• 한국재료학회지
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• 제10권3호
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• pp.204-211
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• 2000

초음파 분무법으로 $(Y,Gd)BO_3:Eu$의 PDP 적색 형광체를 제조하여 147nm VUV 여기에 따른 발광 특성을 분석하였다. 초음파 분무에 사용된 전구체 용액은 Y, Gd, Eu의 아세트산염과 $H_3BO_3$를 증류수에 용해하여 1.7MHz의 초음파 분무기로 고온의 반응관내로 분무하였다. 분무된 액적은 반응관내에서 통과시 불충분한 반응으로 C-C와 C-H를 함유한 비정질 상이었으나, $1100^{\circ}C$에서 추가 열처리 한 시편은 고상반응법으로 제조한 형광체와 동일한 결정구조와 성분을 보였다. 고상반응법으로 제조한 형광체의 분말 크기는 $3{\mu\textrm{m}}$으로 조대하고 불균일한 분포를 보인 반면, $500^{\circ}C$에서 분무한 후 $900^{\circ}C$에서 열처리하여 제조한 $(Y_{0.7}Gd_{0.3})_{0.95}BO_3:Eu_{0.05}\;^{3+}$ 형광체의 모양은 비교적 구형이었으며 평균 입자크기는 $0.7{\mu\textrm{m}}$로 미세하고 균일한 분포를 하고 있었다. 147nm VUV 여기시 초음파 분무로 제조한 $(Y_{0.7}Gd_{0.3})_{0.95}BO_3:Eu_{0.05}\;^{3+}$ 형광체의 적색 발광강도는 고상반응법으로 제조한 시편이나 상용품인 $(Y,Gd)BO_3:Eu$ 형광체에 비해 그 휘도가 증가되었다.

• 한국분말재료학회지
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• 제27권2호
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• pp.146-153
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• 2020

The co-doping effect of aliovalent metal ions such as Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, and Zn²⁺ on the photoluminescence of the Y₂O₃:Eu³⁺ red phosphor, prepared by spray pyrolysis, is analyzed. Mg²⁺ metal doping is found to be helpful for enhancing the luminescence of Y₂O₃:Eu³⁺. When comparing the luminescence intensity at the optimum doping level of each Mg²⁺ ion, the emission enhancement shows the order of Zn²⁺ ≈ Ba²⁺ > Ca²⁺ > Sr³⁺ > Mg²⁺. The highest emission occurs when doping approximately 1.3% Zn²⁺, which is approximately 127% of the luminescence intensity of pure Y₂O₃:Eu³⁺. The highest emission was about 127% of the luminescence intensity of pure Y₂O₃:Eu³⁺ when doping about 1.3% Zn²⁺. It is determined that the reason (Y, M)₂O₃:Eu³⁺ has improved luminescence compared to that of Y₂O₃:Eu³⁺ is because the crystallinity of the matrix is improved and the non-luminous defects are reduced, even though local lattice strain is formed by the doping of aliovalent metal. Further improvement of the luminescence is achieved while reducing the particle size by using Li₂CO₃ as a flux with organic additives.

• 한국응용과학기술학회지
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• 제24권3호
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• pp.238-245
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• 2007

$Eu^{3+}$ doped $YGdO_3$ phosphors particles which have fine size and narrow size distribution with non aggregated uniform morphology were prepared by solvent evaporation method for the improvement of emission efficiency. Several parameters have been investigated in this study such as the influences of composition ratio of host materials, calcination temperature, amount of activator, surfactant, pH and flux on the photoluminescence intensity, particle size and dispersion. $Eu^{3+}$ doped $YGdO_3$ phosphor presented a strong narrow band emission peak at 612nm. The maximum emission intensity of$YGdO_3:Eu^{3+}$ occurred when $Eu^{3+}$ concentration is 3wt% under vacuum ultra violet excitation. Prepared phosphors were found to have small round-shaped particles about 150nm in size. The addition of PVA as a surfactant inhibits the grain growth and the agglomeration of particles efficiently by reducing the oxygen bridge bonds. As the pH reduces, PL intensity increase due to reducing the formation of oxygen bridge bonds. The particles prepared from solvent evaporation method with 5wt% LiCl were found to have 120% PL intensity compare to particles prepared without LiCl flux.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 추계학술대회 논문집
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• pp.566-569
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• 1999

