• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
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• pp.546-547
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• 2002

Ni thin film on the PMN-PT crystal wafer were deposited by using E-beam evaporator technique. Deposited film was patterned by UV-lithography and etching and was in-diffused at 300~600C. Diffusion profile of Ni ions in PMN-PT was measured by secondary ion mass spectroscopy (SIMS).

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.209-210
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• 2006

Organic binders are usually pre-mixed with ceramic powders to enhance the formability during the shape forming process. These binders, however, must be eliminated before sintering in order to avoid pore formation and unusual grain growth during sintering. The present work was performed to investigate the effects of residual binder on grain growth behavior during sintering of $Pb(Mg_{1/3}Nb_{2/3})O_3-PbTiO_3$ piezoelectric ceramics. The microstructures of sintered samples were examined for various thermal processes and atmosphere at debinding. Addition of binder seems to promote abnormal grain growth especially in incompletely debinded regions and to make the grain shape change from corner-rounded to faceted.

• 한국재료학회지
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• 제12권2호
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• pp.160-165
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• 2002

High-frequency dielectric and microwave absorbing properties have been investigated in ferroelectric materials (BaTiO$_3$(BT), (1-x)Pb$Mg_{\frac{1}{3}}Nb_{\frac{2}{3}}$)O$_3$-xPbTiO$_3$(PMN-PT), (1-x)Pb$Mg_{\frac{1}{3}}Nb_{\frac{2}{3}}$O$_3$-xPb(Zn_{\frac{1}{3}}Nb_{\frac{2}{3}}$)O$_3$(PMN-PZN) for the aim of thin microwave absorbers in the frequency range of mobile telecommunication. The specimenns are prepared by conventional ceramic processing and complex permittivity has been measured by transmission/reflection method. The ferroelectric materials show high dielectric constant and dielectric loss in the microwave range and their domiant loss mechanism is considered to be domain wall relaxation. The microwave absorbance of BT 0.9PMN-0.1PT, and 0.8PMN-0.2PZN specimen (determined at 2) are found to be 99.5% (at a thickness of 4.5 mm), 50% (2.5 mm), and 30% (2.5 mm), respectively. It is suggested that PMN-PT or PMN-PZN ferroelectrics are good candidate materials for the spacer of λ/4 absorber. The use of ferroelectric materials is effective in reducing the thickness of absorber with their advantage of high dielectric constant.

• 한국세라믹학회지
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• 제54권2호
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• pp.150-157
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• 2017

Three types of piezoelectric single crystals [PMN-PT (Generation I $[Pb(Mg_{1/3}Nb_{2/3})O_3-PbTiO_3]$), PMN-PZT (Generation II $[Pb(Mg_{1/3}Nb_{2/3})O_3-Pb(Zr,Ti)O_3]$), PMN-PZT-Mn (Generation III)] were grown by the solid-state single crystal growth (SSCG) method, and their dielectric and piezoelectric properties were measured and compared. Compared to (001) PMN-PT and PMN-PZT single crystals, the (001) PMN-PZT-Mn single crystals exhibited a higher transition temperature between the rhombohedral and tetragonal phases ($T_{RT}=144^{\circ}C$), as well as a higher coercive electric field ($E_C=6.3kV/cm$) and internal bias field ($E_I=1.6kV/cm$). The (011) PMN-PZT-Mn single crystals showed the highest coercive electric field ($E_C=7.0kV/cm$), and the highest stability of $E_C$ and $E_I$ during 60 cycles of polarization measurement. These results demonstrate that both Mn doping (for higher electromechanical quality factor ($Q_m$)) and a (011) crystallographic orientation (for higher coercive electric field and stability) are necessary for high power transducer applications of these piezoelectric single crystals. Specifically, the (011) PMN-PZT-Mn single crystal (Gen. III) had the highest potential for application in the fields of SONAR transducers, high intensity focused ultrasound (HIFU), ultrasonic motors, and others.

