Y0.8-x-yF3:Gd3+x , Yb3+0.2,Tm3+y nanocrystals were synthesized through a hydrothermal method. The upconversion(UC) emission properties under a 980 nm continuous wave semiconductor laser diode excitation were studied. The experimental results suggested that the violet and ultraviolet( UV) UC emission enhancement were observed in Y0.595 F3:Gd3+0.200, Yb3+0.200, Tm3+0.005 nanocrystal, as well as the UC emissions of Gd3+ of 6D9/2,6IJ, 6P5/2, and 6P7/2 states to the ground state 8S7/2 were shown, too. The luminescent kinetic analysis implied that, under 980 nm excitation, Yb3+ can transfer energy to populate the 3P2 level of Tm3+ , make UV, violet, and blue UC emissions obtained, further, the 6IJ multiplets of Gd3+ were populated through the energy transfer process 3P2→ 3H6 ( Tm3+ ):87/2 →6 IJ (Gd3+). At the same time, the energy transfer processes occurred between Gd3+ and Yb3+ or Tm + based on the energy matching conditions, leading to the above mentioned UV UC emissions of Gd3+.
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