Crystal Structure Induced Enhanced Afterglow Luminescence from Rare-Earth Ion Doped Strontium Silicate Phosphors

An orange-red (similar to 610 nm) emitting Sr3SiO5:Eu2+,Zn2+,Dy3+ long afterglow phosphor was synthesized using high temperature (1100 degrees C-1500 degrees C) based solid-state reaction method under controlled reducing atmosphere. X-ray diffraction (XRD) study confirms the tetragonal lattice structure having space group P4/ncc. Scherrer's size plot and Williamson-Hall methods have been applied to study the particle size distribution and inherent strain, respectively, using crystallographic data obtained from XRD patterns. Electron microscopy images showed the surface morphology with an average crystallite size of 0.412 mu m. Furthermore, detailed luminescence study was performed to observe photoluminescence (PL) and afterglow characteristics. An optimal PL emission peak was registered at similar to 610 nm when the phosphor was excited by visible blue (similar to 465 nm) light, which is due to the transitions from 4f(6)5d(1) to 4f(7) energy levels of Eu2+ ions. The enhanced afterglow property of >20 minutes has been achieved for dark-adapted human eyes, which could be utilized for designing strategic markings and signage boards that could glow in dark.