• 한국재료학회지
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• 제21권5호
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• pp.250-254
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• 2011

We have synthesized bluish-green, highly-efficient $BaSi_2O_2N_2:Eu^{2+}$ and $(Ba,Sr)Si_2O_2N_2:Eu^{2+}$ phosphors through a conventional solid state reaction method using metal carbonate, $Si_3N_4$, and $Eu_2O_3$ as raw materials. The X-ray diffraction (XRD) pattern of these phosphors revealed that a $BaSi_2O_2N_2$ single phase was obtained. The excitation and emission spectra showed typical broadband excitation and emission resulting from the 5d to 4f transition of $Eu^{2+}$. These phosphors absorb blue light at around 450 nm and emit bluish-green luminescence, with a peak wavelength at around 495 nm. From the results of an experiment involving Eu concentration quenching, the relative PL intensity was reduced dramatically for Eu = 0.033. A small substitution of Sr in place of Ba increased the relative emission intensity of the phosphor. We prepared several white LEDs through a combination of $BaSi_2O_2N_2:Eu^{2+}$, YAG:$Ce^{3+}$, and silicone resin with a blue InGaN-based LED. In the case of only the YAG:$Ce^{3+}$-converted LED, the color rendering index was 73.4 and the efficiency was 127 lm/W. In contrast, in the YAG:$Ce^{3+}$ and $BaSi_2O_2N_2:Eu^{2+}$-converted LED, two distinct emission bands from InGaN (450 nm) and the two phosphors (475-750 nm) are observed, and combine to give a spectrum that appears white to the naked eye. The range of the color rendering index and the efficiency were 79.7-81.2 and 117-128 lm/W, respectively. The increased values of the color rendering index indicate that the two phosphor-converted LEDs have improved bluish-green emission compared to the YAG:Ce-converted LED. As such, the $BaSi_2O_2N_2:Eu^{2+}$ phosphor is applicable to white high-rendered LEDs for solid state lighting.

• 한국재료학회지
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• 제19권3호
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• pp.163-168
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• 2009

$Eu^{3+}$-doped $Y_2O_3$ red phosphor was synthesized in a flux method using the chemicals $Y_2O_3,\;Eu_2O_3,\;H_3BO_3$ and $BaCl_2{\cdot}2H_2O$. The effect of a flux addition on the preparation of $Y_2O_3:Eu_{3+}$ red phosphor used as a cold cathode fluorescence lamp was investigated. $H_3BO_3$ and $BaCl_2{\cdot}2H_2O$ fluxes were used due to their different melting points. The crystallinity, thermal properties, morphology, and emission characteristics were measured using XRD, TG-DTA, SEM, and a photo-excited spectrometer. Under UV excitation of 254 nm, $Eu_2O_3$ 3.7 mol% doped $Y_2O_3$ exhibited a strong narrow-band red emission, peaking at 612 nm. From this result, the phosphor synthesized by firing $Y_2O_3$ with 3.7 mol% of $Eu_2O_3$, 0.25 mol% of $H_3BO_3$ and 0.5 mol% of $BaCl_2{\cdot}2H_2O$ fluxes at $1400^{\circ}C$ for 2 hours had a larger particle size of $4{\mu}m$ on average compared to the phosphor of the $H_3BO_3$ flux alone. In addition, a phosphor synthesized by the two fluxes together had a rounder corner shape, which led to the maximum emission intensity.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.344-344
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• 2007

본 연구에서는 X선 영상 검출기로의 적용을 위하여 $Gd_2O_3$:Eu 형광체 필름을 제작하여 X선에 대한 발광 특성을 분석하였다. $Gd_2O_3$:Eu는 저온 액상법을 이용하여 분말 형태로 제조한 후 Particle-in-binder (PIB)으로 필름 형태로 제작한 후, 도핑된 Europium(Eu)의 농도와 소결 온도에 따른 X선에 대한 발광 특성을 분석하였다. Photolumimescence (PL) spectrum에서 611nm에서 가장 높은 발광 효율을 나타내었으며, 입자의 크기가 줄어듦에 따라 610nm에서 새로운 peak가 형성 되었다. 또한 Eu의 농도에 따라서 발광 강도의 차이가 관찰되었는데, 5wt%의 도핑 농도에서 가장 높은 발광 효율을 나타냈으며, 도핑 농도에 매우 의존적인 결과를 나타냈다. 소결 온도에 따른 발광 특성 분석에서, $500^{\circ}C$에서 소결하였을 때는 623nm에서 강한 peak를 나타내는 단사정계상의 발광 peak는 거의 관찰되지 않았으나 소결 온도가 $700^{\circ}C$와 $900^{\circ}C$에서는 peak가 확인되었다. 이를 통해 $Gd_2O_3$ 모체가 대부분 입방 대칭 구조를 가지는 $Gd_2O_3$:Eu가 합성되었음을 확인할 수 있었다. 또한 소결 온도에 따른 발광 강도를 분석한 결과 $900^{\circ}C$에서 소결하였을 때 가장 높은 발광 강도를 나타냈다. Luminescent decay time 측정 결과에서 도핑된 Eu의 농도가 커질수록 Luminescent decay time이 짧아짐을 확인할 수 있었다.

