Synthesis And Optical Properties Of Rare Earth Doped Oxide Functional Materials

With the rapid development of modern science and technology,the ability of controllable synthesis of nano size functional materials with uniform morphology and excellent dispersion is an essential requirement for applications of functional materials.It is well known that the properties of functional materials are not only related to chemical composition and crystal structure,but also to the morphology,size and spatial dimension.In this thesis,Y2O3:Eu3+,Lu2O3:Eu3+,and Lu2O3:Yb3+/Er3+ nanospheres were synthesized via urea homogeneous precipitation method.We show here the synthetic process,morphology,crystal structure,and up-down conversion luminescent properties.(1)Y2O3 doped with Eu3+ nanospheres phosphors with different sizes have been synthesized via urea homogeneous precipitation method.By changing the molar ratio of rare earth to urea precipitant,the uniform spherical Y2O3:Eu3+ nanospheres with the sizes of 80,55,and 40 nm were obtained in the experiments.The phases,morphologies,and luminescence properties of as-prepared samples were characterized by means of X-ray diffraction(XRD),filed emission scanning electron microscopy(FE-SEM),and photoluminescence spectra,respectively.The growth process of Y2O3:Eu3+nanoparticles were studied.The luminescent properties of Y2O3:Eu3+ nanoparticles were studied in details.Judd-Ofelt parameters of Eu3+ in the Y2O3 phosphors with different sizes were calculated from the emission spectrum.Finally,the temperature dependence of 5D0 fluorescence process was analyzed,and it was deduced that the thermal quenching behavior of 5D0 fluorescence followed well the Crossover model.The activation energy of Y2O3:Eu3+nanospheres phosphors with different sizes were obtained.(2)LU2O3 nanospheres doped with various concentrations of Eu3+ were synthesized via urea homogeneous precipitation method.The crystal structure of the phosphors is identified by the XRD technique.The emission spectra consisting of a group of sharp lines from blue to red light are originating from 5D1,0?7FJ transitions of Eu3+.Moreover,the photoluminescence intensities and decay times vary with increasing Eu3+concentrations,which are attributed to the energy transfer among the Eu3+ ions.The photoluminescence spectra are measured in the temperature range 300-750 K.The Crossover process is the main mechanism for temperature quenching behavior of Eu3+,meanwhile the activation energy was obtained.Finally,the Judd-Ofelt parameters of Lu2O3:1 mol%Eu3+ are calculated.(3)High color purity red emission of Lu2O3:+Yb3+/Er3+ nanospheres with various sizes have been synthesized by urea homogeneous precipitation method.By changing the molar ratio of urea precipitant to rare earth,uniform spherical Lu2O3:Yb3+/Er3+nanoparticles with the sizes of 35,75,100,and 160 nn were obtained in the experiments.From the results of Fourier transform infrared spectra and thermogravimetric analysis,it was further confirmed the reaction mechanism of the chemical reaction.Under the excitation of 980 and 1550 nm diode laser,the Lu2O3:Yb3+/Er3+ samples showed size-dependent upconversion luminescence property.The possible physical mechanism involved in size-dependent upconversion processes was discussed in detail.