| In this thesis, the phosphors Ca2(Ca2x/3In1-xNbx/3)NbO6:Eu3+and Ca2(Ca0.8In0.88Nb0.04)NbO6:Pr3+have been prepared by solid-state reaction, their crystal structure and photoluminescence properties were investigated.The XRD patterns for these Ca2(Ca2x/3In1-xNbx/3)NbO6:0.01Eu3+(x=1,0.75,0.6,0.36,0.12, and0) phosphors were measured. This compound can be considered as solid solution in the system of Ca2.67Nb1.33O6and Ca2InNbO6. With decreasing x, the diffraction peaks of the Ca2(Ca2x/3In1-xNbx/3)NbO6:0.01Eu3+shifted to a larger29. The excitation spectra of Ca2(Ca2x/3In1-xNbx/3)NbO6:Eu3+have two regions:one is assigned to the charge-transfer state (CTS) band of O2-â†'Eu3+at about300nm, and the other is assigned to the intra-4ftransitions of Eu3+at350-600nm. The emission spectra of Ca2(Ca2x/3In1-xNbx/3)NbO6:0.01Eu3+phosphors excited at396nm exhibited a series of sharp peaks from400to700nm (whole visible spectral region) with comparable intensities, which resulted in a white light emission. Moreover, the intensity ratio of blue emission (5D3â†'7F2) to red emission (5D0â†'7F2) was observed to increase with the decrease of x.The XRD pattern of Ca2(Ca0.08In0.88Nb0.04)NbO6:Pr3+was similar to that of Ca2(Ca0.08In0.88Nb0.04)NbO6. The excitation spectrum of Ca2(Ca0.08In0.88Nb0.04)NbO6:Pr3+measured at495nm exhibit an absorption band centered at306nm, which is attributed to the CTS transition of In3+â†'O2-.The4f-4f transitions of Pr3+were also observed in the region of425-475nm, but the intensities were very low. The photoluminescence spectra of Ca2(Ca0.08In0.88Nbo.o4)NbO6:Pr3+excited with306nm showed the strong blue-green emission originated of the3Poâ†'3H4(495nm) transition of Pr3+ions. Meanwhile, the photoluminescence spectrum showed week green and orange emission peaks at538and608nm, which were originated of the transitions of3P1â†'3H5and1D2â†'3H4of Pr3+ions. |
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