Photoluminescence of single-phased white light emission materials based on simultaneous Tb3+, Eu3+ and Dy3+ doping in CaWO4 matrix

The triply-doped xTb(3+)/xEu(3+)/xDy(3+) CaWO4 (x: 0.5, 1.0, 2.0, 3.0, 4.0 and 5.0 mol%) nanomaterials were prepared at room temperature by a coprecipitation method. The luminescence materials were characterized by X-ray powder diffraction (XPD), thermal analysis (TG), infrared absorption spectroscopy (FTIR) and UV excited photoluminescence. The prepared powder phosphors are single-phase scheelite structure with porous morphology and particle sizes around 11 nm. The materials display white color from cool to the warm white, under UV excitation, as a result of the intraconfigurational 4f transitions from trivalent rare earth ions. The non-radiative energy transfer processes from the O -> W and O -> Eu LMCT as well as the 4f(8) -> 4f(7)5d(1) states to the intraconfigurational 4f excited levels of rare earth ions and simultaneous emissions from the F-4(9/2) (Dy3+) -> D-5(4) (Tb3+) -> D-5(1),D-5(0) (Eu3+) emitter levels are reported. Furthermore, CIE parameters and the color correlated temperature (CCT) are discussed in order to characterize the color emission. Based on the results, these luminescence materials may be potential candidates for white light emitting diodes and solid-state lighting. (C) 2016 Elsevier B.V. All rights reserved.