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Gupta K.V.K.,Kwality Photonics Pvt. Ltd. | Yadav P.,Shri Ramdeobaba Kn Engineering College | Joshi C.P.,Shri Ramdeobaba Kn Engineering College | Moharil S.V.,Rashtrasant Tukadoji Maharaj Nagpur University
Applied Physics B: Lasers and Optics | Year: 2011

YAG:Ce is an important phosphor having applications in various fields ranging from solid state lighting to scintillation detectors. YAG phosphors doped with activators are mainly synthesized by solid state reaction techniques that require high sintering temperatures (above 1500° C) to eliminate YAM and YAP phases. Though several soft chemical routes have been explored for synthesis of YAG, most of these methods are complex and phase pure materials are not obtained in one step, but prolonged annealing at temperatures around 1000° C or above become necessary. One step combustion synthesis of YAG:Ce3+ and related phosphors carried out at 500° C furnace temperature is reported here. Activation with Ce 3+ could be achieved during the synthesis without taking recourse to any post-combustion thermal treatment. LEDs prepared from the combustion synthesized YAG:Ce 3+, exhibited properties comparable to those produced from the commercial phosphor. © 2011 Springer-Verlag.


Joshi C.P.,Shri Ramdeobaba KN Engineering College | Moharil S.V.,Rashtrasant Tukadoji Maharaj Nagpur University
International Journal of Self-Propagating High-Temperature Synthesis | Year: 2012

At least four compounds, viz. LiAlO 2, LiAl 5O 8, Li 5AlO 4 and Li 2Al 4O 7, are known in the Li 2O-Al 2O 3 system. These compounds are important for several technological applications. Combustion synthesis of these compounds using urea as a fuel was attempted. LiAlO 2 and LiAl 5O 8 could be successfully prepared by choosing the starting materials in required stoichiometric ratios. Li 2Al 4O 7 was not obtained as a pure phase; γ-LiAlO 2 was formed as an impurity phase. Li 5AlO 4 could not be prepared by combustion process. Some phosphors based on these aluminates could also be prepared. Activation of these aluminates with Fe 3+, Mn 4+, Cu +, etc. was successfully achieved. Excitation and emission spectra for LiAl 5O 8: Fe 3+, LiAl 5O 8: Mn 2+, and Li 2Al 4O 7: Cu + are reported. © 2012 Allerton Press, Inc.


Joshi C.P.,Shri Ramdeobaba Kn Engineering College | Moharil S.V.,Rashtrasant Tukadoji Maharaj Nagpur University | Muthal P.L.,Indian National Environmental Engineering Research Institute | Dhopte S.M.,Indian National Environmental Engineering Research Institute
Journal of Luminescence | Year: 2012

A modified synthesis of La 2BaZnO 5 phosphors activated with rare earths Eu 3+, Tb 3+, Pr 3+ and Sm 3+, and ns 2 ion Bi 3+ is reported. RE 2BaZnO 5 compounds are conventionally prepared by two step solid state reaction. In the first step, carbonates or similar precursors are intimately mixed and heated at 900 °C to decompose the precursors to oxides. To eliminate the unwanted phases like BaRE 2O 4, the resulting powders are reheated at 1100 °C for long time. We prepared La 2BaZnO 5 phosphors activated with various activators by replacing the first step by combustion synthesis. Results on photoluminescence are presented. PL results on Eu 3+ and Tb 3+ are in good agreement with the literature reports. PL emission from Sm 3+, Pr 3+ and Bi 3+ had not been reported earlier. Excitation spectrum of Eu 3+ is dominated by a charge transfer band around 318 nm, while for the other rare earths a band at 240 nm is always present. This is attributed to the host absorption. © 2011 Elsevier B.V. All rights reserved.


Singh V.S.,Shri Ramdeobaba Kn Engineering College | Joshi C.P.,Shri Ramdeobaba Kn Engineering College | Moharil S.V.,Rashtrasant Tukadoji Maharaj Nagpur University
Journal of Alloys and Compounds | Year: 2013

LiBaF3 has great potential applications as X-ray storage phosphor, slow neutron imaging, scintillator, vacuum ultraviolet (VUV) optical lithography, etc. Conventionally, LiBaF3 is prepared by solid state reaction between the constituent fluorides. However, the preparation of phase pure material and especially single crystals is rather tricky due to incongruent melting. For the first time, a wet chemical preparation of rare earth activated LiBaF3 is described here. As precipitated powders containing Ce 3+ or Tb3+ exhibited characteristic luminescence. For observing Eu2+ emission, it was necessary to heat the powders in a reductive atmosphere. It is suggested that phosphors prepared by this method may prove useful in applications like OSL, X-ray imaging, etc. which do not require large single crystals. © 2013 Elsevier B.V. All rights reserved.


Pote S.S.,Shri Ramdeobaba Kn Engineering College | Joshi C.P.,Shri Ramdeobaba Kn Engineering College | Moharil S.V.,Rashtrasant Tukadoji Maharaj Nagpur University | Muthal P.L.,Indian National Environmental Engineering Research Institute | Dhopte S.M.,Indian National Environmental Engineering Research Institute
Physica B: Condensed Matter | Year: 2011

Some compounds with fluorite structures in the system CaF 2YF 3 were prepared by precipitation followed by thermal annealing at 1000 °C. Photoluminescence spectra of Ce 3 and Eu 2 were studied. In this host, Ce 3 exhibits PL, which is totally different from that observed for the constituent fluorides. Eu 2 emission, on the other hand, is almost the same as that for CaF 2. The changes are explained in terms of the defect structure of Ca 1-xY xF 2x. © 2011 Elsevier B.V. All rights reserved.


