• Journal of the Semiconductor & Display Technology
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• v.16 no.4
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• pp.11-15
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• 2017

Red phosphors, $Sr_2Si_5N_8:Eu^{2+}$, were synthesized as a single-phase crystal structure by optimizing carbon and $Eu^{2+}$ contents in a carbothermal reduction nitridation method. With increasing $Eu^{2+}$ contents, the photoluminescence spectra were red-shifted from 600 nm peak for 1 mol% for to 700 nm for 7 mol%. It was suggested that this red shift is attributed to the energy transfer from one low-energy sited $Eu^{2+}$ (1) to other high-energy sited $Eu^{2+}$ (2). Finally, the best red sample (620 nm emission peak and 80 nm half width for 3 mole% of $Eu^{2+}$) was packaged on a Blue LED together with two additional green and yellow phosphors, the fabricated White LED showed a high color-rendering index of 90 and white color coordinates of x= 0.321 and y = 0.305.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.453-453
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• 2010

In this study, zinc germanate ($Zn_2GeO_4$) thin films has been synthesized by using radio frequency magnetron sputtering and the divalent manganese-activated luminescence was characterized. X-ray diffraction patterns of the as-deposited $Zn_2GeO_4$:Mn films showed only a broad feature, indicative of an amorphous structure. Scanning electron microscopy images revealed that the as-deposited $Zn_2GeO_4$:Mn has a smooth surface morphology. The $Zn_2GeO_4$:Mn films were found to be crystallized by annealing in air ambient at temperatures as low as $700^{\circ}C$. The annealed $Zn_2GeO_4$:Mn possessed a rhombohedral polycrystalline structure. The broad-band photoluminescent emission spectrum from 470 to 650nm was obtained at room temperature from the $Zn_2GeO_4$:Mn films. The emission peak was centered at around 535nm in the green range, which originates from the intrashell transition of manganese $3d^5$ electrons from $^4T_1$ excited-state level to the $^6A_1$ ground state. The PL emission spectrum had an asymmetric line shape, which results from the $^3d_5$ electron transitions of divalent manganese ions located at different sites of the zinc germanate host crystal lattice. Electroluminescent devices were fabricated using $Zn_2GeO_4$:Mn as an emission layer. The fabricated devices showed a green EL emission similar to the PL emission. The CIE chromaticity color coordinates of the EL emission were determined to be x=0.308 and y=0.657.

• Journal of Sensor Science and Technology
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• v.8 no.5
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• pp.359-367
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• 1999

CsI(Li) single crystals doped with 0.02, 0.1, 0.2 and 0.3 mole% lithium as an activator were grown by Czochralski method. The lattice structure of grown CsI(Li) single crystal was bcc, its lattice constant was $4.568\;{\AA}$. The absorption edge of CsI(Li) single crystal was 245 nm, and the spectral range of luminescence was $300{\sim}600\;nm$, its maximum luminescence intensity appeared at 425 nm. The energy resolutions of CsI(Li) single crystal doped with 0.2 mole% lithium were 14.5% for $^{137}Cs$(662 keV), 11.4% for $^{54}Mn$(835 keV) and 17.7% and 7.9% for $^{22}Na$(511 keV and 1275 keV), respectively. The relation formula of $\gamma$-ray energy versus energy resolution was ln (FWHM%) = -0.893lnE + 8.456 and energy calibration formula was ${\log}E_r=1.455\;{\log}(ch.)-1.277$. The phosphorescence decay time of CsI(Li) crystal doped with 0.2 mole% lithium was 0.51 s at room temperature, and its time resolution measured by CFT(constant-fraction timing method) was 9.0 ns.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.9
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• pp.546-551
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• 2016

