• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2003.11a
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• pp.161-164
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• 2003

본 연구에서는 수열합성법으로 $SrAl_2O_4:Eu$ 형광체 분말을 합성하여 이들의 발광 특성과 장잔광 특성 등에 대해서 고찰하였다. 증류수에 $Sr(NO_3)_2,\;Al(NO_3)_3{\cdot}9H_2O,\;Eu(NO_3)_3{\cdot}6H_2O$ 등의 금속염을 용해시킨 용액을 $NH_4OH$ 수용액으로 pH를 적당히 조절하고 고온 고압의 Autoclave 반응용기 내에서 반응시켰다. 이렇게 합성된 분말은 균일한 입도 분포를 나타내었으면, sub-micron 크기의 초미세 분말이었다. 합성된 $SrAl_2O_4:Eu$ 초미세 분말을 $Ar-H_2$ 가스 환원분위기에서 $1100-1400^{\circ}C$ 온도로 2시간동안 열처리시켜서 형광 특성을 나타내도록 만들었다. 분말의 여기 및 발광 특성을 측정한 길과, 발광파장을 520 nm로 고정시켜 측정한 여기스펙트럼은 $250\~450nm$의 넓은 파장영역에 걸쳐 여기가 일어났고, 발광스펙트럼은 520 nm에서 최대 피크를 나타내었다. 또한 10분간 여기 시킨 후 520 nm 파장에 대한 잔광 특성이 1000분 이상 지속되는 우수한 장잔광 특성을 나타내었다.

• Transactions of Materials Processing
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• v.12 no.5
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• pp.493-497
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• 2003

The present investigation aims at visualizing the crack tip stress field using a mechanoluminescence material. The well known compound $SrAl_2O_4$:$Eu^{2+}$ was adopted as a mechanolurninescence material. Two more trivalent rare-earth elements such as Dy and Nd were taken into consideration as codopants to provide the appropriate trap levels. Samples of a variety of compositions were prepared by varing $Eu^{2+}$, $Dy^{3+}$, and $Nd^{3+}$ doping contents, for which the combinatorial chemistry method was used. In order to search for the optimum composition for the highest mechanoluminescence, the luminescence induced by a compressive device including a CCD camera. In parallel, a compact tension specimen was prepared by mixing the luminescence powders of optimum composition and epoxy resin. Crack initiation from the mechanically machined sharp note tip and its growth during loading were found to be associated with the extent of light emission from $SrAl_2O_4$.

• Journal of the Korean Chemical Society
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• v.47 no.4
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• pp.370-375
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• 2003

$BaMg_2Al_16O_27:Eu,\SrGa_2S_4:Eu$, and ZnCdS:Ag,Cl phosphors were chosen to produce blue, green, and red emissions, respectively, under excitation from a violet light emitting diode (LED). A four-band white LED was obtained by a combination of nonabsorbed violet emission from a violet LED and blue, green, and red emissions from $BaMg_2Al_16O_27:Eu,\SrGa_2S_4:Eu$, and ZnCdS:Ag,Cl phosphors. The luminescent properties of the four-band white LED were also discussed.

• Proceedings of the Korean Ceranic Society Conference
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• 2003.10a
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• pp.145.2-145
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• 2003

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.11 no.2
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• pp.71-77
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• 2001

We investigated photoluminescence, long-phosphorescent and crystalline properties with various $Dy_2$$O_3$ compositions (0.0~9.5mol%) in $SrAl_2$$O_4$ : $Eu^{2+}$,$Dy^{3+}$ phosphor powders prepared by the solid state reaction. The highest emission wavelength (520nm) of photoluminescence spectra was not affected by the Dy doping concentrations. The$SrAl_2$$O_4$single phase which was determined by X-ray diffraction and photoluminescence was appeared for the concentrations of $Dy_2$$O_3$$\leq$1.0 mol%. After removal of the pulsed Xe-lamp excitation (360nm), also, excellent long phosphorescent properties of the phosphors were obtained with the concentrations of $Dy_2$$O_3$$\leq$1.0mol%, although the decay time for all phosphors decrease exponentially.

