• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.3
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• pp.493-497
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• 1998

The synthesis of $Sr_{1-x}Eu_xAl_2O_4$ (x=0.005~0.2;mol%) phosphors and its properties of both photoluminescence and long-phosphorescent were investigated as a function of $Eu_2O_3$ composition. The peak wavelengths (520 nm) of phosphorescence spectra were found not to vary with the $Eu_2O_3$ composition (x) of $Sr_{1-x}Eu_xAl_2O_4$ crystals. Single phase of $SrAl_2O_4$ which determined by XRD and PL was obtained with the compositions of x<0.05 mol%. After the removal of light excitation (360 nm), the excellent after-glow characteristics of the phosphorescence were obtained with the $Eu_2O_3$ compositions of x<0.05 mol%, although the after-glow intensities for all phosphors vary exponentially with the times.

• Proceedings of the Materials Research Society of Korea Conference
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• 2002.11a
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• pp.173-173
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• 2002

• Journal of the Korean Chemical Society
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• v.46 no.4
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• pp.336-345
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• 2002

In this study, we have screened $Eu^{3+}$- and $Tb^{3+}$-activated candidate phosphors for PDP in the sys-tems of CaO-Gd$_2$O$_3$-Al$_2$O$_3$ by combinatorial chemistry and investigated the synthetic temperature, optimum com-position and luminescent properties about the candidate phosphors. To construct the emission intensity library by VUV PL, we have synthesized 210 different compositional samples using a polymerized-complex method. Good luminescent samples were identified by X-ray diffraction method. $Ca_$\alpha$$G$d_{0.95-$\alpha$-$\beta$}Al_$\beta$O_$\delta$$ : Eu(0.02< $\alpha$+$\beta$ <0.04) phos-phors screened as a red phosphor have good color purity than commercial phosphor. In the candidate phosphors of CaGdAl$_3O_7$ : Tb, Ca$Al_{12}O_{19}$ : Tb, Gd$_4$Al$_2O_9$ : Tb, and Gd$_3Al_5O_{12}$ : Tb CaGdAl$_3O_7$ : Tb, and Ca$Al_{12}O_{19}$ : Tb have shorter decay time than commercial phosphor.

• Electrical & Electronic Materials
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• v.5 no.3
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• pp.329-336
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• 1992

본 논문은 이방성 Sr.페라이트의 자기특성의 개선에 관하여 연구한 것이다. 시편은 SrO.nFe$_{2}$O$_{3}$의 기본조성으로서 비화학양론적 영역인 n=5.9를 택하였다. 그리고 보자력을 증가시키기 위하여 기본첨가제로서 0.7wt% CaCO$_{3}$와 0.3% wt% SiO$_{2}$를 첨가하여 하소시킨 다음 $Na_{2}$SiO$_{3}$의 량을 변화시키면서 복합첨가하였다. 한편, 위의 시료(기본첨가제와 0.5wt% $Na_{2}$SiO$_{3}$)에 Cr$_{2}$O$_{3}$ 및 $Al_{2}$O$_{3}$를 단독 및 복합첨가한 결과, 0.5wt% $Al_{2}$O$_{3}$가 단독첨가되었을 경우, 좋은 자기특성을 나타내었다. 본 연구에서 시행한 복합첨가방식에 의한 Sr.페라이트의 자기특성의 조사를 통하여 등방성의 경우, 기본조성과 기본첨가제와 0.5wt% $Na_{2}$SiO$_{3}$와 0.5wt% $Al_{2}$O$_{3}$조성에서 (BH)$_{max}$=1.15MGOe, 그리고 이방성의 경우, (BH)$_{max}$=3.23MGOe를 얻었으며 시료를 이방성화하므로서 자기특성면에서 등방성인 경우의 2~3배의 개선효과를 얻었다. 그리고 소결온도는 1210.deg.C에서 가장 좋은 특성을 나타내었으며 큐리온도는 등방성의 경우 T$_{c}$=410~420.deg.C에서 이방성의 경우 T$_{c}$=439~445.deg.C로서 약 30.deg.C가 향상되었다.

• Journal of the Korean Ceramic Society
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• v.41 no.1
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• pp.57-61
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• 2004

Zinc Oxide (ZnO) have the crystal structure of wurtzite which is semiconducting oxide with band gap energy of 3.3eV. $In_2O_3$-doped ZnO films were fabricated by electron beam evaporation at $400^{\circ}C$ and their characteristics were investigated. The content of $In_2O_3$ in ZnO films had a marked effect on the electrical properties of the films. As $In_2O_3$ content decreased. $In_2O_3$-doped ZnO films was converted amorphous into crystallized films and showed a better characteristics generally as a transparent conducting oxide. As $In_2O_3$-doped ZnO films were prepared by $In_2O_3$-doped ZnO pellet with 0.2at% of $In_2O_3$ content, the value of resistivity was about $6.0 {\times} 10^{-3} {\Omega}cm$. The transmittance was higher than 85% throughout the visible range.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.5
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• pp.187-190
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• 2023

