Synthesis And Photoluminescence Of New-type Eu～(3+)-doped Oxide Phosphors

CeO₂: Eu³⁺ phosphor powders with various Eu³⁺ concentrations have been prepared by the sol-gel method. X-ray diffraction (XRD), TG-DTA and Photoluminescence (PL) measurements were used for the samples characterization. XRD analysis showed that the powders begin to crystallize at 500℃and pure CeO₂ phase up to 10 at.% concentration of Eu³⁺ is obtained. The CeO₂: Eu³⁺ phosphor powders with 6 at.% concentration of Eu³⁺ sintered at 1250℃revealed the strongest photoluminescence.CeO₂: Eu³⁺ phosphor films with various Eu³⁺ concentrations were prepared by the Pechini method. XRD, atomic force microscopy (AFM) and PL measurements were used to characterize the samples. XRD analysis shows that the films with pure cubic-fluorite structure up to 4 at.% concentration of Eu³⁺ is obtained at the sintered temperatures from 700 to 1000℃. Increase in the sintered temperature promotes the grain growth of CeO₂: Eu³⁺ films and improves their crystallinity. The films sintered at 1000℃show coarse surface structure and small grain size about 25 nm. The PL excitation band at 300～360 nm is due to the charge transfer from O^2- to Ce⁴⁺ and subsequent energy transfer to Eu³⁺ in the films. The characteristic Eu³⁺ emission appears, which exhibits intra-4f transitions at 592 (⁵D₀-⁷F₁), 611 and 632 nm (⁵D₀-⁷F₂). The CeO₂: Eu³⁺ phosphor films sintered at 1000℃reveal the strongest photoluminescence for the Eu³⁺ concentration of 4 at.% and then decrease with increasing Eu³⁺ content, indicating the concentration quenching. The increment of temperature contributes to the enhancement of luminescence intensity.The phosphor powders of BaZrO₃ doped with Eu³⁺ was prepared by solid-state reaction. The powder samples were characterized by XRD and PL. XRD analysis showed the formation of pure solid solution BaZr_1-xEu_xO₃ up to 4 mol% of Eu³⁺ concentration. The room temperature excitation spectra vary with the Eu³⁺ concentration and consist of an intense charge transfer band and weak f-f transitions. The PL spectra, excited at 258.0 nm, consist of 4f-4f emission transitions from the ⁵D₀ excited level of the Eu³⁺ ions to the ⁷F_J (J=0～4) levels. The appearance of intense ⁵D₀-⁷F₀ transition originated from the J-J mixing suggests the distortion of EuO₆ octahedra in the BaZr_1-xEu_xO₃ host lattice. The dependence of luminescence intensity on the Eu³⁺ concentration in BaZrO₃: Eu was studied.The core-shell-structured SiO₂/ZrO₂: Eu³⁺ submicrospheres were prepared by a simply homogeneous precipitation method. The samples were characterized by XRD, scanning electron microscopy (SEM), and PL. SEM observations showed that the size of the core-shell-structured SiO₂/ZrO₂: Eu³⁺ is in the range of 640 nm, and the thickness of shell is about 100 nm. Under 242 nm excitation, the emission spectra show the emission at 608 nm. The PL excitation band at 242 nm is due to absorption of ZrO₂ and at 258 nm is attributed to the charge transfer from O^2- to Eu³⁺.