| NaGd(MoO4)2:Yb3+,Er3+,NaGd(MoO4)2:Er3+,NaY(MoO4)2:Yb3+,Er3+ and NaY(MoO4)2:Er3+ nanocrystals were prepared by hydrothermal method in this paper. X-Ray diffraction,transmission electron microscope,fluorescence spectra and up-conversion luminescence spectra were used to characterize the structure and luminescence properties of the samples prepared in different conditions.The influence of the temperature,doping concentration of rare-earth ions and the annealing processing to the luminescence properties were also discussed.NaGd(MoO4)2:Yb3+,Er3+ and NaGd(MoO4)2 have the same crystal structure and they both belong to tetragonal crystal system.TEM images indicates that the sample is club-shaped with a diameter about 20nm.The up-conversion spectrum of the sample has three peaks at 531nm,552nm and 656nm, which corresponding to the transitions of Er3+2H11/2→4I15/2,4S3/2→4I15/2和4F92→4I15/2, respectively. Up-conversion luminescence intensity increased greatly after heat treatment at 600℃.The excitation spectrum of NaGd(MoO4)2 doped Er3+ includes a series of narrow bands of f-f transition and a broad band from ultraviolet.Luminescence intensity was strongest when the doping concentration of Er3+ was about 35mol%,the luminescence concentration qrenching was found when the concentration increased more.As to NaY(MoO4)2:Yb3+,Er3+ nanocrystal,when the doping concentration of Er3+ was 0.5 mol%, the best proportion of Yb/Er was 6:1.The relationship between up-conversion luminescence intensity and pump power indicates that both the green emissions at 533nm and 554nm and red emission at 655nm were two-photon process. NaY(MoO4)2:Er3+ nanocrystal was prepared by hydrothermal method at 160℃. NaY(MoO4)2:Er3+and NaY(MoO4)2 have the same crystal structure,which indicates that Er3+ replaced Y3+ successfully.And the optimum doping concentration of Er3+ was about 30%. |
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