In this study, antibacterial glasses were developed by the addition of CaO in ZnO-Na₂O-B₂O₃-SiO₂ glass system. The effect of the addition of CaO on the thermal properties, dissolution properties, surface zeta potential and antibacterial activity were analyzed. Differential thermal analysis (DTA) analysis was performed to analyze the thermophysical properties of 30ZnO-xCaO-20Na₂O-30B₂O₃-(20-x)SiO₂ (x = 0, 2, 4, 6, 8, 10 mol%). It was confirmed that the glass transition temperature decreased as the CaO content increased. The amount of released Zn²⁺ ions and surface zeta potential of glass samples increased with increasing CaO concentration. For these reasons, the antibacterial activity was dramatically improved. By the addition of CaO, we could successfully develop an antibacterial glass with 99.9 % antibacterial activity against both Escherichia coli and Staphylococcus aureus.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.138-141
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• 2004

[ $MnO_2$ ]가 첨가된 $0.9Pb(Zr_{0.5}Ti_{0.5})O_3-0.2Pb[(Zn_{0.8}Ni_{0.2})_{1/3}Nb_{2/3}]O_3$(0.8PZT-0.2PZNN) 세라믹스는 그 압전특성과 유전특성이 뛰어나지만 $1000^{\circ}C$ 이하의 낮은 소결 온도에서는 소결되지 않는다. $1000^{\circ}C$이하의 낮은 소결온도에서 소결하기 위해 CuO를 첨가한 결과, 소결온도 $920^{\circ}C$에서 소결성은 우수하였으나 그 압전 특성의 저하가 두드러졌다. 이는 XRD에서 확인한 결과에 따르면 CuO의 첨가가 우수한 MPB 조성으로 판명된 $MnO_2$ 가 첨가된 0.8PZT-0.2PZNN 세라믹스의 결정구조를 Rhombohedral 구조로 바꾸기 때문인 것으로 보였으며 이러한 문제는 PZNN의 비율을 조절하여 0.875PZT-0.125PZNN 세라믹스를 선택함으로 인해 해결할 수 있었다. 그러나 여전히 낮은 $Q_m$값을 높이기 위해서 $Al_2O_3$를 첨가하였고 그 결과 시편의 tetragonality 감소와 $Q_m$값의 증가를 확인할 수 있었으나 그 첨가량이 0.2wt% 이상일 경우에는 밀도의 감소로 인한 압전특성의 저하가 나타났다. 밀도의 향상을 위해 Zn and Ni excess 조성을 선택하였고 그 결과 0.5wt% $MnO_2$와 0.2wt% CuO 그리고 0.3wt% $Al_2O_3$를 첨가한 0.875PZT-0.125PZNN 세라믹스(Zn and Ni excess 조성)를 $920^{\circ}C$에서 소결한 경우 $k_p=0.581,\;Q_m=809,\;d_{33}=345\;pC/N\;and\;{\varepsilon}_{33}/{\varepsilon}_0=1345$의 빼어난 압전 및 유전특성과 $330^{\circ}C$의 높은 $T_c$를 보였고 그 조성의 vibration velocity는 약4.5 m/s로 나타났다.

• Korean Journal of Crystallography
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• v.8 no.2
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• pp.149-153
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• 1997

ZnO varistor based on ZnO-Bi2O3-Co3O4-MnCO3-Cr2-O3-Sb2O3 system with Sb2O3 contents were studied for grain size variation and microstructure properties. The composition of pure ZnO varistor was observed composition was inhibited owing to formation of Zn7Sb2O12 spinel phase and did not observed abnrmal grain growth. With Sb2O3 contents, the grain sizes of ZnO varistor were remarkably decreased and the microstructure had the distribution of dense and homogeneous grains.

• Korean Journal of Materials Research
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• v.5 no.4
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• pp.433-444
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• 1995

BaCe$O_{3}$를 첨가하여 용융공정으로 제조한 단결정형 Y$Ba_{2}$$Cu_{3}$$O_{x}$(1-2-3) 초전도체의 온도에 대한 자화특성을 연구하였다. 고상반응법과 용융공정으로 0에서 30wt% BaCe$O_{3}$를 1-2-3 결정내에 미세 분산시켰다. 초전도체의 자화특성은 VSM(vibrating sample magnetometer)을 사용하여 77K, 60K, 40K와 20K, 2 Tesla 자장범위에서 측정하였다. BaCe$O_{3}$를 첨가하지 않은 겨우나 5wt% BaCe$O_{3}$를 첨가한 1-2-3 결정의 경우, 77K, 외부자장이 증가시 자화율 차이가 증가하는 비정상 자화특성이 관찰된다. 측정온도가 60K에서는 제2차 최대점이 나타나는 자장값이 고자장쪽으로 이동한다. 20K와 40K의 저온에서는 비정상자화특성이 2 T의 자장범위까지 관찰되지 않았다. 15wt%와 20wt% BaCe$O_{3}$첨가한 시편에서는 자장이 증가하면 자화율차이가 단순히 감소한다. Y-Ba-Cu-O의 flux pinning 기구를 BaCe$O_{3}$첨가에 의한 미세조직변화로 설명하였다.

• Journal of the Korean Vacuum Society
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• v.19 no.5
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• pp.385-390
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• 2010

We studied the optical characteristics of ZnO:Al and $Al_2O_3$ coated ZnO nanorods. When ZnO:Al is deposited around the undoped ZnO nanorods, thermal diffusion of Al into ZnO gives rise to decrease the binding energy of neutral donor bound exciton whereas an insulating Al2O3 is coated around ZnO, we found that semiconducor-insulator interface states play an important role in optical quenching.