저널

Dy3+- and Eu3+-codoped BaWO4 phosphors for white light-emitting diode were synthesized with different activator ions via a solid-state reaction process. The structural, morphological, and optical properties of the BaWO4:Dy3+,Eu3+ phosphors were investigated as a function of Eu3+ concentration at a fixed concentration of Dy3+ ions. XRD patterns exhibited that all the synthesized phosphors had a tetragonal system, irrespective of the concentrations of Dy3+ and Eu3+ ions. The excitation spectra of the synthesized phosphors were composed of three intense bands centered at 251, 355, and 393 nm and several weak peaks. For the BaWO4:Dy3+,Eu3+ phosphors synthesized with 1 mol% of Eu3+, the emission spectra under ultraviolet excitation at 393 nm showed two strong blue and yellow bands at 485 and 577 nm corresponding to the 4F9/26H15/2 and 4F9/26H13/2 transitions of Dy3+ ions, respectively and several weak bands in the range of 600–700 nm resulting from the 4f transitions of Eu3+ ions. As the concentration of Eu3+ ions increased, intensities of the blue and yellow emission bands gradually decreased while those of the red emissions increased rapidly and the energy transfer efficiency from Dy3+ to Eu3+ ions was 95.3% at 20 mol% of Eu3+. The optimum white light emission with x=0.363, y=0.357 CIE 1931 chromaticity coordinates was obtained for the sample doped with 5 mol% Dy3+ and 1 mol% of Eu3+.

Phosphor, Photoluminescence, Solid-state reaction