Journal
PHYSICA B-CONDENSED MATTER
Volume 480, Issue -, Pages 131-136Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.physb.2015.10.006
Keywords
Phosphors; Photoluminescence; Oxyorthosilicates; Solid State Lighting
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Funding
- Department of Science and Technology South Africa, under the South African National Nanoscience Postgraduate Teaching and Training Platform
- competitive program for rated researchers (CPRR) of the National Research Foundation (NRF) [CPR20110724000021870]
- rental pool programme of the National Laser Centre (NLC) [NLC-LREGM00-CON-001]
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Powdered dysprosium (Dy3+) doped Lanthanum gadolinium oxyorthosilicate (LaGdSiO5) mixed phosphors were synthesized using urea-assisted solution combustion method. The X-ray diffractometer analysis showed that the samples crystalized in the pure monoclinic mixed phase of LaGdSiO5. The crystallite size and the lattice strain calculated from the X-ray diffraction peaks using Williamson-Hall equation varied from 12 nm to 16 nm and 1.6x10(-2) to 2.43x10(-2) respectively. The photoluminescence (PL) emission spectra recorded using 425, 454 and 475 nm excitation wavelengths exhibit characteristic similar to the YAG:Ce phosphor pumped InGaN LED system, by absorbing portion of the excitation energy and re-emitting it. The emission spectra were characterized by radiative recombination at 425, 454, 475,485 and 575 nm depending on the excitation wavelength. These emission line are ascribed to the f -> f transitions of Dy3+ The peak intensity and hence the color of the emitted visible light were dependent on the concentration of Dy3+ The International Commission on Illumination (CIE) color coordinates of (0.336, 0.313) and (0.359, 0.361) were obtained for Dy3+ molar concentration of 0.05 and 3.0 mol% when the emission was monitored using 454 nm and 475 nm respectively. The band gap measured from the reflectance curve using Tauc plot initially decreased with increasing Dy3+ concentration, but at higher concentration, it started to increase. These materials were evaluated for solid state lighting application. (C) 2015 Elsevier B.V. All rights reserved.
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