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Singh, V.,Sivaramaiah, G.,Rao, J. L.,Singh, N.,Mohapatra, M.,Singh, P. K.,Pathak, M. S.,Dhoble, S. J. Minerals, Metals & Materials Society and the Insti 2017 Journal of Electronic Materials Vol. No.
<P>LiAl5O8 doped with Fe was synthesized by a propellant combustion route at furnace temperature of 773 K. The phosphor was characterized using powder x-ray diffraction, optical absorption, electron paramagnetic resonance (EPR) and photoluminescence spectroscopic techniques. The optical absorption spectrum exhibits a broad band at 242 nm characteristic of charge transfer between Fe3+-O2-. On excitation with 293 nm, emission band for the Fe3+ ion was observed at 687 nm. The CIE (International Commission on Illumination or Commission Internationale de l'Elcairage) coordinates for the system were evaluated adopting standard procedure which suggested that the system can be effective as a deep red emitting phosphor. The EPR spectrum of this phosphor exhibits a number of resonance signals characteristic of Fe3+ ions. The resonance signals at g = 3.16, 2.27 are attributed to Fe3+ present at tetrahedral site with an axial symmetry. The resonance signals at g = 1.98 and 1.43 are attributed to Fe3+ ions in octahedral site with an axial symmetry. Various EPR parameters such as the number of spins, Gibbs free energy, magnetic susceptibility, Curie constant and effective magnetic moment values are calculated and compared at room temperature and 110 K.</P>
Vibhav K. Saraswat,K. Singh,N.S. Saxena,V. Kishore,T.P. Sharma,P.K. Saraswat 한국물리학회 2006 Current Applied Physics Vol.6 No.1
Measurements ofIV characteristics and DC electrical conductivity of Se85. xTe15Sbx (wherex = 2, 4, 6, 8 and 10) glassy thinpellets, prepared by well established melt quenching technique in bulk (pellets of diameter 12mm and thickness. 1m were pre-pared under a constant load of 5 tons), have been carried out at room temperature using Keithley High Resistance Meter/Electrom-eter 6517A. For the recording ofIV characteristics, this equipment was used in FVMI (Force Voltage Measure Current) mode. It isIV characteristics that the glass containing 4 at. wt.% of Sb has the minimum resistance allowing maximumcurrent through the sample as compared to the other at. wt.% of Sb contents e.g. 2, 6, 8 and 10.At 4 at. wt.% of Sb, conductivityrises to 76% of the value obtained for 2 at. wt.% of Sb. Composition dependence of DC conductivity is discussed in terms of thebond formation between Se and Sb at dierent compositions. The conduction mechanism is discussed qualitatively on the basisof PooleFrenkel conduction mechanism. Also the linear relation between ln (I) and V1/2veries that the conduction mechanismis of PooleFrenkel type for both low and high voltage range. The deviation of ohmic behaviour at lower voltage range towardsthe non-ohmic at higher voltage range is due to the high voltage induced temperature eects in the sample.
Observation ofX(3872)inB→X(3872)Kπdecays
Bala, A.,Bhardwaj, V.,Trabelsi, K.,Singh, J. B.,Abdesselam, A.,Adachi, I.,Aihara, H.,Arinstein, K.,Asner, D. M.,Aulchenko, V.,Aushev, T.,Ayad, R.,Aziz, T.,Bahinipati, S.,Bakich, A. M.,Bansal, V.,Barbe American Physical Society 2015 PHYSICAL REVIEW D - Vol.91 No.5
Singh, Vijay,Singh, N.,Dubey, Vikas,Singh, Pramod K.,Shinde, K.N.,Ravi Kanth Kumar, V.V. Elsevier 2018 OPTIK -STUTTGART- Vol.158 No.-
<P><B>Abstract</B></P> <P>Ce<SUP>3+</SUP>-doped CaAl<SUB>12</SUB>O<SUB>19</SUB> phosphors with different Ce<SUP>3+</SUP> contents, as well as those with Mg<SUP>2+</SUP> codoped powders, were successfully synthesized using a rapid combustion method (<5 min) for this paper. The powders were well characterized by the X-ray diffraction (XRD) and photoluminescence (PL) techniques. The emission measurements upon a UV-light excitation (262 nm) showed the emission characteristics of the Ce<SUP>3+</SUP> ion that are due to the 5d–4 f transitions. The emission and excitation spectra were recorded as the Ce<SUP>3+</SUP> concentration was kept constant and the Mg<SUP>2+</SUP> concentration was varied. It became evident that the addition of the Mg<SUP>2+</SUP> along with the Ce<SUP>3+</SUP> resulted in increases of the PL intensity, and the reasons for this behavior are discussed.</P>
