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A Edgar - One of the best experts on this subject based on the ideXlab platform.
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spectroscopic and radioluminescence properties of two bright x ray phosphors strontium Barium Chloride doped with eu2 or sm2 ions
Journal of Luminescence, 2014Co-Authors: Laura Dixie, A Edgar, Murray BartleAbstract:Abstract The optical fluorescence, X-ray phosphor and scintillation properties of europium or samarium-doped solid solutions of strontium and Barium Chloride, together with their preparation and structure, are reported. Strontium Chloride can accommodate up to 30% of Barium ions on the strontium site whilst still retaining the cubic fluorite structure, and it is shown that that polycrystalline samples of volume ~1 cm 3 with high transparency can be produced. The increase in average atomic number provided by the Barium content over pure strontium Chloride means that strontium Barium Chloride with additional (divalent) europium or samarium doping shows good performance as an X-ray phosphor, emitting in the blue or red, respectively. The red-emitting samarium doped material is of particular significance as the emission is well matched to the spectral sensitivity of new silicon-based photodiodes. Europium-doped strontium Barium Chloride shows photoluminescence centred at 406 nm with a lifetime of 1.0 µs. As a scintillator, the conversion efficiency is 26,000 photons/MeV, and the decay time is 1.6 µs, whilst as an X-ray phosphor the relative brightness is 40% that of the commercial X-ray phosphor gadolinium oxysulphide doped with terbium. Samarium-doped strontium Barium Chloride shows intense red 4f 5 5d 1 →4f 6 emission at room temperature which switches to 4f 6 →4f 6 emission at low temperatures. The temperature–induced change in emission intensities and lifetimes is successfully modelled as a thermal crossover between 4f 5 5d 1 and 4f 6 excited states which are in close proximity. At room temperature, the 4f 5 5d 1 →4f 6 emission is centred at 680 nm and has a lifetime of 15 µs; the scintillation efficiency is 22,000 photons /MeV with a lifetime of 30 µs. As an X-ray phosphor, the efficiency compared to gadolinium oxysulphide doped with terbium is 30%. The role of native defects in the performance of the materials as scintillators and phosphors is briefly discussed.
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luminescence and x ray phosphor properties of samarium and lanthanum doped cubic Barium Chloride
Physica Status Solidi (c), 2011Co-Authors: Laura Dixie, A Edgar, Murray BartleAbstract:Lanthanum and samarium-doped Barium Chloride samples with composition of the form Ba1-x-yLaxSmyCl2+x+y with x = 0.125 and 0 < y < 0.01 have been prepared in transparent ceramic form. X-ray diffraction confirms that the material adopts the high temperature cubic (fluorite) phase of Barium Chloride. The photoluminescence spectrum shows a combination of broad band 5d and narrow 4f transitions. The broad band can be decomposed into strong and weak components which we attribute to Sm2+ ions with and without an adjacent interstitial Cl- ion respectively. The temperature dependence of the strongest broad band indicates that the lowest 5d level is 800 cm-1 above the 5D0 level. The X-ray induced fluorescence spectrum shows an additional blue emission band for Sm concentrations y < 0.01 centred at around 420 nm which is ascribed to excitonic processes involving H centres. This emission band coincides with a photoluminescence excitation band for Sm2+ in this material, and so it is likely that the X-ray induced luminescence from Sm2+ arises via an energy transfer process. Scintillation arising from the blue band can be observed, but is characterised by a long tail extending over hundreds of microseconds. The relative efficiency of the material as an X-ray phosphor compared to commercial terbium-doped gadolinium oxysulphide is around 11%. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
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structure and scintillation properties of cerium doped Barium Chloride ceramics effects of cation and anion substitution
IEEE Transactions on Nuclear Science, 2010Co-Authors: A Edgar, Murray Bartle, Chris Varoy, S G Raymond, G V M WilliamsAbstract:Barium Chloride has been doped with cerium Chloride to form ceramic samples of composition Ba1-xCexCl2+x We find from the powder X-ray diffraction patterns that the compounds adopt the cubic fluorite structure for 0.06 <; x <; 0.33, not the usual orthorhombic BaCl2 structure. The cation sublattice in this rare-earth stabilized cubic phase is disordered, whilst the additional Chloride ions are accommodated at interstitial sites. Samples with x ~ 0.125 are translucent, and show a scintillation photopeak for 137Cs gamma rays which can be used to compute a light yield of 7200 photons/MeV. The scintillation decay is characterized by a time constant of 50 ns, compared to a Ce3+ photoluminescence lifetime of 26 ns. We also report the structural effects of alternative cation dopants, including Gd, Lu, Sm and Y, and find that only Gd results in the same structural stabilization, but when additionally Ce doped the scintillation efficiency is only 2600 ph/MeV with a long afterglow. The effects of bromine substitution for chlorine in Ba1-xCexCl2+x to form Ba1-xCexCl2-2xBr3x results in a material of near-cubic symmetry which is not transparent and does not show a photopeak, but for which the largest scintillation pulses correspond to an efficiency of 14,000 ph/MeV.
