Study On Preparation And Modification Of Rare Earth Doped Borate Phosphors

Rare earth phosphors are widely used in the high-tech fields such as ecologicalillumination, dynamic display, communication satellite, optical computer andmolecular probe. Tricolor phosphors are currently the most valuable phosphors instudy, which have rich spectral lines in the visible region, narrow photoluminescencespectra and concentrated light energy. Besides, the tricolor phosphors have ultravioletresistant ability, high temperature stability, luminous efficiency and are able to adaptto the environment of high load. Rare earth doped borate phosphors have became thepreferred luminescent materials of flat panel display imaging such as PDP, HDTV andprojection television due to their stability, relatively low synthesis temperature andexcellent luminescent properties. It is one of the main research directions of rare earthdoped borate phosphors to improve their performance. Non rare earth metal ionsdoping could improve the luminescent properties of phosphors significantly, whichhave been widely reported and confirmed.In this thesis, the YBO33:Eu+phosphors of different molar ratio Y3+to Eu3+andthe YBO33:Tb+phosphors of different molar ratio Y3+to Tb3+are prepared byhydrothermal method. Based on the optimal doping ratio of Eu3+or Tb3+, differentcontent of metal ions (Li+, K+, Mg2+, Al3+) are doping into the phosphors. Thecomposition, microstructure and emission intensity of the phosphors are investigatedby X-ray diffraction(XRD) and field emission scanning electron microscopy(FE-SEM). Luminescent properties of the phosphors are investigated byphotoluminescence(PL) based on the emission intensity, decay lifetime and quantumefficiency. The effects of metal ions doping on luminescent properties of phosphorsare discussed. And then, it gives the main research works and contributions of thisthesis as follows. (1) When the molar ratio Y3+:Eu3+is20:1, the luminescent properties ofYBO+3:Eu3phosphors are better than the others. Based on the optimal doping ratio ofEu3+, the microstructure and luminescent properties of YBO+3:Eu3phosphors dopedwith different content of metal ions (Li+, K+, Mg2+, Al3+) has been changed. Theresults show that K+and Li+doping could improve the luminescent properties ofYBO3:Eu3+phosphors, and Mg2+andAl3+doping are on the opposite.(2) When the molar ratio Y3+:Tb3+is20:1, the luminescent properties ofYBO33:Tb+phosphors are better than the others. Based on the optimal doping ratio ofTb3+, the microstructure and luminescent properties of YBO33:Tb+phosphors dopedwith different content of metal ions (Li+, K+, Mg2+, Al3+) has been changed. Theresults show that K+, Li+and Al3+doping could improve the PL emission ofYBO3+3:Tbphosphor, and Mg2+doping is on the opposite.(3) Metal ions doping phosphors may improve the luminescent properties bychanging the morphology of phosphors. The luminescent properties of phosphorswhich have full particles, tight sub-crystallines and the dispersion of particles isexcellent. The PL emission and fluorescence quantum efficiency of rare earth dopedborate phosphor show positive correlation phenomenon under the experimentalconditions.In summary, the rare earth doped borate phosphors prepared by hydrothermalmethod have good crystallinity. The suitable metal ion and appropriate concentrationof metal ions doping play a certain role in the improvement of the luminescentproperties of the rare earth doped borate phosphors.