• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.7
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• pp.477-482
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• 2014

$CaNb_2O_6:RE^{3+}$ (RE=Sm or Eu) phosphor powders were prepared with different contents of activator ions by using solid-state reaction method. The X-ray diffraction patterns exhibited that the phosphors synthesized with different activator ions showed an orthorhombic system with a main (131) diffraction peak. The maximum size of the grain particles, determined from the measurement of scanning electron microscopy, was observed at 0.05 mol of $Eu^{3+}$ ions and at 0.01 mol of $Sm^{3+}$. As for the $Eu^{3+}$-doped phosphor powders, the excitation spectra were composed of a broad band peaked at 278 nm and several weak bands in the range of 350~500 nm, and the highest red emission spectrum was observed at 0.15 mol of $Eu^{3+}$ ions. As for the $Sm^{3+}$-activated phosphor powders, three strong emission bands under excitation at 273 nm were observed at 570, 612, and 659 nm, respectively. The intensities of all the emission bands approached maxima for 0.05 mol of $Sm^{3+}$ ions. The optical properties show that the $Eu^{3+}$- or $Sm^{3+}$-doped $CaNb_2O_6$ powders are promising red-orange emitting phosphor powders applicable to full-color photonic devices.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.1
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• pp.15-18
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• 2009

To enhance near UV-visible absorption region and to applied phosphor convert-white LEOs (PC-WLEDs), a red phosphor composed of ${Y_2}{SiO_5}:\;EU^{3+}$, $Bi^{3+}$ compounds was prepared by the conventional solid-state reaction. The photoluminescence (PL) shown that samples were excited by near UV light 395 nm for measurement of PL spectra. Emission spectra of samples have shown red emissions at 612 nm ($^5D_0{\to}^7F_2$). The enhanced near $UV{\sim}$ visible excitation spectrum with a broad band centered at 258 nm and 282 nm originated in the transitions toward the charge transfer state (CTS) due to the $Eu^{3+}-Bi^{3+}-O^{2-}$ interaction. The other excitation band at $350\;nm{\sim}480\;nm$, corresponding to the transitions $^7F_0{\to}^5L_9$ (364 nm), $^7F_0{\to}^5G_3$ (381 nm), $^7F_0{\to}^5L_6$ (395 nm), $^7F_0{\to}^5D_3$, (415 nm) and $^7F_0{\to}^5D_2$ (466 nm), occurred due to enhanced the f-f transition increasing $Bi^{3+}$ and $Eu^{3+}$ ions. The PL intensity increased with increased as concentration of $Bi^{3+}$ and the emission intensity becomes with a maximum at 0.125 mol.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.4
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• pp.87-92
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• 2007

A $CaAl_{12}O_{19}:Mn^{4+}$ red phosphor showed the highest emission intensity at a concentration of 0.02mole $Mn^{4+}$ and the high crystallinity and luminescent properties were obtained at $1600^{\circ}C$ firing temperature for 3hr. The synthesized phosphor showed a broad emission band at 658nm wavelength. Red light-emitting diodes(LEDs) were fabricated through the integration of on InGaN UV bare chip and a 1:3 ratio of $CaAl_{12}O_{19}:Mn^{4+}$ and epoxy resin in a single package. This coated LED can be applicable to make White LEDs under excitation energy of UV LED.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.1
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• pp.22-26
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• 2008

Red long persistent phosphors of $CaZrO_3$ : Pr was synthesized by a solid reaction method. $CaCO_3\;and\;ZrO_2$ were used as hosting materials and Pr was doped as luminescence center element, and $B_2O_3$ was used as flux. The XRD pattern confirmed crystalline phase of the phosphor, and photoluminescence investigation showed emission spectrum at $480{\sim}570nm\;and\;590{\sim}700nm$. Phosphor samples were synthesized with $B_2O_3$ flux concentration of 1, 5, 10%, and luminescent peak of maximum intensity at 494 nm was obtained for 1% $B_2O_3$. Luminescent peak of red color at 620 nm was of highest intensity for 10% $B_2O_3$.

• Journal of Ceramic Processing Research
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• v.20 no.1
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• pp.80-83
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• 2019

The Mn4+-activated Li2ZnSn2O6 (LZSO:Mn4+) red phosphors were synthesized by the solid-state reaction at temperatures of 1100-1400 ℃ in air. The synthesized LZSO:Mn4+ phosphors were confirmed to have a single hexagonal LZSO phase without the presence of any secondary phase formed by the Mn4+ addition. With near UV and blue excitation, the LZSO:Mn4+ phosphors exhibited a double band deep-red emission peaked at ~658 nm and ~673 nm due to the 2E → 4A2 transition of Mn4+ ion. PL emission intensity showed a strong dependence on the Mn4+ doping concentration and the 0.3 mol% Mn4+-doped LZSO phosphor produced the strongest PL emission intensity. Photoluminescence emission intensity was also found to be dependent on the calcination temperature and the optimal calcination temperature for the LZSO:Mn4+ phosphors was determined to be 1200 ℃. Dynamic light scattering (DLS) and field-effect scanning electron microscopy (FE-SEM) analysis revealed that the 0.3 mol% Mn4+-doped LZSO phosphor particles have an irregularly round shape and an average particle size of ~1.46 ㎛.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.1360-1363
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• 2006

