• Journal of the Korean Chemical Society
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• v.45 no.6
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• pp.570-576
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• 2001

The europium doped yttrium oxybromide phosphors were synthesized by solid-state reaction method. The YOBr: $Eu^{3+}$ phosphor showed a strong and narrow red emission band at 621 nm and maximum emission intensity obtained when 0.05 mol Eu ions were doped. The red emission of $Eu^{3+}$ originated from $^5D_0$ ${\rightarrow}$ $^7F_2$electric dipole transition. In order to investigate on photoluminescence behavior, several experimental skills and numerical fittings are conducted to the YOBr: $Eu^{3+}$ phosphor. The emission spectrum was measured in the UV range and then decay curve of $^5D_0$ ${\rightarrow}$ $^7F_j$transitions was examined. The energy interaction type of YOBr: $Eu^{3+}$ phosphor was dipole-dipole interaction. In addition to the calculating by critical concentration, the critical distance ($R_0$) was calculated by decay curve fitting parameter from Inokuti-Hirayamas equation, and spectral overlap method. The critical distance was 17.03, 10.51 and 7.18$\AA$ for those methods, respectively. As considering systematic error of measurements, these values are within the same order, so that the above fitting methods are plausible and recommendable.

• Journal of the Korean Society of Radiology
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• v.8 no.7
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• pp.455-459
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• 2014

We grew the $Li_6Gd(BO_3)_3:Ce^{3+}$ scintillator and determined the scintillation and thermoluminescence properties for X-rays. The emission spectrum of $Li_6Gd(BO_3)_3:Ce^{3+}$ is located in the range of 370~500 nm, peaking at 423 nm an 455 nm, due to the $4f{\rightarrow}5d$ transition of $Ce^{3+}$ ions. The fluorescence decay time of the crystal is composed three components. The fast component is 60 ns (25%), the intermediate component is 787 ns (29%) and the slow component is $5.9{\mu}s$ (46%) of the crystal. The after-glow is caused by the electron and hole traps in the crystal lattice. We determined physical parameters of the traps in the crystal. The thermoluminescence trap are composed two traps. The determined activation energy (E), kinetic order (m) and frequency factor (s) of the first trap are 0.65 eV, 1.01 and $6.9{\times}10^8s^{-1}$. And, the determined activation energy, kinetic order and frequency factor of the second trap are 0.96 eV, 1.79 and $3.1{\times}10^{12 }s^{-1}$, respectively.

• Korean Chemical Engineering Research
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• v.40 no.6
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• pp.752-756
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• 2002

Green-emitting $Zn_2SiO_4:Mn$ phosphors for PDP(Plasma Display Panel) application were synthesized by colloidal seed-assisted spray pyrolysis process. The codoping with $Gd^{3+}/Li^+$, which replaces $Si^{4+}$ site in the willemite structure, was performed to improve the luminous properties of the $Zn_2SiO_4:Mn$ phosphors. The particles prepared by spray pyrolysis process using fumed silica colloidal solution had a spherical shape, small particle size, narrow size distribution, and non-aggregation characteristics. The $Gd^{3+}/Li^+$ codoping amount affected the luminous characteristics of $Zn_2SiO_4:Mn$ phosphors. The codoping with proper amounts of $Gd^{3+}/Li^+$ improved both the photoluminescence efficiency and decay time of $Zn_2SiO_4:Mn$ phosphor particles. In spray pyrolysis, the post-treatment temperature is another factor controlling the luminous performance of $Zn_2SiO_4:Mn$ phosphors. The $Zn_{1.9}SiO_4:Mn_{0.1}$ phosphor particles containing 0.1 mol% $Gd^{3+}/Li^+$ co-dopant had a 5% higher PL intensity than the commercial product and 5.7 ms decay time after post-treatment at $1,145^{\circ}C$.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2003.11a
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• pp.161-164
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• 2003

본 연구에서는 수열합성법으로 $SrAl_2O_4:Eu$ 형광체 분말을 합성하여 이들의 발광 특성과 장잔광 특성 등에 대해서 고찰하였다. 증류수에 $Sr(NO_3)_2,\;Al(NO_3)_3{\cdot}9H_2O,\;Eu(NO_3)_3{\cdot}6H_2O$ 등의 금속염을 용해시킨 용액을 $NH_4OH$ 수용액으로 pH를 적당히 조절하고 고온 고압의 Autoclave 반응용기 내에서 반응시켰다. 이렇게 합성된 분말은 균일한 입도 분포를 나타내었으면, sub-micron 크기의 초미세 분말이었다. 합성된 $SrAl_2O_4:Eu$ 초미세 분말을 $Ar-H_2$ 가스 환원분위기에서 $1100-1400^{\circ}C$ 온도로 2시간동안 열처리시켜서 형광 특성을 나타내도록 만들었다. 분말의 여기 및 발광 특성을 측정한 길과, 발광파장을 520 nm로 고정시켜 측정한 여기스펙트럼은 $250\~450nm$의 넓은 파장영역에 걸쳐 여기가 일어났고, 발광스펙트럼은 520 nm에서 최대 피크를 나타내었다. 또한 10분간 여기 시킨 후 520 nm 파장에 대한 잔광 특성이 1000분 이상 지속되는 우수한 장잔광 특성을 나타내었다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.04a
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• pp.160-164
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• 2003

