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Abstract: YVO4:Eu3+ thin films doped with Li ions were grown by the pulsed laser deposition method and their luminescence properties are investigated by the time-resolved laser-excitation spectroscopy. The emission spectra originating in the self-trapped exciton and near-band-edge of YVO4 host lattice are separated by the method of time-resolved spectroscopy. The emission arising from near-band-edge is significantly reduced by Li substitution in the YVO4:Eu3+ lattice leading to luminescence enhancement. [Copyright &y& Elsevier]

Abstract: Luminescence properties of Y2−x Gd x O3:Eu3+ (x =0 to 2.0) thin films are investigated by site-selective laser excitation spectroscopy. The films were grown by pulsed laser deposition method on SiO2 (100) substrates. Cubic phase Y2O3 and Gd2O3 and monoclinic phase Gd2O3 are identified in the excitation spectrum of the 7F0 → 5D0 transition of Eu3+. The emission spectra of the 5D0 → 7FJ (J =1 and 2) transition from individual Eu3+ centers were obtained by tuning the laser to resonance with each excitation line. The excitation line at around 580.60 nm corresponds to the line from Eu3+ with C2 site symmetry of cubic phase. New lines at 578.65 and 582.02 nm for the CS sites of Gd2O3 with monoclinic phase are observed by the incorporation of Gd in Y2O3 lattice. Energy transfer occurs between Eu3+ ions at the CS sites and from Eu3+ ions at the CS sites to those at the C2 site in Y2−x Gd x O3. [Copyright &y& Elsevier]

Abstract: Luminescence properties of Eu3+ ions (0.1, 1.0 and 6.0 mol%) in K2YF5 crystals are investigated by the site-selective laser-excitation spectroscopy. The excitation spectrum of the 5D0 emission exhibits two strong 7F0 → 5D0 excitation lines together with four weaker lines. Six different emission spectra are obtained under the excitation at each excitation line indicating that there existed at least six different sites for Eu3+. The relative intensity of the excitation lines is dependent on the Eu3+ concentrations. The 5D0 emissions of Eu3+ show two types of decay behavior with lifetimes of 0.5 and 5.0ms at 15K. It is suggested that the fast and slow decays correspond to isolated and paired Eu3+ ions in K2YF5. The results are discussed in relation with one dimensional chain structure of the K2YF5 lattice. [Copyright &y& Elsevier]

The influence of the cationic sites on the luminescent properties of Eu3+ in Gd2BaZnO5 has been investigated by the site-selective laser excitation and emission spectroscopy along with luminescence decays. It has been revealed that the Eu3+ ions occupy two cationic sites. The Stark energy levels of Eu3+ at two different sites in Gd2BaZnO5 were assigned from selectively excited emission spectra at 10 K. The energy transfer between two crystallographic Eu3+ centers in Gd2BaZnO5 is detected and discussed. Excitation spectrum in the UV region and UV-excited emission spectrum were also performed, which indicate that an efficient energy transfers from the host and directly Gd3+ to Eu3+ ions in Gd2BaZnO5. [ABSTRACT FROM AUTHOR]

Abstract: A fluorometaphosphate laser glass doped with Eu3+ ions has been synthesized and studied by broad band optical spectroscopy and time-resolved fluorescence line narrowing techniques in order to explore the local field dependent fluorescence properties of the lanthanide ions in this host. From the Raman and the vibronic spectra, various structural phosphate groups coupled to the Eu3+ ions have been identified. Local field dependent 5D0 → 7FJ (J=0–6) emission spectra and the lifetimes of the 5D0 level have been measured under resonant excitation of the Eu3+ ions at different wavelengths within the 7F0 → 5D0 band at 16K. From these data and using the Stark level positions of the 7F1 and 7F2 multiplets, a crystal-field analysis has been carried out assuming a C2v orthorhombic local symmetry. The radiative Judd–Ofelt parameters have been calculated for the different local fields found in the glass and their relative variation has been discussed. The results obtained suggest the existence of a relatively narrow distribution of local fields generated by successive distortions of a unique kind of site for all the Eu3+ ions in this fluorometaphosphate glass. [Copyright &y& Elsevier]

Abstract: Dysprosium-doped oxyfluoride glasses and nanocrystalline glass–ceramics have been synthesized and studied by X-ray diffraction, transmission electron microscope, optical spectroscopy and time-resolved decay curves measurements. From the absorption spectra, Judd–Ofelt intensity parameters have been obtained and are used to predict radiative properties for the excited states of Dy3+ ions. From the visible emission spectra, yellow to blue intensity ratios have been calculated and their relative variations have been discussed based on the concentration of Dy3+ ions and the heat treatment conditions used to prepare the glass–ceramics. Luminescence decay curves of the 4F9/2 emitting level are found to be single exponential for 0.01mol% Dy3+-doped glass and non-exponential for the remaining samples. The nature of energy transfer processes between Dy3+ ions, responsible for the non-exponential behavior of the decay curves, has been analyzed in the frame work of the Inokuti–Hirayama model. Lifetimes of the 4F9/2 level are found to decrease with the concentration of Dy3+ ions as well as with the time of heat treatment. [Copyright &y& Elsevier]