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.

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 $850-950^{\circ}C$.

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.

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.

ADEC-Energy Proficient Four-Level Deterministic Hierarchical Clustering Protocol for Wireless Sensor Network

Mamta Tewari,Kunwar Singh Vaisla 보안공학연구지원센터 2016 International Journal of Future Generation Communi Vol.9 No.5

As the popularity of Wireless sensor network is increasing and they are developed to perform a number of tasks, the issue of constrained energy of the sensor nodes is constantly raised by many researchers in past time. Many algorithms focus on the judicious use of the energy of sensor nodes to extend network lifetime for homogeneous as well as heterogeneous sensor networks. Clustering algorithms have been devised to optimize the energy consumption of a sensor network. In this paper we have extended the concept of heterogeneity in the deterministic energy efficient DEC protocol and proposed an advance deterministic energy proficient clustering technique for Wireless sensor network. We have implemented the DEC clustering algorithm in four level node hierarchies to enhance the sensor network life time, stability, and total remaining energy of the system. The simulated results show improved results in terms of energy consumption and hence in extending the network lifetime.

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.

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.