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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]

Dense and transparent ceramic samples of a (Gd,Y)3Al2Ga3O12:Ce scintillator were obtained by using stereolithography-based Digital Light Processing (DLP) 3D printing for compacting, subsequent burnout, and pressureless sintering. The effects of stoichiometric deviations and green body compaction methods (uniaxial pressing versus DLP 3D printing) on the optical, luminescent, and scintillation properties of ceramics were analyzed. An excess of Y and Gd in the composition led to an increase in transmittance and to the acceleration of the scintillation kinetics. Moreover, transparent ceramics made of 3D-printed green bodies were found to be superior in light yield to the samples, which were prepared from the same powders and densified by uniaxial pressing. [ABSTRACT FROM AUTHOR]

The high durability under harsh environment including high temperature, high humidity, and high radiation is required for scintillators used for decommissioning of nuclear facilities and radiation monitoring in nuclear fusion reactors. α‐SiAlON ceramics are highly potential for such scintillators because of their thermal and mechanical durability and luminescence corresponding to doped rare‐earth ion. In this study, scintillation properties of transparent Lu‐α‐SiAlON:Ce3+ ceramics were investigated for the first time. Lu‐α‐SiAlON:Ce3+ showed the scintillation responses to α‐rays and X‐rays. The α‐rays‐induced scintillation decay curve consists of two components whose decay time are 48 and 652 ns. The faster decay component most presumably results from 4f‐5d transition of Ce3+, whereas the origin of the slower one is unclear but may be defects in α‐SiAlON. The light yield of the Lu‐α‐SiAlON:Ce3+ ceramics was 1300 photons 5.5 MeV−1. [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]

Upconversion nanoparticles (UCNPs), particularly those that are highly doped, possess outstanding properties and have demonstrated tremendous application potential. However, novel fine-tuning strategies are urgently required to enhance the upconversion luminescence (UCL) performance of UCNPs. In this study, a series of core–multishell UCNPs highly doped with Ho3+ and Yb3+ ions were synthesized via the oleate route. The X-ray diffraction (XRD), transmission electron microscopy (TEM), and UCL spectra and decay times, and pump power dependency of the synthesized UCNPs were used to examine their morphology, size, and the UCL properties. Ce3+ ions were introduced to enhance Ho3+-based red UCL, and their doping strategy was also optimized based on summarized UCL trends and detailed UCL mechanism analysis. NaHoF 4 :Gd3+@NaGdF 4 :Yb3+,Ce3+@NaGdF 4 :Yb3+ UCNPs that had 10 mol% Ce3+ dopants in their middle shells exhibited better UCL properties than the larger traditional NaGdF 4 :Yb3+,Ce3+,Ho3+ UCNPs, probably because of the combined influence of the energy interactions between the Ce3+ ions and surface groups, sensitizing energy enhancement by active shells, and the positive cooperation between the Ce3+ ions and highly-doped core–shell structures. In this study, the phenomenon of UCL decrease resulting from Ce3+ ion doping was explored. Using unique core–multishell structures with highly-doped activators and sensitizers placed within and outside the structures, respectively, the UCL decrease due to Ce3+ ion doping was attributed to a competition for photons. Doping the UCNPs with Ce3+ ions near the UCNP surfaces favors Ho3+-based red UCL. Our study findings can deepen the understanding of the Ho3+-based UCL mechanisms and increase the potential uses of NaHoF 4 materials in photo-induced therapy. When Ce3+ ions are doped near the nanoparticle surface, they might have energy interactions with surface groups to relieve phonon energy shortage and thus enhance the efficiency of cross-relaxation between Ho3+ and Ce3+ ions. [Display omitted] [ABSTRACT FROM AUTHOR]

Near‐infrared (NIR) luminescent metal halide (LMH) materials have attracted great attention in various optoelectronic applications due to their low‐temperature solution‐processable synthesis, abundant crystallographic/electronic structures, and unique optoelectronic properties. However, some challenges still remain in their luminescence design, performance improvement, and application assignments. This review systematically summarizes the development of NIR LMHs through classifying NIR luminescent origins into four major categories: band‐edge emission, self‐trapped exciton (STE) emission, ion emission, and defect‐related emission. The luminescence mechanisms of different types of NIR LMHs are discussed in detail by analyzing typical examples. Reasonable strategies for designing and optimizing luminescence/optoelectronic properties of NIR LMHs are summarized, including bandgap engineering, self‐trapping state engineering, chemical composition modification, energy transfer, and other auxiliary strategies such as improvement of synthesis scheme and post‐processing. Furthermore, application prospects based on the optoelectronic devices are revealed, including phosphor‐converted light‐emitting diodes (LEDs), electroluminescent LEDs, photodetectors, solar cells, and x‐ray scintillators, as well as demonstrations of some related practical applications. Finally, the existing challenges and future perspectives on the development of NIR LMH materials are critically proposed. This review aims to provide general understanding and guidance for the design of high‐performance NIR LMHs materials. [ABSTRACT FROM AUTHOR]