$SrSnO_3:Tb^{3+}$ phosphor thin films were prepared on sapphire and quartz substrates in the growth temperature range of $100{\sim}400^{\circ}C$ by using the radio frequency magnetron sputtering deposition. The resulting $SrSnO_3:Tb^{3+}$ thin films were characterized by X-ray diffraction, scanning electron microscopy, ultraviolet-visible-infrared spectrophotometer, and photoluminescence spectrometer. The results indicated that the morphology, optical transmittance, band gap energy, and luminescence intensity of the phosphor thin films significantly depended on the growth temperature. All the thin films, regardless of the type of substrate, showed an amorphous behavior. As for the thin films deposited on sapphire substrate, the maximum crystallite size was obtained at a growth temperature of $400^{\circ}C$ and the strongest emission was green at 544 nm arising from the $^5D_4{\rightarrow}^7F_5$ transition of Tb3+. The average optical transmittance for all the thin films grown on sapphire and quartz substrates was decreased as the growth temperature increased from 100 to $400^{\circ}C$. The results suggest that the optimum growth temperatures for depositing highly-luminescent $SrSnO_3:Tb^{3+}$ phosphor thin films on sapphire and quartz substrates are 400 and $300^{\circ}C$, respectively.

• Korean Journal of Materials Research
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• v.24 no.12
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• pp.658-662
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• 2014

$Eu^{2+}/Dy^{3+}$-doped $Sr_2MgSi_2O_7$ powders were synthesized using a solid-state reaction method with flux ($NH_4Cl$). The broad photoluminescence (PL) excitation spectra of $Sr_2MgSi_2O_7:Eu^{2+}$ were assigned to the $4f^7-4f^65d$ transition of the $Eu^{2+}$ ions, showing strong intensities in the range of 375 to 425 nm. A single emission band was observed at 470 nm, which was the result of two overlapping subbands at 468 and 507 nm owing to Eu(I) and Eu(II) sites. The strongest emission intensity of $Sr_2MgSi_2O_7:Eu^{2+}$ was obtained at the Eu concentration of 3 mol%. This concentration quenching mechanism was attributable to dipole-dipole interaction. The $Ba^{2+}$ substitution for $Sr^{2+}$ caused a blue-shift of the emission band; this behavior was discussed by considering the differences in ionic size and covalence between $Ba^{2+}$ and $Sr^{2+}$. The effects of the Eu/Dy ratios on the phosphorescence of $Sr_2MgSi_2O_7:Eu^{2+}/Dy^{3+}$ were investigated by measuring the decay time; the longest afterglow was obtained for $0.01Eu^{2+}/0.03Dy^{3+}$.

• Journal of the Korean Ceramic Society
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• v.41 no.5
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• pp.381-387
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• 2004

Recently developed Plasma Display Panels (PDP) require phosphors of high luminance at Vacuum Ultraviolet (VUV) excitation. The present investigation developed new PDP phosphors using combinatorial chemistry method. We applied T $b^{3+}$ -activated yttrium gadolinium phosphates system to our combinatorial fine-tuning technique. As a result, the optimum composition was determined to be (G $d_{0.74}$ $Y_{0.11}$T $b_{0.15}$) $P_{1.15}$ $O_{\delta}$ through the two-step combinatorial screening process including excess phosphorous and Gd replacement. We found that the sample of the optimum composition shows a higher luminescence efficiency at VUV excitation and a shorter decay time than the commercially available Z $n_2$ $SiO_4$:Mn phosphor.

• KSBB Journal
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• v.17 no.6
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• pp.571-576
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• 2002

Recombinant E. coli DH5 ${\alpha}$/pSB311 was made by cloning the genes encoding bacterial luciferase and aldehyde substrate proteins from Photohabdus luminescense, to complement defects of Lumistox, which is normally used in bioassays to monitor toxic substances in water environmental systems. The conditions for stable light production by the recombinant strains were investigated with respect to cell growth stage, cell number, and buffer conditions. The optimum growth stage was a middle-exponential stage with an OD$_{660nm}$ value of 0.6-0.7. ADout 10$^{6}$-10$^{7}$ cells per test tube was optimum for stable light emission. The effect of buffer was not significant if an optimum viable cell number was maintained. The bioluminescence of the recombinant E. coli harboring the lux operon of Photohabdus luminescense was not affected by temperature, while the bioluminescence of Lumistox was temperature sensitive. The recombinant E. coli was more sensitive to heavy metals (Cd, Cu, Hg, Zn) than Lumistox, because it does not require high concentrations of NaCl in the buffer.