Singh V.S.,Rashtrasant Tukadoji Maharaj Nagpur University | Joshi C.P.,Shri Ramdeobaba Kn Engineering College | Moharil S.V.,Rashtrasant Tukadoji Maharaj Nagpur University
Optical Materials | Year: 2015

New results on synthesis and luminescence of Ce3+ activated fluoro-elpasolites and some related fluoroaluminates are presented. Wet chemical synthesis of fluoroaluminates with elpasolite (K2NaAlF6) structure and related fluorides such as simmonsite Na2LiAlF6 and pyrochlore derived rhombohedral phases Cs2NaAl3F12 is described. Ce3+ activation also could be achieved using the simple procedure. Intense Ce3+ emission in ultraviolet region could be observed in the fluoro-aluminates prepared by wet chemical method, without resorting to any thermal treatment except for that required for drying. The method will provide a simple route for preparing this important class of materials. © 2015 Elsevier B.V. All rights reserved.


Ingole D.K.,Shri Ramdeobaba Kn Engineering College | Joshi C.P.,Shri Ramdeobaba Kn Engineering College | Moharil S.V.,Rashtrasant Tukadoji Maharaj Nagpur University | Muthal P.L.,Indian National Environmental Engineering Research Institute | Dhopte S.M.,Indian National Environmental Engineering Research Institute
Journal of Luminescence | Year: 2011

Intense photoluminescence is reported for hydrated bromides of Gd, La and Y (LaBr 3·7H 2O, CeBr 3·7H 2O, YBr 3·8H 2O and GdBr 3·n H 2O) prepared by the wet chemical method and activated with Ce 3. Intensities are comparable to that for a commercial phosphor (SrB 4O 7:Eu 2 - Sylvania 2052). Luminescence in hydrated salt is usually quenched. The observation of intense luminescence in hydrated bromides is remarkable. © 2011 Elsevier B.V. All rights reserved.


Yadav P.J.,Rashtrasant Tukadoji Maharaj Nagpur University | Joshi C.P.,Shri Ramdeobaba Kn Engineering College | Moharil S.V.,Rashtrasant Tukadoji Maharaj Nagpur University
International Journal of Self-Propagating High-Temperature Synthesis | Year: 2013

Recently long-lasting luminescence (LL) has been reported in YAG doped with Pr3+ or Ce3+ processed in reducing atmosphere. However, YAG:Ce emission is yellow which is not attractive for long lasting applications. On the other hand, Ga substituted garnets give green emission at shorter wavelengths. We explored Ga substituted garnets prepared by combustion synthesis for LL. These phosphors do exhibit green LL, although the intensities are lower compared to that of YAG:Ce. © 2013 Allerton Press, Inc.


Ingole D.K.,Shri Ramdeobaba Kn Engineering College | Joshi C.P.,Shri Ramdeobaba Kn Engineering College | Moharil S.V.,Rashtrasant Tukadoji Maharaj Nagpur University | Muthal P.L.,Indian National Environmental Engineering Research Institute | Dhopte S.M.,Indian National Environmental Engineering Research Institute
Journal of Luminescence | Year: 2010

Chloroaluminate systems are important due to their use in the production of aluminum and sodium metals, in electro-deposition of aluminum alloys, extraction of aromatic hydrocarbons, etc. However, no data on luminescence in these compounds are available. Low melting points and instability due to the high volatility of AlCl3 seem to be deterrents for carrying out such investigations. Synthesis and photoluminescence spectra of Ce3+ activated alkali chloroaluminates and some alkaline earth chloroaluminate phosphors are described for the first time in the present work. A simple wet chemical method is used for the preparation of the phosphor. Very intense emission was observed for LiCl·AlCl3 and NaCl·AlCl3. For the former, the emission attributable to d-f transitions is entirely in the UVA1 (ultraviolet A1) region. The intensity is comparable to that of a commercial phosphor. Ce3+ activated emission in the alkaline earth compounds CaCl2·AlCl3 and MgCl2·2AlCl3 was relatively much weaker. © 2010 Elsevier B.V. All rights reserved.


Taikar D.R.,Shri Ramdeobaba Kn Engineering College | Joshi C.P.,Shri Ramdeobaba Kn Engineering College | Moharil S.V.,Rashtrasant Tukadoji Maharaj Nagpur University | Muthal P.L.,Indian National Environmental Engineering Research Institute | Dhopte S.M.,Indian National Environmental Engineering Research Institute
Journal of Luminescence | Year: 2010

SrZnO2 phosphors have been synthesized by two new methods viz. carbonate decomposition at 1000 °C and combustion synthesis. Phosphors activated with Pb2+, Sm3+, Tb3+, Bi 3+ and Pr3+ could be prepared in one step using the combustion synthesis. Characteristic emission and excitation were observed for Bi3+. For the remaining activators excitation spectra always contained a band at 283 nm. Presence of this band for all these different types of activators was interpreted as host sensitization. © 2010 Elsevier B.V. All rights reserved.

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