesized. In this study, PbO-doped $Pb[(Mg_{1/3}Ta_{2/3})_{0.7}Ti_{0.3}]O_3$ systems with non-linear behaviors showed ordering-degree dependence at the low temperature range were prepared using the columbite precursor method. And the characteristic of remnant polarization vs. electric field were analyzed. The pyroelectric, dielectric and piezoelectric properties of partially disordered $Pb[(Mg_{1/3}Ta_{2/3})_{0.7}Ti_{0.3}]O_3$+xwt%PbO solid solutions were studied as a function of temperature, frequency, and electric field. It showed distinct features of temperature dependent of pyroelectric coefficient, spontaneous polarization and dielectric constant at about $50^{\circ}C$. The figure of merit was calculated as pyroelectric coefficient, dielectric constant and dissipation factor. It was found that the high voltage responsivity FV, high detectivity FD were $0.0373m^2/C$ and $0.6735{\times}10^{-4}Pa{-1/2}$, respectively, in the $Pb[(Mg_{1/3}Ta_{2/3})_{0.7}Ti_{0.3}]O_3$+3.0 wt%PbO system.

• Korean Journal of Materials Research
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• v.4 no.7
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• pp.783-791
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• 1994

Piezoelectric ZnO thin films were deposited on 7059 glass substrate by rf magnetron sputtering. The effects of deposition parameter, such as rf power, gas pressure and $O_{2}$/Ar gas ratio, on the crystallinity and electrical properties of the deposited ZnO thin films were studied. It was found that the deposition rate was higher than the previously reported values. ZnO films were suitable for SAW filter since a standard deviation of XRD (002) peak rocking curve was less than $6^{\circ}$. ZnO thin films, which were deposited at $O_{2}$/Ar ratio larger than 25%, showed high resistance. SAW filter was fabricated using ZnO film, of which thickness was 0.25 of the wavelength of the propatating surface acoustic wave. The measured frequency response was consistent with the calculated one. The SAW filter had center frequency 39.08 MHz, phase velocity 2501 m/sec and insertion loss 29 dB.

• 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.

• Structural Engineering and Mechanics
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• v.69 no.4
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• pp.439-455
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• 2019

This research deals with thermo-electro-mechanical buckling analysis of the sandwich nano-beams with face-sheets made of functionally graded carbon nano-tubes reinforcement composite (FG-CNTRC) based on the nonlocal strain gradient elasticity theory (NSGET) considering various higher-order shear deformation beam theories (HSDBT). The sandwich nano-beam with FG-CNTRC face-sheets is subjected to thermal and electrical loads while is resting on Pasternak's foundation. It is assumed that the material properties of the face-sheets change continuously along the thickness direction according to different patterns for CNTs distribution. In order to include coupling of strain and electrical field in equation of motion, the nonlocal non-classical nano-beam model contains piezoelectric effect. The governing equations of motion are derived using Hamilton principle based on HSDBTs and NSGET. The differential quadrature method (DQM) is used to calculate the mechanical buckling loads of sandwich nano-beam as well as critical voltage and temperature rising. After verification with validated reference, comprehensive numerical results are presented to investigate the influence of important parameters such as various HSDBTs, length scale parameter (strain gradient parameter), the nonlocal parameter, the CNTs volume fraction, Pasternak's foundation coefficients, various boundary conditions, the CNTs efficiency parameter and geometric dimensions on the buckling behaviors of FG sandwich nano-beam. The numerical results indicate that, the amounts of the mechanical critical load calculated by PSDBT and TSDBT approximately have same values as well as ESDBT and ASDBT. Also, it is worthy noted that buckling load calculated by aforementioned theories is nearly smaller than buckling load estimated by FSDBT. Also, similar aforementioned structure is used to building the nano/micro oscillators.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.3
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• pp.303-307
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• 2022

Magnetoelectric (ME) properties of 3-0 type particulate composites have been investigated with respect to application features for reliable magnetic sensitivity and magnetically-induced output voltage. In order to figure out the magnetoelectric characteristics in the ME composites, frequency dependent ME responses were studied from [0.948 Na_0.5K_0.5NbO₃-0.052 LiSbO₃]-[Co_1-xZn_xFe₂O₄] (NKNLS)/Co_1-xZn_xFe₂O₄ (CZFO, x=0, 0.1, and 0.2). As a result, the maximal α_ME of 23.15 mV/cm·Oe was achieved from the NKNLS-CZFO (x_Zn = 0.1) composites at resonance frequency of 315 kHz and H_dc = 0 Oe. From the frequency dependent ME responses, it is clearly described that the self-biased ME composites can be used for applications as both magnetic sensors and energy harvesters, respectively.