Search

The aim of this study was to experimentally assess the luminescence efficiency of a cerium fluoride (CeF3) inorganic scintillator in crystal form as a possible alternative to high-luminescence but hygroscopic cerium bromide (CeBr3). The experiments were performed under typical diagnostic radiology X-rays (50–140 kVp). Parameters such as the crystal's absolute luminescence efficiency (AE) and the spectral matching with a series of optical detectors were examined. The replacement of bromine with fluorine appeared to drastically reduce the AE of CeF3 compared to CeBr3 and other commercially available inorganic scintillators such as bismuth germanate (Bi4Ge3O12-BGO). CeF3 reaches a maximum luminescence efficiency value of only 0.8334 efficiency units (EUs) at 140 kVp, whereas the corresponding values for CeBr3 and BGO were 29.49 and 3.41, respectively. Furthermore, the emission maximum (at around 313 nm) moved towards the lower part of the visible spectrum, making CeF3 suitable for spectral coupling with various photocathodes and photomultipliers applied in nuclear medicine detectors, but completely unsuitable for spectral matching with CCDs and CMOS. The obtained luminescence efficiency results denote that CeF3 cannot be applied in medical imaging applications covering the range 50–140 kVp; however, examination of its luminescence output in the nuclear medicine energy range (~70 to 511 keV) could reveal possible applicability in these modalities. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of cerium-doped lanthanum fluoride (La(1−x)CexF3) nanocrystals have been carried out. The surfaces of La(1−x)CexF3 nanocrystals were modified with oleic acid using the co-precipitation technique, and then doped with cerium with various mole fractions (x) = 0.05, 0.10, 0.15, 0.20, and 0.25. The nanocrystals produced were characterized for their crystal structure using x-ray diffraction (XRD), their morphology by transmission electron microscopy (TEM), their functional group identification using Fourier-transform infrared (FTIR), and Raman spectroscopy, and their photoluminescence behavior using photoluminescence (PL) spectroscopy. Detailed investigations revealed that, based on the XRD data and TEM images, La(1−x)CexF3 exhibits trigonal-structured nanocrystals with the symmetry space group P-3c1. Among the samples, La0.75Ce0.25F3 exhibited the sharpest PL peak. The PL spectra for La0.75Ce0.25F3 nanocrystals excited at 370 nm and showed an intense emission peak at 495 nm with a lifetime τ = 1.523 × 10−10 s. This emission was assigned to the 5d → 4f (2F5/2 and 2F7/2) transitions of Ce3+ energy levels, indicating a luminescence center mechanism. These results indicate that the synthesized La0.75Ce0.25F3 is a promising phosphor material for detector scintillators. [ABSTRACT FROM AUTHOR]

A rare-earth trihalide scintillator, CeBr3, in 1 cm edge cubic monocrystal form, is examined with regard to its principal luminescence and scintillation properties, as a candidate for radiation imaging applications. This relatively new material exhibits attractive properties, including short decay time, negligible afterglow, high stopping power and emission spectrum compatible with several commercial optical sensors. In a setting typical for X-ray radiology (medical X-ray tube, spectra in the range 50–140 kVp, human chest equivalent filtering), the crystal's light energy flux, absolute efficiency (AE) and X-ray luminescence efficiency (XLE) were determined. Light energy flux results are superior in comparison to other four materials broadly used in modern medical imaging (slope of the linear no-threshold fit was 29.5). The AE is superior from 90 kVp onwards and reaches a value of 29.5 EU at 140 kVp. The same is true for the XLE that, following a flat response, reaches 9 × 10−3 at 90 kVp. Moreover, the spectral matching factors and the respective effective efficiencies (EE) are calculated for a variety of optical sensors. The material exhibits full compatibility with all the flat-panel arrays and most of the photocathodes and Si PMs considered in this work, a factor that proves its suitability for use in state-of-the-art medical imaging applications, such as CT detectors and planar arrays for projection imaging. [ABSTRACT FROM AUTHOR]

X-ray luminescent diamond composite films with embedded yttrium-aluminum nanoparticles were designed. Additionally, the stability limits of single-phase solid solutions in systems based on yttrium-aluminum and yttrium-scandium-aluminum garnets doped with cerium were determined. The most intense X-ray luminescence was achieved with the [Y 2·98 Ce 0.02 ]{Al 2 }Al 3 O 12 powder. The composition-optimized nanoparticles were embedded into a polycrystalline diamond matrix to form a diamond-YAG:Ce composite. For the obtained composite, an intense X-ray luminescence from the Ce3+ ions near 550 nm was demonstrated. The designed composites may be used as adjustable and durable scintillating materials for a wide range of applications. [ABSTRACT FROM AUTHOR]

Crystalline ceramic material (Gd,Y) 3 Al 2 Ga 3 O 12 codoped with Ce and Tb (GYAGG: Ce, Tb) was demonstrated to be a high light yield scintillator. The luminescence kinetics was proven to be formed by the combining of the direct Tb3+→Ce3+ and inverse Ce3+→Tb3+ transfer of electronic excitations. This forms a mechanism leading to the increase of the slow component fraction in the scintillation and limits the application of the material, when a fast response is required. However, a high light yield opens an opportunity to utilize the developed material for application in the detectors operating in a current measurement mode and, in long living, as high-flux sources of optical photons under the ionizing radiation of a different type. • (Gd,Y) 3 Al 2 Ga 3 O 12 : Ce, Tb is high light yield scintillator. • Both direct Tb3+→Ce3+ and inverse Ce3+→Tb3+ transfers form luminescence kinetics. • Prospective material for a high-flux of optical photons under the ionizing radiation. [ABSTRACT FROM AUTHOR]

We report the scintillation properties of the undoped and cerium-doped variations of LiGdCl4 and NaGdCl4. Powder samples of these materials exhibit significant scintillation under X-rays. The samples were synthesized by solid-state methods from a 1:1 molar ratio of lithium or sodium chloride and gadolinium chloride. Cerium trichloride was used as the dopant. The physical, optical, and scintillation properties of these materials were analyzed by powder X-ray diffraction, photoluminescence, X-ray excited luminescence, and pulsed X-ray luminosity measurements. Increases in light yields are observed as the concentration of cerium increases. The highest light yields occurred at 20 percent cerium doping for both compounds. At larger concentrations neither compound formed, indicating a breakdown of the lattice with the addition of large amounts of cerium cations. At 20 percent cerium, LiGdCl4 and NaGdCl4 display scintillation light 3.6 times and 2.2 times the light yield of the reference material, YAlO3:Ce3+, respectively. Both emit in the ranges of 340 ? 350 nm and 365 - 370 nm and display multiexponential decays with cerium-like decay components at 33 ns (LiGdCl4:Ce) and 26 ns (NaGdCl4:Ce).

