• Journal of Magnetics
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• 제17권4호
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• pp.251-254
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• 2012

The electron paramagnetic resonance (EPR) of the $Eu^{2+}$ ion in $SrCl_2$:Eu single crystal has been investigated using an X-band spectrometer. The angular dependence of magnetic resonance positions for the $Eu^{2+}$ impurity ion in the crystallographic aa-plane is analyzed with effective spin-Hamiltonian. The EPR spectra of the isolated $Eu^{2+}$ center merged to each other. The hyperfine splitting of the isolated $Eu^{2+}$ center due to the $^{151}Eu$ nucleus is approximately 35 G. Three kinds of $Eu^{2+}$ centers except the isolated $Eu^{2+}$ center, $Eu^{2+}$ pairs, $Eu^{2+}$ triples, and other $Eu^{2+}$ clusters, are split from the fitting of the integrated experimental spectrum with the Gaussian curve. The calculated spectroscopic splitting parameters of the $Eu^{2+}$ pairs, $Eu^{2+}$ triples, and other $Eu^{2+}$ clusters in $SrCl_2$:Eu crystal are $g_1$ = 2.06, $g_2$ = 1.94, and $g_3$ = 1.93, respectively.

• 한국전기전자재료학회논문지
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• 제20권8호
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• pp.671-679
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• 2007

[ $SrAl_2O_4:Eu^{2+},\;Dy^{3+}$ ] phosphor was synthesized using the impregnation method, and its photoluminescence and long-afterglow properties were investigated, A mixture of $Sr(NO_3)_2,\;Al(NO_3)_2\;9H_2O,\;EuCl_3\;6H_2O,\;DyCl_3\;6H_2O,\;NdCl_3\;6H_2O$ salts were dissolved in distilled water and impregnating into the polymer precursor. After drying, the impregnated mixture was heat treated at $900-1400^{\circ}C$ for 2h in a $N_2-H_2$ reduction atmosphere. The microstructure and crystal structure of the $SrAl_2O_4:Eu^{2+},\;Dy^{3+}$ powders were examined by scanning electron microscopy and X-ray diffraction, respectively. The photoluminescence spectra showed an excitation band along over wide wavelength of 250-450nm, and a broaden emission with a maxima peak at 360nm. In addition, the spectra also showed a good long after glow that decayed over a 1000sec period after 10 min excitation illumination.

• 마이크로전자및패키징학회지
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• 제23권4호
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• pp.63-67
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• 2016

Divalent europium-activated $Ca_2PO_4Cl$ phosphor powders were prepared by a chemical synthetic method followed by heat treatment in reduced atmosphere, and the crystal structures, morphologies and photoluminescence properties of the powders were investigated by x-ray powder diffraction, scanning electron microscope and spectrometer. The effect of Ca/P mole ratio at the starting materials on the final products was evaluated. The optimized synthesis condition obtained in this study was Ca/P mole ratio of 2.0. The present phosphor materials had higher photoluminescence intensity and better color purity than the commercial blue phosphor powders, $(Ca,Ba,Sr)_{10}(PO_4)_6Cl_2:Eu^{2+}$. The result of excitation spectrum measurement indicated that the excitation efficiency of the synthesized powders was higher for the long-wavelength UV region than that of the commercial phosphor. It was thus concluded that the samples prepared in this study can be successfully applied for the light-emitting devices such as LED excited with long-wavelength UV light sources.

• 한국재료학회지
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• 제18권2호
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• pp.77-83
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• 2008

Green-emitting $Ba_{1.468}Sr_{0.5}SiO_4\;:\;Eu_{0.012},\;Y_{0.02}$ phosphor powders under long-wavelength ultraviolet light were prepared via high-temperature flame spray pyrolysis from spray solutions with and without $NH_4Cl$ flux. The effects of the temperature of the diffusion flame and the $NH_4Cl$ flux on the morphologies, crystal structures and photoluminescence intensities of the $Ba_{1.468}Sr_{0.5}SiO_4\;:\;Eu_{0.012},\;Y_{0.02}$ phosphor powders were investigated. The phosphor powders obtained from the spray solution with the $NH_4Cl$ flux had higher photoluminescence intensities compared to phosphor powders obtained from the spray solution without the flux. The photoluminescence intensity of the phosphor powders obtained from the spray solution without the flux decreased as the flow rate of the fuel gas increased. On the other hand, the photoluminescence intensity of the phosphor powders obtained from the spray solution with the flux increased as the flow rate of the fuel gas increased. The difference of in the phase purity and morphology of the powders affected the photoluminescence intensities of the phosphor powders.