Browsing by Author "Correcher, V"
Now showing 1 - 8 of 8
Results Per Page
Sort Options
Item Thermal Effect on the Cathodo- and Thermoluminescence Emission of Natural Topaz (Al2SiO4(F,OH)2)Correcher, V; Garcia-Guinea, J; Martin-Fernandez, C; Can, NThe authors report about the influence of temperature on the thermoluminescence (TL) and cathodoluminescence (CL) behavior of a well-characterized topaz from Badajoz, Spain. Cryogenic treatments induce drastic decrease on the CL and TL intensity over 400nm involving O-Al* intrinsic defects and iron point defects. It suggests that low-energy emissions should be more associated with point defects and low wavebands to structural or intrinsic defects in the lattice. The tests of thermal stability of the UV-blue TL signal at different temperatures (in the range of 473-673 K) seem to confirm a continuous trap distribution system.Item Ionoluminescence of silicates for ceramic uses at cryogenic temperaturesGarcia-Guinea, J; Hole, D; Finch, A; Correcher, V; Valle-Fuentes, FJ; Can, N; Townsend, PDRequirements on accurate physical properties need new characterization techniques for structural defects. The use of light ions such as H+ and He+ with MeV energies allows penetration to a depth of several microns in most materials producing strong luminescence to gain information on the defect structures present. Examples of ionoluminescence spectra of silicates for ceramic uses are included such as Mn2+-Fe2+ coupled pairs in quartz, Dy3+ in zircon, hatch-twinning in microcline and spontaneous strain and sodium in albite. In cryogenic thermal conditions tectosilicates display both, reorganization of Mn2+ and Fe3+ centres plus a large enlargement of the UV-blue emissions by stress mechanisms. Nesosilicates, i.e., zircon, shows: differences such as existence of REE and (Dy3+) and a selective reduction of some UV-blue peaks, e.g., at 340 and 400 nm..Item Thermoluminescence response and kinetic parameters of Tb-doped GdCa4O(BO3)3 under beta irradiationAlajlani, Y; Bulcar, K; Oglakci, M; Kaynar, UH; Arslanlar, YT; Topaksu, M; Correcher, V; Can, NIn this study, the thermoluminescence (TL) properties of Tb3+-doped GdCa4O(BO3)(3) (GdCOB) are investigated with focus on the effects of optical filter selection, preheating, dopant concentration, irradiation dose, heating rate on these properties. Trapping parameters of the traps responsible for the peaks in the phosphor were also determined. The IRSL-TL-565 nm filter was identified as optimal filter for isolating the characteristic green emission of Tb3+ and improving the signal-to-noise ratio. Among the studied dopant concentrations (1, 2, 3, 5, and 7 wt%), 3 wt% Tb3+ was found to maximize TL intensity. Beyond this concentration, quenching effects became dominant, leading to reduced TL efficiency. At 3 wt% doping, TL glow peaks were observed at approximately 80 and 190 degrees C following a 50 Gy beta dose with a heating rate of 2 degrees C/s, with the primary peak (similar to 190 degrees C) favorable for minimizing thermal fading. The TL response of the primary peak was linear with dose within 5-500 Gy. The peak's TL intensity is affected by thermal quenching effects. Reusing of an aliquot of the phosphor ten times produced responses with 0.45 % maximum deviation from their mean. Additionally, the peak temperature (T-m) exhibited a slight decrease beyond 100 Gy, which can be attributed to charge carrier interactions, trap filling effects, and potential thermal quenching at higher doses. Heating rate experiments showed the expected shift of peak temperatures to higher values, emphasizing the need to correct for temperature lag in kinetic analyses. Computerized glow curve deconvolution (CGCD) indicated the presence of at least eight distinct trapping levels with activation energies ranging from 0.90 to 1.69 eV, revealing a complex trap structure. Overall, with its high TL intensity, linear dose response, and aliquot reusability, Tb3+-doped GdCOB is a promising phosphor for personal dosimetry, environmental radiation monitoring, and medical imaging.Item