Structure and site selective luminescence of sol-gel derived Eu:Sr2SiO4

Strontium silicate (Sr2SiO4) samples doped with varying Eu3+ content were prepared via sol-gel route and characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), dynamic light scattering (DLS) and photoluminescence (PL) techniques. The synthesis temperature could be brought down to 600 degrees C for formation of a singe phase sample. The concentration of the dopant ion and the temperature of annealing were optimized for maximum PL intensity. The critical energy-transfer distance for the Eu3+ ions was evaluated based on which the quenching mechanism was verified to be a multipole-multipole interaction. Based on the time-resolved emission data (TRES), it was inferred that, two different types of Eu3+ ions were present in the matrix. The first type was a long lived species (tau=4.7 ms) present at 10-coordinated 'Sr'sites and the other was a short lived species (tau=1.2 ms) present at the 9-coordinated 'Sr'sites which gets selectively excited at 296 nm. Judd-Ofelt (J-O) intensity parameters for both the species were evaluated. The trend observed for the two species in the J-O parameters, Omega(2) and Omega(4) were different confirming their existence in two different environments. The color coordinates of the system were evaluated and plotted on a CIE index diagram. Commercial utility of the phosphor was investigated by comparing it with commercial red phosphor. (C) 2012 Elsevier B.V. All rights reserved.