• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1998년도 PROCEEDINGS OF THE 15TH KACG TECHNICAL MEETING-PACIFIC RIM 3 SATELLITE SYMPOSIUM SESSION 4, HOTEL HYUNDAI, KYONGJU, SEPTEMBER 20-23, 1998
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• pp.73-77
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• 1998

Langasite(La3Ga5SiO14) is a new piezoelectric material which is similar to quartz, LN(LiNbO3) and LT(LiTaO3) in its acoustic behavior. In this study, pure Langasite and Langasite family groups were synthesized by the solid state reactions in air. For the synthesis process, diffusion species were investigated and sintered body of synthesized powders were studied on dielectric property according to surface microstructures.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집
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• pp.418-421
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• 2001

The ceramic filters were developed using technology similar to that of quartz crystal and electro- mechanical filter. However, the key to this development involved the theoretical analysis of vibration modes and material improvements of piezoelectric ceramics. The primary application of ceramic filters has been for consumer-market use. Accordingly, a major emphasis has involved mass production technology, leading to low-priced devices. A typical ceramic filter includes monolithic resonators and capacitors packaged in unique configurations. Nakazawa developed a double-mode resonator as two acoustically coupled single resonators. And he developed 10.7MHz crystal filters using multi-energy trapping mode of thickness shear vibration. He succeeded in realizing a two-pole band pass filter response without external inductance by splitting a dot electrode to creak coupled symmetric and anti- symmetric vibration modes. Accordingly, the simulation for ceramic (inter were important. So that, this paper were investigated the pass frequency of filter on the electrode length and thickness of ceramic.

• 센서학회지
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• 제29권1호
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• pp.59-62
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• 2020

Currently, increasing attention is being paid to relaxor-based ferroelectric single crystals in photoacoustic images, especially for high-end applications. Among the crystals are (1-x)Pb(Mg_1/3Nb_2/3)O₃-xPbTiO₃ (PMN-100xPT) single crystals located near their morphotropic phase boundary (x = 0.30-0.35) because of their ultrahigh piezoelectric and electromechanical coupling properties. The alternating current poling (ACP) treatment, rather than the conventional direct current poling treatment, has recently been spotlighted due to its effectiveness in enhancing the piezoelectric properties. So far, it has been suggested that the enhanced piezoelectricity originates from either a domain miniaturization to nanodomains or from an electric-field-induced monoclinic symmetry. In this study, we demonstrate by thermally stimulated depolarization current measurements that the effect of ACP is too complex to be explained using a single mechanism and that the proposed electric-field-induced monoclinic symmetry is unlikely to exist.

• 한국세라믹학회지
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• 제37권8호
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• pp.731-738
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• 2000

KLN(K3Li2Nb5O15) has attracted a great deal of attention for their potential usefulness in piezoelectric, electro-optic, nonlinear optic, and pyroelectirc devices. Especially, the KLN single crystal has been studied in the field of optics and electronics. However it is hard to produce good quality single crystals due to the crack propagation during crystal growing. One of the solutions of this problem is prepartion of thin film. But the intensive study has not been conducted so far. In this study, after the KLN thin film were prepared by R.F. magnetron Sputtering method on SiO2/Si substrate, the post-annealing methods of RTA(rapid thermal annealin) and IPA(insitu post annealing) were employed. The deposition condition of KLN thin film was RF power(100 W), Working pressure(100 mtorr). The commonness of both RAT and IPA was that the higher were deposition and post annealing temperature, the higher was the intensity of XRD but the less surface roughness. The difference of post-annealing methods affected XRD phase and surface condition very much. And in IPA process, the influence of O2 had much effect on the formation of KLN phase.

• 한국결정성장학회지
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• 제10권4호
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• pp.309-317
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• 2000

Langasite is a promising new piezoelectric material for SAW filter application. Little was known until recently about the methods needed to mechanically polish and chemically polish/etch this material. In this experiment, polishing, slurry chemistry and chemical wet etching for langasite is described. Conventional quartz and LN ($LiNbO_3$) polishing methods did not produce satisfactory polished surfaces, and polishing with a colloidal silica slurries has shown to be most effective. The optimum condition was investigated by changing the slurry chemistry. As the planarization effect is very important in SAW filter applications, the examination of the effective particle number effect and the particle size effect was carried out. Z-cut langasite surface which had been polished with the colloidal silica slurries was etched in a variety of etchants. Conventional quartz etchants destroyed the polished surface. Other etchants formed a thin film on the surfaces. In this experiment, the reaction between langasite and a few etching solution was analysed. And an appropriate selective etchant solution for analyzing the defects was synthesized.

