Browsing by Author "Barbu Tudoran L."

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    Structural and luminescence effects of Ga co-doping on Ce-doped yttrium aluminate based phosphors
    (Elsevier Ltd, 2016) Ayvacikli M.; Canimoglu A.; Muresan L.E.; Barbu Tudoran L.; Garcia Guinea J.; Karabulut Y.; Jorge A.; Karali T.; Can N.
    Herein, we primarily focus on luminescence spectrum measurements of various types of green emitting yttrium aluminate phosphors modified with gallium (Y3Al5-xGaxO12) synthesised by solid state reaction. The luminescent emission of samples depends on sample temperature and excitation radiation such as incident X-ray, electron and laser beam. Here, we measured radioluminescence (RL), cathodoluminescence (CL), photoluminescence (PL) along with XRD in order to clarify relationship between lattice defects and the spectral luminescence emissions. The RL and CL spectra of YAG:Ce exhibit an emission band ranging from 300 to 450 nm related to YAl antisite defects. The broad emission band of garnet phosphors is shifted from 526 nm to 498 nm with increasing of Ga3+ content, while full width at half maximum (FWHM) of the band tends to be greater than the width of unmodified YAG:Ce garnet. Deconvolution of the spectrum reveals that three emission bands centred at 139, 234 and 294°C occur in aluminate host garnets. © 2016 Elsevier B.V. All rights reserved.
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    Tunable luminescence of broadband-excited and narrow line green emitting Y2SiO5:Ce3+, Tb3+ phosphor
    (Elsevier Ltd, 2016) Muresan L.E.; Karabulut Y.; Cadis A.I.; Perhaita I.; Canimoglu A.; Garcia Guinea J.; Barbu Tudoran L.; Silipas D.; Ayvacikli M.; Can N.
    Cerium and terbium activated white emitting yttrium silicate phosphors (Y2-x-yCexTbySiO5) having average size between 96 and 123 nm were synthesised by a gel-combustion, and their phase and crystal structures, morphologies and ultraviolet (UV)-visible spectroscopic properties were studied. All rare earth doped yttrium silicate (YSO) phosphors are well crystallized powders containing only monoclinic X2-Y2SiO5 phase. No significant changes in the cell parameters were observed with increasing of Tb amount as ionic radii of Tb3+ (0.923 Å) and Y3+ (0.9 Å) have almost the same. Under different excitations, YSO:Ce3+ exhibits blue emission due to the 5d-4f transitions of Ce3+ ions. The series of emission states at different wavelengths of YSO:Tb3+ associated to f-f transition of Tb3+ ion were detected from luminescence measurements. The emission observed at 544 nm (green) corresponding to 5D4 → 7F5 of Tb3+ is strongest one. Incorporation of variable amounts of Tb3+ in the YSO host lattice determines the modification of emission colour from blue through light blue and eventually to bluish green. A possible energy transfer mechanism taking place from Ce3+ to Tb3+ was also discussed in terms of excitation and emission spectra. © 2015 Elsevier B.V.