MCBÜ Açıkerişim Sistemi :: Browsing by Author "Henini, M"

Browsing by Author "Henini, M"

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Absorption and photoluminescence spectroscopy of Er3+-doped SrAl2O4 ceramic phosphors
Ayvacikli, M; Khatab, A; Ege, A; Sabikoglu, I; Henini, M; Can, N
A spectroscopic characterization of Er3+-doped SrAl2O4 phosphor materials synthesized by a solid-state reaction method with Er concentrations varying from 0.1 to 1 mol% has been performed by studying photoluminescence (PL) in the temperature range 10 to 360 K and absorption spectra. PL signals containing five emission bands at 1492, 1529, 1541, 1558, and 1600 nm, respectively, have been observed at room temperature for Er3+ transitions in the near infrared region. The samples exhibit a main luminescence peak at 1.54 mu m, which is assigned to recombination via an intra-4f Er3+ transition. Sharp bands centered at around 378, 488, 521, 651, 980, 1492, and 1538 nm in the absorption spectra can be associated with transitions from I-4(15/2) level to H-2(9/2), F-4(7/2), H-2(11/2), F-4(9/2), I-4(11/2), H-2(11/2), and I-4(13/2) levels, respectively. The sharp emission peaks and excellent luminescence properties show that SrAl2O4 is a suitable host for rare-earth-doped phosphors, which may be suitable for optical applications.
Visible to infrared low temperature luminescence Er3+, Nd3+ and Sm3+ in CaSnO3 phosphors
Gordo, VO; Arslanli, YT; Canimoglu, A; Ayvacikli, M; Gobato, YG; Henini, M; Can, N
Novel stannate phosphor, orthorhombic CaSnO3 phosphors doped with Er3+, Nd3+ and Sm3+ have been synthesized by a conventional solid-state method under N2+H-2 gas flow. Visible and near-infrared photoluminescence (PL) properties were investigated as function of laser power and temperature. It was observed that all dopant ions are well incorporated in CaSnO3 and are responsible for the optical emission in the temperature range of 10-300 K. PL peaks at 490, 546, 656, 696, 894, 1065, and 1344 nm were observed for the CaSnO3:Nd3+ phosphor and associated to f-f transition of Nd3+ ion. Emissions at 564, 600-607, 646-656 and 714 nm were detected for the CaSn03:Sm3+. The strongest one, observed at 600 nm, was associated to 4G512-61-17/2 of Sm3+ Emission lines at 528, 548, 662 at 852 nm were afso seen for Ca(5)nO(3):Er3+ and correspond to Er3+ intra-4f shell transitions. In addition, at low temperatures, a stark splitting of the 4f electron energy levels of the Er3+ ions were observed in infrared region (1520-1558 nm) and assigned to the transition between the 4113/2 state and the 4115/2 state. Finally, our results show that the rare earth doped CaSnO3 has remarkable potential for applications as optical material since it exhibits efficient and sharp emissions due to rare earth ions. (C) 2015 Elsevier Ltd. All rights reserved.
Radioluminescence and photoluminescence characterization of Eu and Tb doped barium stannate phosphor ceramics
Ayvacikli, M; Canimoglu, A; Karabulut, Y; Kotan, Z; Herval, LKS; de Godoy, MPF; Gobato, YG; Henini, M; Can, N
In this paper, we report on structural and optical properties of terbium and europium doped barium stannate phosphors (BaSnO3) synthesised by conventional solid state reaction method. We have studied those materials by using X-ray diffraction (XRD), radioluminescence (RL) and photoluminescence (PL) techniques. XRD patterns confirm that the BaSnO3 sintered at 1400 degrees C exhibit orthorhombic structure and that the Tb3+ and Eu3+ substitution of Ba2+ does not change the structure of the BaSnO3 host. The optical emission spectrum is characterized a broad band centered at 897 nm (1.38 eV), with a high-energy tail approximately 750 nm from the host lattice. Other emission signals that are characteristic of the 3 + oxidation state of rare earth elements were generated by Eu and Tb doping. Luminescence measurements show that the series of emission states D-5(4) -> F-7(6), D-5(4) -> F-7(5), D-5(4) -> F-7(4) and D-5(4) -> F-7(3) corresponding to the typical (4)f -> (4)f infra-configuration forbidden transitions of Tb3+ are appeared and the major emission peak at 540 nm is due to D-5(4) -> F-7(5) transitions of Tb3+. On the other hand, the emission spectrum of Eu doped BaSnO3 phosphor exhibits a series of emission bands, which are attributed to the D-5(0) -> F-7(j) (j = 0-4) transitions of Eu3+ ions. The dominant emission of Eu3+ corresponding to the electric dipole transition D-5(0) -> F-7(2) is located at 613 nm. The sharp emission properties exhibited demonstrate that the BaSnO3 is a suitable host for rare-earth ion doped phosphor material. This work clearly confirms the unusual near infrared (NIR) PL discovered by H. Mizoguchi et al. in BaSnO3 at room temperature. (C) 2013 Elsevier B.V. All rights reserved.
Solid state synthesis of SrAl2O4:Mn2+ co-doped with Nd3+ phosphor and its optical properties
Ayvacikli, M; Kotan, Z; Ekdal, E; Karabulut, Y; Canimoglu, A; Guinea, JG; Khatab, A; Henini, M; Can, N
The optical properties of alkaline earth aluminates doped with rare earth ions have received much attention in the last years and this is due to. their chemical stability, long-afterglow (LAG) phosphorescence and high quantum efficiency. However, there is a lack of understanding about the nature of the rare earth ion trapping sites and the mechanisms which could activate and improve the emission centers in these materials. Therefore a new phosphor material composition, SrAl2O4:Mn2+, co-doped with Nd3+ was synthesized by a traditional solid-state reaction method. The influence of transition metal and rare earth doping on crystal structure and its luminescence properties have been investigated by using X-ray diffraction (XRD), Raman scattering, Photoluminescence (PL) and Radioluminescence (RL). Analysis of the related diffraction patterns has revealed a major phase characteristic of the monoclinic SrAl2O4 compound. Small amounts of the dopants MnCO3 and Nd2O3 have almost no effect on the crsytalline phase composition. Characteristic absorption bands from Nd3+ 4f-4f transitions in the spectra can be assigned to the transitions from the ground state I-4(9/2) to the excited states. The luminescence of Mn2+ activated SrAl2O4 exhibits a broad green emission band from the synthesized phosphor particles under different excitation sources. This corresponds to the spin-forbidden transition of the d-orbital electron associated with the Mn2+ ion. In photo- and radio-luminescence spectra, Nd3+ 4f-4f transition peaks were observed. The emitted radiations for different luminescence techniques were dominated by 560, 870, 1057 and 1335 nm peaks in the visible and NIR regions as a result of I-4(9/2) -> (4)G(7/2) and F-4(3/2) -> I-4(J) (J=9/2, 11/2 and 13/2) transitions of Nd3+ ions, respectively. Multiple emission lines observed at each of these techniques are due to the crystal field splitting of the ground state of the emitting ions. The nature of the emission lines is discussed. (C) 2013 Elsevier B.V. All rights reserved.
Enhancement of the luminescence intensity by co-doping Mn2+ into Er3+-doped SrAl2O4
de Herval, LKS; Arslanlar, YT; Ayvacikli, M; Iikawa, F; Nobrega, JA; Pizani, PS; Gobato, YG; Can, N; Henini, M; de Godoy, MPF
Structural and optical properties of erbium- and manganese-doped strontium aluminates (SrAl2O4) phosphor materials synthesized by a solid state reaction were investigated. The samples presented the fundamental optical transitions due to Er3+ and Mn2+ which are typical features of the well-diluted doping process. A significant enhancement of the Er3+ optical emission band at 1530 nm was observed when the matrix is co-doped with Mn. Photoluminescence intensity under ultraviolet excitation was three times larger as compared to samples without Mn content. A model of energy transfer mechanism from Mn2+ to Er3+ ions due to optical energy matching is proposed to explain the experimental results. This result, presented first time, can be applied as useful tool for developments in optical communications. (C) 2015 Elsevier B.V. All rights reserved.

Browsing by Author "Henini, M"

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