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Browsing by Author "Garcia-Guinea, J"

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Radioluminescence and thermoluminescence of albite at low temperature
Can, N; Garcia-Guinea, J; Kibar, R; Çetin, A; Ayvacikli, M; Townsend, PD
Feldspar as an archaeological and geological natural material for dating and retrospective dosimetry is receiving more and more attention because of its useful luminescence properties. In this study, the 25-280 K thermoluminescence (TL) and radioluminescence (RL) spectra in albite, which is a component of the two main feldspar series, the alkali feldspar (Na, K)AlSi(3)O(8) and the plagioclases (NaAlSi(3)O(8)-CaAl(2)Si(2)O(8)) have been presented for aliquots along (001) and (010) crystallographic orientations. There are four main emission bands that are considered to arise from complexes of intrinsic defects linked in larger complexes with impurities such as Na(+), Mn(2+) or Fe(3+) ions. The consequence of their association is to produce different luminescence efficiencies that produce wavelength sensitive TL curves. Radioluminescence data at low temperature for albites is distorted by contributions from the TL sites, even when the RL is run in a cooling cycle. This indicates the potential for a far more general problem for analysis of low temperature RL in insulating materials. (C) 2011 Elsevier Ltd. All rights reserved.
Thermal Effect on the Cathodo- and Thermoluminescence Emission of Natural Topaz (Al2SiO4(F,OH)2)
Correcher, V; Garcia-Guinea, J; Martin-Fernandez, C; Can, N
The 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.
Orientation dependence of the ion beam and cathodoluminescence of albite
Garcia-Guinea, J; Finch, A; Can, N; Hole, D; Townsend, P
Ion beam induced luminescence and cathodoluminescence of albite produce unexpected differences between (010) and (001) aligned samples. The emission spectra are modified by temperature and different components change in their relative intensity as a result of excitation by different ion beams of H+, H-2(+) and He+. A consideration of processes which can induce the orientation dependence and the role of excitation density that influences the component features are both discussed. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Luminescence behavior and Raman characterization of jade from Turkey
Arslanlar, YT; Garcia-Guinea, J; Kibar, R; Çetin, A; Ayvacikli, M; Can, N
Results are presented for the cathodoluminescence (CL), radioluminescence (RL) and thermoluminescence (TL) of jade from Turkey. Jade samples show broad band luminescence from green to red, which, using lifetime-resolved CL, reveals seven overlapping emissions, of which two are dominant. Green emission obtained using spatially resolved CL was associated with Mn2+ and emission bands centered near at 480 and 530 nm were attributed to P-3(0)-H-3(4) and D-1(2)-H-3(4) transitions of Pr3+, respectively. Different shifts of the peak-wavelengths for 326 and 565 nm were observed with varying jade compositions. The incorporation of the larger K ion causes non-linear variations of the cell dimensions and therefore changes in the Fe-O band distance. We suggest that stress of the jade structure can be linked to the luminescence emission at 326 nm. Raman spectra have also been recorded in order to provide an unequivocal identification of the type of jade. The mechanism for the luminescence of the jade is considered. (C) 2011 Elsevier Ltd. All rights reserved.
Luminescence and micro-Raman investigations on inclusions of unusual habit in chrysoprase from Turkey
Ayvacikli, M; Garcia-Guinea, J; Jorge, A; Akalin, I; Kotan, Z; Can, N
Chemical analyses performed on chrysoprase from Turkey have shown many trace elements as well as rare earth impurities. Quantitative chemical analyses of inclusions in minerals can improve our understanding of the chemistry of surface. The environmental scanning electron microscope (ESEM) with an attached X-ray energy dispersive system (EDS) is capable of producing rapid and accurate major element chemical analyses of individual inclusions in crystals larger than about 30 mu m in diameter. The samples were examined with lifetime-resolved and spatially-resolved cathodoluminescence (CL), and inductively coupled plasma-atomic emission spectrometry (ICP-AES). Spatially resolved CL results at room temperature were recorded for two different areas. Bulk area displays with low CL emission and pores contain iron phases such as chromite, hematite and anatase which cause the green color. For the raw data in the lifetime resolved CL spectrum, at least three broad emission bands were detected in a yellow band of the highest intensity at about 550 nm, a weaker orange band at about 650 nm, and a red band at 720 nm. It is assumed that there are links between the CL emissions and the presence of some transition metal and REE elements, but it is obvious that all trace elements do not play a direct role. Micro-Raman measurements were performed on chrysoprase and these showed a characteristic intensive Raman band peaked at 464 cm(-1) which can be inferred to nu(2) doubly symmetric bending mode of [SiO4/M] centers. Raman spectrum of all inclusions found in the material are also given and discussed in detail. (C) 2012 Elsevier B.V. All rights reserved.
