• Journal of the Semiconductor & Display Technology
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• v.6 no.2 s.19
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• pp.65-68
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• 2007

High brightness and long persistent luminescence phosphor $CaAl_2O_4:Eu^{2+}$ was prepared with varying $Eu^{2+}$ concentration by solid state reaction technique. Synthesized materials were investigated by powder X-ray diffractometer (XRD), SEM, TEM, photoluminescence excitation and emission spectra. Broad band UV excited luminescence of the $CaAl_2O_4:Eu^{2+}$ was observed in the blue region (${\lambda}_{max}\;=\;440\;nm$) due to transitions from the $4f^65d^1$ to the $4f^7$ configuration of the $Eu^{2+}$ ion. The decay time of the persistence indicated that the persistent luminescence phosphor has bright phosphorescence and maintains a long duration. These materials have great potential for outdoor night time displays.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.6
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• pp.225-228
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• 2005

We have grown the long persistent $SrAl_2O_4:Eu^{2+},\;Dy^{3+}$ phosphor single crystal by Verneuil method. The obtained single crystals were long persistent phosphorescence peaking at ${\lambda}=520nm$ with a size of about 5 mm diameter, 55 mm length. The melting temperature of $SrAl_2O_4:Eu^{2+},\;Dy^{3+}$ measured $T_{mp}=1968^{\circ}C$. The optimum composition was $SrCO_3:Al(OH)_3:Eu_2O_3:Dy_2O_3$ = 1 : 2 : 0.015 : 0.02. Flow rate of $H_2:O_2$ is about 4 : 1. Growthing rate is about 5 mm/hr. The spectra of the phosphorescence from the crystals are quite similar to those obtained with sintered powders used for luminous pigments. The crystalline structure of long persistent $SrAl_2O_4:Eu^{2+},\;Dy^{3+}$ phosphor single crystal was determined by X-ray diffraction.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2007.06a
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• pp.188-192
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• 2007

High brightness and long persistent luminescence phosphor $CaAl_2O_4:Eu^{2+}$ was prepared with varying $Eu^{2+}$ concentration by solid state reaction technique. Synthesized materials were investigated by powder X-ray diffractometer (XRD), SEM, TEM, photoluminescence excitation and emission spectra. Broad band UV excited luminescence of the $CaAl_2O_4:Eu^{2+}$ was observed in the blue region (${\lambda}_{max}\;=\;440\;nm$) due to transitions from the $4f^65d^1$ to the $4f^7$ configuration of the $Eu^{2+}$ ion. The decay time of the persistence indicated that the persistent luminescence phosphor has bright phosphorescence and maintains a long duration. These materials have great potential for outdoor night time displays.

• Resources Recycling
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• v.16 no.5
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• pp.46-50
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• 2007

Blue phosphor calcium aluminate, $CaAl_2O_4:Eu^{2+}$ co-doped with $Nd^{3+}$ was prepared by solid state synthesis method. Phosphor materials with 1 mol% $Eu^{2+}$ and varying compositions of $Nd^{3+}$ show high brightness and long persistent luminescence. The synthesized phosphor materials were investigated by powder x-ray diffraction (XRD), SEM, TEM, photoluminescence excitation and emission studies. Broad band UV excited luminescence of the $CaAl_2O_4:Eu^{2+}:Nd^{3+}$ was observed in the blue region (${\lambda}_{max}=440\;nm$) due to transitions from the $4f^65d^1$ to the $4f^7$ configuration of the $Eu^{2+}$ ion. $Nd^{3+}$ ion doping in the phosphor results in long afterglow phosphorescence when the excitation light is cut off.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.1
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• pp.27-32
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• 2008

Novel long persistent phosphors of $CaZrO_3:Er^{3+}$ have been synthesized by traditional solid state reaction method. The long persistent phosphor crystalline particles were characterized by the X-ray diffraction (XRD), photoluminescence spectrophotometer, thermoluminescence (TL) and luminance meter. The results reveal that the samples are composed of single $CaZrO_3$ phase. The broadband emission spectra of 446 nm peak and 550 nm peak was revealed by synthesized at high temperature in $N_2$ gas. Green long persistent phosphors have been observed in the sys_em for over 6 h after UV irradiation (254 nm). The main emission peak was ascribed to $Er^{3+}$ ions transition from $^5D_{5/2}{\rightarrow}^4F_{9/2},\;^2H_{12/2},\;^4S_{3/2}{\rightarrow}^4I_{13/2}\;and\;^2G_{9/2}{\rightarrow}^4I_{13/2}$, and the afterglow may be ascribed to the suitable trap centers in the $CaZrO_3$ host lattice.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.1
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• pp.22-26
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• 2008

Red long persistent phosphors of $CaZrO_3$ : Pr was synthesized by a solid reaction method. $CaCO_3\;and\;ZrO_2$ were used as hosting materials and Pr was doped as luminescence center element, and $B_2O_3$ was used as flux. The XRD pattern confirmed crystalline phase of the phosphor, and photoluminescence investigation showed emission spectrum at $480{\sim}570nm\;and\;590{\sim}700nm$. Phosphor samples were synthesized with $B_2O_3$ flux concentration of 1, 5, 10%, and luminescent peak of maximum intensity at 494 nm was obtained for 1% $B_2O_3$. Luminescent peak of red color at 620 nm was of highest intensity for 10% $B_2O_3$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.3
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• pp.130-134
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• 2009

A new long persistent phosphors of $CaZrO_3$ was synthesized at high temperature with weak reduction atmosphere by a traditional solid state reaction method. Photoluminescence spectra analysis showed that the $CaZrO_3$ doped with $Tb^{3+}$ emitted green-yellow emission caused by the energy level transition from the $^5D_3$ and $^5D_4$ to $^7F_1{\sim}^7F_6$. The main emission spectra of 542 nm peak by the $^5D_4{\rightarrow}^7F_5$ transition was revealed through synthesizing at high temperature in $N_2$ gas atmosphere. The afterglow emission spectra of $CaZrO_3:Tb^{3+}$ long persistent phosphores arise at 546 nm peak of narrow range. After the 254 nm ultraviolet light excitation source was switched off, the green-yellow long persistent phosphor can be observed which could last for 8 h in the limit of light perception of dark-adapted human eyes ($0.32\;mcd/m^2$).

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.3
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• pp.109-114
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• 2008

Novel green long persistent phosphors of $CaZrO_3$ : $HO_{3+}$ have been synthesized at high temperature with weak reduction atmosphere by traditional solid state reaction method. The role of $H_3BO_3$ as flux and the suitable concentration of Ho as activator on the $CaZrO_3$ : $HO_{3+}$ long persistent phosphors has been investigated. Crystals of $HO_{3+}$ doped $CaZrO_3$ long persistent phosphores were characterized by fluorescence spectrophotometer and photoluminescence (PL). The main emission spectra of 546 nm peak was revealed through synthesizing at high temperature in $N_2$ gas atmosphere. The after glow emission spectra of $CaZrO_3$ : $HO_{3+}$ long persistent phosphores arise at 546 nm peak of narrow range. because that revealed pure green color. Green long persistent phosphors have been observed in the system for over 5 h after UV irradiation (254 nm). The main emission peak was ascribed to $HO_{3+}$ ions transition from $^5F_4$, $^5S_2{\to}^5I_3$, and the after glow may be ascribed to the trap centers in the $CaZrO_3$ host lattice.