Cerium doped lutetium pyro-silicate Ce3+:Lu2Si2O7 (LPS) is an inorganic scintillator that displays particularly promising performance. The spectroscopic properties of pure and Ce3+-doped Lu2Si2O7 are investigated. X-ray-excited luminescence, time-resolved excitation and emission spectroscopy, as well as decay time spectra are presented. For better understanding of the scintillation mechanism, several approaches were undertaken to locate the Ce3+ energy levels relative to levels of LPS host. To estimate the energy position of Ce3+ 4f levels with respect to the valence band, x-ray photoemission spectroscopy (XPS) was used. Scintillation properties of LPS: Ce are explained in terms of the relative positions of Ce3+-5d levels and the conduction band. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Photoluminescence and thermally stimulated luminescence of Gd 3 (Ga,Al) 5 O 12 :Ce single crystals and epitaxial films co-doped with different concentrations of Mg 2+ ions are investigated in the 77–500 K temperature range under excitation in the 4f - 5d 1 and 4f - 5d 2 absorption bands of Ce 3+ ions. Influence of Mg 2+ ions on the photoluminescence intensity, spectrum, decay kinetics, temperature dependence of the photoluminescence intensity, and the activation energy of luminescence thermal quenching is observed. Co-doping with Mg 2+ is shown to result in a drastic reduction of the afterglow and thermally stimulated luminescence and in a strong shortening of the afterglow decay kinetics. It influences also defects creation spectra and the activation energy of the photostimulated defects creation. The Mg 2+ - induced changes in the characteristics of the Gd 3 (Ga,Al) 5 O 12 :Ce, Mg single crystals and epitaxial films are found to be strongly different, and possible reasons of these differences are discussed. [ABSTRACT FROM AUTHOR]

A novel TlGd2Cl7 single crystal with scintillation properties is presented. TlGd2Cl7 single crystals with different Ce3+-doping concentrations (0, 0.5, 1, and 5 mol%) are grown using the vertical Bridgman technique. All doped samples exhibit typical Ce3+ emission under X-ray excitation between 350 and 550 nm. Among all grown samples, the best light yield (LY) of ~49 700 photons/MeV and good energy resolution of 6% (full-width at half-maximum) are observed for the 5-mol%-Ce3+-doped TlGd2Cl7 crystal under an excitation of 662-keV $\gamma $ -rays at room temperature. Three exponential decay components are observed for all Ce3+- doped samples at room temperature. Faster decays are observed with the increase in the Ce3+ concentration. The effective atomic (Z) number of the proposed crystal is 64; therefore, efficient X- and $\gamma $ -ray detections could be performed with the proposed scintillator. The high LY, high effective Z number, good energy resolution, and fast scintillation response suggest that this scintillator could be employed in various applications. Further investigations are ongoing for the improvement of its scintillation properties with a higher Ce3+ concentration. [ABSTRACT FROM AUTHOR]

Cerium-doped mixed oxide garnets are promising luminescent materials to use as LED phosphors or scintillators for radiation detectors. In this paper, temperature-dependent characteristics of Ce-doped multicomponent garnets ceramics have been studied under photo and X-ray excitation. Ceramic samples of Y3GaxAl5−xO12:Ce0.006 ($x = 1$ , 2, 3, and 4) and of Gd3GaxAl5−xO12:Ce0.006 ($x = 1$ , 2, and 3) have been used. At high temperature, all samples showed decrease in the Ce3+ luminescence intensity, luminescence decay, and luminescence lifetime due to thermal ionization of Ce3+ excited 5d states. Values of activation energies of the thermal ionization process have been determined from photoluminescence lifetime measurements and shown in comparison with literature data. At low temperature, Gd-containing samples showed significant decrease in light output. In the same temperature range, large thermoluminescence peaks have been observed, indicating that the reduction of Ce3+ emission at low temperatures can be attributed to the localization of charge carriers on traps. [ABSTRACT FROM AUTHOR]

The work is dedicated to the growth and investigation of the luminescent and scintillation properties of single crystalline films (SCFs) of Ca 2−x R 1+x Mg 1+x Sc 1−x Si 3 O 12 :Ce (R = Y, Lu) mixed garnets with x = 0–0.25, grown using the liquid phase epitaxy method onto Y 3 Al 5 O 12 substrates from PbO-B 2 O 3 based flux. The absorption, luminescent and scintillation properties of Ca 2−x Y 1+x Mg 1+x Sc 1−x Si 3 O 12 :Ce and Ca 2−x Lu 1+x Mg 1+x Sc 1−x Si 3 O 12 :Ce SCFs with x = 0 and 0.25 were investigated and compared with the reference YAG:Ce and LuAG:Ce SCFs. Using the Ca 2+ , Mg 2+ and Si 4+ alloying, the Ce 3+ emission spectra in Ca 2−x R 1+x Mg 1+x Sc 1−x Si 3 O 12 :Ce (R = Y, Lu; x = 0–0.25) SCFs can be notably extended in the red range in comparison with YAG:Ce and LuAG:Ce SCFs due to the increase of crystal field strength and Ce 3+ multicenter creation in the dodecahedral positions of the lattices of these mixed garnet compounds. Due to the formation of Ce 4+ ions, the as-grown Ca 2−x R 1+x Mg 1+x Sc 1−x Si 3 O 12 :Ce (R = Y, Lu) SCFs at x = 0 and 0.25 show relatively low light yield. However, after annealing in reducing atmosphere (95% N 2 + 5% H 2 ) at T > 1000 °C, a recharging Ce 4+ →Ce 3+ takes place. After that, these SCFs possess the light yield about of 30% and 31% in comparison with the reference YAG:Ce and LuAG:Ce SCFs, respectively, and a fast scintillation response with the decay times in the ns range under α–particles excitation by 239 Pu (5.15 MeV) source. [ABSTRACT FROM AUTHOR]

