Study On Preparation And Luminescence Properties Of NaCa₄Nb₅O₁₇:RE³⁺?RE=Pr,Eu? Phosphors

The red phosphors NaCa4Nb5O17:Pr3+,Bi3+ and NaCa4Nb5O17:Eu3+ have been prepared by solid-state reaction method.In this thesis,their crystal structure and photoluminescence properties were investigated.The XRD patterns indicates that NaCa4Nb5O17:Pr3+ is on the basis of mono-clinic structure with space group P1121/b.The excitation spectra consist of strong excitation band range from 200 to 425 nm and week excitation band range from 425 to 500 nm.The main peak located in 286 nm which resulted from charge transfer in the NbO67-groups.Other shoulder bands at 225,303,345 nm ascribed to 3H4?1S0 transition of Pr3+ ions,intervalence charge transfer of Pr3+?Nb5+,and 4f2?4f15d1 transition of Pr3+ ions.The small peaks in week excitation band range from 425 to 500 nm contributed to 3H4 ? 3P2?3P1?3P0 transition of Pr3+ ions.The emission band from 475 to 500 nm originated form 3P0?3H4 transition of Pr3+ions,the main peak in the emission spectra located at 612 nm,which resulted from 1D?3H4 transition of Pr3+ ions.In order to broaden the excitation band of NaCa4Nb5O17:Pr3+,we co-doped Bi3+ ions into it.The XRD patterns showed no differences compare with the standard card(ICSD#50396).The excitation spectra of NaCa4Nb5O17:Pr3+,Bi3+showed a new peak at 333 nm which was originated from charge transfer of Bi3+?O2-,and intensity of peak at 286 nm decreased.In the same concentration of Bi3+ ions,the intensity of Bi3+?O2-is stronger than the charge transfer in the NbO67-groups,with increasing Bi3+ ions,intensity of Bi3+?O2-get stronger.The emission spectra of NaCa4Nb5O17:Pr3+,Bi3+ excited at 333 nm is very similar with the emission spectra of NaCa4Nb5O17:Pr3+,the emission band from 475 to 500 nm originated from 3P0?3H4 transition of Pr3+ ions,the main peak centered at 612 nm,which resulted from 1D2?3H4 transition of Pr3+ ions.With the increase concentration of Eu3+ ions in the NaCa4Nb5O17:Eu3+ phos-phor,the XRD patterns were matches well with the standard card.The excitation spectra showed a board band from 250-350 nm,which was attributed to the host absorption and Eu3+?O2-transition.A series of sharp peaks range from 350-550 nm attributed to the f-f transition of Eu3+ ions.The main peak located at 393 nm,which was originated from 7F0?5L6 transition of Eu3+ ions.The emission spectrum consisted of peaks located at 531,551,578,596,610 and 653 nm,due to 5D1?7F1?5D1?7F2?5D0?7F0?5D0?7F1?5D0?7F2 and 5D0?7F4 transition of Eu3+ ions.The main peak located at 610 nm.