• 한국재료학회지
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• 제29권9호
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• pp.559-566
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• 2019

$Lu(Nb,Ta)O_4:Eu^{3+}$ powders are synthesized by a solid-state reaction process using LiCl and $Li_2SO_4$ fluxes. The photoluminescence (PL) excitation spectra of the synthesized powders consist of broad bands at approximately 270 nm and sharp peaks in the near ultraviolet region, which are assigned to the $Nb^{5+}-O^{2-}$ charge transfer of $[NbO_4]^{3-}$ niobates and the f-f transition of $Eu^{3+}$, respectively. The PL emission spectra exhibit red peaks assigned to the $^5D_0{\rightarrow}^7F_J$ transitions of $Eu^{3+}$. The strongest peak is obtained at 614 nm ($^5D_0{\rightarrow}^7F_2$), indicating that the $Eu^{3+}$ ions are incorporated into the $Lu^{3+}$ asymmetric sites. The addition of fluxes causes the increase in emission intensity, and $Li_2SO_4$ flux is more effective for enhancement in emission intensity than is LiCl flux. The substitution of $Ta^{5+}$ for $Nb^{5+}$ results in an increase or decrease in the emission intensity of $LuNb_{1-x}Ta_xO_4:Eu^{3+}$ powders, depending on amount and kind of flux. The findings are explained using particle morphology, modification of the $[NbO_4]^{3-}$ structure, formation of substructure of $LuTaO_4$, and change in the crystal field surrounding the $Eu^{3+}$ ions.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.165-165
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• 2013

희토류 발광 물질은 4f 껍질에 위치하는 전자의 독특한 특성 때문에 발광 소자와 디스플레이에 그 응용성을 확장하고 있다. 본 연구에서는 고효율의 적색과 주황색 형광체를 합성하기 위하여 모체 격자 CaNb2O6에 희토류 이온인 유로퓸과 사마륨을 치환 고용하여 최적의 합성 조건을 조사하였다. Ca1-1.5xNb2O6:REx3+ (RE=Eu, Sm) 형광체 분말 시료는 고상반응법을 사용하여 활성제 이온인 Eu3+와 Sm3+의 농도비를 0, 0.01, 0.05, 0.10, 0.15, 0.20 mol 로 변화시키면서 합성하였다. 초기 물질 CaO, Nb2O5, Eu2O3와 Sm2O3을 화학 적량으로 측정하고, 400 rpm의 속도로 24시간 밀링 작업을 수행한 후에, 건조기 $60^{\circ}C$에서 28시간 건조하고, 시료를 막자 사발에서 갈아 세라믹 도가니에 담아 튜브형 전기로에서 분당 $5^{\circ}C$의 비율로 승온시켜 $500^{\circ}C$에서 5시간 동안 하소와 $1,100^{\circ}C$에서 6시간 소결하여 합성하였다. Eu3+가 도핑된 경우에, 발광 스펙트럼은 Eu3+ 이온의 농도비에 관계없이 강한 적색 발광 스펙트럼이 616 nm에서 관측되었다. 이외에도, 596 nm와 708 nm에서 상대적으로 발광 세기가 약한 주황색 발광과 적색 발광 신호가 검출되었으며, 541 nm에서는 매우 약한 녹색스펙트럼이 관측되었다. Eu3+ 이온의 농도비에 0.01 mol에서 0.15 mol로 증가함에 따라 주발광 신호의 세기는 점점 증가하였으며, 0.15 mol에서 최대 발광 세기를 나타내었다. Eu3+ 이온의 농도비가 0.20 mol 로 더욱 증가함에 따라 주 피크의 세기는 농도 소강 현상에 의하여 현저히 감소함을 보였다. 한편, 주된 흡광 스펙트럼은 279 nm에서 나타났는데, 이것은 전하전달밴드 신호이다. Sm3+가 도핑된 형광체 분말의 발광 스펙트럼은 모든 시료의 경우에 613 nm에서 강한 적주황색 발광 스펙트럼이 관측되었고, 상대적으로 세기가 약한 570 nm와 660 nm에 피크를 갖는 황색과 적색 발광 스펙트럼이 발생하였다. 흡광과 발광 스펙트럼의 최대 세기는 0.05 mol에서 나타났으며, Sm3+ 이온의 농도비가 더욱 증가함에 따라 흡광과 발광 세기는 급격하게 감소하였다.

