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 °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 (τ=4.7 ms) present at 10-coordinated ‘Sr’sites and the other was a short lived species (τ=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, Ω2 and Ω4 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.