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Browsing by Author "Canimoglu, A"

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Radioluminescence Properties of Copper- and Terbium-Implanted Strontium Titanate
Arslanlar, YT; Kibar, R; Çetin, A; Canimoglu, A
In this study, the effects of Cu and Tb implantation on the radioluminescence (RL) properties of unimplanted and Cu- and Tb-implanted SrTiO3 (STO) crystals were investigated. The changes induced by heavy ion implants of the surface clearly modify the initial strong RL signals seen near 400750nm. During heating there are step increases in intensity at the RL spectrum near 60, 40, and 82K for unimplanted and Cu- and Tb-implanted samples, respectively.
Strong Visible and Near-Infrared Cathodoluminescence in Alkali Feldspar
Karabulut, Y; Canimoglu, A
In this study, cathodoluminescence (CL) spectroscopy at direct current and alternating current under the sample temperature condition of 40-293K using different modulation frequencies is presented for alkali feldspar from the Dartmoor granite (UK). These feldspars contain strain-controlled lamellar crypto- and microperthites that are cross-cut by strain-free deuteric microperthites. The CL spectra of the alkali feldspar at room and low temperature confirm that the observed emission peaked at similar to 460nm could be associated with Al-O--Al or Ti impurity centers, yellow emission similar to 560nm could be associated with the presence of the centers such as radiation-induced defect centers, and similar to 756nm emission could be associated with the Fe3+ impurity center on T-1 and T-2 sites. The consequence of their association is to produce different luminescence properties such as intensity, peak wavelength, and band shape.
Cathodoluminescence Response From Sanidine Feldspar
Karabulut, Y; Canimoglu, A; Can, N
In the present study, cathodoluminescence (CL) providing information about surface rather than bulk material reveals blue and red emissions within the sanidine feldspar from the Eifel Mountains, Germany. The emission line occurring in the blue region at about 450nm reflects Al-O--Al structural defects, although distribution maps of the major elements, including Si, Al, and K, do not display a clear correlation with the CL properties of the sanidine feldspar. Dominant emission being in the longer-visible wavelength region (red region) approximate to 730nm is assumed to be caused by Fe3+ activation attributed to Fe3+-Al3+ substitution. Much less is known about the spectral characteristic of the feldspar CL emission, and the application of an older luminescence technique yields encouraging results for the practical application of the feldspar identification.
Thermoluminescence behaviour of europium doped magnesium silicate after beta exposure
Uçar, ZGP; Kaynar, UH; Dogan, T; Souadi, GO; Ayvacikli, M; Canimoglu, A; Topaksu, M; Can, N
This article presents a detailed analysis of beta ray exposed thermoluminescence response of a series of Eu3+ doped (0.5-10 mol%) Mg2SiO4 nanocrystalline samples successfully synthesized through solid state reaction method. Optimizing the doping concentration of Eu3+ ion in Mg2SiO4 phosphor was found as 3 mol%. Two main peaks were seen at 246 degrees C and 374 degrees C and also low temperature peak at 78 degrees C. The intensities of these peaks were increased linearly with increasing beta absorbed dose. T-m-T-stop method was used to reveal trap levels. Variable heating rate and computerized glow curve deconvolution methods were also used to evaluate the number of peaks and kinetic parameters, namely activation energy and frequency factor. The results of a series of experiments carried out to investigate some fading characteristics of Mg2SiO4:Eu3+ were also presented. The findings suggest that thermoluminescence properties of Mg2SiO4:Eu(3+ )makes this material suitable and promising dosimetric phosphor material for medical applications.
