• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1990.10a
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• pp.65-67
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• 1990

In this study, (0.80-x)Pb($Mg_{1/3}Nb_{2/3}$)$O_3$-$PbTiO_3$-Pb($Ni_\frac{1}{2}W_\frac{1}{2}$)$O_3$ 0.05$\leq$x$\leq$0.20) ceramics were fabricated by the mixed oxide method, the sintering temperature and time were 950∼1200[$^{\circ}C$], 2[hr], respectively. The dielectric and structural properties with composition and sintering temperature were investigated for the application as multilayer ceramic capacitors. Dielectric constant of 0.70PMN-0.2PT-0.10PNW composition with repeated calcination was increased rapidly. Increasing the Pb($Mg_{1/3}Nb_{2/3}$)$O_3$-$PbTiO_3$-Pb($Ni_\frac{1}{2}W_\frac{1}{2}$)$O_3$ contents from 0.05 to 0.20 [mol], phase transition temperature was shifted from 68 to 2[$^{\circ}C$] and dielectric constant was decreased while sintered density was increased. In the specimens containing 0.10, 0.15[mol] of PNW, dielectri constants at room temperature were exhibited the highest values 11199, 10114, respectively. Resistivity of specimens were $10^{10}$ ∼ $10^{12}$($\Omega$.m) and there was no dependence on sintering temperature and composition.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.7
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• pp.581-586
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• 2007

[ $(Ba_{0.57}Sr_{0.33}Ca_{0.10})TiO_3$ ] (BSCT) powders, prepared by sol-gel method, were mixed with organic vehicle and the BSCT thick films were fabricated by the screen printing method. The structural and dielectric properties were investigated as a function of the $Yb_2O_3$ doping contents. As a result of the TG-DTA, exothermic peak was observed at around $670^{\circ}C$ due to the formation of the polycrystalline perovskite phase. All BSCT thick films showed the typical XRD patterns of a cubic polycrystalline structure. The average thickness of all BSCT thick films was about $70{\mu}m$. The grain size of the BSCT thick film doped with 0.7 mol% $Yb_2O_3$ was approximately $6.2{\mu}m$. The Curie temperature and relative dielectric constant at room temperature decreased with increasing $Yb_2O_3$ amount. Relative dielectric constant and dielectric loss of the specimen doped with 0.1 mol% $Yb_2O_3$ were 4637 and 19 % at Curie temperature, respectively.

• Applied Science and Convergence Technology
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• v.26 no.4
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• pp.70-73
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• 2017

The dielectric constant and loss of poling/non-poling was measured in the $Pb_{1-3x/2}La_x[(Mg_{1/3}Ta_{2/3})_{0.66}Zr_{0.34}]O_3$ samples. The addition of $La^{3+}$ to the $Pb_{1-3x/2}La_x[(Mg_{1/3}Ta_{2/3})_{0.66}Zr_{0.34}]O_3$ did not cause a large change in grain size. But the addition of $La^{3+}$ did show transition temperature, which shifted toward low temperature in the $Pb[(Mg_{1/3}Ta_{2/3})Zr]O_3$ systems. In addition, the dielectric and pyroelectric properties (${\varepsilon}{\sim}20000$, $p{\sim}0.03C/m^2K$) of this system using $La^{3+}$ have been greatly improved. Pyroelectrics $Pb_{0.97}La_{0.02}(Mg_{1/3}Ta_{2/3})_{0.66}Zr_{0.34}]O_3$ system was found to have a relatively high ferroelectric FOMs ($F_V{\sim}0.035m^2/C$, $F_D{\sim}0.52{\times}10^{-4}Pa^{-1/2}$) at room temperature. Spontaneous polarization showed a value of $0.27{\sim}0.35C/m^2$ in the composition added to $La^{3+}$. The piezoelectric constant ($d_{33}=350{\sim}490pC/N$) and electromechanical coupling factor ($k_P=0.25{\sim}0.35$) are obtained in $Pb_{1-3x/2}La_x[(Mg_{1/3}Ta_{2/3})_{0.66}Zr_{0.34}]O_3$ compositions with $La^{3+}$ dopant.

