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Singh, Vijay,Sivaramaiah, G.,Rao, J. L.,Kumaran, R. Senthil,Dhoble, S. J. American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.1
<P>By adopting a facile solution combustion synthesis, crystallized europium doped blue phosphors were successfully prepared. These phosphors were characterized by X-ray diffraction (XRD), Fourier transform infrared absorption (FT-IR), energy dispersive analysis of X-ray, Electron Paramagnetic Resonance (EPR) and Photoluminescence (PL) experimental methods. The photoluminescence spectrum indicates Eu2+ and Eu3+ ions in these phosphors. The band at around 442 nm is attributed to the spin-allowed 4f(6)5d(1) (D-2) -> (4)f(7)(S-6(7/2)) transition of Eu2+ ions. The sharp bands at 591 (D-5(0) -> F-7(1)) and 616 (D-5(0) -> F-7(2)) nm are attributed to the spin-forbidden transitions of Eu3+ ions. The EPR spectra of as-prepared and post-treated LaAl11O18:Eu phosphors exhibit signals characteristic of La2+ and Eu2+ ions. The number of spins, Gibbs energy, magnetic susceptibility, Curie constant and effective magnetic moment values were calculated and compared at 296 and 110 K.</P>
Singh, V.,Sivaramaiah, G.,Mohapatra, M.,Rao, J. L.,Singh, N.,Pathak, M. S.,Singh, P. K.,Dhoble, S. J. Springer Science + Business Media 2017 Journal of Electronic Materials Vol.46 No.2
<P>GdAlO3 phosphor samples have been prepared by a solution combustion method. X-ray diffraction analysis revealed that the GdAlO3 phosphor stabilized in orthorhombic phase. The optical absorption spectrum showed bands due to Gd3+ ions as well as defect level in the host. The excitation spectrum exhibited a dominant band with maximum at 273 nm. Upon excitation at 273 nm, ultraviolet-B (UV-B) emission with maximum at 312 nm was observed from the undoped sample, being attributed to P-6(7/2) -> S-8(7/2) transition of Gd3+ ion. The UV-B emission was enhanced at liquid-nitrogen temperature (77 K), most probably due to increased ground-state population according to the Boltzmann distribution law. Electron spin resonance spectra of samples at both room and liquid-nitrogen temperature exhibited resonance signals at g ae 2, attributed to Gd3+ ions arranged with octahedral symmetry linked via oxygen bridges. Various magnetic and thermodynamic parameters for the phosphor system were evaluated by standard procedures. Correlation of these values with the optical properties suggested that the GdAlO3 phosphor can be effectively used as an UV-B light source for industrial applications at room temperature.</P>
Gupta, K.K.,Kadam, R.M.,Dhoble, N.S.,Lochab, S.P.,Singh, V.,Dhoble, S.J. Elsevier Sequoia 2016 JOURNAL OF ALLOYS AND COMPOUNDS Vol.688 No.2
In this study, we have synthesized Dy<SUP>3+</SUP> activated Sr<SUB>5</SUB>(PO<SUB>4</SUB>)<SUB>3</SUB>F (S-FAP) phosphors by sol-gel synthesis method. The synthesized phosphors were characterized by X-ray diffraction pattern (XRD), scanning electron microscopic (SEM), photoluminescence (PL) and thermoluminescence (TL) for structural, morphological and luminescent properties. Dy<SUP>3+</SUP> activated Sr<SUB>5</SUB>(PO<SUB>4</SUB>)<SUB>3</SUB>F phosphor shows its characteristic PL emission at 481 nm and 574 nm due to <SUP>4</SUP>F<SUB>9/2</SUB> → <SUP>6</SUP>H<SUB>15/2</SUB> and <SUP>4</SUP>F<SUB>9/2</SUB> → <SUP>6</SUP>H<SUB>13/2</SUB> transitions, respectively. TL characteristics of Dy<SUP>3+</SUP> doped Sr<SUB>5</SUB>(PO<SUB>4</SUB>)<SUB>3</SUB>F phosphors were taken after irradiation by <SUP>60</SUP>Co gamma exposure. Two separate TL peaks at 126 <SUP>o</SUP>C and 279 <SUP>o</SUP>C were observed in case of Dy<SUP>3+</SUP> doped phosphor. Sr<SUB>5</SUB>(PO<SUB>4</SUB>)<SUB>3</SUB>F:Dy<SUP>3+</SUP> phosphor was irradiated within a wide range of exposure of 50 Gy to 7 kGy doses. Linearity was found up to 2 kGy and thereafter TL response saturates. Fading study was also carried out over the duration of six weeks for Sr<SUB>5</SUB>(PO<SUB>4</SUB>)<SUB>3</SUB>F phosphor. Trapping parameters were calculated using Chen's peak shape method, initial rise method and various heating rate method. Glow curve is deconvoluted using computerized glow curve deconvolution program. TL sensitivity of Sr<SUB>5</SUB>(PO<SUB>4</SUB>)<SUB>3</SUB>F:Dy<SUP>3+</SUP> phosphor is found to be less by a factor of 2.08 than commercially used CaSO<SUB>4</SUB>:Dy phosphor. In order to identify the defect centers formed upon γ-ray irradiation in Sr<SUB>5</SUB>(PO<SUB>4</SUB>)<SUB>3</SUB>F:Dy<SUP>3+</SUP> phosphor, EPR measurements were carried out on un-irradiated and irradiated phosphors.