Solid state synthesis, characterization and optical properties of Tb doped SrSnO3 phosphor
Kotan, Z; Ayvacikli, M; Karabulut, Y; Garcia-Guinea, J; Tormo, L; Canimoglu, A; Karali, T; Can, N
In the present study, the structural and optical properties of SrSnO3 doped with Tb ions are reported. Novel SrSnO3:Tb3+ phosphors were conventionally synthesized using a solid state reaction process under a mildly reduced atmosphere (5% H-2 and 95% N-2). The crystal structures, morphologies and optical properties of the resultant materials have been characterised by experimental techniques such as X-ray Diffraction (XRD), Raman spectroscopy (RS), Photoluminescence (PL), Radioluminescence (RL) and Cathodoluminescence coupled to an ESEM (ESEM-CL). The new phosphor material has good crystallization without any impurity phases, which matches with the standard JCPDS files (No. 22-1442) from XRD analysis. The PL, RL and CL measurements taken at room temperature showed that the transitions of D-5(4) to F-7(J) (j = 6, 5, 4, 3) corresponding to the typical 4f -> 4f dipole forbidden intra-configurational transitions of Tb3+ are largely independent of the host material. The green emissions of the D-5(4) -> F-7(5) magnetic dipole transition at similar to 540 nm are predominant for three types of luminescence. PL emission spectra recorded in the temperature range from 10 K to 300 K were influenced by temperature. We report anomalies in the PL spectra of SrSnO3:Tb3+ compatible with a structural phase transition at 260 K while simultaneously exciting and cooling the sample. This work clearly confirms the existence of a phase transition discovered by Singh et al. in SrSnO3 at 270 K. (C) 2013 Elsevier B.V. All rights reserved.
Ionoluminescence of silicates for ceramic uses at cryogenic temperatures
Garcia-Guinea, J; Hole, D; Finch, A; Correcher, V; Valle-Fuentes, FJ; Can, N; Townsend, PD
Requirements 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..
Luminescent, Structural, and Thermal Properties of the Unusual Anatolian Diaspore (Zultanite) from Turkey
Canimoglu, A; Garcia-Guinea, J; Correcher, V; Karabulut, Y; Tuncer, Y; Can, N
Results 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.
The role of rare earth elements and Mn2+ point defects on the luminescence of bavenite
Garcia-Guinea, J; Correcher, V; Quejido, A; LaIglesia, A; Can, N
Natural 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.
Luminescent, optical and color properties of natural rose quartz
Kibar, R; Garcia-Guinea, J; Çetin, A; Selvi, S; Karal, T; Can, N
Rose quartz is an interesting mineral with numerous impurities that have been studied by scanning electron microscopy (SEM), X-ray fluorescence (XRF), X-ray diffraction (XRD), cathodoluminescence (CL), ion beam luminescence (IBL), radioluminescence (RL), thermoluminescence (TL) and optical absorption (OA). After HF etching, rose quartz from Oliva de Plasencia (Caceres, Spain) shows under SEM the presence of other silicate phases such as dumortierite [Al6.5-7(BO3)(SiO4)(3)(O, OH)(3)]. The OA spectrum of rose quartz suggests that these inclusions are the cause of coloration of rose quartz. The luminescence (CL, IBL, RL, TL) spectra behavior, at both room temperature and lower, confirms that the similar to 340 nm emission could be associated with Si-O strain structures, including non-bridging oxygen or silicon vacancy-hole centers; the observed similar to 400 nm emission could be associated with recombination of a hole trapped adjacent to a substitutional, charge-compensated aluminum alkali ion center; the similar to 500 nm emission could be associated with substitutional Al3+ and the similar to 700 nm peak could be associated with Fe3+ point defects in Si4+ sites. These results suggest that, while defect properties of rose quartz are not greatly dissimilar to those of purer forms of quartz and silica, further research seems necessary to determine criteria for the evolution of the newly-formed self-organized microstructures in the rose quartz lattice under irradiation. (C) 2007 Elsevier Ltd. All rights reserved.
Cathodoluminescence spectra recorded from surfaces of solids with hydrous molecules
Garcia-Guinea, J; Correcher, V; Can, N; Garrido, F; Townsend, PD
Modern 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.