• Nano
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• v.13 no.11
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• pp.1850127.1-1850127.13
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• 2018

Bi metal deposited on $Bi_2MoO_6$ composite photocatalysts have been successfully synthesized via a simple reduction method at room temperature with using $NaBH_4$ as the reducing agent. The photocatalytic activity of the composite was evaluated by degradation of rhodamine B (RhB) and bisphenol A (BPA) solution under visible light. The rate constant of $Bi/Bi_2MoO_6$ composite to RhB is 10.8 times that of $Bi_2MoO_6$, and the degradation rate constant of BPA is 6.9 times of that of $Bi_2MoO_6$. Nitrogen absorption-desorption isotherm proved that the increase of specific surface area is one of the reasons for the improvement of photocatalytic degradation activity of $Bi/Bi_2MoO_6$ composites. The higher charge transfer efficiency of $Bi/Bi_2MoO_6$ is found through the characterization of the photocurrent and impedance, which are attributed to the surface plasmon resonance (SPR) effect produced by the introduction of the metal Bi monomer in the composite. Free radical capture experiments proved that cavitation is the main active species. Based on the above conclusions, a possible mechanism of photocatalytic degradation is proposed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.62-62
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• 2008

As micro-system move toward higher speed and miniaturization, requirements for embedding the passive components into printed circuit boards (PCBs) grow consistently. They should be fabricated in smaller size with maintaining and even improving the overall performance. Miniaturization potential steps from the replacement of surface-mount components and the subsequent reduction of the required wiring-board real estate. Among the embedded passive components, capacitors are most widely studied because they are the major components in terms of size and number. Embedding of passive components such as capacitors into polymer-based PCB is becoming an important strategy for electronics miniaturization, device reliability, and manufacturing cost reduction Now days, the dielectric films deposited directly on the polymer substrate are also studied widely. The processing temperature below $200^{\circ}C$ is required for polymer substrates. For a low temperature deposition, bismuth-based pyrochlore materials are known as promising candidate for capacitor $B_2Mg_{2/3}Nb_{4/3}O_7$ ($B_2MN$) multi layers were deposited on Pt/$TiO_2/SiO_2$/Si substrates by radio frequency magnetron sputtering system at room temperature. The physical and structural properties of them are investigated by SEM, AFM, TEM, XPS. The dielectric properties of MIM structured capacitors were evaluated by impedance analyzer (Agilent HP4194A). The leakage current characteristics of MIM structured capacitor were measured by semiconductor parameter analysis (Agilent HP4145B). 200 nm-thick $B_2MN$ muti layer were deposited at room temperature had capacitance density about $1{\mu}F/cm^2$ at 100kHz, dissipation factor of < 1% and dielectric constant of > 100 at 100kHz.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.8
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• pp.597-601
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• 2013

The accelerated thermal aging of a CSPE were carried out for 0, 80.82, 161.63 days at $100^{\circ}C$, which are equal to 0, 40 and 80 years of aging at $50^{\circ}C$, respectively. The volume electrical resistivities of the seawater and freshwater flooding were measured through 3-terminal circuit diagram. The volume electrical resistivities of the 0y, 40y and 80y were $2.454{\times}10^{13}{\sim}1.377{\times}10^{14}{\Omega}{\cdot}cm$, $1.121{\times}10^{13}{\sim}7.529{\times}10^{13}{\Omega}{\cdot}cm$ and $1.284{\times}10^{13}{\sim}8.974{\times}10^{13}{\Omega}{\cdot}cm$ at room temperature, respectively. The dielectric constant of the 0y, 40y and 80y were 2.922~3.431, 2.613~3.285 and 2.921~3.332 at room temperature, respectively. It is certain that the ionic ($Na^+$, $Cl^-$, $Mg^{2+}$, ${SO_4}^{2-}$, $Ca^{2+}$, $K^+$) conduction current was formed by the salinity of the seawater. The volume electrical resistivity of the cleaned CSPE via freshwater trends slightly upward with the number of dried days at room temperature. As a result, the $CH_2$ component of thermally accelerated aged CSPE decreased after seawater and freshwater flooding for 5 days respectively, whereas the atoms such as Cl, O, Pb, Al, Si, Sb, S related with the conducting ion ($Na^+$, $Cl^-$, $Mg^{2+}$, ${SO_4}^{2-}$, $Ca^{2+}$, $K^+$) component increased relatively.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.421-424
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• 2007

