Luminescent properties of R+ doped Sr2SiO4:Eu3+ (R+=Li+, Na+ and K+) red-emitting phosphors for white LEDs

Sr2SiO4:Eu3+ and Sr2SiO4:Eu3+ doped with R+ (R+=Li+, Na+ and K+) phosphors were prepared by conventional solid-state reaction and investigated by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and photoluminescence spectroscopy. XRD patterns and SEM reveal that the optimal firing condition for Sr2SiO4:Eu3+ was 1300 degrees C for 4 h. The excitation and emission spectra indicate that the phosphor can be effectively excited by ultraviolet (395 nm) and blue (466 nm) light and emits intense red light peaked at around 614 nm corresponding to the D-5(0)-> F-7(2) transitions of Eu3+. In the research work, the effect of R+ contents on luminescence property and the Eu3+ concentration quenching process have also been investigated. The Eu3+ concentration quenching mechanism was verified to be a multipole-multipole interaction and the critical energy-transfer distance was calculated to be around 14.6 angstrom. The dopant R+(R+=Li+, Na+ and K+) as charge compensator in Sr2SiO4:Eu3+ can further enhance luminescence intensity, and the emission intensity of Sr2SiO4:Eu3+ doping Li+ is higher than that of Na+ or K. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.