Search

WOS: 000378835200012, In this study, manganese (Mn) doped Calcium Tetraborate (CaB4O7) samples were prepared by the wet chemical method. Under beta irradiated, CaB4O7:Mn showed thermally stimulated luminescence (TSL) glow peaks at approximately 85 degrees C and 220 degrees C with a heating rate of 5 degrees C/s. Peak shape (PS) and various heating rates (VHR) methods were applied for determining the trap parameters such as order of kinetic (b), activation energy (E) and frequency factor (s). The results indicate that the main dosimetric peak of CaB4O7:Mn follows the second-order kinetic model. The thermal fading ratio of the material is around 15% at the end of one month period of storage. The results of the TL studies carried out on the CaB4O7:Mn dosimeter revealed that it has high sensitivity, which makes it very valuable in various dosimetric applications like space, medical, personal dosimetry and dating. Radioluminescence (RL) of CaB4O7:Mn was also studied. It is shown that the RL spectrum contains a wide band centered at 530 nm assigned to Mn2+ ion emission. A broad band emission feature peaked at 350 nm assigned to the non-bridging oxygen hole center (NBOHC) is also discussed and a model is proposed to explain this broad band feature. (C) 2016 Elsevier B.V. All rights reserved.

WOS: 000374605100014, PubMed ID: 26943903, In this paper, the influence of a series of rare earth (Eu, Tm, Nd) and Cr ion doping on the optical properties of BGO was investigated by means of photoluminescence (PL) from visible to IR region in the 10-300 K temperature range using different types of detectors, namely, photomultiplier tube (PMT), InGaAs (IGA), and Si. Several samples were investigated having dopants concentrations of 03 wt%Nd, 0.4 wt%Tm, 0.06 wt% Cr and 3 ppm Eu. The PL spectra of the samples showed different luminescence behaviour which is assigned to the 4f intra shell transition from rare earth ions. The temperature dependence of the PL from rare earth doped BGO crystals is also examined. (C) 2016 Elsevier Ltd. All rights reserved.

WOS: 000352663500055, The physical characterization and phosphor emission spectra are presented for CaSO4 doped with Tm and Cu. All spectral wavelengths are related to electronic transitions of Tm3+ ions. The powder X-ray diffraction pattern showed that the compound exhibits orthorhombic structure and all reflections were indexed without any other secondary impurity phases. Chemical and structural properties of the samples have been characterized by means of Raman spectroscopy and environmental scanning electron microscope (ESEM) with an attached X-ray energy dispersive system (EDS). Group frequencies concept is essential point to the interpretation of the bands due to the main SO4 vibrational units and these displayed main characteristic intensive Raman bands including typical strong intensity at 1016 cm(-1) that corresponds to v(1)SO(4) vibrational mode. From the spatially-resolved cathodoluminescence (CL) spectrum, main emission bands of Tm3+ centered at 346, 362, and 452 nm, due to the respective transitions of P-3(0) -> H-3(4), D-1(2) -> H-3(6), D-1(2) -> F-3(4) were clearly identified. The study is novel as no such CL-ESEM data are available for this doped compound. (C) 2015 Elsevier B.V. All rights reserved., TUBITAK - HAS European Scientific Exchange Program [2227], This research is partly supported by the grants from TUBITAK - HAS European Scientific Exchange Program (2227). The authors would like to thank Dr. I. Kasa from Centre for Energy Research, Hungary for the phosphor materials.

The kinetic parameters of a newly developed Li2B4O7:Mn single crystal phosphor have been presented. Li2B4O7 single crystal doped with Mn were grown via the Czochralski method. Thermoluminescence (TL) glow curve of Li2B4O7:Mn single crystal exhibits two well separated TL peaks at about 363 and 478 K, later being more intense, with a heating rate of 1 K/s. The high-temperature glow curve at 478 K is important for dosimetric studies of Li2B4O7 (LBO) doped with Mn. The kinetic parameters (activation energy (E), frequency factor (s) and kinetic order (b)) of the main glow peak (478 K) have been calculated using initial rise (IR), isothermal decay (ID) and peak shape (PS) methods. Activation energies obtained by IR, ID and PS were found to be 1.24, 1.18 and 1.20 eV, respectively. Similarly, the frequency factors were determined using isothermal decay and peak shape methods and found as 7.85 x 10(11) and 3.27 x 10(11) s (1), respectively. All results obtained using these methods are compared and discussed. (C) 2013 Elsevier B. V. All rights reserved.