• 한국재료학회지
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• 제22권7호
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• pp.342-345
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• 2012

The dielectric properties and phase transformation of poled <001>-oriented $Pb(Mg_{1/3}Nb_{2/3})O_3-x%PbTiO_3$(PMN-x%PT) single crystals with compositions of x = 20, 30, and 35 mole% are investigated for orientations both parallel and perpendicular to the [001] poling direction. An electric-field-induced monoclinic phase was observed for the initial poled PMN-30PT and PMN-35PT samples by means of high-resolution synchrotron x-ray diffraction. The monoclinic phase appears from $-25^{\circ}C$ to $100^{\circ}C$ and from $-25^{\circ}C$ to $80^{\circ}C$ for the PMN-30PT and PMN-35PT samples, respectively. The dielectric constant (${\varepsilon}$)-temperature (T) characteristics above the Curie temperature were found to be described by the equation$(1/{\varepsilon}-1/{\varepsilon}_m)^{1/n}=(T-T_m)/C$, where ${\varepsilon}_m$ is the maximum dielectric constant and $T_m$ is the temperature giving ${\varepsilon}_m$, and n and C are constants that change with the composition. The value of n was found to be 1.82 and 1.38 for 20PT and 35PT, respectively. The results of mesh scans and the temperature-dependence of the dielectric constant demonstrate that the initial monoclinic phase changes to a single domain tetragonal phase and a to paraelectric cubic phase. In the ferroelectric tetragonal phase with a single domain state, the dielectric constant measured perpendicular to the poling direction was dramatically higher than that measured in the parallel direction. A large dielectric constant implies easier polarization rotation away from the polar axis. This enhancement is believed to be related to dielectric softening close to the morphotropic phase boundary.

• 한국재료학회지
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• 제23권6호
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• pp.329-333
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• 2013

The structural phase transformations of $0.7Pb(Mg_{1/3}Nb_{2/3})O_3-0.3PbTiO_3$ (PMN-0.3PT) were studied using high resolution x-ray diffraction (HRXRD) as a function of temperature and electric field. A phase transformational sequence of cubic (C)${\rightarrow}$tetragonal (T)${\rightarrow}$rhombohedral (R) phase was observed in zero-field-cooled conditions; and a $C{\rightarrow}T{\rightarrow}$monoclinic $(M_C){\rightarrow}$ monoclinic ($M_A$) phase was observed in the field-cooled conditions. The transformation of T to $M_A$ phase was realized through an intermediate $M_C$ phase. The results also represent conclusive and direct evidence of a $M_C$ to $M_A$ phase transformation in field-cooled conditions. Beginning from the zero-field-cooled condition, a $R{\rightarrow}M_A{\rightarrow}M_C{\rightarrow}T$ phase transformational sequence was found with an increasing electric field at a fixed temperature. Upon removal of the field, the $M_A$ phase was stable at room temperature. With increasing the field, the transformation temperature from T to $M_C$ and from $M_C$ to $M_A$ phase decreased, and the phase stability ranges of both T and $M_C$ phases increased. Upon removal of the field, the phase transformation from R to $M_A$ phase was irreversible, but from $M_A$ to $M_C$ was reversible, which means that $M_A$ is the dominant phase under the electric field. In the M phase region, the results confirmed that lattice parameters and tilt angles were weakly temperature dependent over the range of investigated temperatures.