• 한국재료학회지
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• 제32권10호
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• pp.425-428
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• 2022

In this study, Y₃Al₅O₁₂:Eu³⁺ red phosphors were synthesized at different temperatures using a solid state reaction method. The crystal structures, surface and optical properties of the Y₃Al₅O₁₂:Eu³⁺ red phosphors were investigated using X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), and photoluminescence (PL) analyses. From XRD results, the crystal structure of the Y₃Al₅O₁₂:Eu³⁺ red phosphors was determined to be cubic. The maximum emission spectra were observed for the Y₃Al₅O₁₂:Eu³⁺ red phosphor prepared by annealing for 4h at 1,700 ℃. The 565~590 nm photoluminescent spectra of the Y₃Al₅O₁₂:Eu³⁺ red phosphors is associated with the ⁵D₀ → ⁷F₂ magnetic dipole transition of the Eu³⁺ ions. The intensity of the photoluminescent spectra in the red phosphors is more dominant for the magnetic dipole transition than the electric dipole transition with increasing annealing temperature. The International Commission on Illumination (CIE) coordinates of Y₃Al₅O₁₂:Eu³⁺ red phosphors prepared by 1,700 ℃ annealing temperature are X = 0.5994, Y = 0.3647.

• Bulletin of the Korean Chemical Society
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• 제28권12호
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• pp.2477-2480
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• 2007

MgAl2O4:Eu3+ red-light emitting powder phosphor was prepared at temperature as low as 500 oC within a few minutes by using the combustion route. The prepared powder was characterized by X-ray diffraction, scanning electron microscopy and Fourier-transform infrared spectrometry. The luminescence of Eu3+-activated MgAl2O4 shows a strong red emission dominant peak around 611 nm, which can be attributed to the 5D0-7F2 transition of Eu3+ ions from the synthesized phosphor particles under excitation (394 nm). Electron paramagnetic resonance (EPR) measurements at the X-band showed that no signal could be attributed to Eu2+ ions in MgAl2O4.

• Bulletin of the Korean Chemical Society
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• 제27권6호
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• pp.841-846
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• 2006

$Y_2O_2S$:Eu phosphors were synthesized via solid-state reactions. $Y_2O_2S$:Eu phosphor particles of various sizes were obtained by varying the firing temperature and firing time. The photoluminescence properties of these $Y_2O_2S$:Eu phosphors were examined. In addition, the cathodoluminescence properties of the $Y_2O_2S$:Eu phosphors were examined for applied voltages of 3-8 kV. The relationship between the luminescence intensity and particle size of the$Y_2O_2S$:Eu phosphors was investigated. The photoluminescence and cathodoluminescence of the $Y_2O_2S$:Eu phosphors are affected differently by variations in particle size.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2002년도 International Meeting on Information Display
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• pp.253-256
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• 2002

$Gd_2O_3$:Eu phosphor particles were prepared by largescale ultrasonic spray pyrolysis process. The morphological control of $Gd_2O_3$:Eu particles in spray pyrolysis was performed by adding polymeric precursors into spray solution containing nitrate salts. The effect of composition and amount of polymeric precursors on the morphology, crystallinity, and photoluminescence characteristics of $Gd_2O_3$:Eu particles was investigated. The influence of chain length of PEG on the morphology and photoluminescence intensity was investigated. $Gd_2O_3$:Eu particles prepared from aqueous solution containing no polymeric precursors had a hollow structure and rough surfaces after annealing process. The phosphor particles prepared from solution containing 0.1M CA and 0.lM PEG with high molecular weight as 1,500 had a spherical and filled morphology and the highest photoluminescence intensity, which was 48% higher than that of the $Y_2O_3$:Eu commercial product.

• 한국재료학회지
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• 제16권3호
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• pp.163-167
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• 2006

The transition of europium-doped gadolinium oxide phosphor to gadolinium borate phosphor with the concentration of boron in the spray pyrolysis was investigated. The particles prepared from spray solution below 10 wt% boric acid of prepared phosphor had crystal structure of $Gd_2O_3:Eu$ phosphor, in which the crystallinity of the particles decreased with increasing the boron concentration. A single phase $GdBO_3:Eu$ phosphor particles were prepared from spray solution above 50 wt% boric acid of prepared phosphor. The phosphor particles prepared from spray solution with 20 wt% boric acid of prepared phosphor had no XRD peaks of $Gd_2O_3:Eu$ and $GdBO_3:Eu$ Therefore the phosphor particles prepared from spray solution with 20 wt% boric acid of prepared phosphor had the lowest photoluminescence intensity under ultraviolet and vacuum ultraviolet. $GdBO_3:Eu$ and $Gd_2O_3:Eu$ phosphor particles prepared from spray solutions with proper concentrations of boric acid had good photoluminescence intensity under vacuum ultraviolet. The morphology of the phosphor particles were strongly affected by the concentrations of boric acid added into spray solution.