In this study, thermoluminescence (TL) characterization of newly developed Li2B4O7:Mn single crystal phosphor is reported. It is a very attractive material in personal dosimetry because of its near tissue equivalency (Z(eff) = 7.25). The crystal was grown by the Czochralski method from high purity compounds. Glow curve, dose response, and fading and reproducibility properties of this material were investigated. Its TL glow curve showed two well separated peaks at about 105 and 220 degrees C with a heating rate of 2 degrees C s(-1). The main peak at 220 degrees C has a linear dose response of up to 60 Gy. The thermal fading ratio of the material is about 8% for the main peak in 10 days. The results showed that there is no significant variation of TL responses for 15 sequential measurements. Apart from the dosimetric properties above, the TL kinetic parameters of the main peak at 220 degrees C of Li2B4O7:Mn single crystal phosphor were also calculated using the various heating rates method. Activation energy and frequency factor were found as 1.21 eV and 3.75 x 10(11) s(-1), respectively. (C) 2013 Elsevier Ltd. All rights reserved.

WOS: 000324823000018, 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.

Yttrium tantalate (YTaO4), yttrium niobium-tantalate (YTaNbO4), yttrium niobate (YNbO4), europium and terbium activated yttrium tantalate (YTaO4:Eu, YTaO4:Tb) and europium activated yttrium niobate (YNbO4:Eu) phosphors were prepared by solid-state reaction, from a homogeneous mixture consisting of Y2O3, Eu2O3, Tb4O7, Ta2O5, Nb2O5 and Na2SO4 as flux. Photoluminescence (PL), thermally stimulated luminescence (TSL), X-ray diffraction (XRD) and scanning electron microscopy (SEM) of yttrium tantalate based phosphors are reported. In the present study TSL characteristics of these phosphors were first investigated and reported after exposure to beta, UV (311 nm) and X-ray radiations.

In this study, thermal properties and thermal decompositions of dehydration behaviour of gem-quality translucent blue chalcedonies, without banding or crystalline centre structure, from the Sancakaya-Eskisehir region in Turkey were studied by means of X-ray diffraction (XRD), inductively coupled plasma-atomic emission spectrometry (ICP-AES), Fourier transform infrared (FT-IR), thermoluminescence (TL), and simultaneously two thermal analyses of (DTA/TGA) spectroscopy. X-ray diffraction patterns of the blue chalcedony indicate the presence of two important chalcedonic silica phases with overlapped peaks at 4.26, 3.34, 2.28, 2.13, 1.82, 1.54, 1.38, and 137 A. During heating from the room temperature to 300 degrees C, the thermoluminescence pattern of the blue chalcedony shows a characteristic peak at 210 degrees C. This peak may be due to unusually high traces of the impurities S. Th, TI, U, and W. During heating from the room temperature to 1400 degrees C, the TGA pattern of the blue chalcedony indicates that the weight loss is due to the silanol water loss only, and that this loss occurs in a wide temperature range between about 170 and 954 degrees C. In addition, after making some corrections concerning the artefact mass gain, being due to the drift with buoyancy effect of the atmosphere in its TGA curve, the moganite-rich blue chalcedony shows a relatively lower mass loss of 0.202%. The DTA pattern of the blue chalcedony displays both endothermic and exothermic behaviours because of silica phase transformations. There are one distinctive sharp endotherm and three weaker endotherms at 806 degrees C. In addition, there is one distinctive sharp exotherm and one weaker exotherm at 1270 degrees C. (C) 2010 Elsevier B.V. All rights reserved.