• Korean Chemical Engineering Research
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• v.52 no.2
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• pp.205-208
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• 2014

Here, we reported mass-produced organic nanowires with uniform sizes based on poly(9,9-dioctylflurorene) (PFO), poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT), (regioregular poly(3-hexylthiophene) (P3HT) which are well known as organic semiconductors for opto/electronics applications, using a melt-assisted wetting method with anodic alumina membrane. The conjugated polymer nanowires showed uniformed diameters (D=250~300 nm) and lengths ($L={\sim}30{\mu}m$) with defect free smooth surface regardless of a kinds of semiconductors. In addition, the nanowires were uniformly deposited onto glass substrates by spray-coating method. Under the UV light irradiation, PFO and F8BT nanowires showed blue and yellow emissions, respectively.

• Korean Journal of Materials Research
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• v.32 no.1
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• pp.9-13
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• 2022

Bullets flying with a light from the back are called "tracers". Tracers are ignited by the combustion gas of the propellant and emit bright light that allows the shooter to visually trace the flight path. Therefore, tracers mark the firing point for allies to assist shooters to hit target quickly and accurately. Conventional tracers are constructed with a mixture of an oxidizing agent, raw metal, and organic fuel. Upon ignition, the inside of the gun can be easily contaminated by the by-products, which can lead to firearm failure during long-term shooting. Moreover, there is a fire risk such as forest fires due to residual flames at impact site. Therefore, it is necessary to develop non-combustion type luminous material; however, this material must still use the heat generated from the propellant, so-called "thermoluminescence (TL)". This study aims to compare the TL emission of Dy³⁺, La³⁺ and Ho³⁺ doped MgB₄O₇ phosphors prepared by solid state reaction. The crystal structures of samples were determined by X-ray diffraction and matched with the standard pattern of MgB₄O₇. Luminescence of various doses (200 ~ 15,000 Gy) of gamma irradiated Dy³⁺, La³⁺ and Ho³⁺ (at different concentrations of 5, 10, 15 and 20 %) doped MgB₄O₇ were recorded using a luminance/color meter. The intensity of TL yellowish (CIE x = 0.401 ~ 0.486, y = 0.410 ~ 0.488) emission became stronger as the temperature increased and the total gamma-ray dose increased.

• Transactions on Electrical and Electronic Materials
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• v.8 no.6
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• pp.255-259
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• 2007

We have synthesized $CaS:Eu^{2+}$ phosphor by using a sealing vessel and evaluated its photoluminescence properties. The method using a sealing vessel is simple and economical in comparison with other methods reported up to date. As an activator concentration was increased from 0.1 mol% to 4 mol%, the main emission wavelength of the phosphor was increased from 642 nm to 651 nm due to the crystal field splitting of 5d levels of $Eu^{2+}$ ion. Although the same amount of $Eu_2O_3$ was used, the concentration of the activator ions, which were reduced from $Eu^{3+}\;to\;Eu^{2+}$ and substituted $Ca^{2+}$ ions, was increased with increase of firing temperature. Therefore, the main emission wavelength was also. shifted from 645 nm to 651 nm with increase of firing temperature from $1100^{\circ}C\;to\;1300^{\circ}C$. The critical distance($R_{c1}=20.65\;{\AA}$) between $Eu^{2+}$ ions calculated from the critical concentration was well matched with that($R_{c2}=19.17\;{\AA}$) calculated from the Dexter formula.