• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
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• pp.591-593
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• 2008

In this report, cerium doped lutetium aluminate ($Lu_3Al_5O_{12}$:Ce) phosphor has been synthesized by the solid state method under reduction atmosphere with mixture gas. The prepared phosphor shows a main luminescent peak at 555nm. Consequently, this phosphor is possible to be applicable to white LED lamp by InGaN chips.

• ETRI Journal
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• 제31권6호
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• pp.803-805
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• 2009

Improvement of the color rendering index (CRI) and luminance of a white alternate current powder electroluminescent (ACPEL) device has been attempted using ZnS:Cu,Cl, $Tb_3Al_5O_{12}$:Ce (TAG:Ce), and CaS:Eu phosphors with a layered structure. The device with TAG:Ce and ZnS:Cu,Cl phosphors showed a CRI of 75, with a luminance increase of about 30% depending on the thickness of the TAG:Ce. Further CRI improvement was attempted using CaS:Eu. When they were separately screen-printed, the CRI was increased up to 89 with no decrease in luminance.

• 한국전기전자재료학회논문지
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• 제20권6호
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• pp.536-540
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• 2007

The Ce-doped YAG(Yttrium Aluminum Garnet, $Y_3Al_5O_{12}$) phosphor powders were synthesized by combustion method. The luminescence, formation process and structure of phosphor powders were investigated by means of XRD, SEM and PL. The XRD patterns show that YAG Phase can form through sintering at $1000^{\circ}C$ for 2 h. This temperature is much lower than that required to synthesize YAG phase via the conventional solid state reaction method. There were no intermediate Phases such as YAP(Yttrium Aluminum Perovskite, $YAlO_3$) and YAM(Yttrium Aluminum Monoclinic, $Y_4Al_2sO_9$) observed in the sintering process. The powders absorbed excitation energy in the range $410{\sim}510\;nm$. Also, the crystalline YAG:Ce showed broad emission peaks in the range $480{\sim}600\;nm$ and had maximum intensity at 528 nm.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.386-386
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• 2012

For white light emitting diode (LED) applications, it has been reported that Y3Al5O12:Ce3+ (YAG:Ce) in nano-sized phosphor performs better than it does in micro-sized particles. This is because nano-sized YAG:Ce can reduce internal light scattering when coated onto a blue LED surface. Recently, there have been many reports on the synthesis of nano-sized YAG particles using bottom-up method, such as co-precipitation method, sol-gel process, hydrothermal method, solvothermal method, and glycothermal method. However, there has been no report using top-down method. Top-down method has advantages than bottom-up method, such as large scale production and easy control of doping concentration and particle size. Therefore, in this study, nano-sized YAG:Ce phosphors were synthesized by a high energy beads milling process with varying beads size, milling time and milling steps. The beads milling process was performed by Laboratory Mill MINICER with ZrO2 beads. The phase identity and morphology of nano-sized YAG:Ce were characterized by X-ray powder diffraction (XRD) and field-emission scanning electron microscopy (FESEM), respectively. By controlling beads size, milling time and milling steps, we synthesized a size-tunable and uniform nano-sized YAG:Ce phosphors which average diameters were 100, 85 and 40 nm, respectively. After milling, there was no impurity and all of the peaks were in good agreement with YAG (JCPDS No. 33-0040). Luminescence and quantum efficiency (QE) of nano-sized YAG:Ce phosphors were measured by fluorescence spectrometer and QE measuring instrument, respectively. The synthesized YAG:Ce absorbed light efficiently in the visible region of 400-500 nm, and showed single broadband emission peaked at 550 nm with 50% of QE. As a result, by considering above results, high energy beads milling process could be a facile and reproducible synthesis method for nano-sized YAG:Ce phosphors.

• 반도체디스플레이기술학회지
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• 제18권1호
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• pp.10-14
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• 2019

In this study, we synthesized two $Y_3Al_5O_{12}:Ce^{3+}$ phosphors ($7{\mu}m$-sized and $2{\mu}m$-sized YAG) with different sizes by controlling particles sizes of starting materials of the phosphors for white LED. In the smaller one ($2{\mu}m$-sized YAG), its photoluminescence intensity in the reflective mode was 63 % that of the bigger one ($7{\mu}m$-sized YAG); the quantum efficiencies were 93 % and 70 % for the smaller and the bigger ones. Two kinds of white LED packages with the same color coordinates were fabricated with a blue package (chip size $53{\times}30$) and two phosphors. The luminous flux of the white LED package with the smaller YAG phosphor was 92 % of that with the bigger one, indicating that the quantum efficiency of phosphor dispersed inside LED package was higher than that of the pure powder. It was consistently confirmed by the optical simulation (LightTools 6.3). It is notable according to the optical simulation that the white LED with the smaller phosphor showed 24 % higher luminous efficiency. If the smaller one had the same quantum efficiency as the bigger one (~93 %). Therefore, it can be suggested that the higher luminous efficiency of white LED can be possible by reducing the particle size of the phosphor along with maintaining its similar quantum efficiency.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.441-442
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• 2008