Novel Dy incorporated Ca3Y2B4O12 phosphor: Insights into the structure, broadband emission, photoluminescence and cathodoluminescence characteristics
Qaisi, AH; Kaynar, UH; Ayvacikli, M; Garcia-Guinea, J; Alajlani, Y; Topaksu, M; Can, N
This study reports cathodoluminescence (CL) and photoluminescence (PL) properties of undoped borate Ca3Y2B4O12 and Ca3Y2B4O12:x Dy3+ (x = 0.5, 1, 2, 3, 5, and 7) synthesized by gel combustion method. Micro-X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), CL and PL under electron beam and 359 nm pulse laser excitation, respectively were used to investigate characterization and luminescence studies of synthesized samples in the visible wavelength. As-prepared samples match the standard Ca3Y2BO4 phase that belongs to the orthorhombic system with space group Pnma (62) based on XRD results. Under electron beam excitation, this borate host shows a broad band emission from about 250 to 450 nm, peaked at 370 nm which is attributed to NBHOC. All as-prepared phosphors exhibited the characteristic PL and CL emissions of Dy3+ ions corresponding to F-4(9/2)-> H-6(J) transitions when excited with laser at 359 nm. The CL emission spectra of phosphors were identical to those of the PL spectra. Concentration quenching occurred when the doping concentration was 1 mol% in both the CL and PL spectra. The underlying reason for the concentration quenching phenomena observed in the discrete orange-yellow emission peaked at 574 nm of Dy3+ ion-doped Ca3Y2B4O12 phosphor is also discussed. According to these data, we can infer that this new borate can be used as a yellow emitting phosphor in solid-state illumination.
On the spectra luminescence properties of charoite silicate
Garcia-Guinea, J; Townsend, PD; Can, N; Correcher, V; Sanchez-Muñoz, L; Finch, AA; Hole, D; Avella, M; Jimenez, J; Khanlary, M
Charoite 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.
Structural and temperature-dependent luminescence of Terbium doped YAl3(BO3)4 phosphor synthesized by the combustion method
Hakami, J; Kaynar, UH; Ayvacikli, M; Coban, MB; Garcia-Guinea, J; Townsend, PD; Oglakci, M; Can, N
A series of Y1-xAl3(BO3)4:x Tb3+ (x = 0.5 to 7 wt%) phosphors synthesized by a gel combustion method have been systemically investigated by X-ray diffraction (XRD), Fourier transform infrared (FTIR), energy dispersive spectroscopy (EDS), and photoluminescence (PL) as a function of temperature from 300 K to 10 K and 300 K-550 K. An XRD analysis confirms that the phosphors crystallized, and its crystal structure was analysed. The synthesized phosphor matches the XRD pattern provided in the ICSD File No 96-152-6006. The FTIR analysis indicates that nitrates and organic matter have been completely removed and the BO3 groups are present. The broad PL band peaked at 420 nm with a shoulder circa 460 nm of YAl3(BO3)4 is associated with hydrous components which attached to the sample in environmental conditions after synthesis. The PL spectra of YAl3(BO3):Tb3+ phosphors exhibit a bright and narrow green main emission peak at 543 nm corresponding to the 5D4 -> 7F5 transition under 359 nm excitation. The PL intensity increases with increasing Tb3+ ion concentration up to 5 wt %, followed by evidence for concentration quenching. There is a possibility that higher concentration quenching could be from confinement effects of localised resonant energy transfer. PL data revealed that acti-vation energies for thermal quenching at 485 nm and 543 nm were found to be 0.659 and 0.092 eV, and 0.585 and 0.087 eV, respectively.
Catholuminescence properties of rare earth doped CaSnO3 phosphor
Canimoglu, A; Garcia-Guinea, J; Karabulut, Y; Ayvacikli, M; Jorge, A; Can, N
The present study describes cathodoluminescence (CL) properties of CaSnO3 phosphors doped with Eu3+, Tb3+ and Dy3+ synthesized by a solid-state method. X-ray diffraction (XRD) patterns confirm that CaSnO3 sintered at 1200 degrees C exhibits orthorhombic structure. The evidence and rationale for two strong broad emission bands appeared at 360 and 780 nm for undoped CaSnO3 are presented. The CL measurements exhibit that the 4f-4f emissions from D-5(4) -> F-7(5) (490 nm), D-5(4) -> F-7(5) (544 nm), D-5(4) -> F-7(4) (586 nm) and D-5(4) -> F-7(3) (622 nm), assigned to possible transitions of Tb3+ ions are seen. The strongest one, observed at 544 nm, due to its probability of both magnetic and electric transitions make the sample emission green. Emissions at 480, 574, 662 and 755 nm were detected for the CaSnO3:Dy3+ and attributed to the transitions from the F-4(9/2) to various energy levels H-6(15/2), H-6(13/2), H-6(11/2) and H-6(9/2)+F-6(11/12) of Dy3+, respectively. CL spectra of Eu doped CaSnO3 reveal that there is a strong emission peak appeared at 615 am due to the electric dipole transition D-5(0) -> F-7(2) (red). Finally, our results show that the rare earth doped CaSnO3 have remarkable potential for applications as optical materials since it exhibits efficient and sharp emission due to rare earth ions. (C) 2015 Elsevier Ltd. All rights reserved.

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