• Journal of the Korean Ceramic Society
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• v.43 no.6 s.289
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• pp.333-337
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• 2006

In this study, the $Sr_{1-x}Ba_{x}Al_{2}O_{4}:Eu^{2+},Dy^{3+}$ phosphor were prepared by the solid-state reaction method and its photoluminescence properties were investigated. Starting powders of $SrCO_3,\;BaCO_3,\;and\;Al_{2}O_3$ were mixed with $Eu_{2}O_3$ as activator, $Dy_{2}O_3$ as co-activator and $B_{2}O_3$ as flux. Then, the mixed powders were heated at the temperature of $1100{\sim}1400^{\circ}C$ for 3 h under the reducing ambient atmosphere of $95%Ar+5%H_2$. The effect of Ba addition from 0.0 to 1.0 mol on photoluminescence was investigated. As the amount of Ba increased, the intensity of emission increased and the optimum long phosphorescence occurred at the amount of 0.1 mol Ba. The optimum sintering condition for long phosphorescent phosphor of $Sr_{1-x}Ba_{x}Al_{2}O_{4}:Eu^{2+},Dy^{3+}$($x=0{\sim}1.0mol$) was found at $1400^{\circ}C$. The excitation spectra showed a broad band of $250{\sim}450nm$ with maximum peak at 360 nm. The maximum peak intensity of emission spectra occurred at the range of $480{\sim}520nm$, depending on Ba content.

• Proceedings of the Korean Ceranic Society Conference
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• 2004.10a
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• pp.86.1-86.1
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• 2004

• Korean Journal of Materials Research
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• v.18 no.1
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• pp.1-4
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• 2008

The phase transformations and luminescent properties of Eu-doped $Ca_{1-x}Sr_xAl_2O_4$ phosphors were investigated. $Ca_{1-x}Sr_xAl_2O_4:Eu^{2+}$ phosphors were synthesized by a solid-state reaction with a flux, $H_3BO_3$. A phase transformation from monoclinic $CaAl_2O_4$ to monoclinic $SrAl_2O_4$ was observed as the x values increased. A high-temperature hexagonal phase of $SrAl_2O_4$ was formed during this transformation as an intermediate phase under an $H_2$ atmosphere due to oxygen vacancies; this did not occur in an air atmosphere. Accordingly, the emission spectra shifted from a blue region to a green region as x increased.

• Journal of the Korean Ceramic Society
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• v.45 no.3
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• pp.146-149
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• 2008

Strontium-substituted $Sr_{1-x}Ba_xAl_2O_4:Eu^{2+},\;Dy^{3+}$ compositions were prepared by the solid state synthesis method. These compositions were characterized for their phase, crystallinity and morphology using powder x-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. Photoluminescence properties were investigated by measuring excitation spectra, emission spectra and decay time for varying Ba/Sr concentrations. Photoluminescence results show higher luminescence and long decay time for $Sr_{1-x}Ba_xAl_2O_4:Eu^{2+},\;Dy^{3+}$(x=0). This is probably due to the influence of the 5d electron states of $Eu^{2+}$ in the crystal field. Long persistence was observed for these compositions due to $Dy^{3+}$ co-doping.

• Korean Journal of Materials Research
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• v.24 no.7
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• pp.351-356
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• 2014

A spherical $Sr_4Al_{14}O_{25}:Eu^{2+}$ phosphor for use in white-light-emitting diodes was synthesized using a liquid-state reaction with two precipitation stages. For the formation of phosphor from a precursor, the calcination temperature was $1,100^{\circ}C$. The particle morphology of the phosphor was changed by controlling the processing conditions. The synthesized phosphor particles were spherical with a narrow size-distribution and had mono-dispersity. Upon excitation at 395 nm, the phosphor exhibited an emission band centered at 497 nm, corresponding to the $4f^65d{\rightarrow}4f^7$ electronic transitions of $Eu^{2+}$. The critical quenching-concentration of $Eu^{2+}$ in the synthesized $Sr_4Al_{14}O_{25}:Eu^{2+}$ phosphor was 5 mol%. A phosphor-converted LED was fabricated by the combination of the optimized spherical phosphor and a near-UV 390 nm LED chip. When this pc-LED was operated under various forward-bias currents at room temperature, the pc-LED exhibited a bright blue-green emission band, and high color-stability against changes in input power. Accordingly, the prepared spherical phosphor appears to be an excellent candidate for white LED applications.