Abstract
The white light emitting dysprosium doped calcium sulfide (CaS) nanophosphors were synthesized via solid-state diffusion method. The prepared phosphors were characterized using X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), photoluminescence (PL) spectroscopy and UV–Vis absorption spectroscopy. The average crystallite size of CaS:Dy phosphors was found to be in the range of 24–27 nm from the XRD measurements. The PL emission spectrum exhibited two prominent peaks at 480 and 572 nm followed by a weak peak at 665 nm which are due to the transition from 4F to 6H states of Dy3+ ions in the CaS host lattice. The values of Commission Internationale de l’Eclairage (CIE) coordinates, yellow to blue intensity ratio (Y/B) and the correlated color temperature (CCT) of the samples were calculated using the PL emission spectra in order to evaluate the emitted light. The CIE coordinates of CaS:Dy nanophosphors were found to be very close to the standard white light point given by (0.333,0.333). The optical bandgap of the samples was estimated from diffuse reflectance spectra and its value varied from 4.03 to 4.30 eV. The obtained results suggest the possibility of these phosphors being used in white light LEDs when excited with near ultraviolet light.
Published Version
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