Tunable Luminescence And White Light Emitting Of Rare Earth Ions Doped Bismuth Tungstate/ Bismuth Molybdate Phosphors

LED devices which are made of solid nanometer luminescent materials with rare earth ions as activators have gained wide attention. With stable crystal structure and thermal stability, tungstate and molybdate have absorption in visible light, so they can be used as a kind of self-excited fluorescence substrate material with high performance. When rare earth ions with different mixing ratios doped into molybdate and tungstate, the tunable luminescence can be realized by adjusting the ratio of the rare earth ions. Phosphor has shown its luminescence capability in white area. As the single host of white solid nanometer luminescent materials, rare earth ions doped molybdate and tungstate compounds are valuable for searching suitable phosphors for w-LED.In this paper, the Eu³⁺, Tb³⁺ and Dy³⁺ doped tungstate luminescent materials by using bismuth tungstate/bismuth molybdate were synthesized by co-precipitation method. Multicolor luminescence and white light emitting of rare earth ions were realized, and its luminescence properties were studied as well.The Dy³⁺ doped bismuth tungstate luminescent materials were synthesized by co-precipitation method. Tungstate hosts have wide and strong absorption in near-ultraviolet. It is found that it can sensitize the luminescence of Dy³⁺ through the energy transfer from nonradiative transition activated by high energy. The results showed that new luminescent materials Bi2WO6:Dy³⁺ could be synthesize when annealing temperature reached 700? at pH of 5. Dy³⁺could emit characteristic peak of 4F9/2?6H15/2 magnetic dipole transitions and 4F9/2?6H13/2 electric transitions. This material matched the output wave length of blue light LED chips, which was the basis of the preparation of Eu³⁺ and Dy³⁺ doped tungstate single-phase white phosphor luminescent materials.In Eu³⁺ and Dy³⁺ doped tungstate substrate luminescent materials, Bi2W06:Eu³⁺,Dy³⁺ multicolor luminescence and white light emitting of luminescent materials were synthesized by using an energy transfer of Eu³⁺?Dy³⁺ in the obtained phosphors.The results showed that when doping concentration of the ion of Eu³⁺,Dy³⁺ were 10% and 8%?mole fraction?, respectively,Bi2W06 had excellent white luminescence properties.It has been proved that obtained samples were phosphors of single-phase w-LED,which was confirmed by the calculated color coordinate value in white light?0.3121, 0.2634?.Tb³⁺ doped ?-Bi2MoO6 green nanometer solid phosphors were synthesized by co-precipitation method by using EDTA as complexing agent. The structure,component and luminescence property of the samples also have been systematically studied by DTA-TG,XRD and XRF.The results showed that when the annealing temperature reached 800?,pH was from 1 to 3, orthorhombic phase ?-Bi2Mo3O12 was appeared.When pH changed from 5 to 13,orthorhombic phase ?-Bi2MoO6 was appeared and the most strong motivated peak of ?-Bi2MoO6:Tb³⁺ appeared at 488 nm monitored by 544nm light.The strong emission peak of ?-Bi2MoO6:Tb³⁺ appeared at 544nm ?5D4?7F5?monitored by 488nm blue light.When the mole ratio of Tb³⁺ was 20%,the emission peak of phosphor had maximum value.Eu³⁺ and Tb³⁺ doped ?-Bi2MoO6 phosphors were synthesized by co-precipitation method and the influence of concentration of the rare earth ion of Eu³⁺,Tb³⁺ on synthesis materials was also studied.The results showed that the color of phosphors could change by controlling the concentration of Eu³⁺ and Tb³⁺ when annealing temperature reached 800?at pH of 5. Phosphors could be tuned from red,light red to green by simply adjusting the relative doping ratios of the activator ion of Eu³⁺ and Tb³⁺. The color coordinate value of ?-Bi2MoO6:Eu³⁺?Tb³⁺ was?0.3121,0.2634?,which was in white light.Eu³⁺ and Tb³⁺ doped single-phase molybdate hosts as phosphors of w-LED were realized as well.Color controllable single-doped or co-doped phosphors were synthesized by using bismuth tungstate/bismuth molybdate as substrate and Dy³⁺, Eu³⁺ and Tb³⁺as activators, and phosphors could emit in white light. It extends the applications of bismuth tungstate/bismuth molybdate in white light luminescent materials.