A borate compound was adopted as new host material for $EU^{3+}$ activator. The $Eu^{3+}-doped\;YCa_3(GaO)_3(BO_3)_4$ (YCGB) phosphors were successfully synthesized. Also, their photoluminescence properties under the excitation of UV ray were measured. In the XRD patterns of the synthesized powders, most peaks were well-matched to a gaudefroyite phase. The emission of $Eu^{3+}$ in YCGB consists of a strong peak centered at 622 nm, which is attributed to $^5D_O-^7F_2$ transition of $Eu^{3+}$ and several weak peaks at near the wavelength. Optimum $Eu^{3+}$ concentration of the red phosphor under the excitation with the wavelength of 395 nm was about 75 mol%. This indicates that the red phosphor has a relatively higher critical concentration than that of the other $Eu^{3+}-doped$ phosphors. The dominant interaction character of $Eu^{3+}$ might be dipole-dipole interaction.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.04a
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• pp.151-154
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• 2003

The synthesis and luminescent properties of trivalent europium activated gadolinium oxide red phosphors by sol-gel process have been investigated. Aqueous metal nitrate solution was mixed with EDTA which was chosen by the most suitable material of sol-gel formation as chelating agents. We noticed that the samples when are heated with EDTA at a temperature of $100^{\circ}C$ for lhrs, produced brownish and crisp powders due to condensation reaction on decomposition, dehydration and formation of sol-gel. Hence, when the powder pre-heated at about $100^{\circ}C$ was then heated at $1200^{\circ}C$ for 3hrs in atmosphere, the luminescence properties of resultant $Gd_{2}O_{3}:Eu^{3+}$ phosphor was measured by SEM, FT-IT and brightness intensity was shown 20% higher than those prepared by conventional method and by other chelating agent.

• Current Optics and Photonics
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• v.1 no.2
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• pp.118-124
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• 2017

Color rendering index (CRI) and luminous efficacy (LE) are two key performance factors of white LEDs (WLED). While most recent works in optics focus on methodology to improve these factors, little attention has been dedicated to chemical composition of materials. This paper studies the effect of $Sr_{2.4}1F_{2.59}B_{20.03}O_{74.8}:Eu_{0.12},Sm_{0.048}$ phosphor (SrSm), in terms of concentration and particle size on CRI and LE of 8500 K - WLEDs. Importantly, the molar mass of the componential ions in SrSm are calculated to shed light on the connection between the chemical composition of the material of interest and the performance of WLEDs. Results show that CRI can be improved to a value of around 86 by boosting red-light components in WLEDs, for all 3 major configurations: conformal, in-cup, and remote phosphor. CRI value tends to decrease with larger size of particles, while LE value goes in the reverse direction. On the other hand, both CRI and LE appear to be reduced at higher concentration of SrSm. This light attenuation is analyzed by using the Lambert-Beer law and Mie-scattering theory.

• Journal of the Korean Ceramic Society
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• v.48 no.3
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• pp.241-245
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• 2011

A red strontium aluminate phosphor ($Sr_3Al_2O_6:Eu^{3+},Eu^{2+}$) is synthesized using a solid state reaction method in air and reducing atmosphere. The investigation of firing temperature indicates that a single phase of $Sr_3Al_2O_6$ is formed when the firing temperature is higher than $1300^{\circ}C$. The effect of firing temperature and doping concentration on luminescent properties are investigated. $Sr_3Al_2O_6$ phosphor exhibits the typical red luminescent properties of $Eu^{3+}$ and $Eu^{2+}$.

• Macromolecular Research
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• v.17 no.11
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• pp.907-911
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• 2009

To improve the moisture stability of the $CaS:Eu^{2+}$ red phosphor, surface coatings with silica nanoparticles were performed using five different methods, i.e., $P_1$, $P_2$, $P_3$, $P_4$, and $P_5$. The phosphors were coated with silica nanoparticles using a dip coating method ($P_1$) and sol-gel method ($P_2$). The phosphors were coated using a solution containing silica nanoparticles and poly(1-vinyl-2-pyrrolidone), PVP, $(P_3$). The phosphors were also coated with silica nanoparticles by reacting with the 1-vinyl-2-pyrrolidone (VP) monomer ($P_4$) or by reacting with mixtures containing VP and tetraethylorthosilicate ($P_5$). A decrease in the photoluminescence (PL) intensity was observed regardless of the coating methods. However, the moisture stability of the phosphors was enhanced by the coating when aged in a temperature-controlled humidity chamber. Among these methods, the $P_4$ (or $P_5$) method exhibited the greatest increase in moisture stability of the phosphors. The coated phosphors showed a relatively constant intensity with aging time, whereas the uncoated phosphor showed a decrease.