Tb-doped MgAl2O4 phosphors: A study of structural and luminescence characteristics
Halefoglu, YZ; Souadi, G; Ayvacikli, M; Bulcar, K; Topaksu, M; Canimoglu, A; Madkhali, O; Karmouch, R; Can, N
In the MgO-Al2O3 system, magnesium aluminate spinel (MgAl2O4) is a technologically significant compound due to its unique properties, including a high melting point, low thermal conductivity, excellent thermal shock resistance, chemical inertness, and robust mechanical strength. This compound has diverse applications in re-fractory materials, catalyst supports, moisture sensors, nuclear techniques, insulating materials, and even mili-tary applications. While rare-earth elements are commonly used as dopants in luminescent materials, limited research exists on doping of Tb3+ ions in magnesium aluminate. This study investigates the luminescence properties of Tb3+ doped synthesis magnesium aluminate materials, shedding light on this underexplored area. The combustion method is employed for synthesis, known for producing nano-sized powders with exceptional luminescent properties. Additionally, this study explores Sm3+ ion doping in magnesium aluminate materials and their luminescence properties. Using the combustion synthesis method, structural attributes of Tb3+-doped MgAl2O4 nanophosphors are meticulously examined. Through X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) analyses, coupled with excitation and emission spectra, a comprehensive investigation of the luminescent provide behavior at room temperature is provided. The XRD data reveal Tb3+ doped MgAl2O4 phosphors exhibit a single phase with face centred cubic structure belonging to the Fd3 m space group, consistent with the standard JCPDS files (No. 21-1152). Excitation and emission spectra offer valuable insights into the energy transitions within the Tb3+-doped MgAl2O4 phosphors. Furthermore, the study explores the effects of varying Tb3+ ion concentrations on the luminescent properties, revealing an optimal doping concentration of 5 wt% Tb for maximizing emission intensity. Concentration quenching, primarily attributed to dipole-dipole (d-q) interactions, is observed at higher Sm3+ concentrations. In conclusion, this research enhances our understanding of rare-earth ion doping in luminescent materials and highlights the potential applications of Tb3+-doped MgAl2O4 nanophosphors, which offer promise for various technological applications, including lighting and displays.
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.
Comparative studies on thermoluminescence characteristics of non-doped Mg2SiO4 prepared via a solid-state reaction technique and wet-chemical method: An unusual heating rate dependence
Dogan, T; Akça, S; Yüksel, M; Kucuk, N; Ayvacikli, M; Karabulut, Y; Canimoglu, A; Topaksu, M; Can, N
Magnesium orthosilicate (Mg2SiO4) was synthesized via a traditional solid-state reaction and a wet chemical route. This study primarily reported the thermoluminescence (TL) behavior of Mg2SiO4 host. X-ray diffraction pattern revealed that Mg2SiO4 exhibits orthorhombic structure matched with JCPDS card 900-6398. Dose response, reproducibility and trap parameters of TL glow curves were evaluated to clearly reveal TL features. Two TL glow peaks situated at 81 degrees C and 192 degrees C were monitored at a heating rate of 2 degrees Cs-1. We observed anomalous heating rate effect for the peak centered at 192 degrees C whilst TL intensity of the peak at 81 degrees C decreases with elevating heating rate. Trap depths of the electrons within the trap centers were found to be 1.04 +/- 0.01eV and 1.37 +/- 0.01eV for both methods using peak shape (PS) method. Distribution of trap centers was examined using the T-max - T-stop method and this case indicated that the glow curves consist of single TL peaks. The intensity of TL glow curves exhibited a good linear dose response under total area up to 20 Gy. A comparison of the two preparation techniques revealed that TL characteristics of this phosphor are partly dependent and Mg2SiO4 could be a promising material for dosimetric application. (C) 2019 Elsevier B.V. All rights reserved.
Synthesis and Luminescence Properties of Trivalent Rare-Earth Element-Doped Calcium Stannate Phosphors
Karabulut, Y; Ayvacikli, M; Canimoglu, A; Guinea, JG; Kotan, Z; Ekdal, E; Akyuz, O; Can, N
The phosphors of calcium stannate activated with individual trivalent rare-earth element (REE) ions (Neodymium III, Europium III, Terbium III, Dysprosium III, and Samarium III) were synthesized by high-temperature solid-state reaction (SSR), and their characterization and luminescent properties were investigated. The crystal structures and morphologies of the resultant materials were well characterized by experimental techniques such as X-ray powder diffraction (XRD) and environmental scanning electron microscopy (ESEM). The XRD results display that the rare-earths substitution of Calcium II does not change the structure of calcium stannate host. Obviously, the ESEM image exhibits that phosphors aggregate and their particles with irregular shape exist. The calcined powders of the Europium III, Neodymium III, Samarium III, Dysprosium III, and Terbium III ions doped in calcium stannate exhibits bright red, reddish orange, yellowish, orange white, and green light, respectively. Although there is some intrinsic emission ranging from UV to near-infrared (NIR) due to the host lattice, the dominant signals are from the rare-earth sites, with signals characteristic of the trivalent rare-earth states. The emission spectrum from undoped-calcium stannate phosphor is characterized by two broad bands centered at similar to 800 and similar to 950nm. The shapes of the emission bands are different for each dopant. The sharp emission properties show that the calcium stannate is a suitable host for rare-earth ion-doped phosphor material. Furthermore the influence of different rare-earth dopants, that is, Europium III, Neodymium III, Samarium III, Dysprosium III, and Terbium III, on thermally stimulated luminescence (TSL) of calcium stannate phosphor under the beta irradiation was discussed. Among these trivalent rare-earth-doped phosphors samarium-doped material showed maximum TSL sensitivity with favorable glow curve shape.
