• Journal of the Korean Vacuum Society
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• v.17 no.2
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• pp.122-129
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• 2008

Ferroelectric properties of the PMT-PT were also studied from the temperature dependence of hysteresis loops using a method slightly modified from Sawyer-Tower's. Dielectric, pyroelectric and piezoelectric properties of the ceramics in the system PMT-PT were investigated. The resulted densities of the PMT-PT ceramics system were greater than 97 % of the theoretical value. As observed SEM micrograph of the fracture surfaces of the PMT-PT ceramics system, the average grain sizes were increased about 3-5 ${\mu}m$ to 6-8 ${\mu}m$ with increasing sintering temperature. The specimens with PT<0.30 for PMT-PT solid solution system exhibited the dielectric and pyroelectric properties of a typical relaxor ferroelectrics. The composition with the maximum dielectric constant exhibits relatively superior pyroelectric and piezoelectric properties.

• Journal of the Korean Vacuum Society
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• v.10 no.4
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• pp.416-423
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• 2001

Microstructural, optical and dielectric properties of $SrTiO_3$ thin films were investigated. These films were deposited on the ITO glasses by rf-magnetron sputtering at room temperature and subequently heat treated in $O_2$ atmosphere at various temperatures. It has been found from X-ray diffraction patterns that as-deposited films prepared at room temperature are amorphous, while the films heat treated at temperature range of 400~$600^{\circ}C$ reveal the structure of pyrochlore. On the other hand, the structure of perovskite is dominantly observed in the films heat treated at temperatures over $650^{\circ}C$ in which the drastic changes of optical band gap and dielectric constant are observed. In addition, the phase transition peak is observed at $272^{\circ}C$ in the films heat treated at $600^{\circ}C$, while the dielectric dispersion is observed at near $310^{\circ}C$ in the films heat treated at $650^{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.38 no.4
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• pp.393-399
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• 2001

Pb(In$_{1}$2/Nb$_{1}$2/)O$_3$의 제조시 전구체로서 tetragonal pyrochlore(Pb$_3$Nb$_2$O$_{8}$)를 사용하였을 때, 페로브스카이트상의 상합성을 촉진시키고 유전특성을 향상시키기 위해 A(B$_1$,B$_2$) 구조에서 A자리에 해당하는 PbO와 B$_1$자리에 해당하는 In$_2$O$_3$를 각각 과량으로 첨가하여 900-110$0^{\circ}C$의 소결온도범위에서 상합성, 소결특성, 유전특성에 미치는 영향에 대해 고찰하였다. 과량으로 첨가된 PbO는 상합성 및 소결특성을 향상시킬 수 있어서 유전특성을 향상시킬 수 있었으나 과량으로 첨가된 In$_2$O$_3$에서는 그러한 결과를 얻을 수 없었다. 이러한 원인은 Pb$_3$Nb$_2$O$_{8}$을 전구체로 사용할 경우, PbO 공융액상이 페로브스카이트상 형성 직전까지 남아 있어서 활발한 PbO 휘발이 일어나는데, 과량으로 첨가된 PbO가 이를 효과적으로 보상하기 때문인 것으로 판단된다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.11
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• pp.941-948
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• 2009

The present study aims at the examination of the effects of 1 mol% NiO addition on the reaction, microstructure development, resultant electrical properties, and especially the bulk trap and interface state levels of $ZnO-Bi_2O_3-Sb_2O_3$ (Sb/Bi=0.5, 1.0, and 2.0) systems (ZBS). The samples were prepared by conventional ceramic process, and characterized by density, XRD, SEM, I-V, impedance and modulus spectroscopy (IS & MS) measurement. The sintering and electrical properties of Ni-doped ZBS (ZBSN) systems were controlled by Sb/Bi ratio. Pyrochlore ($Zn_2Bi_3Sb_3O_{14}$) was decomposed more than $100^{\circ}C$ lowered in ZBS (Sb/Bi=1.0) by Ni doping. The reproduction of pyrochlore was suppressed by the addition of Ni in ZBS. Between two polymorphs of $Zn_7Sb_2O_{12}$ spinel ($\alpha$ and $\beta$), microstructure of ZBSN (Sb/Bi=0.5) composed of a-spinel was more homogeneous than $Sb/Bi{\geq}1.0$ composed of $\beta$-spinel phase. In ZBSN, the varistor characteristics were not improved drastically (non-linear coefficient $\alpha\;=\;6{\sim}11$) and independent on microstructure according to Sb/Bi ratio. Doping of Ni to ZBS seemed to form ${V_0}^{\cdot}$ (0.33 eV) as dominant bulk defect. From IS & MS, especially the grain boundaries of Sb/Bi=0.5 systems were divided into two types, i.e. sensitive to oxygen and thus electrically active one and electrically inactive intergranular one with temperature.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.3
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• pp.211-215
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• 2010