The luminescence and scintillation properties of gadolinium terbium aluminium garnet single crystalline films, Gd 3−x Tb x Al 5 O 12 , doped with Ce 3+ are investigated as a function of the Gd/Tb ratio with the aim of an improved understanding of the energy transfer processes between Ce 3+ and Tb 3+ ions in the aluminium garnet hosts. Upon replacing the Gd 3+ by Tb 3+ , the crystal field splitting for the 5d energy level of Ce 3+ does not change significantly, due to comparable sizes of the Gd 3+ and Tb 3+ cations. Temperature dependence of the decay time of Tb 3+ and Ce 3+ luminescence confirms an efficient energy transfer from the Tb 3+ to Ce 3+ and provides a qualitative understanding of this process. Furthermore, bidirectional energy transfer processes between the Ce 3+ and Tb 3+ are revealed. Scintillation decays under α-particles excitation show the presence of the fast and slow sub-microsecond components. [ABSTRACT FROM AUTHOR]

Ce 3+ activated Li 2 O–Gd 2 O 3 –BaO–B 2 O 3 glass scintillator containing neutron-capture elements ( 7 Li, 11 Band 158 Gd)were developed by conventional melt-quenching technique. Luminescence spectra under UV and X-ray excitation showed Ce 3+ ion emission due to 5d→4f transition at 391 nm. Energy transfer from the host glass to Ce 3+ ions were confirmed by VUV–UV and XEL spectra. The highest emission intensity of Ce 3+ ions were observed at 0.5 mol%of CeF 3 . For the same concentration the decay time was obtained to be 19.7 ns and their mean critical distance was calculated about 22.33 Å. The observed decay constants revealed that direct electron-hole capture was a dominant scintillation process in the present glass matrix. [ABSTRACT FROM AUTHOR]

Temperature dependences of the intensity and decay kinetics of the Ce 3+ - related photoluminescence and characteristics of thermally stimulated luminescence are investigated in the 77–500 K temperature range for the epitaxial films of the multicomponent garnets of the type of Lu 3−x Gd x Ga y Al 5−y O 12 :Ce with Ce content of 0.3–0.7 at. %, where x varies from 0.14 to 3 and y varies from 0 to 3.54. Different methods are used for the determination of energy distances between the excited 5d 1 and 5d 2 levels of Ce 3+ ions and the conduction band (CB) and their applicability is compared. The dependences of the 5d 1,2 – CB energy distances on the multicomponent garnet composition are clarified. The 5d 1 – CB energy distance is found to decrease by about an order of magnitude with the increasing Ga 3+ content. The most drastic decrease, observed at the Ga 3+ content around y ≈ 1.7, is suggested to arise from the change in the Ga 3+ position from the smaller tetrahedral to larger octahedral Al 3+ sites. This effect is explained by the lattice distortion due to the substitution of smaller Lu 3+ and Al 3+ ions by larger Gd 3+ and Ga 3+ ions. Application potential of these epitaxial films for fast 2D-imaging is discussed. [ABSTRACT FROM AUTHOR]

The time resolution of scintillation detectors of ionizing radiation is one of the key parameters sought for in the current and future high-energy physics experiments. This study is encouraged by the necessity to find novel detection methods enabling a sub-10-ps time resolution in scintillation detectors and is focused on the exploitation of fast luminescence rise front. Time-resolved photoluminescence (PL) spectroscopy and thermally stimulated luminescence techniques have been used to study two promising scintillators: self-activated lead tungstate (PWO, PbWO 4 ) and Ce-doped gadolinium aluminum gallium garnet (GAGG, Gd 3 Al 2 Ga 3 O 12 ). A sub-picosecond PL rise time is observed in PWO, while longer processes in the PL response in GAGG:Ce are detected and studied. The mechanisms responsible for the PL rise time in self-activated and doped scintillators are under discussion. [ABSTRACT FROM AUTHOR]

Cerium doped Barium Fluoride (BaF 2 Ce) transparent ceramic was fabricated and its luminescence and scintillation properties were studied. The photoluminescence shows the emission peaks at 310 nm and 323 nm and is related to the 5d-4f transitions in Ce 3+ ion. Photo peak at 511 keV and 1274 keV were obtained with BaF 2 Ce transparent ceramic for Na-22 radioisotopes. Energy resolution of 13.5% at 662 keV is calculated for the BaF 2 Ce transparent ceramic. Light yield of 5100 photons/MeV was recorded for BaF 2 Ce(0.2%) ceramic and is comparable to its single crystal counterpart. Scintillation decay time measurements shows fast component of 58 ns and a relatively slow component of 434 ns under 662 keV gamma excitation. The slower component in BaF 2 Ce(0.2%) ceramic is about 200 ns faster than the STE emission in BaF 2 host and is associated with the dipole-dipole energy transfer from the host matrix to Ce 3+ luminescence center. [ABSTRACT FROM AUTHOR]

In this work, the Ce 3+ doped gadolinium-calcium-silicaborate glass scintillators of the composition ratio 25Gd 2 O 3 :10CaO:10SiO 2 :(55−x)B 2 O 3 :xCeF 3 , have been fabricated by using the melt-quenching technique. The doping concentration of the Ce 3+ was varied from 0.05 mol% to 2.5 mol%. The 4f-5d transition of the Ce 3+ allowed scintillation with a fast decay time. The absorption spectrum, X-ray induced emission spectrum, photo luminescence spectrum, laser luminescence spectrum and decay time of the scintillators were measured for studying the luminescence properties. From the X-ray induced emission spectrum result, we checked the trend between doping concentration and light yield. The laser induced luminescence spectrum was measured while changing the temperature from 300 K to 10 K. We also measured the decay time by using the laser excitation of the 0.15 mol% Ce 3+ doped glass scintillator. [ABSTRACT FROM AUTHOR]