Borate based thermoluminescence dosimeters (TLD) show high sensitivity and good TL characteristics. One of the promising material amongst the dosimeters is Dy doped CaB4O7. Spectrally resolved thermoluminescence of Dy doped CaB4O7 shows three glow peaks at about 50 degrees C, 240 degrees C and 380 degrees C, the intensity of the 240 degrees C glow peak being the maximum. All TL experiments were conducted on a high sensitivity TL spectrometer at Sussex University with a heating rate of 50 degrees C min(-1). Two main emissions associated with the Dy dopant are observed at similar to 480 and 580 nm. The samples were subjected to a series of treatments including excitation by X-rays and UV laser radiation. As part of the present research CaB4O7:Dy materials were subjected to two different heat treatments; quenching and slow cooling in order to investigate the changes in TL characteristics. (C) 2010 Elsevier Ltd. All rights reserved.

Room and low temperature cathodoluminescence (CL) of rare earth doped Bi4Ge3O12 (BGO) has been recorded. Luminescence signals noted in the wavelength range (300–800 nm) include intrinsic broad emission bands and signals related to Eu3+, Nd3+, and Tm3+. CL measurements made on Bi4Ge3O12 (BGO) doped with rare earth ions are reported for the temperature range 40 to 300 K with different CL excitation modulation frequencies. Dopant levels used in the present study are 1.1, 0.4, and 0.3 wt% Nd, 0.4 wt% Tm and 3 ppm Eu. All dopant levels exhibited different CL spectra with evidence for lines due to the rare-earth dopants intra-4f transitions. The temperature dependence of the intensity of the emission band is discussed.

Rare earths, especially Dy or Tm doped CaSO4 phosphors are actively studied. They have high sensitivity, a large dynamic range, thermal stability and ease of preparation. Nevertheless, they can be enhanced by inclusion of lithium and this study reports some effects of lithium co-dopant on the TL and radioluminescence (RL) emissions of two TL phosphors. Addition of Li as a co-dopant ion was made either during chemical preparation of the phosphors, or as a binder component mixed with the basic phosphors matrix during the process of pressing and sintering the TLD pellets.

The kinetic parameters of a newly prepared tissue-equivalent, highly sensitive thermoluminescent detector, Li 2 B 4 O 7 : Cu , Ag , P of sintered pellets have been calculated. Thermoluminescence (TL) glow curves of Li 2 B 4 O 7 : Cu , Ag , P samples after β -irradiation showed peaks at about 384 and 446 K with a heating rate of 1 K s - 1 . The kinetic parameters, namely activation energy ( E ) and frequency factor ( s ) associated with the main glow peak (446 K) of Li 2 B 4 O 7 : Cu , Ag , P have been determined using isothermal decay (ID) and peak shape (PS) methods. The activation energies obtained by ID and PS methods are calculated to be 1.12 and 1.13 eV (mean), respectively. The frequency factors obtained by both methods are 7.61 × 10 11 and 3.53 × 10 11 s - 1 (mean), respectively. Results obtained using both methods are compared and discussed.

ZnO [0001] single crystals were implanted at room temperature with 400 keV Tb + ions at fluences in the range of 1 × 10 16 –2 × 10 17 ions/cm 2 . Zinc oxide was chosen because of its potential for photonic applications as a semiconductor with high radiation resistance. After implantation and post-irradiation annealing, optical absorption was measured in a UV–VIS–NIR range and radioluminescence spectra were recorded at room temperature. Emission signals were generated by the Tb + ion implants and intrinsic emission of the ZnO matrix were observed. The implant signal intensities were comparable with the host radioluminescence, even though the implants modify the surface of the crystal. It is suggested that the presence of Tb at high concentration generates stresses which influence the bulk material and also potentially forms precipitates or nanoparticles in the near surface region. Overall ion implantation of ZnO results in strongly modified luminescence.

