%0 Journal Article
%T Giant Improvement on the Afterglow of Sr4Al14O25:Eu2+,Dy3+ Phosphor by Systematic Investigation on Various Parameters
%A Hom Nath Luitel
%A Takanori Watari
%A Rumi Chand
%A Toshio Torikai
%A Mitsunori Yada
%J Journal of Materials
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/613090
%X Highly intense, long persistent Sr4Al14O25:Eu2+,Dy3+ blue-green phosphor with different B3+, Eu2+, Dy3+, and Ag+ contents was prepared by solid-phase reaction at various temperatures in reductive atmosphere of 10% H2 in N2. The effects of synthesis parameters like calcination temperature and time, calcination environment, effect of stoichiometry of the host composition, and additives like addition of boron and rare earth ions (Eu, Dy) were studied in detail. Results revealed that the phosphor containing ~40£¿mol% H3BO3 showed dense and pure Sr4Al14O25 phase with higher emission intensity, but in the samples containing less than 20£¿mol% H3BO3 mixed phases consisting of Al2O3, SrAl12O19 and SrAl2O4 were observed, while in higher H3BO3 content, SrAl2B2O7 phases predominated. When the stoichiometry of Al/Sr was 3.7, the best phosphorescence and afterglow were noted. The phosphor containing 4£¿at.% of Eu and 8£¿at.% of Dy, and 3£¿at.% Ag exhibited the maximum initial intensity of 5170£¿mcd¡¤m£¿2 and the longest persistency of greater than 30 hours over the value of 5£¿mcd¡¤m£¿2, higher than the commercial products and applicable for various display applications involving indoor as well as outdoor uses. 1. Introduction Phosphor materials with long afterglow is a kind of energy storing materials that can absorb UV-visible light from sun light, and gradually release the absorbed energy in the darkness at a certain wavelength [1]. Among the various phosphors, ZnS-based materials doped with Cu or Mn ions were first prepared and applied for various fields [2]; however, the luminescent intensity of these phosphors are not bright enough and the afterglow time is short. Therefore, some radio-active elements such as Co and Pm had to be codoped into the ZnS-matrix so as to prolong the afterglow time. Compared to sulfide-based phosphors, oxide-based phosphors have been recognized as the efficient host materials because of their high quantum efficiency [3], chemical stability, no radio-active radiations, environmental capability, and long persistence of phosphorescence [4]. As far as the development of phosphor is concerned, Eu2+ ions were used frequently as an activator ion for various host lattices. This occurs because the 4f7 electron configuration of the Eu2+ ion shows efficient luminescence owing to the 4f ¡ú 5d transition, and the luminescence colors or wavelengths change widely from near UV to red regions depending on the nature of host lattice [5]. As a new phosphor, strontium aluminates doped with Eu divalent ion (SAE) have been investigated as an efficient phosphor that
%U http://www.hindawi.com/journals/jma/2013/613090/