The blue emitting BAM Phosphor Particles with various compositions were Prepared by the spray Pyrolysis. The effect of composition on the morphology of BAM particles was Investigated. In the case of BaMgAl$_{10}$ /O$_{22}$ : Eu$^{2+}$, the morphology of particles with sphericity and non-aggregation characteristics disappeared after post-treatment at 1400 $^{\circ}C$ for 3 hrs. On the other hand, the ocher composition particles except BaMgAl$_{10}$ /O$_{22}$ : Eu$^{2+}$ maintained their original morphology after post-treatment, even if the particles were prepared at low temperatures in the spray pryrolysis. The BAM particles with MgAl$_{2}$/O$_4$as intermediate material at low post-treatment temperature had high thermal stability and maintained sphericity of particles after post-treatment. All the samples had main omission peak at 450 nm, which corresponds to blue emission. The optimum post-treatment temperature of BAM:Eu$^{2+}$ particles for the maximum PL(photoluminescence) intensity in the spray pylolysis was 1200 $^{\circ}C$ because of high crystallinity, Phase-Purity, and good morphology.ology.

• 공업화학
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• 제26권3호
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• pp.319-325
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• 2015

분무열분해법을 이용하여 서브 미크론 크기의 $CeO_2:Er^{3+}/Yb^{3+}$ 상향 변환 형광체 입자를 합성하고 $Er^{3+}$ 및 $Yb^{3+}$ 농도 변화에 따른 발광특성을 조사하였다. 합성한 $CeO_2:Er^{3+}/Yb^{3+}$는 $Er^{3+}$ 활성이온의 $^4S_{3/2}/^2H_{11/2}{\rightarrow}^4I_{15/2}$ 및 $^4F_{9/2}{\rightarrow}^4I_{15/2}$ 전이에 기인한 강한 녹색 및 적색 발광을 보였다. 가장 높은 발광을 보이는 활성제 농도는 Er = 1.0% 그리고 Yb = 2.0%이며, 농도소광 현상은 쌍극자-쌍극자 상호작용을 통해 일어남이 확인되었다. 레이저 다이오드 여기 광 세기에 대한 발광강도 의존성을 활성이온 농도에 따라 조사하였고, 발광 중간 에너지 레벨의 주 소멸과정을 고려하여 발광 메커니즘을 조사하였다. $Yb^{3+}$에서 $Er^{3+}$으로 에너지 전달은 바닥 상태 흡수(ground state absorption, GSA)에 기여하고, $Yb^{3+}$ 도핑은 $^4I_{11/2}{\rightarrow}^4I_{13/2}$ 전이를 가속화시켜 적색/녹색 발광세기 비를 상승시킨다. 최종적으로 분무열분해법으로 제조된 $CeO_2:Er^{3+}/Yb^{3+}$ 형광체의 발광은 선형 감쇠가 중간 에너지 레벨의 고갈을 지배하는 2 광자 프로세스에 의해 일어남을 확인하였다.