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lanthanum stabilized europium doped cubic Barium Chloride an efficient x ray phosphor
Journal of Applied Physics, 2010Co-Authors: A Edgar, J Zimmermann, H Von Seggern, C VaroyAbstract:We report the photoluminescence and x-ray luminescence of lanthanum-stabilized cubic Barium Chloride with europium (Eu2+) doping, of general composition Ba1−x−yEuyLaxCl2+x. X-ray diffraction patterns confirm that the material adopts a cubic fluorite structure for x=0.125 and 0
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structure and neutron imaging characteristics of lithium borate Barium Chloride glass ceramics
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 2006Co-Authors: G A Appleby, A Edgar, G V M Williams, Peter VontobelAbstract:Abstract A glass-ceramic has been developed which can be used as a thermal neutron imaging plate (NIP) for neutron radiography. The plate consists of nanocrystallites of the storage phosphor BaCl 2 :Eu 2+ embedded within a neutron sensitive lithium borate glass-matrix. Details of their preparation and structure are discussed. Neutron images were read out using a Fuji BAS2500 imaging plate scanner and the quality of the images obtained is comparable to those recorded on a commercial NIP. Details of the response to neutron and X-irradiation as well as the obtained spatial resolution of the images are presented. The neutron activation of the materials studied is also calculated.
Robert W Schurko - One of the best experts on this subject based on the ideXlab platform.
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solid state 137ba nmr spectroscopy an experimental and theoretical investigation of 137ba electric field gradient tensors and their relation to structure and symmetry
Journal of Physical Chemistry B, 2010Co-Authors: Hiyam Hamaed, Konstantin A Udachin, Robert W SchurkoAbstract:Ultrawideline 137Ba SSNMR spectra of several Barium-containing systems (Barium nitrate, Barium carbonate, Barium chlorate monohydrate, Barium Chloride dihydrate, anhydrous Barium Chloride, and Barium hydrogen phosphate) were acquired at two different magnetic field strengths (9.4 and 21.1 T) using frequency-stepped techniques. The recently reported WURST−QCPMG pulse sequence (O’Dell et al. Chem. Phys. Lett. 2008, 464, 97−102) is shown to be very useful for rapidly acquiring high signal-to-noise 137Ba SSNMR spectra. The breadths of the second-order quadrupolar-dominated spectra and experimental times are notably reduced for experiments conducted at 21.1 T. Analytical simulations of the 137Ba SSNMR spectra at both fields yield the quadrupolar parameters, and in select cases the Barium chemical shift anisotropies (CSAs). Quadrupolar interactions dominate the 137Ba powder patterns, with quadrupolar coupling constants, CQ(137Ba), ranging from 7.0 to 28.8 MHz. The 137Ba electric field gradient (EFG) parameters ...
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solid state 137ba nmr spectroscopy an experimental and theoretical investigation of 137ba electric field gradient tensors and their relation to structure and symmetry
Journal of Physical Chemistry B, 2010Co-Authors: Hiyam Hamaed, Konstantin A Udachin, Robert W SchurkoAbstract:Ultrawideline (137)Ba SSNMR spectra of several Barium-containing systems (Barium nitrate, Barium carbonate, Barium chlorate monohydrate, Barium Chloride dihydrate, anhydrous Barium Chloride, and Barium hydrogen phosphate) were acquired at two different magnetic field strengths (9.4 and 21.1 T) using frequency-stepped techniques. The recently reported WURST-QCPMG pulse sequence (O'Dell et al. Chem. Phys. Lett. 2008, 464, 97-102) is shown to be very useful for rapidly acquiring high signal-to-noise (137)Ba SSNMR spectra. The breadths of the second-order quadrupolar-dominated spectra and experimental times are notably reduced for experiments conducted at 21.1 T. Analytical simulations of the (137)Ba SSNMR spectra at both fields yield the quadrupolar parameters, and in select cases the Barium chemical shift anisotropies (CSAs). Quadrupolar interactions dominate the (137)Ba powder patterns, with quadrupolar coupling constants, C(Q)((137)Ba), ranging from 7.0 to 28.8 MHz. The (137)Ba electric field gradient (EFG) parameters extracted from these spectra are correlated to the local environments at the Barium sites, via consideration of molecular symmetry and structure, and first principles calculations of (137)Ba EFG tensors performed using CASTEP software. The rapidity with which (137)Ba SSNMR spectra can be acquired using the WURST pulse sequence and/or at ultrahigh magnetic fields and the sensitivity of the (137)Ba EFG tensor parameters to the changes in the Barium environment suggest that (137)Ba SSNMR has great potential for structural characterization of a variety of Barium-containing materials.
Zhichang Wang - One of the best experts on this subject based on the ideXlab platform.