• 한국재료학회지
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• 제25권6호
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• pp.288-292
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• 2015

New lead-free piezoelectric ceramics $0.96[\{Bi_{0.5}(Na_{0.84}K_{0.16})_{0.5}\}_{1-x}La_x(Ti_{1-y}Nb_y)O_3]-0.04SrTiO_3$ (BNKT-ST-LN, where $x=y=0.00{\leq}(x=y){\leq}0.015)$ were synthesized using the conventional solid-state reaction method. Their crystal structure, microstructure, and electrical properties were investigated as a function of the La and Nb (LN) content. The X-ray diffraction patterns revealed the formation of a single-phase perovskite structure for all the LN-modified BNKT-ST ceramics in this study. The temperature dependence of the dielectric curves showed that the maximum dielectric constant temperature ($T_m$) shifted towards lower temperatures and the curves became more diffuse with an increasing LN content. At the optimum composition (LN 0.005), a maximum value of remnant polarization ($33C/cm^2$) with a relatively low coercive field (22 kV/cm) and high piezoelectric constant (215 pC/N) was observed. These results indicate that the LN co-modified BNKT-ST ceramic system is a promising candidate for lead-free piezoelectric materials.

• 한국음향학회지
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• 제14권2호
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• pp.73-79
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• 1995

현재 사용중인 초음파 트랜스듀서는 종피 또는 횡피 중 하나를 발생하도록 구성되어 있다. 본 연구는 단일 PZT소자로서 종파와 횡파를 동시에 발생 할 수 있는 2 중 모우드 트랜스듀서 의 초음파 발생 메커니즘을 조사하였다. 분극처리한 압전 세라믹 PZT의 결정구조는 상온에서 hexagonal (6mm) 이다. 트랜스듀서가 종. 횡액를 동시에 큰 강도로 발생하는 최적 절단면을 결정하기 위하여 PZT 소자의 효율을 회전각의 함수로 조사하였다 그리고 선택된 절단면에 대하여 소자의 임피던스 변화를 유한요소법으로 분석하고, pulse-echo 시뮬레이션으로 파형을 관찰하였다. 이론적 결과를 실험을 통해 확인하였다.

• 한국음향학회지
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• 제6권4호
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• pp.5-11
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• 1987

본 연구에서는 압전 세라믹에서 탄성 표면파의 속도 측정에 대한 실험 방법을 제시한다. Oscilloscope와 Pulse Generator만으로 실시할 수 있으며 특히 feed-through에 의한 신호가 있는 경우에도 측정 가능한 방법이다. IDT응답이 Convolution 이론에 따르는 것에 주목하여 파가 진행한 거리를 정확히 산출하여 속도를 구할 수 있었다. 본 연구의 방법으로 측정한 결과 상온에서 $YZ-LiNbO_3$에 대하여 3,480m/sec를 구할 수 있었으며 feed-through가 큰 $PbTiO_3$계 압전 세라믹에 대해서는 2,770m/sec를 측정하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집 Vol.14 No.1
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• pp.418-421
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• 2001

The ceramic filters were developed using technology similar to that of quartz crystal and electromechanical filter. However, the key to this development involved the theoretical analysis of vibration modes and material improvements of piezoelectric ceramics. The primary application of ceramic filters has been for consumer-market use. Accordingly, a major emhpasis has involved mass production technology, leading to low-priced devices. A typical ceramic filter includes monolithic resonators and capacitors packaged in unique configurations. Nakazawa developed a double-mode resonator as two acoustically coupled single resonators. And he developed 10.7MHz crystal filters using multi-energy trapping mode of thickness shear vibration. He succeeded in realizing a two-pole band pass filter response without external inductance by splitting a dot electrode to creat coupled symmetric and antisymmetric vibration modes. Accordingly, the simulation for ceramic filter were important. So that, this paper were investigated the pass frequency of filter on the electrode length and thickness of ceramic.

• 한국재료학회지
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• 제15권11호
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• pp.683-689
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• 2005

The structural, piezoelectric and ferroelectric properties of $(1-x)(Bi_{0.5}Na_{0.5})TiO_3$ x=0.00, 0.02, 0.04, 0.06, 0.08, and 0.10) ceramics were investigated. A gradual change in the crystal and microstructures with tile increase of $BaTiO_3$ (BT) concentration was observed. The $(Bi_{0.5}Na_{0.5})TiO_3$ (BNT) samples show unusual properties as ferroelectric relaxer materials. We observed a phase transition in BNT solid solutions with BT having normal ferroelectric phase transition. At room temperature, BNT presents a single phase without the morphotropic phase boundary (MPB). In the case of samples doped with $4\~8 mol\%$ BT, rhombohedral-tetragonal MPB was formed and the piezoelectric properties were improved.