• 한국세라믹학회지
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• 제53권4호
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• pp.463-467
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• 2016

$Si^{4+}-N^{3-}$ was incorporated into $Ce^{3+}-doped$ lutetium aluminum garnet ($Lu_{2.965}Ce_{0.035}Al_5O_{12}$, $LuAG:Ce^{3+}$) lattices, resulting in the formation of $Lu_{2.965}Ce_{0.035}Al_{5-x}Si_xO_{12-x}N_x$ [(Lu,Ce)AG:xSN]. For x = 0-0.25, the synthesized powders consisted of the LuAG single phase, and the lattice constant decreased owing to the smaller $Si^{4+}$ ions. However, for x > 0.25, a small amount of unknown impurity phases was observed, and the lattice constant increased. Under 450 nm excitation, the PL spectrum of $LuAG:Ce^{3+}$ exhibited the green band, peaking at 505 nm. The incorporation of $Si^{4+}-N^{3-}$ into the $Al^{3+}-O^{2-}$ sites of $LuAG:Ce^{3+}$ led to a red-shift of the emission peak wavelength from 505 to 570 nm with increasing x. Corresponding CIE chromaticity coordinates varied from the green to yellow regions. These behaviors were discussed based on the modification of the $5d^1$ split levels and crystal field surroundings of $Ce^{3+}$, which arose from the Ce-(O,N)8 bonds.

• 반도체디스플레이기술학회지
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• 제18권4호
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• pp.51-56
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• 2019

LuAG:Ce(Lu₃Al₅O₁₂:Ce³⁺) nano phosphor were synthesized by applying the coprecipitation method. It is used to increase the color rendering of phosphor ceramic plate for high power LEDs and laser lighting. Internal quantum efficiency and absorption of LuAG:Ce nano phosphor are 51.5 % and 64.4 %, respectively, which is higher than the previously studied nano phosphors. The maximum absorption wavelength of this phosphor is 450 nm blue light, and the emission wavelength is 510 nm. The emission wavelength shifted to longer wavelength when the concentration of Ce increased in the heat treatment of the reducing atmosphere. Thermal quenching of LuAG nano phosphor was 70 % at 200 ℃, it was explained by their significant quenching of all raman scattering modes, implying the restriction of electron-phonon couplings caused by their defects.

• 한국결정성장학회지
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• 제25권3호
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• pp.121-126
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• 2015

A novel $Ce^{3+}$ doped $Lu_3MgAl_3SiO_{12}$ phosphor ($Lu_{2.94}Ce_{0.06}MgAl_3SiO_{12}$) was successfully synthesized by a conventional solid-state reaction at $1450^{\circ}C$ for 5 h. The crystal structure of the synthesized phosphor powder was characterized by X-ray diffraction and Rietveld refinement. The prepared phosphor powder showed a broad peak at 550 nm, and the temperature dependence on photoluminescence properties of the prepared $Lu_{2.94}Ce_{0.06}MgAl_3SiO_{12}$ phosphor was investigated from 300 to 525 K. The activation energy for thermal quenching was determined by Arrhenius fitting. The experimental results clearly indicate that prepared $Lu_{2.94}Ce_{0.06}MgAl_3SiO_{12}$ phosphor has great potential for a down-conversion yellow phosphor in white light-emitting diodes.

• Nuclear Engineering and Technology
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• 제55권12호
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• pp.4642-4646
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• 2023

The Tb³⁺ or Eu³⁺-doped Lu₂Gd₁Ga₂Al₃O₁₂ phosphor were fabricated by funace at 1500 ℃ for 12 h using a solid state reaction. The XRD (X-ray diffraction_Panalytical X'Pert Pro) and FE-SEM (field emission scanning electron microscope) are measured to confirm the crystalline structure and surface morphology of the phosphor. The Tb³⁺-doped Lu₂Gd₁Ga₂Al₃O₁₂ phosphor emits the lights in 470~650 nm wavelength range due to transitions from ⁵D₄ to ⁷F_j. Therefore, it shows the green region in the CIE chromaticity diagram under both UV and X-rays excitations. The Eu³⁺-doped Lu₂Gd₁Ga₂Al₃O₁₂ phosphor emits the lights in 550~750 nm wavelength range because of ⁵D_i to ⁷F_j. The emission is confirmed to be in the red region using the CIE chromaticity diagram. The Tb³⁺ or Eu³⁺-doped Lu₂Gd₁Ga₂Al₃O₁₂ phosphor shows the characteristic f-f transition with a long decay time, which is about several milliseconds. They have the high efficiency of light emission for X-ray because of their high effective Z number (Z_eff = 58.5) and density. Therefore, they are very much promising phosphors for X-ray imaging application in medical fields.