Cerium-doped lutetium oxyorthosilicate (Lu2SiO5: 0.5 mol%Ce, LSO:Ce) scintillation ceramics was fabricated by pre-sintering at 1650^\circ C for 4 h in air followed by a post hot isostatic pressing (HIP) at 1600^\circ C under 150 MPa for 1 h in Ar atmosphere. Luminescent and scintillation properties of the as-HIPed LSO:Ce ceramics was seriously affected by these oxygen vacancies. They were effectively filled through a post-annealing at 1300^\circ C for 4 h in air. Ce LIII edge X-ray absorption near edge structure (XANES) spectra of LSO:Ce ceramics manifest that most of Ce ions in LSO ceramics still remain Ce(III) valence state after annealing in air. Photoluminescence (PL) and PL excitation (PLE) spectra show that emission intensity of the as-HIPed LSO:Ce ceramics was about 3 times lower than that of post-annealed sample. Light yield of the post-annealed LSO:Ce ceramics reaches 2.7 times of that of the as-HIPed sample, which exceeds 3 times of the light yield of BGO crystal. [ABSTRACT FROM AUTHOR]

The paper is dedicated to development of the novel scintillating screens based on single crystalline films (SCF) of Ce doped Lu3 - x{Tb_x}{Al5 - y}{Ga_y}{O12} multicomponent garnets at x = 2 - 3 and y = 0 - 2.5 onto Y_3Al_5O12 (YAG) and Gd_3Al2.5{Ga2.5}{O12} (GAGG) substrates using the liquid phase epitaxy (LPE) method. We report the optimized content and high scintillation figure of merit of SCF of these garnets grown by the LPE method with using PbO based flux. Namely, the Tb_3Al2.5{Ga2.5}{O12}:Ce SCFs possess the highest values of light yield (LY) compared to all earlier investigated SCF samples, with their LY exceeding by 2.35 and 1.15 times the LY values for YAG:Ce and LuAG:Ce SCF scintillators, respectively. The SCFs of the mentioned compounds show very lower thermoluminescence in the above room temperature range and relatively fast scintillation decay. [ABSTRACT FROM AUTHOR]

Growth, luminescence and scintillation characterizations of the new Tl 2 LiGdCl 6 :Ce 3+ (TLGC:Ce 3+ ) single crystals are reported. This crystal was grown by the Bridgman technique and the composition belongs to the elpasolites family. X-ray induced emission spectra of the Ce-doped samples show the emission between 360 and 440 nm and peaking at 387 nm. The emission was attributed to the Ce 3+ ions in the host lattice. The highest light yield of 58,000±6000 ph/MeV and 4.6±0.2% (FWHM) energy resolution was obtained for 10% Ce doped sample. Three decay time components were observed for the 10% Ce-concentration under γ-ray excitation at room temperature. Among the decay time constants, the fast decay time constant of 34 ns (81%) due to Ce 3+ luminescence was obtained. Further investigation to improve scintillation material is underway. [ABSTRACT FROM AUTHOR]

The Mg, Ca, Sr and Ba 200 ppm co-doped Ce:Lu 3 Al 5 O 12 single crystals were prepared by micro pulling down method. Absorption and luminescence spectra were measured together with several other scintillation characteristics, namely the scintillation decay and light yield to reveal the effect of the co-doping. The scintillation decays were accelerated by both Mg and Ca co-dopants. The Mg co-doped samples showed the fastest decay and the highest light yield among the co-doped samples. [ABSTRACT FROM AUTHOR]

Single crystals of Ce-doped Cs 3 LaCl 6 and Cs 3 LaBr 6 show promising scintillation properties in gamma-ray detection. Their thermal response in the range from 40 K to 500 K is discussed in this work. The steady state photoluminescence spectra, photoluminescence decay time, and X-ray excited radioluminescence of Ce-doped and undoped Cs 3 LaCl 6 and Cs 3 LaBr 6 were studied. The photoluminescence and radioluminescence emission intensity of the Ce-doped crystals decreases less than 25% from 40 K to 500 K. The photoluminescence decay time of Ce 3+ increases with increasing temperature. [ABSTRACT FROM AUTHOR]

Ce doped SrHfO 3 /SrAl 12 O 19 eutectics were grown by the micro pulling down (μ-PD) method and their directionally solidified eutectic system has been investigated. Investigations of obtained eutectic structure, luminescence and scintillation performances were also performed. Eutectics were grown at the speed of 0.60–0.90 mm/min. In the eutectics, Ce 3+ 4f–5d emission was observed at 410 nm. The eutectics showed light yield of around 300 photon/5.5 meV alpha-ray by 241 Am excitation. Scintillation decay time was 26.4 ns (45%) with slower decay component of 263 ns (55%). [ABSTRACT FROM AUTHOR]

The Ce 3+ doped mixed crystals of Li 6 Y(BO 3 ) 3 and Li 6 Gd(BO 3 ) 3 are grown by Czochralski technique with equal mole ratios of both Yttrium and Gadolinium i.e. Li 6 Y 0.5 Gd 0.5 (BO 3 ) 3 . The grown crystals have the dimensions of ∅10×30 mm 2 . Powder X-ray diffraction (XRD) analysis confirmed single phase of the grown crystals. X-ray and laser induced luminescence spectra are presented. Scintillation properties such as energy resolution, light yield, decay time and α/β ratio under the excitation of 137 Cs γ-ray photons and 241 Am α-particles are also reported in this article. [ABSTRACT FROM AUTHOR]

Ce3+-doped lutetium aluminum garnet (LuAG) phosphors have been successfully synthesized by a facile carbon-free sol-gel method without using any organic gelling agent. Phase transitions from gel to LuAG were well investigated by X-ray diffraction and thermal analysis. The results confirmed that a pure LuAG phase can form at around 920 °C by directly crystallizing from amorphous material. Particle size of the LuAG phosphor can be controlled by adjusting the heat treatment process; therefore, both nano and micron-scale products can be obtained and they are suitable for the fabrication of laser scintillators and white light emitting diodes, respectively. Agglomeration can be observed in the nano-sized phosphor. For the micron-sized LuAG, a two-step process was used to avoid hard agglomeration. Particles of the obtained micron-sized phosphor are uniform and well-dispersed. Luminescence properties of the phosphors were characterized. Relative intensity of the micron-sized product is comparable with commercial phosphor. [ABSTRACT FROM AUTHOR]

