| Considerable research attention in the long lasting photoluminescence (LLP) has been shown over the last few years for its potential technological application, such as road signs, graphic arts, interior decoration and automobile instrument with high luminous efficiency and so on. Nowadays, in tricolor, phosphors of the green and blue phosphorescence, which have high brightness and good chemical stability, can be successfully prepared to meet the demand of all-night luminescence, but the red persistent phosphors are still under the stage of research. CaTiO3:Pr3+ is of special interest because it has better chemical stability and its chromatic coordinates (x= 0.680, y= 0.311) very close to "ideal red", however, the decay time of CaTiO3:Pr3+ is as short as a few minutes and the initial intensity is very weak, so a great number of efforts have been focused on the improvement of the fluorescence and phosphorescence of this phosphor by adding different dopants.Firstly, the best milling time 6h, sintering temperature 1300℃and constant temperature time 4h were obtained through experiments on CaTiO3:Pr3+, Nb5+ in this paper. In order to improve the luminescence properties of CaTiO3:Pr3+, a series of CaTiO3:Pr3+, CaTi0.97Nb0.03O3:Pr3+, Ca0.8Zn0.2TiO3:Pr3+, Ca0.8Zn0.2 Ti0.97Nb0.03O3:Pr3+ and doped-B3+ Ca0.8Zn0.2Ti0.97Nb0.03O3:Pr3+ were prepared through conventional solid state reaction method. The results of the photoluminescence excitation and emission spectra showed that all the samples emitted red phosphorescence at 612 nm originating from 1D2 to 3H4 emission of Pr3+ under the 337 nm excitation. When examined by the X-Ray diffraction (XRD), all the samples presented a predominant phase of CaTiO3 (JCPD#42-423) except Zn2+ doped samples which also revealed another phase of Zn2Ti3O8 (JCPD#73-579). The results of the afterglow decay curves showed that co-doping Zn2+ ions, Nb5+ ions or adding a small amount of B3+ into Ca0.8Zn0.2Ti0.97Nb0.03O3:Pr3+ were effective in improving the photoluminescence properties of CaTiO3:Pr3+ phosphor. Thermoluminescence results showed that the trap existing in all the samples was the same as in CaTiO3:Pr3+ and doping singlely Nb5+ or Zn2+ hardly change the trap depth but co-doping Nb5+ and Zn2+ could modify the trapping level from 0.63 eV to 1.26 eV distinctively, in addition, adding a certain amount of B3+ into CTO-PZN could also deepen the trap depth. Nb5+ and B3+ doped Ca0.8Zn0.2TiO3:Pr3+ red long afterglow phosphors are synthesized by solid-state reaction methods. X-ray diffraction, photoluminescence spectroscopy and thermally stimulated spectrometer are used to investigate the effects of Nb5+ and B3+ content on the crystal characteristics and luminescent properties of Ca0.8Zn0.2Ti1-xNbxO3:Pr3++ymol%B3+ [y=n(H3BO3) /n(CaTiO3)] phosphors. The results show that the addition of a small quantity of Nb5+ and B3+ have negligible effect on the crystal characteristics of Ca0.8Zn0.2Ti1-xNbxO3:Pr3+, ymol%B3+, but they can change the trapping parameters (the depth of trap, frequency factors and the concentration of trapped charges at t= 0) of Ca0.8Zn0.2Ti1-xNbxO3:Pr3+, ymol%B3+ phosphors, and then lead to the enhancement of red fluorescence and phosphorescence at 612 nm originating from 1D2 to 3H4 transition of Pr3+. Both of the red fluorescence intensity and afterglow time reach the largest values in the sample of Ca0.8Zn0.2Ti1-xNbxO3:Pr3+,3mol%B3+ with x= 0.05. And both of the red fluorescence intensity and afterglow time reach the largest values in the sample of Ca0.8Zn0.2Ti0.97Nb0.03O3:Pr3+,ymol%B3+ with y= 7mol%. The afterglow time of Ca0.8Zn0.2Ti0.95Nb0.05O3:Pr3+,3mol%B3+ phosphors lasts for over 24 min(≥1 mcd/m2) and of Ca0.8Zn0.2Ti0.97Nb0.03O3:Pr3+,7mol%B3+ phosphors lasts for over 22min (≥1 mcd/m2) when the excited source is cut off.Al3+ doped Ca0.8Zn0.2Ti1-xAlxO3:Pr3+ red long afterglow phosphors are synthesized by solid-state reaction methods. X-ray diffraction, photoluminescence spectroscopy and thermally stimulated spectrometer are used to investigate the effects of Al3+ content on the crystal characteristics and luminescent properties of Ca0.8Zn0.2Ti1-xO3:Pr3+ phosphors. The results show that the addition of Al3+ have an effect on the crystal characteristics of Ca0.8Zn0.2Ti1-xAlxO3:Pr3+ and it can change the trapping parameters (the depth of trap, frequency factors and the concentration of trapped charges at t= 0) and then lead to the enhancement of red fluorescence and phosphorescence at 612 nm originating from1D2 to 3H4 transition of Pr3+. Both of the red fluorescence intensity and afterglow time reach the largest values in the sample of Ca0.8Zn0.2Ti1-xAlxO3:Pr3+ with x=0.1 The afterglow time of Ca0.8Zn0.2Ti0.9Al0.1O3: Pr3+ phosphors lasts for over 19min (≥1mcd/m2) when the excited source is cut off. |
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