• 한국재료학회지
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• 제30권8호
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• pp.413-420
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• 2020

Lu₃Al_5-xGa_xO₁₂:Ce³⁺,Cr³⁺ powders are prepared using a solid-state reaction method. To determine the crystal structure, Rietveld refinement is performed. The results indicate that Ga³⁺ ions preferentially occupied tetrahedral rather than octahedral sites. The lattice constant linearly increases, obeying Vegard's law, despite the strong preference of Ga³⁺ for the tetrahedral sites. Increasing x led to a blue-shift of the Ce³⁺ emission band in the green region and a change in the emission intensity. Persistent luminescence is observed from the powders prepared with x = 2-3, occurring through a trapping and detrapping process between Ce³⁺ and Cr³⁺ ions. The longest persistent luminescence is achieved for x = 2; its lifetime is at least 30 min. The findings are explained using crystal structure refinement, crystal field splitting, optical band gap, and electron trapping mechanism.

• 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.

• 한국결정성장학회지
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• 제26권1호
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• pp.14-18
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• 2016

$Ce^{3+}$ 이온을 도핑한 $(Ce_xLu_{1-x})_3MgAl_3SiO_{12}$ 형광체 샘플을 고상합성법으로 합성하였다. 열처리 온도를 1250부터 $1550^{\circ}C$ 온도영역에서 조절하면서 5 h 동안 소성하였으며, 소성된 샘플들의 XRD와 PL 특성을 조사하여 가장 최적의 열처리 온도를 구하고자 하였다. 또한 $Ce^{3+}$ 이온의 도핑농도를 2.0에서 10.0 mol%로 변화시키면서 $Ce^{3+}$ 이온의 도핑농도와 광학적 특성과의 관계를 고찰하였다. $Ce^{3+}$ 이온의 도핑농도에 따른 형광체들의 PL 강도, 피크위치, 반치폭을 계산하여 실제적인 LED 패키징에 가장 적절한 Ce 도핑 농도를 구하고자 하였다. 또한 최적의 소성온도와 Ce 도핑농도 조건에서 합성한 형광체 샘플의 입도와 입형을 분석하였다.

• Journal of Magnetics
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• 제13권1호
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• pp.19-22
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• 2008

ZnO nanotips, grown on c-$Al_2O_3$ and quartz, were implanted variously with 200 keV Fe or Mn ions to a dose level of $5{\times}10^{16}cm^{-2}$. The magnetic properties of these samples were measured using a superconducting quantum interference device (SQUID) magnetometer. Fe-implanted ZnO nanotips grown on c-$Al_2O_3$ showed a coercive field width of 209 Oe and a remanent field of 12% of the saturation magnetization ($2.3{\times}10^{-5}emu$) at 300K for a sample annealed at $700^{\circ}C$ for 20 minutes. The field-cooled and the zero-field-cooled magnetization measurements also showed evidence of ferromagnetism in this sample with an estimated Curie temperature of around 350 K. The Mn-implanted ZnO nanotips grown on c-$Al_2O_3$ showed superparamagnetism resulting from the dominance of a spin-glass phase. The ZnO nanotips grown on quartz and implanted with Fe or Mn showed signs of ferromagnetism, but neither was consistent.

• 자원환경지질
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• 제42권3호
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• pp.177-193
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• 2009