Dry sliding wear behavior of ultra-fine grained (UFG) plain low carbon dual phase steel, of which microstructure consists of hard martensite in a ductile ferrite matrix, has been investigated. The wear characteristics of the UFG dual phase steel was compared with that of a coarse grained dual phase steel under various applied load conditions. Dry sliding wear test were carried out using a pin-on-disk type tester at various loads of 1N to 100N under a constant sliding speed condition of 0.20m/s against an AISI 52100 bearing steel ball at room temperature. The sliding distance was fixed as 1000m for all wear tests. The wear rate was calculated by dividing the weight loss, measured to the accuracy of 10-5g by the specific gravity and sliding distance. The worn surfaces and wear debris were analyzed by SEM, EDS and profilometer. Micro-vickers hardness of the cross section of worn surfaces were conducted to analyze strain hardening underneath the contact surfaces. The wear mechanism of the UFG dual phase steel was investigated with emphasis on the unstable nature of the grain boundaries of the UFG microstructure.

• Korean Journal of Materials Research
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• v.12 no.11
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• pp.875-879
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• 2002

$Pb_{1-x}$ $Cd_{x}$ $I_2$ (x=0.0, 0.2, 0.5, 0.7, 0.9, 1.0) single crystals were grown by using Bridgman method and their structural and optical properties were investigated from the measurement of X-ray diffraction, optical absorption and photoluminescence. As-grown single crystals have hexagonal closed packed layered structure. The values of lattice constant c decrease with increasing composition x. Direct and indirect transition optical energy band gaps are calculated from optical absorption spectra measured at room temperature. They increase exponentially from 2.3eV to 3.2 eV with increasing composition x. The energies of photoluminescence peak due to donor bound exciton measured at 6K increase with increasing composition . However, the peak energies of donor-acceptor pair (DAP) are independent of the optical energy band gaps of $Pb_{1-x}$/$Cd_{x}$ $I_2$ single crystals.

• Journal of the Korean Magnetics Society
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• v.5 no.2
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• pp.123-127
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• 1995

$CuFe_{2}O_{4}$ was accomplished by chemical rrethod and the crystallographic and magnetic properties have been studied by $M\"{o}ssbauer$ spectroscopy and X-ray diffraction. The slowly cooled sample is found to have a tetragonal spinel structure with the lattice constant $a=8.26{\pm}0.05{\AA},\;c=8.75{{\pm}}0.05{\AA}$. The $M\"{o}ssbauer$ spectra between the room temperature to the Curie temperature show that the $Cu_{2+}$ ions at octahedral site have the Jahn-Teller effect and the sample exhibits a structural phase transition near 630K due to the Jahn-Teller effect. The Curie temperature is found to be 690K and it is lower than that of ceramic method.

• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1022-1024
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• 1995

In this study, $Pb(Zr_xTi_{1-x})O_3$(x=0.65, 0.52, 0.35) thin films were fabricated by Sol-Gel method. A stock solution with excess Pb 10[mol.%] of $Pb(Zr_xTi_{1-x})O_3$ was made and spin-coated on the Pt/$SiO_2$/Si substrate at 4000[rpm] for 30[sec.]. Coated specimens were dried on the hot-plate at $400[^{\circ}C]$ for 10[min.]. Sintering temperature and time were $500{\sim}800[^{\circ}C]$ and $1{\sim}60$[min.]. To investigate crystallization condition, PZT thin films were analyzed with sintering temperature, time and composition by the XRD. The microstructure of thin films were investigated by SEM. The ferroelectric perovskite phases precipitated under the sintering of $700[^{\circ}C]$ for 1 hour. In the PZT(52/48) composition, dielectric constant and dielectric loss were 2133, 2.2[%] at room temperature, respectively.