Eu Doping Effect on $CaAl_2O_4:Eu^{2+}$ Phosphor Material

Bartwal, Kunwar Singh,Ryu, Ho-Jin The Korean Society Of Semiconductor Display Techno 2007 반도체디스플레이기술학회지 Vol.6 No.2

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.

Preparation of Y3Al5O12 Nanocrystals by a Glycol Route

Kunwar Singh Bartwal,Sujan Kar,Nanda Kaithwas,Monica Deshmukh,Mangla Dave,Hojin Ryu 한국세라믹학회 2007 한국세라믹학회지 Vol.44 No.5

Yttrium aluminum garnet, Y3Al5O12 (YAG) is an extensively used solid-state laser host material. YAG nanocrystals were synthesized using low-temperature glycol method, a modified sol–gel method performed at low temperature that consists of a mixture of salts that are mostly nitrates in an aqueous media. Single-phase nanocrystalline YAG was obtained at 850oC, which is a much lower temperature than with other techniques such as a wet-chemical technique. The structural characterization is done by powder X-ray diffraction, scanning electron microscopy and transmission electron microscopy. A crystallite size range of 20-50 nm was observed for the materials prepared at 850-950oC.

Preparation of Y₃Al₅O₁₂ Nanocrystals by a Glycol Route

Bartwal, Kunwar Singh,Kar, Sujan,Kaithwas, Nanda,Deshmukh, Monica,Dave, Mangla,Ryu, Ho-Jin The Korean Ceramic Society 2007 한국세라믹학회지 Vol.44 No.5

Yttrium aluminum garnet, $Y_3Al_5O_{12}$ (YAG) is an extensively used solid-state laser host material. YAG nanocrystals were synthesized using low-temperature glycol method, a modified sol-gel method performed at low temperature that consists of a mixture of salts that are mostly nitrates in an aqueous media. Single-phase nanocrystalline YAG was obtained at $850^{\circ}C$, which is a much lower temperature than with other techniques such as a wet-chemical technique. The structural characterization is done by powder X-ray diffraction, scanning electron microscopy and transmission electron microscopy. A crystallite size range of 20-50 nm was observed for the materials prepared at $850-950^{\circ}C$.

Effect of $Mg^{2+}$ co-doping on luminescent properties of $ZnGa_2O_4:Mn^{2+}$

Singh, Binod Kumar,Bartwal, Kunwar Singh,Ryu, Ho-Jin The Korean Society Of Semiconductor Display Techno 2007 반도체디스플레이기술학회지 Vol.6 No.4

Zinc gallate, $ZnGa_2O_4:Mn^{2+}$ co-doped with different concentrations of $Mg^{2+}$ (0.001- 0.5 mol%) was prepared by solid state synthesis method. These compositions were investigated for their photoluminescence and cathodoluminescence properties. The optimized composition $Zn_{0.990}Mg_{0.005}Ga_2O_4:Mn_{0.005}$ shows higher luminescence intensity compared to the parent phosphor. The intense green emission peak was found at 504 nm. The $Mg^{2+}$ doping does not affect much the decay time. It remains <10 ms for these compositions which make them potential candidate for application in TV screens.

Eu Doping Effect on CaAl2O4: Eu2+ Phosphor Material

류호진,Kunwar Singh Bartwal 한국반도체디스플레이기술학회 2007 반도체디스플레이기술학회지 Vol.6 No.2

High brightness and long persistent luminescence phosphor CaAl2O4:Eu2+ was prepared with varying Eu2+ 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 CaAl2O4:Eu2+ was observed in the blue region (λmax = 440 nm) due to transitions from the 4f65d1 to the 4f7 configuration of the Eu2+ 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.

Optimization of $Nd^{3+}$ ion co-doping in $CaAl_2O_4:\;Eu^{2+}$ blue phosphor

류호진,Bartwal, Kunwar Singh,Ryu, Ho-Jin 한국자원리싸이클링학회 2007 資源 리싸이클링 Vol.16 No.5

[ $Eu^{2+},\;Nd^{3+}$ ]로 도핑된 $CaAl_2O_4$ 청색 형광체를 고상반응법으로 제조하였다. 1 mol% $Eu^{2+}$로 doping된 형광체에 다양한 조성의 $Nd^{3+}$를 co-doping함에 따라 고휘도, 장잔광 특성을 보였다. 제조한 형광체에 대하여 XRD, SEM, TEM, 빛발광 특성을 조사하였다. $CaAl_2O_4:Eu^{2+}:Nd^{3+}$의 넓은 밴드의 UV로 여기된 빛발광 특성이 $Eu^{2+}$의 $4f^65d^1$에서 $4f^7$ 상태로 천이에 의해 기인된 청색영역(${\lambda}_{max}=440\;nm$)에서 관찰되었다. $Nd^{3+}$로 co-doping한 형광체는 여기광을 차단하였을 때 장잔광 발광 특성을 나타내었다. 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.

Synthesis and Photoluminescence Studies on Sr1-xBaxAl2O4 : Eu2+, Dy3+

류호진,Binod Kumar Singh,Kunwar Singh Bartwal 한국세라믹학회 2008 한국세라믹학회지 Vol.45 No.3

Strontium-substituted Sr1−xBaxAl2O4:Eu2+, Dy3+ 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 Sr1−xBaxAl2O4:Eu2+, Dy3+ (x=0). This is probably due to the influence of the 5d electron states of Eu2+ in the crystal field. Long persistence was observed for these compositions due to Dy3+ co-doping. Strontium-substituted Sr1−xBaxAl2O4:Eu2+, Dy3+ 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 Sr1−xBaxAl2O4:Eu2+, Dy3+ (x=0). This is probably due to the influence of the 5d electron states of Eu2+ in the crystal field. Long persistence was observed for these compositions due to Dy3+ co-doping.

Synthesis and Photoluminescence Studies on Sr_1-xBa_xAl₂O₄ : Eu²⁺, Dy³⁺

Ryu, Ho-Jin,Singh, Binod Kumar,Bartwal, Kunwar Singh The Korean Ceramic Society 2008 한국세라믹학회지 Vol.45 No.3

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.

Effect of Mg2+ co-doping on luminescent properties of ZnGa2O4:Mn2+

류호진,Binod Kumar Singh,Kunwar Singh Bartwal 한국반도체디스플레이기술학회 2007 반도체디스플레이기술학회지 Vol.6 No.4

Zinc gallate, ZnGa2O4:Mn2+ co-doped with different concentrations of Mg2+ (0.001- 0.5 mol%) was prepared by solid state synthesis method. These compositions were investigated for their photoluminescence and cathodoluminescence properties. The optimized composition Zn0.990 Mg0.005Ga2O4:Mn0.005 shows higher luminescence intensity compared to the parent phosphor. The intense green emission peak was found at 504 nm. The Mg2+ doping does not affect much the decay time. It remains <10 ms for these compositions which make them potential candidate for application in TV screens.