Pulsed laser deposition is a very efficient technique for fabricating thin films of complex compounds. In the present work, $Bi_2O_3$-MgO-ZnO-$Nb_2O_5$ (BMZN) pyrochlore thin films were deposited on platinized Si substrates at various temperatures by using pulsed laser deposition technique. These films have been characterized by X-ray diffractometer (XRD), atomic force microscopy (AFM) to investigate their structural, morphological properties. MIM structure was manufactured to analyze di-electrical properties of BMZN thin films. XRD results reveal the thin films deposited at less than $400^{\circ}C$ show only amorphous phase, the crystallized thin films was observed when the thin films were prepared temperature at above $500^{\circ}C$. From AFM, it was known that the thin film grown at $400^{\circ}C$ is the densest. Dielectric constant increased with increasing temperature up to $400^{\circ}C$ at 100 kHz and dramatically decreased at the higher temperature. A aspect of dissipation factor was the exact opposite of dielectric constant. BMZN thin films grown at $400^{\circ}C$ exhibited a high dielectric constant of 60.9, a low dissipation factor of 0.007 at 100 kHz.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.4 no.2
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• pp.199-209
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• 1994

$PbTiO_3$ thin films were prepared on soda-lime-silica slide glasses, Si-wafer and sapphire substrate by the dip-coating of precursor solution. As starting materials, titanium tetra iso-propoxide and lead acetate trihydrate were used. Then acetylacetone was added to prepare stable sol. The effect of the parameters such as viscosity and composition of sol were investigated. The optical transmittance at visible range, refractive index, IR spectra were measured in varying compositions, thickness and heat treatment temperature. The crystallization of $PbTiO_3$ films were measured by using XRD and SEM. Diffusion of compositions from slide glass to thin film were investigated by using EDX, too. These sols not precipitated for 20 days. Transmittance of $PbTiO_3$ films at visible range were decreased with the increase of thickness and heat treatment temperatures, and were exhibited flat spectra. Pyrochlore type appeared in the films on slide glass and perovskite type appeared in the films on Si-wafer or sapphire at $600^{\circ}C$. Perovskite crystals transformed to $PbTi_3O_7$ phase at $800^{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.34 no.1
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• pp.31-36
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• 1997

The effects of 0 to 10mol% excess MgO addition on the microstructure and dielectric properties in 30Pb(Mg1/3Nb2/3)O3-20PbTiO3-50Pb(Mg1/2W1/2)O3 ternary system were investigated. Samples were prepared by mixed oxide and precursor methods to compare the role of excess MgO. Excess MgO enhanced grain growth and increased dielectric constant. The dielectric constant and tesmperature dependence of dielectric constant of the sample sintered at 100$0^{\circ}C$ with 5mol% MgO were above 5,000 and +25% to -50% from - 55$^{\circ}C$ to 1$25^{\circ}C$, respectively. For these specimens the phases percent were mainly perovskite and Pb2WO5, which was confirmed by XRD analysis. Also the amount of cubic pyrochlore Pb3Nb4O13 and PbWO4 were de-creased with sintering temperature and MgO addition. BSE image showed the chemical inhomogeneous dis-tribution. Crystal phase formed at each sintering temperature and the chemical inhomogeneous distribution caused the decrease of the temperature dependence of dielectric constant.

• Electrical & Electronic Materials
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• v.7 no.6
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• pp.496-503
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• 1994

In recent years Sol-Gel processing provides an interesting alternative method for the fabrication of ferroelectric thin layers and powder. PZT powder was prepared from an alkoxide-based solution by a Sol-Gel method. Gelation of synthesized complex solutions, microstructure, thermal analysis and crystallization behaviors of the calcined powder were studied in accordance with a water content and a catalyst. Especially gelation and crystallization behavior were analysed with the change of pH. The gelation time decreased as the pH of the mixed solution increased. For PZT powder with 650.deg. C heat treatment, 100% perovskite phase was formed by using either acidic or basic catalyst. By using either acidic or basic catalyst, we were able to get very fine powders of uniform shape with an average particle size of 0.8-1.mu.m.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.245-246
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• 2006

A propyl alcohol based sol-gel method was used as to replace the 2-methoxyethanol with 1,1,1 tris (hydroxymethyl) ethane for preparation of pzt piezoelectric ceramic. The powder obtained by this sol-gel process were calcined at $900^{\circ}C$ and followed by the sintering at $1100^{\circ}C$ for ca2 hrs as to reach a pyrochlore-free crystal phase. The characterization of synthesized material was carried out by the XRD analysis and the surface morphology were determined by high resolution scanning electronmicroscopy. Further, the prepared small sized pzt thin powders are likely to be used m various applications.

• Journal of the Korean Ceramic Society
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• v.29 no.9
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• pp.675-680
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• 1992

The purpose of this investigation was to study the stability of perovskite structure, the variation of electrical properties and a microstructure with varing amount of PbTiO3 additive in PZN-PT-BT system. The results are as follows: 1. The pyrochlore phase was reduced as the amount of PbTiO3 additive was increased and completely eliminated at 0.15PT in PZN-PT-BT system. 2. The aging rate was increased in proportion to tetragonality because the internal stress was increased in proportion to tetragonality. 3. On increasing the amount of PbTiO3 additive, the Curie temperature was increased in proportion to tetragonality. 4. As the amount of PT in the composition increase, the variation of dielectric constant was sharpened and the diffuseness of the transition decreased.