Effects of Bi3+ ions on luminescence properties of ZnWO4:Eu3+, Sm3+, Bi3+ nanorods

Abstract

To develop red emitting phosphors for white LEDs, a series of ZnWO4:xEu3+, ySm3+, zBi3+ (x, y and z are values in mol%, x = 5; y = 0, 0.6; 0 ≤ z ≤ 11) phosphors were prepared by hydrothermal method, and their structures, characteristic photoluminescence properties and energy transfer mechanism were studied in detail. The causes for the morphological changes after doping Sm3+ and Bi3+ ions were also analyzed in our work. It could be determined that all the samples were pure monoclinic ZnWO4. For Bi3+ doped ZnWO4:Eu3+, the dominant emission band located at 617 nm (when λex = 357 nm) was significantly enhanced by the efficient energy transfer (from Bi3+ to Eu3+). In addition, the experiment also found that Bi3+ doped ZnWO4:Eu3+ had a stronger emission than ZnWO4:Eu3+ (without Bi3+ sensitization) excited at 465 nm. This phenomenon appeared in ZnWO4:Eu3+, Sm3+, Bi3+ as well. Thus, we suggest that the introduction of Bi3+ leads to structural distortion that affects the f–f transition of Eu3+ in ZnWO4:RE3+. The obtained results clearly indicate the beneficial influence of introduction of Bi3+ ions on luminescence properties of Eu3+ in our work.