For this study, Yttrium aluminum garnet (YAG) particles co-doped with $Ce^{3+}$ and $Eu^{3+}$ were prepared via the combustion process using the 1:1 ratio of metal ions to reagents. The characteristics of the synthesized nano powder were investigated by means of X-ray diffraction (XRD), Scanning Electron Microscope (SEM), and photoluminescence (PL). The various YAG peaks, with the (420) main peak, appeared at all Eu concentrationin XRD patterns. The YAG phase crystallized with results that are in good agreement with the JCPDS diffraction file 33-0040. The SEM image showed that the resulting YAG:Ce,Eu powders had uniform sizes and good homogeneity. The grain size was about 50nm. The photoluminescence spectra of the YAG:Ce,Eu nanoparticles were investigated to determine the energy level of electron transition related to luminescence processes. It was composed a broad band of $Ce^{3+}$ activator into the weak line peak of $Eu^{3+}$ in YAG host. The PL intensity of $Ce^{3+}$ has the wavelengths of 480-650 nm and The PL intensity of $Eu^{3+}$ has main peak at 590nm.

• Bulletin of the Korean Chemical Society
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• 제33권4호
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• pp.1141-1146
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• 2012

Ce-doped $Y_3Al_5O_{12}$ (YAG:Ce) phosphor powder was prepared using a ${NO_3}^-$-malonic acid-$NH_4NO_3-NH_3{\cdot}H_2O$ system. The YAG:Ce precursor was ignited at $240^{\circ}C$ and the resulting powder contained YAG:Ce crystallites (42%) - active in the visible region at 460 nm - amorphous particles (53%) - inactive at visible wavelengths - and less than 3% oxide (3%) crystallite impurities. The impurities transformed to acitive YAG:Ce crystallites at above $800^{\circ}C$. At above $1000^{\circ}C$, the amorphous phase became YAG phase and isolated $Ce_2O$ crystallites emerged. The powder particles comprised < $4{\mu}m$ secondary aggregates of 20 nm primary particles. The thermal dusting of the secondary particles coincided with the aggregation of the secondary particles at above $900^{\circ}C$.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 추계학술대회 논문집
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• pp.525-528
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• 1999

The luminescence of bismuth and cerium doped yttrium aluminum based Phosphors $Y_{3}$/Al$_{5}$/O$_{12}$ and (Y$_{0.8}$/Gd$_{0.2}$)$_3$Al$_{5}$/O$_{12}$ prepared by a solid-state reaction method were studied. These samples which were fired at 1, 20$0^{\circ}C$ show the characteristic X-ray diffraction patters for the main phase(420) of YAG. This study indicates that the both flux and remained bismuth after the firing phosphor materials give rise to affect the photoluminescence properties. Therefore, it was investigated that both the XRD patterns arid the PL properties were affected by the controlling experimental process variables.riables.les.

• Progress in Superconductivity
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• 제11권2호
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• pp.123-127
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• 2010

The properties of buffer layer for thermal and chemical stability in coated conductor is a very important issue. $CeO_2$ has desirable thermal and chemical stability as well as good lattice match. In this study, $CeO_2$ was deposited by electron beam deposition. The MgO(001) single crystal and LMO buffered IBAD substrate(LMO/IBAD-MgO/$Y_2O_3/Al_2O_3$/Hastelloy) were used as substrates, which have $\Delta\phi$ values of ${\sim}8.9^{\circ}$. The epitaxial $CeO_2$ films was deposited with high deposition rate of $12{\sim}16\;{\AA}/sec$. During deposition, the change of oxygen partial pressure(${\rho}O_2$) does not cause change in c-axis texture. In case of $CeO_2$ on MgO single crystal, the substrate temperature was optimized at $750^{\circ}C$ with superior $\Delta\phi$ and $\Delta\omega$ value. Otherwise, In case of LMO buffered IBAD substrate, It was optimized at $650^{\circ}C$ with increasing its deposition thickness of $CeO_2$, which was finally obtained with best $\Delta\phi$ value of $5.5^{\circ}$, $\Delta\omega$ value of $2^{\circ}$ and Ra value of 2.2 nm.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.489-490
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• 2006

The Ce-doped YAG(Yttrium Aluminum Garnet, $Y_3Al_5O_{12}$) phosphor powders were synthesized by Sol-gel method. The luminescence, formation process and structure of phosphor powders were investigated by means of XRD, SEM and PL. The XRD patterns show that YAG phase can form through sintering at $1000^{\circ}C$ for 2h. This temperature is much lower than that required to synthesize YAG phase via the conventional solid state reaction method. There were no intermediate phases such as YAP(Yttrium Aluminum Perovskite, $YAlO_3$) and YAM(Yttrium Aluminum Monoclinic, $Y_4Al_2O_9$) observed in the sintering process. The powders absorbed excitation energy in the range 410~510nm. Also, the crystalline YAG:Ce showed broad emission peaks in the range 480~600nm and had maximum intensity at 528nm.