Ultraviolet and blue up-conversion fluorescence of NaY _0.793-xTm_0.007Yb_0.2Gd_xF₄ phosphors

The NaY_0.793-xTm_0.007Yb_0.2Gd _xF₄ (x = 0.1, 0.2, 0.3) phosphors were synthesized through a combinational method of co-precipitation and argon atmosphere annealing procedures. Crystallizations of the phosphors were characterized by X-ray diffraction (XRD) analysis. Under a 980-nm continuous wave laser diode (LD) excitation, the phosphors exhibited UV UC fluorescence of Gd³⁺ peaking at 246.4, 252.8, 276.2, 279.2, 305.8, and 311.4 nm, respectively. At the same time, UV UC fluorescence centering at 264.6, 289.6, 344.2, 361.0 nm and blue UC fluorescence peaking at 449.8 and 472.8 nm of Tm³⁺ were observed. The up-converted process analysis indicated that the energy transfer from Tm³⁺ to Gd³⁺ played a vital role in UV UC emissions of Gd³⁺. And the optical property analysis suggested that both excitation powers and host material compositions had great effects not only on UV UC fluorescence of Gd³⁺, but also on UV and blue UC fluorescence of Tm³⁺.