Scintillators, which can convert high‐energy particles (X‐rays) into detectable low‐energy ultraviolet–visible–near‐infrared photons, are essential components of X‐ray detectors and show extensive practical applications in nondestructive detection and medical imaging. Traditionally, inorganic scintillators represented by CsI:Tl have achieved definite progress. However, the harsh preparation conditions, high production cost, and poor mechanical properties impede their potential development in the high‐end X‐ray imaging field. Organic–inorganic hybrid metal complexes could be excellent alternatives, by virtue of their structural and spectral tunability, good solution processability, and excellent photophysical properties. This review mainly focuses on eco‐friendly lead‐free metal (Mn2+, Cu+, Sb3+, Sn2+, Ge2+, Ln3+, etc.) complex scintillators. The luminescence mechanisms are introduced and the scintillation performance, such as light yield, limit of detection, imaging resolution, etc., is highlighted. Moreover, the current challenges and perspectives in this emerging field are described. It is hoped to provide some theoretical guidance for the continuous development of the new scintillator systems. [ABSTRACT FROM AUTHOR]

This work is devoted to examining the influence of energy transfer processes between Ce3+ and Pr3+ ions on the luminescent and scintillation properties of LuAG:Ce and LuAG:Ce,Pr scintillators, grown by liquid phase epitaxy onto undoped LuAG substrates with a PbO–B2O3-based flux. To characterize them, measurements of the absorption, cathodoluminescence, photoluminescence emission and excitation spectra as well as the photoluminescence decay kinetics of the SCFs under study were performed. The investigation confirmed simultaneous energy transfer processes between d-f and f-f states of Pr3+ ions and between Pr3+ (d-f) and Ce3+ (d-f) ions, as well as from Ce3+ (d-f) to Pr3+ (f-f) ions in LuAG host. Furthermore, the energy transfer from Pb2+ flux-related impurity to Ce3+ (d-f) and Pr3+ (f-f) ions also were found in the LuAG:Ce and LuAG:Ce,Pr SCFs. An energy diagram of the Pb2+, Pr3+ and Ce3+ ion levels was constructed, which provides a deeper overview of the mentioned energy transfer processes.

Er3+ doped high density germanate glasses with compositions of 50GeO 2 -10BaO–10Al 2 O 3 -15Lu 2 O 3 -(15-x) La 2 O 3 -xEr 2 O 3 (x = 0, 0.1, 0.5, 1.0, 1.5, and 2.0, in mol%) have been prepared by the melt-quenching method. The optical and physical properties of the samples were characterized by differential scanning calorimetry (DSC), density, transmittance spectra, photoluminescence (PL) spectra, and X-ray excited luminescence (XEL) spectra. The densities were in the range from 5.90 to 6.07 g/cm3. The strong green emissions around 552 nm of Er3+ were observed upon the excitations of 378 nm light and the X-ray, and the lifetimes of 552 nm emission were in the range of 20.88–96.47 μs. The results show that Er3+ doped high density germanate glasses could be used as potential scintillators for X-ray CT. [ABSTRACT FROM AUTHOR]

The photoluminescence (PL) and scintillation properties of Ce-doped BaHfO3 crystals were investigated. The Ce-doped BaHfO3 crystal is transparent and colorless after annealing treatment under a reduction condition. The broad luminescence band at ~370 nm was observed under ~280 nm excitation with the decay time of ~17 ns. The X-ray-induced scintillation spectra also showed the broad luminescence band at ~380 nm with a fast decay. The origin of the broad luminescence band at ~380 nm is attributed to the 5d-4f transition of Ce3+. The pulse height distribution under 137Cs gamma ray irradiation using Ce-doped BaHfO3 exhibited a distinguishable photoabsorption peak. The light yield of Ce-doped BaHfO3 is ~1600 photons/MeV. [ABSTRACT FROM AUTHOR]

