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Energy transfer dynamics and time resolved photoluminescence in BaWO4:Eu3+ nanophosphors synthesized by mechanical activation

Abstract

This work reports synthesis of nanocrystalline undoped and europium doped BaWO4:Eu3+ nanophosphors by a mechanical activation process using high energy ball mill (HEBM) technique. The prepared nanophosphors were characterized systematically by Rietveld analysis of the X-ray powder diffraction (XRD) data, Raman spectroscopy, energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The synthesized nanophosphors were found to be of spherical morphology and of very small particle size ~ 25nm. To explore this material for application in luminescence, detailed time resolved photoluminescence studies was carried out. It was observed that it is rare breed of phosphor material which exhibit exceptional luminescence properties such as capability to give high emission output till 5.0 mol % without undergoing quenching and unique property to get excited by mid ultra violet (MUV) light, near ultraviolet (NUV) light, as well as, by visible light such as blue and green. It was also observed that energy transfer primarily takes place from tungstate group of host to Eu3+. In fact energy transfer from the host to Eu3+ becomes more and more efficient with the increasing concentration of Eu3+ ions. Two life time values are observed for all europium ion (Eu3+) concentrations, one of the order of 465-650 µs (TS, short lifetime) and the other of the order of 1050-1320 ms (TL, longer lifetime). This reflects the fact that Eu3+ ions occupy two sites; regular symmetric Ba2+ site (S1) and asymmetric site (S2) which will be closer to charge compensating defects. Calculation of Judd-Ofelt parameter illustrated that at all europium concentrations, the local surrounding around it lacks inversion symmetry (asymmetric environment) and the exact point group symmetry around europium ion was found to be C6v. The red purity (intense 5D0-7F2) and high quantum efficiency (78%) of BaWO4:Eu3+ projects it as a new red phosphor for application in white light emitting diodes.

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Publication details

The article was received on 04 May 2017, accepted on 08 Jul 2017 and first published on 10 Jul 2017


Article type: Paper
DOI: 10.1039/C7NJ01249G
Citation: New J. Chem., 2017, Accepted Manuscript
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    Energy transfer dynamics and time resolved photoluminescence in BaWO4:Eu3+ nanophosphors synthesized by mechanical activation

    P. Jena, S. K. Gupta, N. K. Verma, A. K. Singh and R.M. Kadam, New J. Chem., 2017, Accepted Manuscript , DOI: 10.1039/C7NJ01249G

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