Synthesis and photoluminescence characteristics of a novel Eu and Tb doped Li2MoO4 phosphor
Souadi, G; Kaynar, UH; Ayvacikli, M; Coban, MB; Oglakci, M; Canimoglu, A; Can, N
Li2MoO4:x Eu3+ and Li2MoO4:xTb(3+) phosphors, where x = 0.5, 1, 2, 3, 5 and 7 wt%, were synthesized through a gel-combustion method. The XRD data reveals that Eu3+ and Tb3+ doped Li2MoO4 phosphors exhibit a Rhombohedral structure belonging to the space group R3 which matched well with the standard JCPDS files (No.0120763). We present photoluminescence (PL) spectra from Eu and Tb doped Li2MoO4 under 349 nm Nd:YLF pulses laser excitation over the temperature range of 10-300 K. Undoped Li2MoO4 shows a wide broad band around 600 nm because of the intrinsic PL emission of tetrahedral of MoO42- which was in good agreement with previous findings. Under the excitation of 394 nm, the as-synthesized phosphors exhibited sharp and strong intensity PL emission signals in the red (612 nm, D-5(0) -> F-7(2) transition) and green (544 nm, D-5(4) -> F-7(5) transition), respectively. The critical doping concentration of Eu3+ and Tb3+ ions in the Li2MoO4 were estimated to be 2 wt%. The concentration quenching phenomena were discussed, and the critical distances for energy transfer have also been evaluated by the concentration quenching.
Preparation and characterization of Yttrium based luminescence phosphors
Muresan, LE; Ayvacikli, M; Guinea, JG; Canimoglu, A; Karabulut, Y; Can, N
Ce doped Yttrium aluminate modified by replacing different molar part of aluminium or gallium (Y(3)Al(5-x)GaxO(12)) and Yttrium silicate phosphors activated with Ce and Tb (Y2SiO5:Ce3+,Tb3+) were synthesized by solid state reaction and a gel combustion method, respectively. X-ray diffraction and Scanning electron microscope (SEM) techniques are used to identify their structures and morphologies. Luminescence characteristics are measured and spectroscopic data confirm that Y2SiO5:Ce3+, Tb3+ phosphors can be effectively excited upon UV excitation light and X-ray irradiation, resulting in intense blue and green emissions, respectively. This energy transfer takes place by means of a non-radiative process inside Ce3+-Tb3+ clusters formed in the host matrix. Tb3+ doped Y2SiO5 yields both blue emission D-5(3) -> F-7(j) (j = 3,4,5,6) and green emission D-5(4) -> F-7(J) (J = 3,4,5,6) of Tb3+. Y(3)Al(5-x)GaxO(12):Ce3+ phosphors exhibit a broad blue emission band originating from allowed 5d-4f transition of the Ce3+ ions under different excitation sources but the broad emission band shifts with increasing of Ga3+ content. This work presents a quantitative understanding of host material's on dopant's luminescence properties and thereby provides an optimization guideline, which is extremely demanding for the development of new luminescent materials. (C) 2017 Elsevier B.V. All rights reserved.
Comparison of thermoluminescence characteristics of undoped and europium doped YAl3(BO3)4 phosphor synthesized by combustion method: Anomalous heating rate, dose response and kinetic analyses
Kaynar, UH; Oglakci, M; Bulcar, K; Benourdja, S; Bakr, M; Ayvacikli, M; Canimoglu, A; Topaksu, M; Can, N
In this study, undoped and YAl3(BO3)(4) phosphors doped with Eu3+ at varying concentrations (x = 0.5 to 7 wt%) produced by a combustion process have been thoroughly examined by using the X-ray diffraction (XRD) and thermoluminescence (TL) techniques. The crystallized phosphors were confirmed by XRD analysis, and its crystal structure was examined. XRD analyses of the synthesized phosphor is in accordance with ICSD File No 96-152-6006. TL glow curve of undoped sample produced three glow peaks located at 80 degrees C, 240 degrees C, and 360 degrees C with a heating rate of 2 degrees Cs-1 whilst Eu3+ doped one appears at 90 degrees C, 230 degrees C, and 390 degrees C. The undoped example complied with the theory as expected, namely, as the heating rate increased, the TL glow curve shifted towards lower temperatures and decreased in intensity. However, an anomalous change was observed in the sample with Eu3+ additive. The experimental findings from the dose-response of YAl3(BO3)(4):0.5 wt%Eu3+ demonstrate that the intensity of TL provided by the total area under glow curves has an acceptable linearity (r(2):0.999) up to 100 Gy. The intensity of each maximum on the TL glow curve augments proportionally as the heating rate is augmented. Possible reasons of this behaviour are discussed. Various heating rate (VHR) methods (such as Hoogenstraaten's and Booth-Bohun-Parfianovitch) have also been used to estimate kinetic parameters (e.g., energy and frequency factor), which seem to be in good agreement with each other.