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isopiestic studies on the saturated quinary systems water sodium Chloride sat glycine sat sorbitol sucrose and water sodium Chloride sat Barium Chloride sat sorbitol sucrose at the temperature 298 15 k comparison with the ideal like solution model
The Journal of Chemical Thermodynamics, 2001Co-Authors: Mei Wang, Hui Zhang, Dongmei Yang, Zhichang WangAbstract:Abstract Isopiestic measurements have been carried out at the temperature 298.15 K for two saturated quinary aqueous solutions: (water + sodium Chloride + glycine + sorbitol + sucrose) saturated with sodium Chloride and glycine and (water + sodium Chloride + Barium Chloride + sorbitol + sucrose) saturated with sodium Chloride and Barium Chloride. Total molalities are within (12 to 17)mol · kg − 1in the former case and within (7 to 12)mol · kg − 1in the latter case. The results are well represented by the ideal-like solution model.
Hiyam Hamaed - One of the best experts on this subject based on the ideXlab platform.
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solid state 137ba nmr spectroscopy an experimental and theoretical investigation of 137ba electric field gradient tensors and their relation to structure and symmetry
Journal of Physical Chemistry B, 2010Co-Authors: Hiyam Hamaed, Konstantin A Udachin, Robert W SchurkoAbstract:Ultrawideline 137Ba SSNMR spectra of several Barium-containing systems (Barium nitrate, Barium carbonate, Barium chlorate monohydrate, Barium Chloride dihydrate, anhydrous Barium Chloride, and Barium hydrogen phosphate) were acquired at two different magnetic field strengths (9.4 and 21.1 T) using frequency-stepped techniques. The recently reported WURST−QCPMG pulse sequence (O’Dell et al. Chem. Phys. Lett. 2008, 464, 97−102) is shown to be very useful for rapidly acquiring high signal-to-noise 137Ba SSNMR spectra. The breadths of the second-order quadrupolar-dominated spectra and experimental times are notably reduced for experiments conducted at 21.1 T. Analytical simulations of the 137Ba SSNMR spectra at both fields yield the quadrupolar parameters, and in select cases the Barium chemical shift anisotropies (CSAs). Quadrupolar interactions dominate the 137Ba powder patterns, with quadrupolar coupling constants, CQ(137Ba), ranging from 7.0 to 28.8 MHz. The 137Ba electric field gradient (EFG) parameters ...
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solid state 137ba nmr spectroscopy an experimental and theoretical investigation of 137ba electric field gradient tensors and their relation to structure and symmetry
Journal of Physical Chemistry B, 2010Co-Authors: Hiyam Hamaed, Konstantin A Udachin, Robert W SchurkoAbstract:Ultrawideline (137)Ba SSNMR spectra of several Barium-containing systems (Barium nitrate, Barium carbonate, Barium chlorate monohydrate, Barium Chloride dihydrate, anhydrous Barium Chloride, and Barium hydrogen phosphate) were acquired at two different magnetic field strengths (9.4 and 21.1 T) using frequency-stepped techniques. The recently reported WURST-QCPMG pulse sequence (O'Dell et al. Chem. Phys. Lett. 2008, 464, 97-102) is shown to be very useful for rapidly acquiring high signal-to-noise (137)Ba SSNMR spectra. The breadths of the second-order quadrupolar-dominated spectra and experimental times are notably reduced for experiments conducted at 21.1 T. Analytical simulations of the (137)Ba SSNMR spectra at both fields yield the quadrupolar parameters, and in select cases the Barium chemical shift anisotropies (CSAs). Quadrupolar interactions dominate the (137)Ba powder patterns, with quadrupolar coupling constants, C(Q)((137)Ba), ranging from 7.0 to 28.8 MHz. The (137)Ba electric field gradient (EFG) parameters extracted from these spectra are correlated to the local environments at the Barium sites, via consideration of molecular symmetry and structure, and first principles calculations of (137)Ba EFG tensors performed using CASTEP software. The rapidity with which (137)Ba SSNMR spectra can be acquired using the WURST pulse sequence and/or at ultrahigh magnetic fields and the sensitivity of the (137)Ba EFG tensor parameters to the changes in the Barium environment suggest that (137)Ba SSNMR has great potential for structural characterization of a variety of Barium-containing materials.
Mei Wang - One of the best experts on this subject based on the ideXlab platform.
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isopiestic studies on the saturated quinary systems water sodium Chloride sat glycine sat sorbitol sucrose and water sodium Chloride sat Barium Chloride sat sorbitol sucrose at the temperature 298 15 k comparison with the ideal like solution model
The Journal of Chemical Thermodynamics, 2001Co-Authors: Mei Wang, Hui Zhang, Dongmei Yang, Zhichang WangAbstract:Abstract Isopiestic measurements have been carried out at the temperature 298.15 K for two saturated quinary aqueous solutions: (water + sodium Chloride + glycine + sorbitol + sucrose) saturated with sodium Chloride and glycine and (water + sodium Chloride + Barium Chloride + sorbitol + sucrose) saturated with sodium Chloride and Barium Chloride. Total molalities are within (12 to 17)mol · kg − 1in the former case and within (7 to 12)mol · kg − 1in the latter case. The results are well represented by the ideal-like solution model.