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

To develop red emitting phosphors for white LEDs, a series of ZnWO 4 : x Eu 3+ , y Sm 3+ , z Bi 3+ ( 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 Sm 3+ and Bi 3+ ions were also analyzed in our work. It could be determined that all the samples were pure monoclinic ZnWO 4 . For Bi 3+ doped ZnWO 4 :Eu 3+ , the dominant emission band located at 617 nm (when λ ex = 357 nm) was significantly enhanced by the efficient energy transfer (from Bi 3+ to Eu 3+ ). In addition, the experiment also found that Bi 3+ doped ZnWO 4 :Eu 3+ had a stronger emission than ZnWO 4 :Eu 3+ (without Bi 3+ sensitization) excited at 465 nm. This phenomenon appeared in ZnWO 4 :Eu 3+ , Sm 3+ , Bi 3+ as well. Thus, we suggest that the introduction of Bi 3+ leads to structural distortion that affects the f – f transition of Eu 3+ in ZnWO 4 :RE 3+ . The obtained results clearly indicate the beneficial influence of introduction of Bi 3+ ions on luminescence properties of Eu 3+ in our work.