Synthesis and Photoluminescence of BaCeO3:Eu3+ and SnO2:Eu3+ Oxide Phosphors

Synthesis and Photoluminescence of BaCeO3:Eu3+ and SnO2:Eu3+ Oxide Phosphors
　　The phosphor powders of BaCeO3:Eu3+, SnO2:Eu3+ and the core-shell-structured SiO2@SnO2:Eu3+ submicrospheres were synthesized by the solid state reaction method, sol-gel process, and precipitation process, respectively. The samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), photoluminescence (PL) and fluorescence lifetime measurement.For the phosphor powders of BaCeO3:Eu3+, XRD analysis showed that the formation of pure solid solution BaCe1-xEuxO3 up to 6 mol% of Eu3+ rare earth magnets concentration. The excitation spectra vary with the Eu3+ concentration and consist of an intense charge transfer band, host absorption band and some weak f-f transitions. The PL spectra, excited at 323 nm, mainly consist of 4f-4f emission transitions from the 5D0 excited level to the 7FJ (J= 0-4) levels of Eu3+. The PL intensity of the phosphor powders depents on the Eu3+ concentration and is quenched for the Eu3+ concentration of 15 mol%.
　　The lifetime of emission transition 5D0-7FJ (J= 1, 2) of Eu3+, is about 1 ms and decresses with increasing Eu3+ concentration in the samples.SnO2:Eu3+ phosphor powders were prepared by sol-gel method. XRD analysis showed the formation of pure tetragonal rutile crystalline phase of tin oxide up to 5 mol% of Eu3+ concentration. The excitation spectra consist of the charge transfer band, host absorption band and some weak f-f transitions. The PL spectra, excited at 310 nm, consist of 4f-4f emission transitions of Eu3+. The existence of three intense emission peaks belong to the 5D0-7F1 transitions indicats that the Eu3+ ions have been doped into the SnO2 host lattice and occupied the sites of the Sn4+ ions. The PL intensity of Sn1-xEuxO2 with various Eu3+ concentrations showed the optimal concentration of Eu3+ is 2 mol%.Sn1-xLixO2-δ:Eu3+ phosphor powders with various Li+ concentrations were prepared by ammonia precipitation method. SEM and XRD analysis http://www.chinamagnets.biz indicated that the Li+ doping enhances the crystallization and growth of SnO2. The PL spectra of Sn1-xLixO2-δ:Eu3+ phosphors indicated that the incorporation of Li+ ions into SnO2 lattice and the increase of sintered temperatures could induce a remarkable increase of photoluminescence intensity.The core-shell-structured SiO2@SnO2:Eu3+ submicrospheres were prepared by urea homogeneous precipitation method. SEM observations showed that the size of the core-shell-structured SiO2@SnO2:Eu3+ is in the range of 670 nm, and the thickness of shell is about 110 nm. The PL spectra indicated that the core-shell structure of SnO2:Eu3+ can improve its photoluminescence. The emission transition 5D0-7F1 (λem=587.6 nm) of the Eu3+ ions of the core-shell-structured SiO2@SnO2:Eu3+ have an average lifetime of about 20 ms.