In recent years, the cerium-doped lanthanum bromide, LaBr (Ce = 5 %) detector is increasingly playing an important role in radiation measurements because of its higher energy resolution (~3 % at 662 keV), faster luminescence decay time (~35 ns) and higher detection efficiency compared to 7.65 cm × 7.65 cm NaI(Tl) detector. Intrinsic spectra between 1,800 and 3,000 keV derived from internal radioactivity within LaBr(Ce) scintillators have been investigated in some literatures, and these results are confirmed by the experiments in this work. In this paper, a new method for LaBr(Ce) detector energy calibration from 100 to 2,000 keV is proposed using the intrinsic spectra (self-calibration) instead of the standard gamma sources. Proof-of-concept experiment results show that self-calibration can guarantee energy accuracy of better than 0.815 % and can be applied outside the laboratory. The stability and applicability of this method are also investigated systematically. [ABSTRACT FROM AUTHOR]

New single crystals of Ce-doped Cs2NaGdCl6 are investigated under x-ray and \gamma-ray excitation. These scintillation crystals are grown by two zone vertical Bridgman technique and belong to elpasolite crystal family. Energy resolution, scintillation light yield, non-proportionality, energy resolution as a function of \gamma-rays energies and scintillation decay time measurements are presented. Ce^3+-related x-ray excited emission is observed between 360 and 450 nm wavelength region at room temperature. At higher Ce-concentration both self-trapped exciton (STE) and Gd^3+ emissions are disappeared and enhance Ce^3+ emission. Under 662 keV \gamma-rays excitation, Cs2NaGdCl6 shows an energy resolution of 5.2%, (FWHM) at 1% Ce-concentration. Best energy resolution of 4.8% (FWHM) is obtained for 10% Ce-concentration. No significant improvement is observed in the energy resolution of Cs2NaGdCl6 with the increase of Ce-concentration. The highest light yield of about 21,000 ph/MeV is obtained for 10% Ce-doped crystal. At room temperature three decay time components are found under \gamma-ray excitation for all Ce-doped samples. This material is highly hygroscopic. [ABSTRACT FROM PUBLISHER]

In this work, the scintillation properties of Cs3LaCl6 and Cs3LaBr6 single crystals doped with various Ce concentrations (0.5 at.%–40 at.%) were studied. In the decay time profiles, both the fast (\sim 50 ns) and slow (\sim 500 ns) components decrease with increasing Ce concentration. The fast decay component dominates with high Ce concentration. Cs3LaCl6:Ce has a light yield of \sim 20\ 000 photons/MeV for 20 at.% Ce, while Cs3LaBr6:Ce has a light yield of 35 000 photons/MeV for 10% Ce. Energy resolution was improved from 20 at.% to 8 at.% with higher Ce concentration. Cs3LaCl6:Ce and Cs3LaBr6:Ce are 30 and 8 times less hygroscopic than LaBr3:Ce. [ABSTRACT FROM PUBLISHER]

Abstract: We report on the luminescence and scintillation characterizations of cerium doped Cs2LiGdBr6 (CLGB) single crystal. This is a new scintillation material and belongs to elpasolite family. Single crystals of CLGB: Ce3+ with dimensions up to ∅10×5mm3 are successfully grown by the Bridgman technique. Under X-ray excitation, broad emission band between 370 to 478nm wavelengths is obtained. Such emission is attributed to the cerium ion. At 662keV γ-rays CLGB: Ce3+ shows energy resolutions of 7.1%, 9.4%, and 8.6% (FWHM) at 1%, 5%, and 10% Ce-concentrations, respectively. Light yield of CLGB depends on cerium concentration and maximum light yield of ~30,500ph/MeV is measured for 10% Ce sample crystal. Under γ-ray excitation, CLGB: Ce3+ crystals showed three exponential decay time components. [Copyright &y& Elsevier]

Abstract: Sr2+ co-doped LaBr3:5%Ce scintillators show a record low energy resolution of 2% at 662keV and a considerably better proportional response compared to standard LaBr3:5%Ce. This paper reports on the optical properties and time response of Sr co-doped LaBr3:5%Ce. Multiple excitation and emission bands were observed in X-ray and optically excited luminescence measurements. Those bands are ascribed to three different Ce3+ sites. The first is the unperturbed site with the same luminescence properties as those of standard LaBr3:Ce. The other two are perturbed sites with red-shifted 4f-5d1 Ce3+ excitation and emission bands, longer Ce3+ decay times, and smaller Stokes shifts. The lowering of the lowest 5d level of Ce3+ was ascribed to larger crystal field interactions at the perturbed sites. Two types of point defects in the LaBr3 matrix were proposed to explain the observed results. No Ce4+ ions were detected in Sr co-doped LaBr3:5%Ce by diffuse reflectance measurements. [Copyright &y& Elsevier]

Abstract: A novel ion-scintillator technique used to evaluate the scintillation response is demonstrated using YAlO3:Ce crystal under H+, He+ and O3+ ions irradiation. The experiment setup, including a forward-scatter target and a time-of-flight telescope, allows quantitative measurement of each ion-scintillator interaction event over a continuous ion energy range, and the related response properties of YAlO3:Ce, including the luminescent photon yield, nonlinear response and energy resolution, have been studied by detailed analysis of the total electronic energy deposition, electronic energy loss density and the displacement damage during ion irradiation process. The measured response properties of YAlO3:Ce under ion irradiation are consistent with that from the gamma tests, which demonstrates that this technique, applicable to small crystals or thin films, can rapidly and effectively evaluate the scintillator performance and, therefore, assist accelerated discovery of radiation detection materials. [Copyright &y& Elsevier]

Abstract: The structural and luminescent properties of blue-emitting (Lu1−x−y Y x Ce y )2SiO5 (0.1≤x≤0.4, y=0.05, 0.005) phosphors prepared by combustion synthesis and post-annealed at 1200°C for different annealing times are reported. X-ray diffraction analysis revealed the formation of a (Lu,Y)2SiO5 solid solution as a majority phase with small traces of a residual phase that was identified as Lu2SiO7. Under long-UV excitation, the powders yield a very bright blue-emission consisting of two bands with maximum emissions located at λ=405nm and λ=440nm, both corresponding to the Ce3+ allowed transitions 2D3/2→2F5/2 and 2D5/2→2F7/2, respectively. Moreover, luminescence decay times of 38–45ns were measured, which depend on the composition, making these powders excellent candidates for application as scintillators in medical imaging. [Copyright &y& Elsevier]

