The Synthesis And Luminescence Properties Of Rare Earth Ions Doped Gadolinium Tungstate Nano-phosphors

With the technical developments of display, lighting and fluorescence labeling, the demands for the luminescent materials with advanced performance are placed on the desk of researchers. The luminescent materials with low producing cost, high efficiency and being free from pollution are still preferred by the scientists. Rare earth ions doped luminescent materials are key content in the studied scope of luminescence physics and spectroscopy, meanwhile rare earth ions luminescent nanomaterials became present a hot issue which is concerned by the researchers. Amongst all the luminescent nanomaterials, the rare earth ions doped tungstate systems exhibit excellent durability, chemical and thermal stability, and eximious spectroscopic properties, and have evoked much interest. Moreover, tunstate compounds can exist in different forms with different molecular formulas, in which the rare earth ions are featured various luminescent properties. In this thesis, the studies are focused on the synthesis and spectral properties of gadolinium tungstates nanoparticles, the new findings we gained are listed below.1/The co-precipitation route for synthesizing nanosized Gd2(WO4)3, Gd2WO6 and Gd6WO14 phosphors doped with rare earth ions was examined, and that the optimum conditions including compositions and the pH value for achieving the different pure phase compounds were confirmed. XRD, SEM were used to characterize the crystal structure and morphologies of the products.2/Spectral properties of Gd6WO12:Dy3+ nanophosphor were studied by means of spectroscopy, and that the energy level positions of the complex ion WO1218- was confirmed. The energy transfers between complex ion WO1218- and Dy3+ ions and the excitation-dependent colorimetric properties were studied.3/Based on the measurements of spectra and fluorescence decays and the calculations of color coordinates, the spectroscopic properties and energy transfer behaviors of Dy3+ in the nanosized Gd2(WO4)3,Gd2WO6 phosphors were studied. By studying on the concentration quenching and luminescent dynamics, the physical mechanisms of the energy transfers between Dy3+ ions was assigned to the electric dipole-dipole interaction. It was also found that the color coordinates of the phosphors depend on the concentration.4/Upconversion luminescence properties of Er3+/Yb3+ doped Gd2(WO4)3, Gd2WO6 and Gd6W12 nanophosphors were studied. In the case of constant Yb3+ concentration of 10% and various Er3+ concentrations of 1% or 25%, the upconversion emission spectra were measured for these three phase tungstates, the upconversion mechanisms were analyzed.