• 한국재료학회지
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• 제21권7호
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• pp.391-395
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• 2011

The structure and dielectric properties of poled <001>-oriented 0.7Pb($Mg_{1/3}Nb_{2/3})O_3-0.3PbTiO_3$ (PMN-0.3PT) crystals have been investigated for orientations both parallel and perpendicular to the [001] poling direction. An electric field induced monoclinic phase was observed for the initial poled sample. The phase remained stable after the field was removed. A quite different temperature dependence of dielectric constant has been observed between heating and cooling due to an irreversible phase transformation. The results of mesh scans and temperature dependence of the dielectric constant demonstrate that the initial monoclinic phase changes to a single domain tetragonal phase at 370K and to a paraelectric cubic phase at 405K upon heating. However, upon subsequent cooling from the unpoled state, the cubic phase changes to a poly domain tetragonal phase and to a rhombohedral phase. In the ferroelectric tetragonal phase with a single domain state, the dielectric constant measured perpendicular to the poling direction was dramatically higher than that of the parallel direction. A large dielectric constant implies easier polarization rotation away from the polar axis. This enhancement is believed to be related to dielectric softening close to the morphotropic phase boundary and at the phase transition temperature.

• 한국세라믹학회지
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• 제43권11호
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• pp.680-687
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• 2006

An overview is given to optimize the solid state processes toward phase pure and well-crystallized fine particulates of mixed oxides, serving as electroceramic materials in various genres. Elevation of the reactivity and preservation of stoichiometry of the starting mixture are of universal importance. Mechanical activation is versatile for these purposes, particularly when an oxygen atom as a hinge promotes formation of hetero-bridging bonds between dissimilar cationic species prior to calcination. Case studies carried out recently in the author's laboratory are displayed and compared for ferroelectric materials, i.e. $PbMg_{1/3}Nb_{2/3}O_3$ $xPbTiO_3$(PMN-PT), $(1-y)Pb(Zn_xMg{1-x})_{1/3}$ $yNb_{2/3}O_3$ (PZN-PMN), $BaBi_2Ta_2O_9$ (BBT), $Ba(Mg_{1/3}Ta_{2/3})O_3$ (BMT), and ferromagnetics, i.e. M-, Y-, and Z-phases of Ba-hexaferrites.

• 한국광학회지
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• 제7권2호
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• pp.162-166
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• 1996

전왜재질 0.9 PMN/0.1PT에 각각 조성비율이 1%, 2%, 3%의 La이 첨가된 3종류의 재질을 광섬유에 부착하여 광섬유 전왜변환기를 제작하였다. 실험결과 La 3% 첨가된 재질의 전왜계수가 3.38kHz에서 3.87*$10^{-16}$(m/V)$^{2}$로 가장 크다는 것을 알 수 있었으며 La을 첨가함으로 해서 이력이 줄어듬을 알 수 있었다. La 3%인 재질로 구현된 광섬유 전계센서의 최소감지전계는 2.08(V/m).root.Hz였으며 가변영역 40dB 이상에 걸쳐서 선형성이 우수하였다.

• 마이크로전자및패키징학회지
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• 제27권4호
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• pp.91-96
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• 2020

Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3계 압전 단결정의 유전특성과 압전특성을 전계 및 압축응력 인가 조건 하에서 33-모드 방식으로 측정하였다. 110~140℃ 영역에서 저온 rhombohedral 구조에서 고온 tetragonal 구조로의 상전이가 관찰되었으며, cubic 구조로 변화하는 큐리온도는 165℃ 정도로 나타났다. 압축응력 및 전계 변화에 따른 분극의 크기변화를 측정하였다. 전계인가 분극 곡선의 기울기로부터 비유전율을 계산하였고, 인가되는 응력의 크기가 증가할수록 계산된 비유전율의 크기는 증가하고, 인가되는 전계의 크기가 증가할수록 비유전율의 크기는 감소하는 경향성을 나타내었다. 압축응력 및 전계 변화에 따른 변위 거동을 측정하였으며, 곡선의 기울기로부터 압전상수를 계산하였고 압력인가에 따른 상전이를 확인하였다. 수중 또는 의료용 초음파 발진자로 실제 응용할 경우 선형성을 유지하여 구동이 가능하기 위하여 소자 기구물을 형성하는 단계에서 인가하게 되는 압축응력의 크기와 구동 전계의 DC 바이어스의 크기를 적절하게 설계할 필요가 있다.