Luminescent, Structural, and Thermal Properties of the Unusual Anatolian Diaspore (Zultanite) from TurkeyCanimoglu, A; Garcia-Guinea, J; Correcher, V; Karabulut, Y; Tuncer, Y; Can, NResults are presented for the cathodoluminescence (CL) probe of an environmental scanning electron microscopy (ESEM) with an energy-dispersive spectrometry analyzer (EDS), thermoluminescence (TL), thermo X-ray diffraction in situ (TXRD), and simultaneous differential thermal analysis and thermogravimetric analysis (DTA/TGA) techniques of gem-quality zultanite samples collected from the Mugla region of southwest Turkey. Micro-Raman measurements were also performed on different zultanite orientations and preheated aliquots to study the spectral phase transition diaspore-corundum also detected by the other thermal techniques in the 450 degrees C-500 degrees C thermal range. The thermal phenomena of TL are synchronous with this dehydroxylation process, involving consecutive breaking-linking bonds of Al-O, Cr-O, Fe-O, Al-OH, Cr-OH, and Fe-OH, including the formation of hydrolyzed ions such , and and redox reactions. Assuming that zultanite oxygen atoms are distributed as a hexagonal close packed layer, the experimental spectrum CL of zultanite is characteristic of the E-2 ->(4)A(2) transitions of substitutional Cr3+ luminescent centers in positions of Al3+ in sixfold coordination.Item The role of rare earth elements and Mn2+ point defects on the luminescence of baveniteGarcia-Guinea, J; Correcher, V; Quejido, A; LaIglesia, A; Can, NNatural fibrous crystals of bavenite (Ca4Be2Al2Si9O26(OH)(2)) collected in intra-granitic pegmatite bodies of Bustarviejo (Madrid, Spain) have been examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), electron microprobe (EMPA) and inductively coupled plasma-mass spectrometry (ICP-MS). The strong luminescence emissions of bavenite using thermoluminescence (TL), cathodoluminescence (CL) and its thermal stability have been recorded, looking for new physical properties and new phosphor or dosimetric uses. The bavenite luminescence takes place in the 5d electron shell that interacts strongly with the crystal field; the spectra bands assignment are Gd3+ (319 nm), Sm3+ (562 and 594 nm), Dy3+ (572 nm) and Tb3+ (495 nm). A Mn2+ band at about 578 nm in Ca2+ sites is present as a broad band that overlaps with the Dy3+, Sm3+ and Tb3+ bands. Mn2+ is a transition metal ion that has an electron configuration of 3d(5) and interacts strongly with the crystal field (d --> d) transition. Stability tests at different temperatures show clearly that the TL glow curves at 400 nm in both irradiated and non-irradiated bavenite samples track the typical pattern of a system produced by a continuous trap distribution. The ICP-MS analyses show concentrations of Yb = 29.7 ppm, Dy = 22.7 ppm, Sm = 9.45 ppm, Nd = 8.95 ppm and Gd = 8.15 ppm in the bavenite lattice. (C) 2004 Elsevier B.V. All rights reserved.Item Cathodoluminescence spectra recorded from surfaces of solids with hydrous moleculesGarcia-Guinea, J; Correcher, V; Can, N; Garrido, F; Townsend, PDModern cathodoluminescence detectors coupled to Environmental Scanning Electron Microscopes (ESEM) with X-ray microanalysis are increasingly sensitive and, nowadays, low intense luminescence spectra may be recorded from nominally non-luminescent solid materials. Structural or attached hydroxyl groups are universally present in solid samples kept in environmental conditions being potentially active luminescence emitters. Hence, we collected cathodoluminescence (CL) spectra of sixty solid materials of minerals and synthetic compounds, organics and inorganics, metallic and non-metallic, crystalline and amorphous, including widespread CL bands at circa 315 nm and 620 and 650 nm from surfaces of solids with hydroxyl and hydrous molecules. We observed as iron bearing materials, such as biotite, olivine or native iron, show appreciable cathodoluminescence spectral bands associated with hydroxyl groups (315 nm) and water molecules (620 and 650 mn), being probable precursors of non-bridging oxygen hole