Singh, N.,Singh, V.,Sivaramaiah, G.,Rao, J.L.,Singh, P.K.,Pathak, M.S.,Dhoble, S.J.,Mohapatra, M. Elsevier [etc.] 2016 Journal of luminescence Vol.178 No.-
<P>Strong blue-green light emitting MgSrAl10O17:Eu2+,Mn2+ phosphor was synthesized by a low temperature initiated, self-propagating and gas producing combustion process in a very short time (< 5 min). Structural characterization of the luminescent material was studied with X-ray diffraction analysis and energy-dispersive X-ray analysis. The absorption spectrum exhibits bands due to Eu2+ and Mn3+ ions. The excitation spectrum shows a peak at 337 nm. Upon excitation at 337 nm, the emission spectrum exhibits an intense band centered at 462 nm due to transitions from the 4f(6)5d(1) to the 4f(7) configuration of the Eu2+ ions, whereas sharp peak at 513 nm attributed to T-4(1) -> (6)A(1) transition of Mn2+ ions. The X-band EPR spectra of MgSrAl10O17:Eu2+,Mn2+ showed the presence of Eu2+ and Mn2+ ions. (C) 2016 Elsevier B.V. All rights reserved.</P>
Studies of Radiation-Induced Defects in Li2SiO3:Sm Phosphor Material
Singh, N.,Singh, V.,Watanabe, S.,Gundu Rao, T. K.,Chubaci, J. F.,Cano, N. F.,Pathak, M. S.,Singh, P. K.,Dhoble, S. J. Springer Science + Business Media 2017 Journal of electronic materials Vol.46 No.1
<P>Li2SiO3:Sm was synthesized by the solution combustion method. Powder x-ray diffraction technique was used to find the phase formation. Li2SiO3:Sm exhibits thermoluminescence (TL) peaks at approximately 140 degrees C, 155 degrees C, 190 degrees C, 250 degrees C, and 405 degrees C. Three defect centers contribute to the observed electron spin resonance spectrum from the gamma irradiated phosphor. Center I with principal g-values g(parallel to) = 2.0206 and g(perpendicular to) = 2.0028 is identified as an O-2(-) ion while center II, with an isotropic g-factor 2.0039, is assigned to an F+-type center. Center III is assigned to a Ti3+ center. The Ti3+ center is related to the 250 degrees C TL peak while the O-2(-) ion also correlates with the main TL peak at 250 degrees C. An additional defect center is observed during thermal annealing experiments, and the center (assigned to F+ center) seems to originate from an F center. The F center appears to be associated with the high temperature TL peak in a Li2SiO3: Sm phosphor. The luminescence spectrum reveals the dominant emission peaks at 605 ((4)G(5/2) -> H-6(7/2)) nm under the excitation wavelength of 402 nm.</P>
Cr3+-Doped Yb3Ga5O12 Nanophosphor: Synthesis, Optical, EPR, Studies
Singh, V.,Sivaramaiah, G.,Rao, J. L.,Singh, N.,Pathak, M. S.,Jirimali, H. D.,Singh, P. K.,Srivastava, A. K.,Dhoble, S. J.,Mohapatra, M. Springer Science + Business Media 2016 Journal of electronic materials Vol.45 No.8
<P>Gallium garnets of lanthanides are multifunctional materials especially known for their complicated structure and magnetic properties. In addition, with a suitable transition metal dopant ion, these matrices have been proved to be excellent materials for lasers. In particular, gallium garnet of ytterbium (Yb3Ga5O12) is known to possess excellent properties with regards to these applications. In this connection, Yb3Ga5O12 doped with Cr3+ nanophosphors were synthesized by a solution combustion route. The synthesized material was characterized by powder x-ray diffraction and scanning electron microscopy for phase purity and homogenous morphology. In order to ascertain the oxidation state of the doped ion, diffuse reflectance (DRF), photoluminescence (PL) and electron paramagnetic resonance (EPR) experiments were performed on the sample. The DRF and PL data suggested the stabilisation of the trivalent Cr ion in the matrix. The EPR spectra exhibited two resonance signals with effective g values at g approximate to 7.6 and 4. The EPR data corroborated the DRF and PL results, suggesting the stabilisation of Cr3+ in the matrix at octahedral-type geometries.</P>
