Tunable Luminescence And White Light Emitting Of The Single-phase Multicolor Phosphors

Due to the ultraviolet/near-ultraviolet luminescence properties and good stability of molybdate, it can be used as an important luminescence material. When different rare earth ions doped into molybdate,4fâ†'4f transitions of rare earth ions make light from the ultraviolet to the infrared light emission. By adjusting the ratio of the rare earth ions, the tunable luminescence can be realized. So rare earth ions doped molybdate compounds are valuable for searching suitable phosphors for w-LEDs.In this thesis, several rare earth doped molybdate phosphors have been prepared. The main content is as follows:Ca0.8La0.2-x-yMoO4:xTb3+, yEu+phosphors were prepared via hydrothermal method. There is an energy transfer of Tb3+â†'Eu3+in the obtained phosphors. Moreover, the luminescence colors of the Ca0.8La0.16-yMoO4:0.04Tb3+, yEu3+samples can be tuned from green, green-yellow and yellow to red by simply adjusting the relative doping concentrations of the activator ion of Eu+under a single wavelength excitation.Ca0.8La0.2-xMoO4:xDy3+phosphors were prepared by a hydrothermal method. Upon excitation of353nm UV light, white light is realized by combining a yellow emission band at575nm and a blue emission band at488nm attributed to the transition of Dy3+. The obtained Ca0.8La0.19MoO4:0.01Dy3+showed bright white emission with a color temperature of6429K, and CIE color coordinates of (0.3123,0.3434).CaLa1.98-x(MoO4)4:0.02Dy3+, xEu3+phosphors were prepared by sol-gel method. Upon excitation of353nm, the as-prepared Eu3+or Dy3+doped samples show strong red,blue and yellow emission, there is an energy transfer from Dy3+to Eu3+. The obtained CaLa2-x-y(MoO4)4:0.02Dy3+,0.006Eu3+shows bright white emission with a color temperature of5087K, and CIE color coordinates of (0.3489,0.3125).CaLa2(MoO4)4:Tb3+/Eu3+/Tm3+phosphors and SrLa2(MoO4)4:Dy3+/Eu3+fluorescent materials were prepared by hydrothermal method. Under353nm UV excitation, the obtained CaLa1.885(MoO4)4:0.04Tb3+,0.06Eu3+,0.015Tm3+and SrLa1.93(MoO4)4:0.05Dy3+,0.02Eu3+show bright white emission.