centers. The wide set of very different samples analyzed shows spectral similarities among separated sample types but with the only common factor of the hydrous molecules. These conclusions seem crucial for remote sensing detection of water; environmental dosimetry; degradation of phosphor materials, etc. Analyzing spectral luminescence emissions of hydrated materials it is frequent to observe erroneous interpretations of their defect-emission relationships which should be avoided.Item On the spectra luminescence properties of charoite silicateGarcia-Guinea, J; Townsend, PD; Can, N; Correcher, V; Sanchez-Muñoz, L; Finch, AA; Hole, D; Avella, M; Jimenez, J; Khanlary, MCharoite is a hydrous alkali calcium silicate mineral [K4NaCa7Ba0.75Mn0.2Fe0.05(Si6O15)(2)(Si2O7)Si4O9(OH) center dot 3(H2O)] exhibiting an intense lilac colour related to Mn2+ and Fe3+ colour centres. These ions also contribute to a strong luminescence at similar to 585 and 705 nm. This work studies the thermal dependence of these luminescent centres by (i) thermoluminescence (TL) of pre-heated and pre-irradiated charoite aliquots, (ii) by time-resolved cathodoluminescence (TRS-CL) at room and cryogenic temperatures (RT and CT), (iii) by spatially resolved spectra CL under scanning electron microscopy (SRS-CL-SEM) and (iv) by ion beam spectra luminescence (IBL) with H+, H-2(+) and He-4(+) ions at RT and LT. The main peak, similar to 585 nm, is linked to a transition T-4(1,2)(G)->(6)A(7)(S) in Mn2+ ions in distorted six-fold coordination and the emission at similar to 705 nm with Fe2+ -> Fe3+ oxidation in Si4+ lattice sites. Less intense UV-blue emissions at 340 and 390 nm show multi-order kinetic TL glow curves involving continuous processes of electron trapping and de-trapping along with an irreversible phase transition of charoite by de-hydroxylation and lattice shortening of Delta a = 0.219 angstrom, Delta b = 0.182 angstrom; Delta c = 0.739 angstrom. The Si-O stressed lattice of charoite has non-bridging oxygen or silicon vacancy-hole centres, and Si-O bonding defects which seem to be responsible for the 340 nm emission. Extrinsic defects such as the alkali (or hydrogen)-compensated [AlO4/M+] centres could be linked with the 390 nm emission. Large variations in 585 and 705 nm intensities are strongly temperature dependent, modifying local Fe-O and Mn-O bond distances, short-range-order luminescence centres being very resistant under the action of the heavy ion beam of He-4(+). The SRS-CL demonstrates strong spatial heterogeneity in the luminescence of the charoite. (C) 2007 Elsevier B.V. All rights reserved.Item Thermoluminescence glow curve analysis and kinetic parameters of Eu doped Li2MoO4 ceramic phosphorsSouadi, G; Oglakci, M; Kaynar, UH; Correcher, V; Benavente, JF; Bulcar, K; Ayvacikli, M; Hiziroglu, A; Topaksu, M; Can, N; Karali, EELiMoO4: x Eu ceramic phosphors with x = 0.5, 1, 2, 3, 5, and 7 mol% were synthesized using a gel combustion method. X-ray diffraction (XRD) measurements confirmed a rhombohedral structure (space group R-3) of synthesized compounds. Following irradiation with 50 Gy beta dose, the sample doped with 5 mol% Eu exhibited the highest integrated thermoluminescence (TL) intensity. In order to evaluate dose-response, samples were irradiated with beta radiation for 10-1000 Gy. TL intensity with 1000 Gy dose without saturation yielded the highest integrated value. Different methods were employed to determine the number of peaks, the trap structure, and the kinetic parameters of the thermoluminescence glow curve of Eu doped Li2MoO4: the Hoogenstraaten method, the Booth-Bohun-Parfianovitch method, the initial rise method (IR), combined with the T-M-T-stop experiment, various heating rates (VHR), and glow curve fitting with two different software packages. Based on the glow curve deconvolution obtained using both software packages, the component TL glow peaks present in the complex glow curve are composed of well-isolated nine overlapping glow peaks. Two software packages have shown quite similar activation energies and frequency factors.