Synthesis and influence of ultrasonic treatment on luminescence of Mn incorporated ZnS nanoparticles
Cadis, AI; Muresan, LE; Perhaita, I; Munteanu, V; Karabulut, Y; Guinea, JG; 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 T-4(1) -> (6)A(1) 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 similar to 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. (C) 2017 Elsevier B.V. All rights reserved.
Thermoluminescence properties of beta particle irradiated Ca3Al2O6 phosphor relative to environmental dosimetry
Bakr, M; Portakal-Uçar, ZG; Yüksel, M; Kaynar, ÜH; Ayvacikli, M; Benourdja, S; Canimoglu, A; Topaksu, M; Hammoudeh, A; Can, N
Undoped Ca3Al2O6 phosphor was successfully synthesized through a gel-combustion method using different fuels. It was characterized by X-ray diffraction (XRD) technique and its cubic phase structure was confirmed from XRD pattern. TL data were recorded from room temperature (RT) to 500 degrees C in the heating rate of 2 degrees C/s. The glow curves of Ca3Al2O6 sample exposed to different beta doses (0-200 Gy) exhibited a significant glow peak at about 184 degrees C. The TL intensity of the glow peak exhibited very good linearity between 0.1 and 10 Gy. Following this, it was decreased at higher doses which was referred to this effect as monotonic dose dependence. Initial rise (IR), peak shape (PS), and variable heating rate (VHR) methods were used to estimate trapping parameters. Computerized glow curve deconvolution (CGCD) method via TLAnal software was also applied to estimate the number of peaks and kinetic parameters corresponding to the main glow curve in Ca3Al2O6 sample. The trapping activation energy of the main dosimetric peak was calculated to be around 1.30 eV for all methods. Present findings confirm that Ca3Al2O6 host is a promising candidate for applications in environmental dosimetry as one depicts good TL dose response with adequate sensitivity and linearity.
Thermoluminescence characteristics of a novel Li2MoO4 phosphor: Heating rate, dose response and kinetic parameters
Souadi, G; Kaynar, UH; Oglakci, M; Sonsuz, M; Ayvacikli, M; Topaksu, M; Canimoglu, A; Can, N
Lithium molybdate (Li2MoO4) phosphor was synthesized by a gel combustion method and its thermoluminescence properties were studied with the irradiation of beta. Various Heating Rate (VHR), Initial Rise (IR), and Computerized Glow Curve Deconvolution (CGCD) methods were used to determine the kinetic parameters (activation energy E (eV), frequency factor s (s(-1)), and kinetic order b) of the visible glow peaks. According to the kinetic study, the TL glow curve is made up of seven separate peaks with activation energies of 1.05, 0.76, 0.40, 0.60, 0.78, 1.81 and 1.25 eV and these peaks follow general-order kinetics. The results clearly showed that undoped Li2MoO4 has a potential to be considered in dosimetric applications where high doses have to be monitored as in the case of clinical dosimetry.
Broadband luminescence of Cu nanoparticles fabricated in SiO2 by ion implantation
Nguyen, TK; Le, KQ; Canimoglu, A; Can, N
In this study, we investigate optical properties of metal nanoparticle crystals fabricated by implanting copper (Cu) ions into single silica (SiO2) crystals with 400 key at various ion doses. The Cu implanted SiO2 (SiO2:Cu) crystal produces a broadband luminescence emission, ranging from blue to yellow, and having a blue luminescence peak at 546 nm. Such anomalous luminescence emission bands suggest that the ion implantation may give rise to aggregation of Cu nanoparticles in the host matrix. The boundary element method-based modelling of a given Cu nanoparticle aggregation was employed to justify the broadband luminescence emission. Formation of Cu nanoparticles in SiO2 is predicted through their optical absorption data. The experimental results are compared with results of Mie calculations and we observe that the higher ion dose produces the larger particle size. (C) 2016 Elsevier Ltd. All rights reserved.