Eu2+ and Mn2+ Co-doped BaMgAl10O17 Blue- and Green-Emitting Phosphor: A Luminescence and EPR Study
Singh, V.,Sivaramaiah, G.,Rao, J. L.,Singh, N.,Srivastava, A. K.,Jirimali, H. D.,Li, J.,Gao, H.,Kumaran, R. S.,Singh, P. K. Springer Science + Business Media 2016 Journal of electronic materials Vol.45 No.6
<P>Eu2+ and Mn2+ co-doped BaMgAl10O17 phosphor has been prepared by a solution combustion method. The structural, morphological and compositional analysis of the BaMgAl10O17:Eu2+ and Mn2+ powders have been studied by x-ray diffraction, scanning electron microscopy and energy dispersive x-ray spectroscopy. The electron paramagnetic resonance (EPR) spectrum exhibited resonance signals with the effective g values of g a parts per thousand 4.88 and g a parts per thousand 1.98. The resonance signal with the effective g value of g a parts per thousand 4.88 is characteristic of Eu2+ ions whereas g a parts per thousand 1.98 is due to Mn2+ ions. The number of spins participating in resonance, Gibbs free energy, magnetic susceptibility, Curie constant, effective magnetic moment, zero-field splitting parameter and hyperfine splitting constant have been evaluated. From optical and EPR correlation, it is inferred that Eu2+ and Mn2+ are present in the BaMgAl10O17 matrix.</P>
Singh, Vijay,Singh, N.,Pathak, M.S.,Singh, Pramod K.,Natarajan, V. Elsevier 2018 Optik Vol.171 No.-
<P><B>Abstract</B></P> <P>Tb<SUP>3+</SUP>-doped Ca<SUB>2</SUB>La<SUB>8</SUB>(SiO<SUB>4</SUB>)<SUB>6</SUB>O<SUB>2</SUB> phosphors with different Tb<SUP>3+</SUP> content powders were successfully synthesized using the sol-gel process for this paper. A series of green-emitting Tb<SUP>3+</SUP>-doped Ca<SUB>2</SUB>La<SUB>8</SUB>(SiO<SUB>4</SUB>)<SUB>6</SUB>O<SUB>2</SUB> phosphors was well characterized using the XRD and PL techniques. The emission measurements upon a UV-light excitation of 232 nm showed the Tb<SUP>3+</SUP>-emission characteristics. The emission and excitation spectra were recorded as the Tb<SUP>3+</SUP> concentration was varied. It became evident that the addition of the Tb<SUP>3+</SUP> increased the PL intensity, and the reasons for this behavior are discussed.</P>
Visible upconversion in Er<sup>3+</sup>/Yb<sup>3+</sup> co-doped LaAlO<sub>3</sub> phosphors
Singh, Vijay,Rai, V.K.,Singh, N.,Pathak, M.S.,Rathaiah, M.,Venkatramu, V.,Patel, Rahul V.,Singh, Pramod K.,Dhoble, S.J. Elsevier 2017 Spectrochimica acta. Part A, Molecular and biomole Vol.171 No.-
<P><B>Abstract</B></P> <P>The Er<SUP>3+</SUP> doped and Er<SUP>3+</SUP>/Yb<SUP>3+</SUP> co-doped LaAlO<SUB>3</SUB> phosphors have been synthesized by the combustion method and characterized their structural, morphological, elemental, vibrational and optical properties. The optical absorption and upconversion properties of the synthesized phosphors have been studied. Upon co-doping Yb<SUP>3+</SUP> ions into Er<SUP>3+</SUP>:LaAlO<SUB>3</SUB>, the blue, green and red upconversion emissions of Er<SUP>3+</SUP> ions have been enhanced about ~20, ~54 and ~22 times, under 978nm laser excitation. The observed upconversion emissions could be due to excited state absorption in Er<SUP>3+</SUP>:LaAlO<SUB>3,</SUB> whereas energy transfer is dominant mechanism in Er<SUP>3+</SUP>/Yb<SUP>3+</SUP>:LaAlO<SUB>3</SUB> phosphors. The tuning in the color emitted from the synthesized phosphors towards the green region has been found due to incorporation of the Yb<SUP>3+</SUP> ions. With increase in the pump power, the color emitted from the co-doped phosphor is not tuned significantly, showing its applicability in making the green display devices.</P> <P><B>Highlights</B></P> <P> <UL> <LI> By facile combustion synthesis, Er<SUP>3+</SUP> and Er<SUP>3+</SUP>/Yb<SUP>3+</SUP> doped LaAlO<SUB>3</SUB> phosphors are obtained. </LI> <LI> Phosphor was characterized using XRD, SEM-EDX, FTIR and Up-conversion spectroscopy. </LI> <LI> Upon excitation at 978nm, intense up-conversion emission is observed. </LI> <LI> Prepared materials could be suitable for up-conversion lasers and green display device. </LI> </UL> </P> <P><B>Graphical Abstract</B></P> <P>[DISPLAY OMISSION]</P>