Browsing by Author "Perhaita I."

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    Optical spectroscopy of the Ce-doped multicomponent garnets
    (Elsevier Ltd, 2016) Canimoglu A.; Karabulut Y.; Ayvacikli M.; Muresan L.E.; Perhaita I.; Barbu-Tudoran L.; Garcia Guinea J.; Karali T.; Can N.
    Here, we report our results referring to the preparation of Ce doped Y2.22MgGa2Al2SiO12, Y1.93MgAl4SiO12 and Y2.22Gd0.75Ga2Al3O12 using solid state reaction at high temperature. Several complementary methods (i.e. powder x-ray diffraction (XRPD), energy dispersive analysis of X-rays (EDX), scanning electron microscopy (SEM) and Fourier transforms infrared spectroscopy (FTIR)) were studied to examine the effects of the synthesis procedure on the morphology and structure. XRD analyses revealed that all compounds include yttrium aluminate phase with garnet structure. Cathodoluminescence (CL), radioluminescence (RL) and photoluminescence (PL) measurements were carried out for clarification of relationship between host lattice defects and the spectral luminescence emissions. Luminescence emission of phosphors is peaked at 530 nm assigned to 5d-4f transitions of the dopant Ce3+ ions with a broad emission band in 400-700 nm range. Under electron irradiation, the emission spectrum of Ce doped (YGd)3Ga2Al3O12 is well defined and has a characteristic fairly narrow and sharp emission band peaking at 312 nm and 624 nm corresponding to transition of 6P7/2 →8S7/2 and 6GJ→6PJ (Gd3+), respectively. We suggest some of phosphors might be excellent phototherapy phosphor materials under electron excitation. © 2016 Elsevier Ltd.
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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.
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    The role of calcination temperature on structural and luminescence behaviour of novel apatite-based Ca2Y 8(SiO4)6O2: Ce3+,Tb3+ phosphors
    (Elsevier Ltd, 2017) Perhaita I.; Muresan L.E.; Silipas D.T.; Borodi G.; Karabulut Y.; Guinea J.G.; Ayvacikli M.; Can N.
    A series of novel apatite-based Ca2Y8(SiO4)6O2 phosphors doped with Ce3+ and Tb3+ were synthesized by a solid-state reaction method at different calcination temperatures and times. The comparative results of thermal analysis (TG-DTA), FTIR, X-ray diffraction (XRD) and environmental scanning electron microscope (ESEM) reveal that the firing temperature for Ca 2Y 8 (SiO4)6O2:Ce3+, Tb3+ was optimized to be 1200 °C. The systematic studies on the influences of thermal treatment conditions on photoluminescence (PL) and cathodoluminescence (CL) properties were also reported. The excitation spectra of Ca2Y8(SiO4)6O2:Ce3+, Tb3+exhibited one strong excitation band at 325 nm. The PL and CL results indicated that the violet-blue emission intensities about 400 nm from the Ce3+ and efficient green emission at 544 nm from Tb3+ were highly dependent on the calcination conditions. © 2017 Elsevier Ltd
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    Synthesis and influence of ultrasonic treatment on luminescence of Mn incorporated ZnS nanoparticles
    (Elsevier B.V., 2017) Cadis A.-I.; Muresan L.E.; Perhaita I.; Munteanu V.; Karabulut Y.; Garcia Guinea J.; Canimoglu A.; Ayvacikli M.; Can N.
    Manganese (Mn) doping of ZnS phosphors was achieved by precipitation method using different ultrasound (US) maturation times. The structural and luminescence properties of the samples were carried out by means of X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), photoluminescence (PL), and cathodoluminescence (CL). The real amount of manganese incorporated in ZnS lattice was calculated based on ICP-OES results. According with XRD patterns, the phase structure of ZnS:Mn samples is cubic. EDS spectra reveal deviations of the Mn dopant concentration from the target composition. Both 300 K PL and CL emission spectra of the Mn doped ZnS phosphors display intense orange emission at 590 and 600 nm, respectively, which is characteristic emission of Mn ion corresponding to a 4T1→6A1 transition. Both PL and CL spectra confirmed manganese is substitutionally incorporated into the ZnS host as Mn2+. However, it is suggested that the origin of broad blue emission around 400 nm appeared in CL is due to the radiative recombination at deep level defect states in the ZnS. The ultrasound treatment at first enhances the luminescent intensity by ∼3 times in comparison with samples prepared by classical way. This study gives rise to an optimization guideline, which is extremely demanded for the development of new luminescent materials. © 2017 Elsevier B.V.