Abstract: Lu3Al5O12:Ce3+ (LuAG:Ce) is a scintillator with a fast response time. The light yield is lower than theoretically expected and to increase the light yield co-doping with Pr3+ is investigated. To better understand the energy flow to the Ce3+ ion, first low temperature emission and excitation spectra of Pr3+ doped LuAG were investigated, allowing the accurate determination of the zero-phonon lines for the 5d states of Pr3+ in LuAG and the temperature dependent energy transfer from the Self Trapped Exciton to Pr3+. In addition VUV excitation and soft X-ray excited emission spectra of the co-doped LuAG:Ce,Pr were studied. The results show that energy transfer from Pr3+ to Ce3+ occurs but it is followed by back transfer to the 4f states of Pr3+. [Copyright &y& Elsevier]

Lu3Al5O12(LuAG) dopedwith Ce3 a promising scintillator material with a highdensityand a fast response time. The light output under X-ray or γ-rayexcitation is, however, well below the theoretical limit. In thispaper the influence of codoping with Tb3 investigatedwith the aim to increase the light output. High resolution spectraof singly doped LuAG (with Ce3 Tb3) arereported and provide insight into the energy level structure of thetwo ions in LuAG. For Ce3췪phonon lines and vibronicstructure are observed for the two lowest energy 5d bands and theStokes’ shift (2 350 cm–1) and Huang–Rhyscoupling parameter (S= 9) have been determined.Tb3–5d transitions to the high spin (HS) andlow spin (LS) states are observed (including a zero-phonon line andvibrational structure for the high spin state). The HS–LS splittingof 5400 cm–1is smaller than usually observed andis explained by a reduction of the 5d–4f exchange couplingparameter Jby covalency. Upon replacing the smallerLu3誉 with the larger Tb3誉, the crystalfield splitting for the lowest 5d states increases, causing the lowest5d state to shift below the 5D4state of Tb3橷 allowing for efficient energy transfer from Tb3 Ce3皌 to the lowest temperatures. Luminescencedecay measurements confirm efficient energy transfer from Tb3 Ce3橷 provide a qualitative understanding of theenergy transfer process. Co-doping with Tb3皇 not resultin the desired increase in light output, and an explanation basedon electron trapping in defects is discussed. [ABSTRACT FROM AUTHOR]

Abstract: Cerium-doped lanthanum bromide (LaBr3:Ce) crystals offer a range of improved scintillation properties over traditional NaI:Tl crystals for in situ gamma spectrometry. At present, however, it remains unclear whether the internal radioactivity of LaBr3:Ce detectors compromises their suitability for low-level activity radioisotope measurements of natural sedimentary deposits, such as those required in luminescence and electron spin resonance (ESR) dating. In this study we investigate the suitability of a commercial LaBr3:Ce detector for measuring individual concentrations of 40K, 238U and 232Th using predefined ‘energy windows’ from gamma ray spectra. Performance tests have been undertaken using reference materials with well-constrained radioisotope concentrations (the Oxford calibration blocks) and compared with results obtained for a NaI:Tl detector of the same geometry. These tests reveal that the LaBr3:Ce detector has a non-negligible intrinsic activity that needs to be accurately quantified prior to measuring any gamma ray spectra in the field. Compared to the NaI:Tl detector, the energy resolution of the LaBr3:Ce detector is improved by a factor of two, or more, for the main indicator isotope photopeaks in the 40K, 238U and 232Th decay series. Signal-to-noise ratios for the LaBr3:Ce detector show a 25–35% improvement over those of the NaI:Tl detector. In addition, the LaBr3:Ce detector is characterised by suitable energy linearity over the full spectral range of interest for the 40K, 238U and 232Th decay series. Replicate gamma ray measurements made with the LaBr3:Ce and NaI:Tl detectors for 20 natural sedimentary samples from the Lower Tejo River basin, Portugal, and the Duero River basin, Spain, yield consistent radioisotope concentrations and gamma dose rate estimates. These results are encouraging and suggest that LaBr3:Ce detectors can provide suitable estimates of individual radioisotope concentrations in low-level activity (0.5–1.5 Gy/ka) environments, providing that their intrinsic activity is adequately measured and subtracted from field spectra. Our comparison also reveals that subtraction of the intrinsic activity from LaBr3:Ce spectra produces a significant reduction in the precision with which radionuclide concentrations can be determined using the ‘energy windows’ approach. This shortcoming necessitates longer counting times in natural sedimentary environments and overshadows the practical advantages that LaBr3:Ce detectors might otherwise offer for luminescence and ESR dating applications. [Copyright &y& Elsevier]

Abstract: The scintillation properties of cerium-doped oxyhalides following the general formula REOX (RE=Y, La, Gd, and Lu; X=F, Cl, Br, and I) are reported. These materials were synthesized under dry conditions as microcrystalline powders from conventional solid state reactions. The room temperature X-ray excited emission and scintillation decay curves were measured and analyzed for each material. Additionally, the hygroscopic nature of the oxychlorides and oxybromides was compared to that of their corresponding rare earth halides. The yttrium, lanthanum, and gadolinium oxychlorides, and all of the oxybromides and oxyiodides are found to be activated by Ce3+. GdOBr doped with 0.5% Ce3+ has the highest light output with a relative luminosity of about one-half that of LaBr3: Ce3+. It displays a single exponential decay of 30ns. [Copyright &y& Elsevier]

Abstract: Phosphate glasses doped with different concentrations of Ce3+ and Tb3+ were prepared by high temperature melting method. Effects of Tb3+ concentration and sensitization of Ce3+ on photoluminescence and radio-luminescence properties of terbium doped phosphate glass have been investigated by absorption, excitation and emission spectroscopy. Results showed the phosphate glass exhibit high broad absorption band attribute to the allowed 4f8–4f75d transition of Tb3+, which is beneficial for the 542nm emission of Tb3+. It is found that the emission intensity of Tb3+ at 542nm increased as the concentration of Tb3+ and Ce3+increasing. The suitable concentration of Ce3+ and Tb3+ in phosphate glass is 2mol% and 10mol% respectively, and the emission intensity of Ce3+/Tb3+-codoped phosphate glass at 542nm shows 8 times stronger than that of the commercial Bi4Ge3O12 (BGO) crystal at 500nm. The phosphate glass doped with Ce3+ and Tb3+ ions would be potential candidates for scintillating material for static X-ray imaging. [ABSTRACT FROM AUTHOR]