삼광광상은 선캠브리아기 경기육괴의 화강편마암내에 발달된 단열대(NE, NW)를 따라 충진한 8개의 괴상맥으로 구성된 중열수 석영맥광상이다. 이 광상의 광화작용은 여러번의 단열작용에 의해 형성된 두시기의 석영+방해석시기(광화I시기)와 방해석시기(광화II시기)로 구성된다. 광화I시기의 열수작용에 의한 변질작용은 견운모화, 녹니석화, 탄산염화, 황철석화, 규화, 및 점토화작용등이 관찰되며 견운모대는 석영맥과 접촉한 부분에서 녹니석대는 석영맥으로부터 멀어짐에 따라 관찰된다. 견운모대의 모암변질광물은 대부분이 견운모 및 석영이며 일부 일라이트, 탄산염광물, 녹니석으로 구성된다. 녹니석대의 모암변질광물은 주로 녹니석, 석영과 소량 견운모, 탄산염광물 및 녹염석으로 구성된다. 견운모의 Fe/(Fe+Mg) 값은 0.45${\sim}$0.50(0.48$\pm$0.02)이며 백운모-펜자이트족에 해당되고 녹니석의 Fe/(Fe+Mg) 값은 0.74${\sim}$0.81(0.77$\pm$0.03)이고 대부분 브런스비자이트에 해당된다. 견운모와 녹니석에 대한 $Al_{IV}$-FE/(FE+Mg)의 다이어그램은 변질시 같은 광종의 견운모와 녹니석의 형성온도를 나타내는 지시자로써 유용하다. 이것은 계산된 녹니석 단종의 활동도가 $a3(Fe_5Al_2Si_3O_{10}(OH)_6$=0.0275${\sim}$0.0413, $a2(Mg_5Al_2Si_3O_{10}(OH)_6$=1.18E-10${\sim}$7.79E-7, $a1(Mg_6Si_4O_{10}(OH)_6$=4.92E-10${\sim}$9.29E-7로서 삼광광상의 녹니석은 iron-rich 녹니석으로 비교적 고온 (T>450$^{\circ}C$에서 모암과 평형상태에서 온도가 감소함에 따라 형성되었음을 알 수 있다. 모암변질시 ${\alpha}Na^+$, ${\alpha}K^+$, ${\alpha}Ca^{2+}$ 및 ${\alpha}Mg^{2+}$는 각각 ${\alpha}Na^+$=0.0476($400^{\circ}C$), 0.0863($350^{\circ}C$), ${\alpha}K^+$=0.0154($400^{\circ}C$), 0.0231($350^{\circ}C$), ${\alpha}Ca^{2+}$=2.42E-11($400^{\circ}C$), 7.07E-10($350^{\circ}C$), ${\alpha}Mg^{2+}$=1.59E-12($400^{\circ}C$), 1.77E-11($350^{\circ}C$)이며 열수용액의 pH는 5.4${\sim}$6.4($400^{\circ}C$), 5.3${\sim}$5.7($350^{\circ}C$)로서 모암변질시 열수용액는 약산성이었음을 알 수 있다. 모암변질시 이득원소(부화원소)는 $TiO_2$, $Fe_2O_3(T)$,CaO, MnO, MgO, As, Ag, Cu, Zn, Ni, Co, W, V, Br, Cs, Rb, Sc, Bi, Nb, Sb, Se, Sn 및 Lu 등이며 특히 대부분의 광상에서 Ag, As, Zn, Sc, Sb, S,$CO_2$ 등의 원소가 현저하게 증가하므로 중열수 및 천열수 금-은광상의 탐사에 지시원소로서 활용될 수 있을 것이다.

• 동굴
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• 제45권46호
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• pp.9-31
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• 1996

The Mt. Peakdu is situated in north of the main peninsula, commanding geographically coordinated between longitude W($127^{\circ}$ 15' - $128^{\circ}$ 00') to E($128^{\circ}$ 15'- $129^{\circ}$ 00'), between latitude from S($41^{\circ}$ 15'- $42^{\circ}$ 00') to N($42^{\circ}$ 10'- $42^{\circ}$ 40'). The Manjyang-Gul in Cheju volcanic island is situated in the south of the main peninsula, commanding the Korean Strait, geographically coordinated longitude N($33^{\circ}$ 32' 26") and E($126^{\circ}$ 46' 48"). The quantitative analysis using XRF of volcanic rock samples for the north of Lu- Ming- Feng in Mt. Peakdu Group and the Manjang-Gul in Cheju island was Performed. The major chemical components by group analysis are as follows; Peakdu-Mt. Cheju Peakdu-Mt. Cheju (1) $Na_2O$(3.29Wt% and 3.27Wt%) (2) MgO (3.95Wt% and 6.l5Wt%) (3) $Al_2O_3$((17.64Wt% and 15.l7Wt%) (4) $SiO_2$((50.62Wt% and 50.99Wt%) (5) $P_2O_5$ (0.36Wt% and 0.30Wt%) (6) $K_2O$ (1.37Wt% and 1.04Wt%) (7) CaO (8.56Wt% and 8.06Wt%) (8) $TiO_2$ (2.37Wt% and 2.l5Wt%) (9) MnO (0.llWt% and 0.l6Wt%) (10) $Fe_2O_3$(9.l2Wt% and 12.56Wt%) The Group analysis data were compared in the relation within the age of formation for $0.16{\pm}0.08Ma$ in Mt. Peakdu Group, and $0.42{\pm}42Ma$ or $0.42{\pm}42Ma$ in Cheju island for K-Ar age. The crystal structure are mixed crystal of monoclinic, hexagonal and triclinic system in Mt. Peakdu Group and mixed structure of triclinic and cubic system in Cheju volcanic island.ic island.