| In recent years, white light-emitting diodes(W-LEDs), as a new generation of lighting source, has shown its remarkable superiorities, such as high luminous, energy-efficient and non-pollution, which make it is widely used in landscape lighting, traffic light lamps, liquid crystal displaying, along with indoor and outdoor lighting. At present, YAG:Ce3+ phosphors excited by blue LED chips has realized commercialization. However, this kind of phosphors lack of red light wavelength and has bad color rendering. While W-LEDs made by coating ultraviolet LED chips with trichromatic phosphors could solve the problems. Therefore, the research of new trichromatic phosphors excited by ultraviolet light is of extreme significance. In this paper, the blue phosphors are successfully synthesized by sol-gel method. The structures of the phosphors are studied, the effects of sintering temperature and doping concentration on luminescence properties are focused on, luminous mechanism of phosphors is analyzed.The Y2M2O7:0.01Tm3+(M=Ti4+,Zr4+)phosphors sintering at different temperature are synthesized by sol-gel method. XRD patterns show that the structure of Y2Ti2O7:Tm3+ belongs to cube pyrochlore structure, and Y2Zr2O7:Tm3+ belongs to cube fluorite structure. Blue emissions center at the range of 450-460 nm, corresponding to 1D2â†'3F4 transition of Tm3+ ions. The sintering temperature has a great influence on the luminous intensity, the luminous intensity increases with the increasing of sintering temperature, and then decrease. The best luminescence performance is obtained for Y2Ti2O7:0.01Tm3+ and Y2Zr2O7:Tm3+ by sintering at 1000℃.The Y2M2O7:x Tm3+(M=Ti4+,Zr4+;x=0.005,0.01,0.03,0.05) phosphors sintering at 1000 ℃ are prepared. The effect of doping concentration on luminescence performance is studied. Blue emissions center at the range of 450-460 nm, corresponding to 1D2â†'3F4 transition of Tm3+ ions. The shape and position are not changed by Tm3+-doping concentration. Furthermore, the emission intensity of Y2Ti2O7:Tm3+ increases with the increasing of Tm3+-doping concentrations, then reaches a maximum when the Tm3+-doping concentration is at 1 mol%, and decreases with increasing of Tm3+-doping concentration. The same phenomenon is observed in Y2Zr2O7:Tm3+ phosphors. Compared with the luminous intensity of Y2Ti2O7:0.01Tm3+ phosphor, Y2Zr2O7:0.01Tm3+ phosphor has improved to 20 %, and would be well fited in blue phosphors for W-LEDs.The Y2Zr2O7:0.01Tm3+/x Bi3+(x=0, 0.01, 0.02, 0.03) and Y2Zr2O7:0.02Bi3+ phosphors sintering at 1000 ℃ are synthesized. The crystal structures of all the samples belong to single fluorite structure, and are not changed by the invasion of Tm3+. Blue emission band centered at 454 nm, corresponding to 1D2â†'3F4 transition of Tm3+-ion, is detected under 359 nm excitation. The doping concentration of Bi3+-ion has a great effect on the luminous intensity. The emission intensity of samples increases, then decreases with the increasing of Bi3+-doping concentration. The phosphor has the best luminescence performance when Bi3+-ion concentration is 2 mol%. Compared with the samples without doping Bi3+, the emission intensity of Y2Zr2O7:0.01Tm3+/Bi3+ is improved to 43 %. The energy transition mechanism of Bi3+â†'Tm3+ is studied on the basis of energy level diagrams.3+ 4+4+3+3+... |
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