Abstract: The dependence of structural characteristics of cerium-doped lutetium scandium orthoborate (Lu1−x Sc x )BO3:Ce solid solutions on Sc/Lu ratio was investigated. It was found that the calcite phase of LuBO3 can be stabilized up to 1550°C at least when the n(Sc)/n(Lu+Sc) ratio was ≥10at.%. The closed correlations between Sc3+ or Ce3+ molar ratio in the host and luminescence mechanism were discussed in detail. Based on the requirements of steady phase structure, better luminescence efficiency and higher density, the reasonable n(Sc)/n(Lu+Sc) and n(Ce)/n(RE) ratio should be in the range of 30–50at.% and 0.3–0.5at.%, respectively. A modified composition, (Lu0.5Sc0.5)0.995Ce0.005BO3 solid solution, was selected to grow single crystal. Its X-ray excited luminescence intensity can be as high as about 27% of LYSO:Ce standard crystal and the effective lifetime is round 20.1ns. Hence, the cerium-doped lutetium scandium orthoborate crystal is a promising scintillator for X-ray detection or γ-ray detection. [Copyright &y& Elsevier]

Cerium-doped lutetium pyrosilicate (LPS:Ce) crystal with dimension of Φ 10 x 40 mm was grown successfully by Czochralski method. Its crystal structure was determined to be monoclinic with space group of C2/m. The optical transmission, UV and X-ray excited emission spectra, as well as decay curves were measured from 77 K to 500 K. Two emission peaks, 380 nm and 403 nm result from the transition of electrons from 5d1 to two ground levels (²F5/2 and ²F7/2) of Cerium ions (Ce3+) in the LPS:Ce crystals. The decay time of the fluorescence is weakly increasing from 77 K to 400 K and then decreases sharply. The light output of LPS:Ce can be improved greatly by annealing at 1400°C in air. TSL peak at 543 K in LPS:Ce is suggested to be related to oxygen vacancies which are one of the reasons of the poor light output. [ABSTRACT FROM AUTHOR]

Abstract: Thin film samples of CeCl3, CeBr3, and combinatorial compositions along the CeCl3–CeBr3 join were produced using thermal evaporation, which is being evaluated as a method for rapid screening of scintillator materials. The combinatorial thin films were shown to be compositionally reproducible from run-to-run within reasonable limitations. Analytical results suggest a continuous variation in the combinatorial samples in terms of their compositions, crystal structures, and luminescence characteristics. [Copyright &y& Elsevier]

Abstract: The single crystalline Lu3Al5O12 (LuAG) and Y3Al5O12 (YAG) garnet layers doped by Ce3+ ions were grown by the liquid phase epitaxy from the flux. The effect of the flux composition, growth conditions, and substrate polishing on the layer morphology, creation of defects, and on optical and emission properties of layers was studied. The defects typical of the epitaxial growth are discussed. [Copyright &y& Elsevier]

The Ce-doped yttrium ortho- and pyrosilicate powders were prepared in a powder form by the formamide-modified sol-gel method. Crystal structure was checked by x-ray diffraction and sample morphology by transmission electron microscopy measurements. Both ortho- and pyrosilicate pure phases were obtained by the previously mentioned preparation procedure and proper annealing temperature was determined to obtain the maximum scintillation efficiency. Luminescence spectra and decays were measured to better evaluate the source of efficiency losses in the scintillator mechanism of samples heat-treated at lower temperatures. The potential of this preparation method for manufacturing the nanocomposite scintillators was discussed. [ABSTRACT FROM AUTHOR]

The aim of the present work is to study the performance of scintillators currently used in PET and animal PET systems, under conditions met in radiation therapy and PET/CT imaging. The results of this study will be useful in applications where both CT and PET photons as well as megavoltage cone beam CT (MV CBCT) photons could be detected using a common detector unit. To this aim crystal samples of GSO, LSO, LYSO, LuYAP and YAP scintillators, doped with cerium (Ce3+) were examined under a wide energy range of photon energies. Evaluation was performed by determining the absolute luminescence efficiency (emitted light flux over incident X-ray exposure) in the energy range employed in X-ray CT, in Nuclear Medicine (70 keV up to 662 keV) and in radiotherapy 6 MV (approx. 2.0 MeV mean energy)-18 MV (approx. 4.5 MeV mean energy). Measurements were performed using an experimental set-up based on a photomultiplier coupled to a light integration sphere. The emission spectrum under X-ray excitation was measured, using an optical grating monochromator, to determine the spectral compatibility to optical photon detectors incorporated in medical imaging systems. Maximum absolute luminescence efficiency values were observed at 70 keV for YAP:Ce and LuYAP:Ce and at 140 keV for LSO:Ce, LYSO:Ce and GSO:Ce. Highest absolute efficiency between the scintillators examined was observed for LSO:Ce, followed by LYSO:Ce. The detector optical gain (DOG) exhibited a significant variation with the increase of energy between 70 keV to 2.0 MeV. All scintillators exhibited low compatibility when combined with GaAsP (G5645) photodetector. [ABSTRACT FROM AUTHOR]

A theoretical approach based on first-principles calculations is used to select candidate Ce activated scintillator materials for synthesis. Our theoretical approach involves the calculation of the ground state band structure of the Ce-doped material as well as the calculation of the (Ce3+)* excited state. From our theoretical studies of known scintillators and non-scintillators we have developed a set of criteria that are necessary characteristics of bright Ce activated scintillators. Applying these criteria to new compounds we were able to successfully predict that Ba2YCl7 : Ce would be a bright scintillator. [ABSTRACT FROM AUTHOR]