Preparation and cathodoluminescence characteristics of rare earth activated BaAl2O4 phosphors
Benourdja, S; Kaynar, ÜH; Ayvacikli, M; Karabulut, Y; Guinea, JG; Canimoglu, A; Chahed, L; Can, N
Undoped and Pr, Sm and Tb activated BaAl2O4 phosphors have been synthesized by solid state reaction method and combustion method. The structure and morphological observation of the phosphor samples were monitored by X-ray powder diffraction (XRD) and environmental scanning electron microscope (ESEM) coupled to an energy dispersive X-ray spectrometer (EDS). The all diffraction peaks are well assigned to standard data card (PDF#17-306). Emission properties of the samples were explored using light emission induced by an electron beam (i.e cathodoluminescence, CL) at room temperature (RT). Undoped BaAl2O4 sample exhibits a broad defect emission from 300 to 500 nm from the aluminate defect centres. CL spectra recorded at room temperature display that the as-prepared BaAl2O4:Ln (Ln = Pr, Sm and Tb) phosphors exhibit different luminescence colors coming from different rare earth activator ions. The transition (4)G(5/2) -> H-6(7/2) located at 606 and 610 nm for Sm3+ can occur as hypersensitive transition having the selection rule Delta J = +/- 1. For the Tb3+ doped samples, they exhibit D-5(4) green line emissions. The proposed luminescent mechanisms of all doped rare earth ions are also discussed.
Thermoluminescence properties of Tb doped Mg2SiO4 after beta irradiation
Akça, S; Portakal, ZG; Dogan, T; Kucuk, N; Canimoglu, A; Topaksu, M; Can, N
In this study, we performed Thermoluminescence (TL) experiments to extract the trapping parameters and dosimetric properties of Tb-doped Mg2SiO4 phosphors. Glow peaks located at 193, 270, and 350 degrees C were observed in the glow curve but the peak at 193 degrees C was especially investigated as a dosimetric peak in this study. We also observed an anomalous heating rate effect in which the maximum TL intensity of the glow curve augmented with an increasing heating rate. The computerized glow curve deconvolution (CGCD) method, initial rise (IR) and Hoogenstraaten's method were used to determine the activation energies of associated trapping centers for both BSL-TL 365 nm and IRSL-TL wideband blue filters. The TL characteristics of this phosphor indicate that Mg2SiO4:Tb3+ could be a promising material for dosimetric applications. Efforts should be made to improve the fading behaviour by adding other activators as co-dopants.
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.
Synthesis and photoluminescence characteristics of Dy incorporated MoO3 phosphor: Suppression concentration quenching
Ayvacikli, M; Kaynar, ÜH; Karabulut, Y; Canimoglu, A; Bakr, M; Akca, S; Can, N
A series of MoO3:Dy3+ phosphors have been synthesized via the gel-combustion method. The X-ray and photoluminescence (PL) emission spectra were employed to characterize the obtained phosphors. The prepared samples were characterized through XRD measurements and exhibited that Dy3+ ions can be successfully incorporated into the host material. The PL emission bands of Dy3+ doped MoO3 were observed at 486 nm, 574 nm and 666 nm which are assigned to the transitions of F-4(9/2) -> H-6(15/2), F-4(9/2) -> H-6(13/2) and F-4(9/2) -> H-6(11/2), respectively. Concentration quenching were largely taken into consideration as one of the crucial aspects limiting the application range of phosphors in today's modern world. An abnormal thermal quenching dependence was reported when Dy3+ ions were incorporated into MoO3 host matrix. In order to understand the origin of this beneficial behaviour, energy transfer processes occurring via radiative and nonradiative mechanisms were investigated to elucidate this suppression of the concentration quenching.
Studies on luminescence from a cerium-doped strontium stannate phosphor
Karabulut, Y; Ayvacikli, M; Canimoglu, A; Guinea, JG; Can, N
The crystal structure and morphology of Ce3+-doped SrSnO3 materials prepared using the solid-state reaction method were extensively characterized using experimental techniques. X-Ray diffraction results show that the cerium substitution of strontium does not change the structure of the strontium stannate. Raman spectroscopy was used to investigate the microstructures and lattice vibrations. Environmental scanning electron microscopy images showed that phosphors aggregate and their particles form irregular shapes. SrSnO3 exhibits an intense green emission with a broad band originating from the 5d(1)4f(1) transition of cerium. It was observed that, after exposure to beta-irradiation, the glow curve of this material has two broad thermoluminescence peaks, one centered at similar to 127 degrees C and the other at similar to 245 degrees C for a heating rate of 5 K/s. The kinetic parameters, which include the frequency factor and the activation energy of the material, were calculated using Chen's method, after beta-irradiation. The fading and reusability of the phosphor were also studied and it was found that the phosphor is suitable for radiation dosimetry. Copyright (c) 2014 John Wiley & Sons, Ltd.

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