The aim of this study is to determine the enhancement in natural radioactivity level of soils due to the usage of fertilizers, particularly phosphate fertilizers in agricultural lands of Gediz River basin, Western Turkey. In addition, the activity concentrations of naturally occurring radionuclides in some vegetables collected from the same lands were investigated in order to assess any contribution to the effective internal dose after ingestion. Radioactivity concentrations of natural radionuclides, namely Ra 226 , Th 232 and K 40 , in fertilized, non-fertilized soils and vegetables were measured by NaI(Tl) gamma spectrometer in order to assess the implications of the extended use of phosphate fertilizers in agriculture in recent years. Activity concentration of Po 210 , an alpha particle emitter, were also analysed using a ZnS(Ag) alpha counter after electrodeposition process. In addition, physical and chemical characteristics of soil samples were investigated and analysed for any correlation between the soil characteristics and their radionuclide contents. In vegetables collected from agricultural fields of the basin the ranges of the relative activity concentrations of K 40 , Ra 226 , Th 232 and Po 210 are found to be 491.62–2324.51, 15.96–52.80, ND–10.54 and 8.40 – 22.20 Bq kg - 1 , respectively. In soils of agricultural lands, where vegetables are collected, the activity concentrations of K 40 , Ra 226 , Th 232 and Po 210 are 325.89–530.52, 46.05–68.83, 9.29–50.57 and 36.75 – 56.70 Bq kg - 1 , respectively. For non-fertilized fields, activity concentrations of soils are found to be within 240.40 – 403.09 Bq kg - 1 for K 40 , 35.61 – 62.64 Bq kg - 1 for Ra 226 , 7.40 – 38.53 Bq kg - 1 for Th 232 and 32.50 – 41.14 Bq kg - 1 for Po 210 .

Nanoparticles of Cu have been made in zinc oxide crystals by ion implantation. The Cu ions were implanted at 400 keV into the (0 0 0 1) face of a single crystal. After implantation and after post-irradiation annealing there are numerous changes in the luminescence responses which include a variety of green and yellow emission bands. Following annealing at temperatures up to 1000 °C a green luminescence near 525 nm was observed which has been associated with the isolated Cu ions. The changes between as implanted and annealed luminescence signals suggests that the implants generate clustering or nanoparticle formation of Cu but anneals dissociate them.

In this study concentrations of 210Po and 210Pb radionuclides in soils and vegetables collected from both cultivated and uncultivated agricultural lands of the Kucuk Menderes basin were determined. 210Po and 210Pb activity concentrations of vegetables collected from cultivated lands were found to be slightly higher than those collected from undisturbed lands. The activity concentrations in vegetables were detected between 0.15 – 9.40 Bq kg - 1 and 0.23 – 0.62 Bq kg - 1 for 210Po and 210Pb, respectively. In the bulk soil cores sampled from phosphate fertilizer-applied agricultural lands, the ranges for activity concentrations of 210Po and 210Pb are 30.10 – 47.15 Bq kg - 1 and 31.27 – 61.53 Bq kg - 1 , respectively. 210Po and 210Pb activity concentrations in soil cores collected from uncultivated soils were also determined for comparison. The annual effective dose equivalents to man from 210Po and 210Pb due to consumption of leafy vegetables are calculated to be 30.51 and 22.73 μ Sv a - 1 , respectively. Likewise root vegetables give a dose equivalent of 22.89 μ Sv a - 1 from 210Po and 44.77 μ Sv a - 1 from 210Pb.

Copper nanoparticles have been formed in a zinc oxide (ZnO) substrate by Cu implantation at 160 keV. The implant layer shows amorphised behaviour as monitored by the RBS data and optical absorption indicates the surface plasmon resonance peak characteristic of copper nanoparticles. There is nonlinear optical absorption from the Cu nanoparticles. There are numerous changes in the luminescence responses which include a variety of green and yellow emission bands. During excitation there were changes in the cathodoluminescence intensity and lifetime influenced by the surface events, including some unusual features, which may be considered in terms of interactions with surface water and ice. Radioluminescence signals oscillate between the normal emission bands and the wide red line emission from free Zn. Overall ZnO is, therefore, an unexpectedly interesting host for dispersed Cu nanoparticles, not least because the optical features may be compatible with the semiconductor aspects of ZnO.

210Po in environmental samples has been accumulated on various metals using the chemical electrodeposition technique. The 210Po was deposited spontaneously on metal discs after decomposition of the sample in HCl acid and then measured using a ZnS(Ag)α-particle detector. Silver was observed to have the highest deposition efficiency when 210Po deposition on different metals was studied. Copper discs were used in the application of activity assessment in cigarette smoke as this is more available and more economical although silver has a higher efficiency than that of other materials examined. The technique is applied for the analysis of 210Po in tobacco, ash and butt for several brands of imported and domestic cigarettes smoked in Turkey.