Enhanced photoluminescence response of Ca2+/Ba2+ substituted solid solutions of SrS: Ce phosphors

Abstract

The quest of improving luminescence efficiency in alkaline earth sulfide phosphors has been of great interest due to their applications in diverse areas. We synthesized SrS:Ce-0.05, Sr0.75Ba0.20S:Ce-0.05, Sr0.75Ca0.20S:Ce-0.05 and Sr0.75Ca0.10Ba0.10S:Ce-0.05 phosphors using solid state diffusion method. X-ray diffraction patterns of all the samples were found similar to the cubic SrS phase except minor shifts in angles. To ascertain the valence state of Ce, near edge X-ray absorption fine structure spectroscopy was employed using synchrotron radiations. We simulated Ce M-5,M-4-edges of Ce3+ ions using atomic multiplet calculations, which agrees well with the experimental data, clearly suggesting that Ce enters as Ce3+ in all the samples. The photoluminescence spectra of synthesized phosphors exhibit blue-green emission assigned to the 5d-4f transitions in Ce3+ levels, with minor shifts in wavelength. Interestingly, Ca2+/Ba2+ substitution in SrS: Ce phosphors increases the PL intensity considerably. In comparison to SrS: Ce-0.05, PL intensity of Sr0.75Ca0.10Ba0.10S:Ce-0.05 phosphors was enhanced by 2.7 times, which may be exploited in many optical applications. (C) 2018 Elsevier B.V. All rights reserved.