• Korean Chemical Engineering Research
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• 제40권6호
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• pp.752-756
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• 2002

PDP(Plasma Display Panel)용 녹색 형광체인 $Zn_2SiO_4:Mn$ 형광체의 제조에 있어 콜로이드 분무 열분해법을 도입하고, $Zn_2SiO_4$ wellimite 결정의 $Si^{4+}$ 자리를 치환하는 $Gd^{3+}/Li^+$ 부활성제를 첨가하여 형광체의 발광특성을 향상시키고자 하였다. 14 nm 크기의 fumed silica 입자를 규소 전구체로 도입한 콜로이드 분무열분해법에 의해서 제조되어진 $Zn_2SiO_4:Mn$ 입자는 응집이 없는 구형의 형상, 작은 입자 크기 및 좁은 입도 분포를 가졌다. $Gd^{3+}/Li^+$ 함량은 $Zn_2SiO_4:Mn$ 형광체 입자의 발광특성에 영향을 끼쳤으며, 적정한 함량의 $Gd^{3+}/Li^+$ 부활성제를 첨가함으로써 진공 자외선하에서 형광체의 발광휘도를 향상시키고, 잔광시간을 크게 줄일 수 있었다. 분무 열분해법에 의한 $Gd^{3+}/Li^+$이 코도핑된 $Zn_2SiO_4:Mn$ 형광체 입자의 제조에 있어서 후열처리 온도는 형광체의 발광특성을 결정짓는 주요한 인자이다. 0.1 mol%의 $Gd^{3+}/Li^+$ 부활제를 포함하고 $1,145^{\circ}C$ 온도에서 소결된 $Zn_2SiO_4:Mn$ 형광체 입자는 상업용 형광체에 비해 5% 높은 발광 휘도과 5.7 ms의 잔광시간을 가졌다.

• 한국재료학회지
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• 제24권9호
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• pp.469-473
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• 2014

$SrSnO_3$ phosphor powders were synthesized with two different contents of activator ions $Eu^{3+}$ and $Tb^{3+}$ using the solid-state reaction method. The structural, morphological, and optical properties of the phosphors were investigated using X-ray diffractometry, field-emission scanning electron microscopy, and fluorescence spectrophotometry, respectively. All the phosphors showed a cubic structure, irrespective of the type and the content ratio of activator ions. For $Eu^{3+}$-doped $SrSnO_3$ phosphors, the intensity of the 620 nm red emission spectrum resulting from the $^5D_0{\rightarrow}^7F_2$ transition of $Eu^{3+}$ was stronger than that of the 595 nm orange emission signal due to the $^5D_0{\rightarrow}^7F_1$ transition in the range 0.01-0.05 mol of $Eu^{3+}$, but the ratio of the intensity was reversed in the range 0.10-0.20 mol of $Eu^{3+}$. The variation in the emission intensity indicates that the site symmetry of the $Eu^{3+}$ ions around the host crystal was changed from non-inversion symmetry to inversion. For the $Tb^{3+}$-doped $SrSnO_3$ phosphors under excitation at 281 nm, one strong green emission band at 550 nm and several weak bands were observed. These results suggest that the optimum red and green emission signals can be realized when the activator ion content for $Eu^{3+}$- or $Tb^{3+}$-doped $SrSnO_3$ phosphors is 0.20 mol and 0.15 mol, respectively.

• 한국표면공학회지
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• 제50권3호
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• pp.206-211
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• 2017

$BiNbO_4:RE^{3+}$ (RE = Dy, Eu, Sm, Tb) phosphors were prepared by solid-state reaction at $1100^{\circ}C$ and their structural, photoluminescent, and morphological properties were investigated. XRD patterns exhibited that all the synthesized phosphors exhibited a triclinic system with a dominant (210) diffraction peak, irrespective of the type of activator ions. The surface morphologies of rare-earth-ion-doped $BiNbO_4$ phosphors were found to depend strongly on the type of activator ions. The $Eu^{3+}$ and $Dy^{3+}$ doped $BiNbO_4$ phosphors revealed a strong red (613 nm) emission resulting from the $^5D_0{\rightarrow}^7F_2$ transition of $Eu^{3+}$ and a dominant yellow (575 nm) emission originating from the $^4F_{9/2}{\rightarrow}^6H_{13/2}$ transition of $Dy^{3+}$ respectively, which were the electric dipole transitions, indicating that the activator ions occupy sites of non-inversion symmetry in the $BiNbO_4$ phosphor. The main reddish-orange emission spectra of $Sm^{3+}$-doped $BiNbO_4$ phosphors were due to the $^4G_{5/2}{\rightarrow}^6H_{7/2}$ (607 nm) magnetic dipole transition, indicating that the $Sm^{3+}$ ions were located at inversion symmetry sites in the $BiNbO_4$ host lattice. As for $Tb^{3+}$-doped phosphors, green emission was obtained under excitation at 353 nm and its CIE chromaticity coordinates were (0.274, 0.376). These results suggest that multicolor emission can be achieved by changing the type of activator ions incorporated into the $BiNbO_4$ host crystal.

