• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.228-231
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• 2017

The surface temperature of a combustor such as an aircraft engine is one of the important measuring factors related to the combustion performance. However, a conventional temperature measurement technique have a large measurement error due to a bad environment such as a combustion flame, vibration, and dust. In order to solve this problem, a technology has been developed which can measure the surface temperature of the combustor in real time using the wavelength change or attenuation time change according to the temperature of the phosphor. In this study, we developed a technique that can measure surface temperature of scram-jet combustor using phosphor thermometry. The calibration curve was obtained according to the temperature from $200^{\circ}C$ to $800^{\circ}C$ in the calibrated temperature chamber. So, we confirmed that phosphor thermometry can be used for measuring surface temperature of scram-jet combustor.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.32-35
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• 2006

For the white UV-LED applications, $Eu^{2+}$-activated calcium aluminium silicate phosphors were synthesized for the first time and the structures and luminescence characteristics of these phosphors were investigated. The phosphors in this study emitted blue. green or blue-green light depending on the starting materials for synthesis. In addition, the structure was also changed when the different starting materials were used. When CaO and $CaCO_3$ was used as a starting material. tetragonal $Ca_2Al_2SiO_7$ was formed and blue-green and pure green light was emitted. respectively. However. in the case of $CaSiO_3$, triclinic $CaAl_2Si2O_8$ was formed and only pure blue emission was detected. The maximum emission intensity was obtained from $CaAl_2Si_2O_8:Eu^{2+}$ phosphors, which intensity was about 1.4 times higher than that of YAG:$Ce^{3+}$ phosphor used for blue LED.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.46 no.3
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• pp.59-68
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• 2023

Currently, yellow phosphor of Y3Al5O12:Ce3+ (YAG:Ce) fluorescent material is applied to a 450~480nm blue LED light source to implement a white LED device and it has a simple structure, can obtain sufficient luminance, and is economical. However, in this method, in terms of spectrum analysis, it is difficult to mass-produce white LEDs having the same color coordinates due to color separation cause by the wide wavelength gap between blue and yellow band. There is a disadvantage that it is difficult to control optical properties such as color stability and color rendering. In addition, this method does not emit purple light in the range of 380 to 420nm, so it is white without purple color that can not implement the spectrum of the entire visible light spectrum as like sunlight. Because of this, it is difficult to implement a color rendering index(CRI) of 90 or higher, and natural light characteristics such as sunlight can not be expected. For this, need for a method of implementing sunlight with one LED by using a method of combining phosphors with one light source, rather than a method of combining red, blue, and yellow LEDs. Using this method, the characteristics of an artificial sunlight LED device with a spectrum similar to that of sunlight were demonstrated by implementing LED devices of various color temperatures with high color rendering by injecting phosphors into a 405nm deep blue LED light source. In order to find the spectrum closest to sunlight, different combinations of phosphors were repeatedly fabricated and tested. In addition, reliability and mass productivity were verified through temperature and humidity tests and ink penetration tests.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.644-646
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• 2004

We have investigated luminescence properties of Ln-SiAlON materials doped with $Ce^{3+}$. Low-energy 4f${\leftrightarrow}$5d transitions were observed as compared to the luminescence of this ion doped in oxidic host-lattices.$^1$ Ce-doped Y-a-SiAlON show bright long wavelength luminescence with high absorption for 305 and 455nm excitation. In our experiment, the sintering temperature of this material(1400$^{\circ}C$) was lower than that of normal sintering temperature (1700$^{\circ}C$). However, Single phase of SiAlON was not composed we observed the YAG phase.

• Journal of Applied Reliability
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• v.12 no.3
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• pp.177-186
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• 2012

This paper presents a comparison of the failure mechanism for high power converted white LEDs(3W) with the commercially available YAG:Ce and silicate phosphor. We carry out the normal aging life test for 10,000 hours, the high temperature aging test for 8,000 hours, the high temperature and humidity aging test for 8,000 hours and the current aging testing for 5,000 hours. The optical and electrical parameters of LEDs were monitored, such as lumen, correlated color temperature (CCT), chromaticity coordinates(x, y), thermal resistance, I -V curve and spectrum intensity. The stress induced a luminous flux decay on LED in all experiments and causes a failure. So we try to find out what's a main failure mechanism for a high power LED.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.49-49
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• 2009