LCD를 TV 향으로 적용하기 위해서는 몇 가지 해결해야만 하는 문제가 있으며, 이중 하나가 동화상 재생시에 발생하는 잔상현상의 해결이다. LCD는 기존의 CRT와 같은 불연속 자발광 소자가 아니라, 연속수광소자로서, 잔상현상이 치명적인 약점으로 나타난다. 기종의 Monitor 대응품에서는 실제로 Monitor를 통해서 사용자가 관찰하는 이미지 정보가 정지화상 중심으로 구성되어 있기 때문에 문제가 되지 않았으나, TV의 경우 연속적인 동화상만을 취급하고 있어, 잔상현상의 해결 없이는 TV 향 제품에 적용할 수 없다. 따라서 본 연구에서는 잔상현상을 근본적으로 없애기 위해서 LCD를 CRT와 같이 불연속적의 분절적 이미지로 구동하는 방법을 실험하였으며, VIDEO 입력 신호에 대해서 16.7msec의 1Frame을 기준으로 점등 구간과 비점등 구간을 6:4로 나누어 BL(Back Light)을 점멸하는 방법을 구현하였다. 또한 종래의 CCFL(cold Cathod Flourescent Lamp)로는 점멸 속도에 대한 대응이 불가하므로, 이를 해결하기 위해서 광원의 형광체에 대해서 잔광시간특성의 개선도 동시에 실시하였다. 실험 결과 육안 및 사진촬영에서 잔상없는 화면을 얻을 수 있었으며, 응답파형 측정 결과 CRT 측정시와 마찬가지로 분절적인 이미지의 생성이 가능한 것을 알 수 있었다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.3
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• pp.315-319
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• 1999

Properties of both photoluminescence and long-phosphorescent for Eu, Dy-codoped $SrAl_2O_4$ powder phosphor synthesized by solid reaction method were investigated by PL instrument. Two intense peaks in the emission spectrum measured at 10 K are observed near 450 nm (2.755 eV) and 520 nm (2.384 eV) wavelength, but at 300 K the main peak of 520 nm wavelength is presented. After the removal of light excitation (360 nm), the excellent after-glow characteristic of the phosphorescence were obtained as a result of low decay tiem, although the after-glow intensities of phosphor vary exponentially with the times.

• Journal of the Korean Ceramic Society
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• v.35 no.10
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• pp.1101-1106
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• 1998

Various $Zn_{2-x}SiO_4$:xMn based green phosphors were investigated in association with a co-dopant. The co-dopant incorporated into the phosphors are believed to alter the internal energy state of $Zn_{2-x}SiO_4$ : xMn So that the improvement in their intensity could be expected. Phosphor samples were prepared using the solid state reaction therein raw powders are mixed in the acetone and successively fired at $1300^{\circ}C$ for 4 hour. The fired powders are also heated up to $900^{\circ}C$ for 2 hour in the reduced atmoshpere and thereby giving The fired powders are also heated up to $900^{\circ}C$ for 2 hour in the reduced atmosphere and thereby giving rise to conspicuous enhancement of radiative efficiency. Basically the 0.08 mole ratio of the Mn con-centrations has the maximum value of the intensity so that a co-dopant are added to this Mn con-centration. When the Mg is co-doped with Mn luminescent intensity is proven to be promoted significantly.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.2
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• pp.492-497
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• 2012

In this paper, we determined the scintillation and thermoluminescence properties of $Cs_2NaCeBr_6$ elpasolite scintillation crystal. The emission spectrum of $Cs_2NaCeBr_6$ is located in the range of 300 ~ 450 nm, peaking at 377 nm and 400 nm. And, the fluorescence decay time of the crystal is composed two components. The fast component is 140 ns (94%), and the slow component is 880 ns (6%) of the crystal. The after-glow is caused by the electron and hole traps in the crystal lattices. We determined thermoluminescence parameters of the traps in the crystal. The determined activation energy(E), kinetic order and frequency factor of the traps are 0.67 eV, 1.71 and $2.51{\times}10^8s^{-1}$ respectively. In this crystal, re-combination rate is more dominant phenomenon than the re-trapping rate.

• 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.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.14 no.3
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• pp.123-128
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• 2004

Both photoluminescence and the long-phosphorescent properties for $SrAl_2O_4$ : Eu$^{+2}$, $Dy^{+3}$ phosphor powder synthesized by the solid phase reaction were investigated as a function of $B_2O_3$ composition (0-10 wt%). The highest emission wavelength (520nm) of photoluminescence spectra was not affected by $B_2O_3$concentration. The highest emission intensity was obtained by the concentration of 3 wt% $B_2O_3$.After the removal of the Xenon lamp excitation (360nm), also, the excellent long-phosphorescent property of the phosphors was obtained by the concentration of 3 wt% $B_2O_3$ although the decay times for all phosphors decreased exponentially.