• Imaging Science in Dentistry
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• 제45권2호
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• pp.81-87
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• 2015

Purpose: Contrast, sharpness, enhancement, and density can be changed in digital systems. The important question is to what extent the changes in these variables affect the accuracy of caries detection. Materials and Methods: Forty eight extracted human posterior teeth with healthy or proximal caries surfaces were imaged using a photostimulable phosphor (PSP) sensor. All original images were processed using a six-step method: (1) applying "Sharpening 2" and "Noise Reduction" processing options to the original images; (2) applying the "Magnification 1:3" option to the image obtained in the first step; (3) enhancing the original images by using the "Diagonal/"option; (4) reviewing the changes brought about by the third step of image processing and then, applying "Magnification 1:3"; (5) applying "Sharpening UM" to the original images; and (6) analyzing the changes brought about by the fifth step of image processing, and finally, applying "Magnification 1:3." Three observers evaluated the images. The tooth sections were evaluated histologically as the gold standard. The diagnostic accuracy of the observers was compared using a chi-squared test. Results: The accuracy levels irrespective of the image processing method ranged from weak (18.8%) to intermediate (54.2%), but the highest accuracy was achieved at the sixth image processing step. The overall diagnostic accuracy level showed a statistically significant difference (p=0.0001). Conclusion: This study shows that the application of "Sharpening UM" along with the "Magnification 1:3" processing option improved the diagnostic accuracy and the observer agreement more effectively than the other processing procedures.

• 한국재료학회지
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• 제23권1호
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• pp.31-34
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• 2013

Trivalent cerium-ion-doped $Y_3(Al,\;Ga)_5O_{12}$ nanoparticle phosphor nanoparticles were synthesized using the reverse micelle process. The Ce doped $Y_3(Al,\;Ga)_5O_{12}$ particles were obtained from nitrate solutions dispersed in the nanosized aqueous domains of a micro emulsion consisting of cyclohexane as the oil phase and poly(oxyethylene) nonylphenyl ether (Igepal CO-520) as the non-ionic surfactant. The crystallinity, morphology, and thermal properties of the synthesized $Y_3(Al,\;Ga)_5O_{12}:Ce^{3+}$ powders were characterized by thermogravimetry-differential thermal analysis (TGA-DTA), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), and transmission electron microscopy. The crystallinity, morphology, and chemical states of the ions were characterized; the photo-physical properties were studied by taking absorption, excitation, and emission spectra for various concentrations of cerium. The photo physical properties of the synthesized $Y_3(Al,\;Ga)_5O_{12}:Ce^{3+}$ powders were studied by taking the excitation and emission spectra for various concentrations of cerium. The average particle size of the synthesized YAG powders was below $1{\mu}m$. Excitation spectra of the $Y_3Al_5O_{12}$ and $Y_3Al_{3.97}Ga_{1.03}O_{12}$ samples were 485 nm and 475 nm, respectively. The emission spectra of the $Y_3Al_5O_{12}$ and $Y_3Al_{3.97}Ga_{1.03}O_{12}$ were around 560 nm and 545 nm, respectively. $Y_3(Al,\;Ga)_5O_{12}:Ce^{3+}$ is a red-emitting phosphor; it has a high efficiency for operation under near UV excitation, and may be a promising candidate for photonic applications.