Preparation And Properties Of Rare Earth Phosphate Vanadate Micro And Nano Luminescent Materials

Rare earth vanadate luminescent material can better absorb the UV irradiation, and then efficiently transfer these energies to the rare earth active ions, resulting in the emitting of characteristic spectra of the rare earth ions. As phosphor host materials, the rare earth phosphate-vanadate solid solution possesses high luminous intensity, quantum efficiency and stability, due to the presence of phosphate substituted part of vanadate. In this thesis, the YPxV1-xO4:Ln3+ luminescent materials with novel structure and shape (e.g. core-shell, sphere-like which was composed of nanorods/nanosheets), have been fabricated hydrothermally. The effect of the synthesis parameters and reaction conditions on the structures and shapes of the prepared materials, the possible crystalline growth mechanism and luminescence properties of assembled spherical YPxV1-xO4:Ln materials were investigated. The main results are summarized as follows.The YPxVi-xO4 solid solutions with tetragonal phase were prepared by the hydrothermal method. The influences of the P/V, the amount of EDTA, pH, organic additive and reaction time on the structure and shape of the prepared samples were investigated. The spherical YP0.3V0.7O4 samples with tetragonal phase has been prepared at 180℃ for 24 h with the synthesis solution (EDTA= 4 mmol) at different pH of 0.57-1.The light color of the YP0.3V0.7O4:Ln3+(Ln= Eu, Sm, Dy and Tm) microsphere can be tuned by doping different lanthanide activators under UV excitation. The quenching concentration, decay time and quantum efficiency of the phosphors were investigated. The results showed that, Y0.93Sm0.07P0.3V0.7O4 phosphor exhibited longer decay time and higher quantum efficiency. The YPxV1-xO4:Dy3+(x=0.4-0.6) phosphors excited bright white light. For the Y0.97Dy0.03PxV1.xO4 samples, emission intensities of Dy+ increased with increasing the P amount, and the quantum efficiency of Y0.97Dy0.03P0.9V0.1O4 can reach 92%.The Y(P,V)O4 materials with core-shell and tetragonal phase structure were successfully prepared by using dual ligand (EDTA+PVP)-assisted hydrothermal method. The YP0.3V0.7O4 crystals with different sizes and morphologies were prepared by controlling the reaction parameters. The size of the prepared sample was about 500 nm when the volume ratio of water/ethanol was 5:3. The quenching concentration of YP0.3V0.7O4:Ln3+ (Ln= Eu and Dy) materials was 5%and 3%, respectively.