This work presents the results of first principles electronic structure calculations for Cerium (Ce) doped Yttrium (Y) and Lanthanum (La) oxyhalides performed using the pseudopotential method based on the local density approximation in the density functional theory. The relative position of the Ce 4f and 5d levels in the energy gap of the host are determined from the ground-state density of states for the Ce-doped material. Localization of the excited electron is determined from the calculations of the (Ce3+)* excited state. A qualitative prediction of Ce-activated scintillation is made based on these theoretical calculations. Our approach indicates that Ce-doped Y and La oxyhalides show progressively better luminescence as we move down the periodic table from oxyfluorides to oxyiodides. These families of materials have been synthesized and the experimental results agree qualitatively with our calculations. [ABSTRACT FROM AUTHOR]

Cerium-doped lutetium oxyorthosilicate (LSO:Ce) is a well-known scintillator whose high density (7.4 g/cc), high light yield (∼6 times that of BGO), and fast decay time (∼43 ns) make it especially well suited for use in Positron Emission Tomography. Recent work suggests that divalent calcium co-doping eliminates many of the shallow electron traps, thus facilitating fast energy transfer to the Ce3+ luminescence centers and shortening the scintillation decay time to ∼30 ns. Here we report preliminary observations of the effect of Ca2+ co-doping on the crystal growth, photoluminescence, and scintillation properties of LSO:Pr. Single crystals with Pr concentrations ranging from 0.05% to 0.2% and Ca2+ concentrations up to 0.2% were grown via the Czochralski. technique. Absorption, emission, and excitation spectra revealed the numerous 5d-4f and 4f-4f transitions characteristic of trivalent Pr. The main optical absorption due to Ca2+ occurs in the far UV, similar to previous observations of LSO:Ce, but with a more in- tense tail extending through the visible region. Consequently, 4f to 5d optical excitation (∼260 nm) is greatly reduced in Ca co-doped samples, and the related Sd to 4f emission (∼400 nm) is largely absent. Optical excitation (∼450-500 nm) of the red (∼610 nm) emission appears to be unaffected, for the most part, by the presence of Ca2+. The scintillation decay of LSO:Pr is the sum of two exponential components with time constants of 7-8 and 26-29 ns, similar to previous reports. The addition of Ca2+ appears to relatively enhance the shorter component while reducing the longer one, although one or more additional slow components appear. [ABSTRACT FROM AUTHOR]

Recently, scintillation has been observed in Ce-doped YI3, YBr3,and YCl3 crystals. In particular, YI3 has been reported to be among the scintillators with the highest luminosity. In this work, we present a systematic study of scintillation in any of the four YHa3 :Ce materials where Ha = F, Cl, Br, I, using ab initio calculations. Last year, our group demonstrated successful application of a method of gauging scintillation properties of Ce-doped crystals based on first-principle calculations using density functional theory. This method has been developed as an integral component of a High Throughput Scintillator Discovery facility based at the Lawrence Berkeley National Lab. By analyzing the energies and spatial localization of the highest occupied band in the ground state and in the lowest excited state, we are able to make qualitative predictions about the possibility of scintillation in Ce-doped compounds. In this paper we present the details of our theoretical approach in application to yttrium halides and compare them with the available experiments. Our results yield a prediction of Ce-based scintillation for all four materials: YF3, YCl3, YBr3 and YI3 and are in correspondence with the available experimental data. We believe that our method is the first use of first-principles calculations to predict some of the factors necessary for the activation of Ce3+ ions in crystals. [ABSTRACT FROM AUTHOR]

We report the scintillation properties of the undoped and cerium-doped variations of LiGdCl4 and NaGdCl4. Powder samples of these materials exhibit significant scintillation under X-rays. The samples were synthesized by solid-state methods from a 1:1 molar ratio of lithium or sodium chloride and gadolinium trichloride. Cerium trichloride was used as the dopant. The physical, optical, and scintillation properties of these materials were analyzed by powder X-ray diffraction, photoluminescence, X-ray excited luminescence, and pulsed X-ray luminosity measurements. Increases in light yields are observed as the concentration of cerium increases. The highest light yields occurred at 20% cerium doping for both compounds. At larger concentrations neither compound formed, indicating a breakdown of the lattice with the addition of large amounts of cerium cations. At 20% cerium, LiGdCl4 and NaGdCl4 display scintillation light 3.6 times and 2.2 times the light yield of the reference material, YAlO3 :Ce3+, respectively. Both emit in the ranges of 340-350 nm and 365-370 nm and display multiexponential decays with cerium-like decay components at 33 ns (LiGdCl4 : Ce) and 26 ns (NaGdCl4 Ce). [ABSTRACT FROM AUTHOR]

We report the scintillation properties of the undoped and cerium-doped variations of LiGdCl4 and NaGdCl4. Powder samples of these materials exhibit significant scintillation under X-rays. The samples were synthesized by solid-state methods from a 1:1 molar ratio of lithium or sodium chloride and gadolinium trichloride. Cerium trichloride was used as the dopant. The physical, optical, and scintillation properties of these materials were analyzed by powder X-ray diffraction, photoluminescence, X-ray excited luminescence, and pulsed X-ray luminosity measurements. Increases in light yields are observed as the concentration of cerium increases. The highest light yields occurred at 20% cerium doping for both compounds. At larger concentrations neither compound formed, indicating a breakdown of the lattice with the addition of large amounts of cerium cations. At 20% cerium, LiGdCl4 and NaGdCl4 display scintillation light 3.6 times and 2.2 times the light yield of the reference material, YAlO3 :Ce3+, respectively. Both emit in the ranges of 340-350 nm and 365-370 nm and display multiexponential decays with cerium-like decay components at 33 ns (LiGdCl4 : Ce) and 26 ns (NaGdCl4 Ce). [ABSTRACT FROM AUTHOR]

Luminescence properties of cerium doped Y3 Al5 O12 (YAG) nanocrystals in form of nanopowders and nanoceramics have been studied. The comparative analysis of luminescence characteristics for nano- and single-crystals has been done. It was detected that an excitonic mechanism of the energy transfer from the host lattice to cerium ions does not work in nanopowders and nanoceramic. It was also shown that antisite-related and self-trapped exciton-related luminescence bands are suppressed strongly in nanopowders, and it can be excited only under certain circumstances. These bands practically disappeared in the nanoceramic samples. It was suggested that nanoparticle's surface, which is an efficient trap for excitons and charge carriers, plays the crucial role in peculiarities of luminescence characteristics in nanocrystals. [ABSTRACT FROM AUTHOR]