Phosphors with oxide host material, YAG:$Ce^{3+}$ and $(Ca,Sr,Ba)_2SiO_4:Eu^{2+}$ yellow phosphor, has been used for LED applications. The WLEDs using these phosphors are widely used for LCD backlighting, automobile, and general lighting applications since they have high conversion efficiency and good thermal and chemical stability which can meet necessary life time of LED products up to now. With advances of LED chip technology, the external quantum efficiency and driving current in chip get higher so that the phosphors for high power chip are required to maintain high conversion efficiency and stability at high temperature due to the heat dissipated from LED chips. In addition, higher color rendering index of LED lighting and color reproducibility of LCD than those of LEDs with single yellow phosphors are required. In order to overcome these technical issues rising from evolution of LED technology, new phosphors are in demand and nitride phosphors, one of the promising new candidate materials, will be discussed here.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.152-152
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• 2000

차세대 평판 디스플레이로 주목박고 있는 FED는 현재 저전압 환경에서 기존의 CRT와 비슷한 해상도와 밝기를 얻지 못하고 있다. 이는 형광체 입자의 표면에 존재하는 결함, 오염, band - bonding과 같은 비발광층과 제조공정 중에 산화되거나 공기중에 노출되어 막 표면이 쉽게 오염되기 때문이다. 따라서 본 연구에서는 전기영동법으로 제작된 형광체의 효율 향상을 위해 레이저 표면 처리효과를 연구하였다. 실험에 사용한 레이저 표면처리 방법은 Nd:YAG pulse(355nm), continuous laser를 이용하였으며 레이저 power와 처리 시간을 변화시키면서 실시하였다. 형광체 막의 표면 두께 측정을 위해 Scanning Electron Microscopy(SEM), 처리된 막의 발광세기를 비교 분석하기 위해 Photoluminescence(PL), Cathodoluminescence(CL) intensity를 측정하였다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.22 no.5
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• pp.233-240
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• 2012

White LEDs (light-emitting diodes) are promising new-generation light sources which can replace conventional lamps due to their high reliability, low energy consumption and eco-friendly effects. This paper briefly reviews recent progress of oxy/nitride host phosphor and quantum dot materials with broad excitation band characteristics for phosphor-converted white LEDs. Among oxy/nitride host materials, $M_2Si_5N_8$ : $Eu^{2+}$, $MAlSiN_3$ : $Eu^{2+}$ M-SiON (M = Ca, Sr, Ba), ${\alpha}/{\beta}$-SiAlON : $Eu^{2+}$ are excellent phosphors for white LED using blue-emitting chip. They have very broad excitation bands in the range of 440~460 nm and exhibit emission from green to red. In this paper, In this review we focus on recent developments in the crystal structure, luminescence and applications of the oxy/nitride phosphors for white LEDs. In addition, the application prospects and current trends of research and development of quantum dot phosphors are also discussed.

• New Physics: Sae Mulli
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• v.68 no.11
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• pp.1196-1202
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• 2018

$Li_2Sr_{1-x}Eu_xSiO_{4-{\alpha}}N_{\alpha}$ ($Li_2SrSiO_{4-{\alpha}}N_{\alpha}:Eu^{2+}$) phosphors were synthesized by using a solid state reaction (SSR) method with submicron $Si_3N_4$ and nano $Si_3N_4$ powders as the sources of Si and N, and the optical properties of those phosphors were studied. The studied phosphors showed efficient excitation characteristics over the broad range from 230 to 530 nm. Also, They showed broad emission spectra covering a range from 500 to 700 nm, with a peak at 568 nm, which was shifted longer wavelength by 18 nm as compared with that of commercial $YAG:Ce^{3+}$. Combined with a 450 nm blue LED chip, the results support the application of the $Li_2SrSiO_{4-{\alpha}}N_{\alpha}:Eu^{2+}$ phosphor as a luminescent material for a white-light source thaat is warmer than the commercial $YAG:Ce^{3+}$ white-light source. In addition, the $Li_2SrSiO_{4-{\alpha}}N_{\alpha}$ phosphors prepared from a submicron $Si_3N_4$ powder was found to emit a previously unreported self-activated luminescence in $Li_2SrSiO_{4-{\alpha}}N_{\alpha}$.

• Korean Journal of Materials Research
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• v.23 no.1
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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.