On the infrared emissions of Er<sup>3+</sup>/Yb<sup>3+</sup> co-doped SrAl<sub>2</sub>O<sub>4</sub>
Pawar, S.U.,Senthil Kumaran, Rangarajulu,Kumar, M.,Yun, K.S.,Dhoble, S.J.,Singh, Vijay WISSENSCHAFTLICHE VERLAGSGESELLSCHAFT MBH 2017 OPTIK -STUTTGART- Vol.136 No.-
<P><B>Abstract</B></P> <P>Infrared emitting SrAl<SUB>2</SUB>O<SUB>4</SUB>:Er<SUP>3+</SUP> and SrAl<SUB>2</SUB>O<SUB>4</SUB>:Er<SUP>3+</SUP>,Yb<SUP>3+</SUP> powder samples were prepared by the urea combustion route. Powder X-ray diffraction technique was used to find the phase formation. Upon excitation at 980nm, broad infrared emission of Er<SUP>3+</SUP> ions at around 1.54μm was observed. The dependency of infrared luminescence intensity with co-doping was discussed.</P>
Baig, N.,Dhoble, N.S.,Yerpude, A.N.,Singh, V.,Dhoble, S.J. Wissenschaftliche Verlagsgesellschaft m. b. H 2016 Optik Vol.127 No.16
<P>In this paper we report the photoluminescence (PL) characteristics of Dy3+, Sm3+, Eu3+ and Tb3+ doped Na3Pb2(SO4)(3)Cl phosphors prepared by wet chemical method. Prepared phosphors were characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), color co-ordinates and photoluminescence (PL) properties. The emission spectra of Na3Pb2(SO4)(3)Cl:Dy3+ phosphor show the characteristic emission of Dy3+ ions peaking at 478 nm and 573 nm (lambda ex = 390 nm), owing to transitions of F-4(9/2) -> H-6(15/2) and F-4(9/2) -> (6)H(13/)2 receptively. Under 396 nm excitation the Na3Pb2(SO4)(3)Cl:Eu3+ phosphor shows emission at 594 nm and 616 nm due to D-5(0) -> F-7(1) and D-5(0) -> F-7(2) transitions of Eu3+ ions respectively. When Na3Pb2(SO4)(3)Cl:Tb3+ phosphor was excited by 380 nm, the emission spectrum showed intense green band at 545 nm due to D-5(4) -> F-7(5) transition in Tb3+ ion. The PL emission spectrum of Na3Pb2(SO4)(3)Cl:Sm3+ phosphors by 405 nm excitation gave an emission at 562 nm ((4)G(5/2) -> H-6(5/2)), 598 nm ((4)G(5/2) -> H-6(7/2)) and 643 nm ((4)G(5/2) -> H-6(9/2)). The CIE color coordinates indicated that all the above phosphors were suitable as a white light -emitting phosphor. SEM studies of the phosphors show that grain size of the powders prepared by the wet chemical method is about ten micrometers range. From the obtained results it can be concluded that Dy3+, Sm3+ Eu3+ and Tb3+ doped Na3Pb2(SO4)(3)Cl phosphors are potential candidates for solid state lighting applications in green technology. (C) 2016 Elsevier GmbH. All rights reserved.</P>
Shinde, K N,Dhoble, S J,Yoon, S J,Park, K American Scientific Publishers 2014 Journal of Nanoscience and Nanotechnology Vol.14 No.8
<P>A series of Tb(3+)-activated NaLi2PO4 novel nano-crystalline phosphors was synthesized by the solution combustion method. The prepared Na(1-x)Li2PO4:xTb(3+) (0.01 x 0.1) phosphors crystallized in the orthorhombic crystal structure. Its effective absorption in the near ultraviolet range allowed highly efficient green emission. The Na(1-x)Li2PO4:xTb(3+) phosphors showed characteristic (5)D4 --> (7)FJ (J = 3, 4, 5, and 6) transitions of Tb(3+), i.e., (5)D4 --> (7)F6 (488 nm), (5)D4 --> (7)F5 (545 nm), (5)D4 --> (7)F4 (583 nm), and (5)D4 --> (7)F3 (622 nm). The Na0.95Li2PO4:0.05Tb(3+) phosphor showed the most excellent emission efficiency. The present work suggests that the Na0.95Li2PO4:0.05Tb(3+) is a potential green-emitting phosphor for near ultraviolet excited light emitting diodes.</P>
Optical Properties of EuxRe(1−x)(TTA)3Phen Organic Complexes in Different Solvents
N. Thejo Kalyani,S. J. Dhoble,안정선,Ramchandra Balaji Pode 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.4
Optical absorption spectra of Eu(TTA)3Phen (TTA: Thenoyl Trifluro Acetone) and EuxRe(1−x)(TTA)3Phen (where Re = Y, Tb) organic luminescent complexes in different organic solvents are measured to study the shift of the π → π* and the n → π* optical transitions due to Eu3+ion and β-diketonate moieties. All complexes show good solubility in different basic and acidic solvents. Two optical absorption peaks observed in the UV region of the spectra of solvated complexes shift when the solvent is changed. With a variation in the solvent from basic to acidic, staggering differences in optical absorptions are noticed. Absorption peaks shift bathochromically by a few nm as the solvent varies from basic to acidic. The optical energy band gaps of EuxRe(1−x)(TTA)3Phen are very similar for all the solvents used. A substantial dependence of the electronic absorption spectra of Eu complexes on the solvent is reported.
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>