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Subject: search.filters.subject.Fluorophosphate glasses

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    Photoluminescence and energy transfer studies in Ce3+ and Sm3+ activated P2O5+K2O+Al2O3+BaF2+NaF2 glasses for solid state lighting
    (2020-01-01)
    Rao, V. Rajeswara
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    Doddoji, Ramachari
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    Pecharapa, Wisanu
    ;
    Kaewkhao, J.
    ;
    Depuru, Shobha Rani
    A color of blue-red emission by Ce<sup>3+</sup> and Sm<sup>3+</sup> activated fluorophosphate glasses (PKABfNf:P<inf>2</inf>O<inf>5</inf>+K<inf>2</inf>O + Al<inf>2</inf>O<inf>3</inf>+BaF<inf>2</inf>+NaF<inf>2</inf>) were successfully fabricated by using usual melt and sudden quenching method. The FTIR, SEM, EDS, luminescence spectra, the decay rates, and energy transfer (ET) mechanism in the co-doped (Ce<sup>3+</sup>,Sm<sup>3+</sup>):PKABfNf glasses were systematically investigated in detail. The luminescence spectra of co-doped glasses show broadband blue de-excitation that belongs to Ce<sup>3+</sup> ions and it obviously intensify the red de-excitation of Sm<sup>3+</sup> through an effective ET process. The decrease in lifetime could support the existence of ET between Ce<sup>3+</sup> and Sm<sup>3+</sup> in PKABfNf glasses. This ET from Ce<sup>3+</sup> to Sm<sup>3+</sup> can be proposed to be the interaction due to quadrupole-quadrupole, based on the Dexter's ET formula and Reisfeld's approximation. Furthermore, CIE chromaticity coordinates, color correlated temperature, color purity, ET luminous efficiency (η<inf>ET</inf>), critical energy transfer distance (R<inf>c</inf>), and ET parameter (Q) were calculated. The findings show that (Ce<sup>3+</sup>,Sm<sup>3+</sup>):PKABfNf glass might be a promising candidate in lighting field applications.
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    Luminescence and energy transfer studies of Ce3+/Dy3+ doped fluorophosphate glasses
    (2019-04-01)
    Rao, V. Rajeswara
    ;
    Devi, L. Lakshmi
    ;
    Jayasankar, C. K.
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    Pecharapa, Wisanu
    ;
    Kaewkhao, J.
    The fluorophosphate (PKABfNf:P<inf>2</inf>O<inf>5</inf>+K<inf>2</inf>O+Al<inf>2</inf>O<inf>3</inf>+BaF<inf>2</inf>+NaF<inf>2</inf>) glasses doped with single and co-doped (Ce and/or Dy) were prepared by conventional melt quenching technique and characterized their luminescence properties. The emission spectra of co-doped glass (PKABfNfCeDy) showed a broad blue band of Ce<sup>3+</sup> ions combined with the sharp peaks of Dy<sup>3+</sup> ions. Judd-Ofelt (JO) intensity parameters have been obtained from the optical absorption spectra of 1.0 mol% of Dy<sup>3+</sup> (PKABfNfDy1.0) glass. JO theory has been used to find the radiative properties of PKABfNfDy1.0 glass by using Futchbauer-Ladenbergh formula. The (Ce<sup>3+</sup>/Dy<sup>3+</sup>) co-doped glass exhibit radiative energy transfer (ET) from Ce<sup>3+</sup> to Dy<sup>3+</sup> upon UV excitation and then intensity is increased with increase in Dy<sup>3+</sup> ion concentration. The ET mechanism from Ce<sup>3+</sup> to Dy<sup>3+</sup> ion has been analyzed. The theoretical ET efficiency and quantum yield values were calculated from the emission spectrum of the Ce<sup>3+</sup> and (Ce<sup>3+</sup>/Dy<sup>3+</sup>) co-doped glasses. These results suggest that the co-doped PKABfNfCeDy glasses are promising candidate for commercial white light applications.