The photoluminescence (PL), scintillation, and thermally stimulated luminescence (TSL) properties of Eu-doped (0.01, 0.1, and 1%) Al2O3 single crystals grown by the floating zone method were investigated systematically. The PL of the samples showed several sharp emission peaks across 550-750 nm originating from the 4f-4f transitions of Eu3+ and the 3d-3d transitions of Cr3+ impurity ions. The scintillation spectrum of the samples showed a broad emission peak at 320 nm due to the F+ center and an emission peak at 700 nm due to the 3d-3d transitions of Cr3+ impurity ions. All the samples showed TSL glow peaks at around 200, 320, and 375 °C. The TSL intensity of the 1% Eu-doped sample was the highest among the present three samples, and the TSL response was proportional to the irradiated X-ray dose in the range from 10 to 1000 mGy. The Eu-doped Al2O3 single crystal could be a novel candidate for personal dose monitoring applications. [ABSTRACT FROM AUTHOR]

We synthesized an undoped La2Be2O5 single crystal by the floating zone method and investigated its scintillation properties. The synthesized sample was confirmed to have a singlephase structure of La2Be2O5 as shown by the powder X-ray diffraction pattern. The diffuse transmittance spectrum of the synthesized sample had transmittance at 80% in the range of 250-850 nm. The scintillation spectrum had a broad emission band from 280 to 600 nm, which was derived from unidentified lattice defects. In the scintillation decay profile, the obtained decay time constants were 1.1, 6.2, and 386 ns. From pulse height spectra, the light yield of the La2Be2O5 single crystal was 1000 photons/MeV. In afterglow profiles, the afterglow level was 42.9 ppm. [ABSTRACT FROM AUTHOR]

Thermoluminescence (TL) often involves the liberation of a charge carrier (an electron or a hole) from a charge carrier trapping centre into the conduction band (CB) or the valence band (VB) with subsequent recombination with a counter charge carrier at a luminescence centre. TL glow peak analysis can provide the energy ΔEt needed to liberate such charge carrier which then defines the location of the charge transition levels (CTL) of the carrier trapping centres below the CB-bottom or above the VB-top. The temperature at the maximum of the TL glow peak changes 3–4 K per 0.01 eV change in ΔEt thus providing an extremely sensitive probe of energy changes in CTLs. This work collects and reviews data on glow peaks due to electron or hole release from lanthanide dopants in 36 different inorganic compounds. To compare results from different literature sources, data were always re-analysed using the same method that is solely based on the temperature at the maximum of the glow peak. The changes in ΔEt along the lanthanides series provides insight at the sub 0.1 eV level on the changes in CTL energies. We will use a compound-dependent parameter to account for the nephelauxetic effect and a compound dependent parameter to account for lattice relaxation around the lanthanide. Together with information from lanthanide luminescence spectroscopy, the vacuum referred binding energy (VRBE) diagram will be constructed for each compound. The lanthanide electron or hole trap depth read from the VRBE scheme will be compared with that derived from the TL glow peak. Surprisingly good agreement will be demonstrated.

The paper presents the results of a comprehensive study of the structural-phase composition, morphology, optical, luminescent, and scintillation characteristics of thick ZnO films fabricated by magnetron sputtering. By using a hot ceramic target, extremely rapid growth (~50 µm/h) of ZnO microfilms more than 100 µm thick was performed, which is an advantage for the industrial production of scintillation detectors. The effects of post-growth treatment of the fabricated films in low-temperature plasma were studied and a significant improvement in their crystalline and optical quality was shown. As a result, the films exhibit intense near-band-edge luminescence in the near-UV region with a decay time of <1 ns. Plasma treatment also allowed to significantly weaken the visible defect luminescence excited in the near-surface regions of the films. A study of the luminescence mechanisms in the synthesized films revealed that their near-band-edge emission at room temperature is formed by phonon replicas of free exciton recombination emission. Particularly, the first phonon replica plays the main role in the case of optical excitation, while upon X-ray excitation, the second phonon replica dominates. It was also shown that the green band peaking at ~510 nm (2.43 eV) is due to surface emission centers, while longer wavelength (>550 nm) green-yellow emission originates mainly from bulk parts of the films. [ABSTRACT FROM AUTHOR]

Alkali metal halides have long been used as scintillators for applications as sensors and detectors. Usually, a small amount of impurities are added to these inorganic materials to improve their luminescence efficiencies. We investigate the structures and luminescent properties of un-doped sodium iodide (NaI) and cesium-doped NaI (NaI:Cs) films deposited by thermal vacuum evaporation. Instead of using the toxic element thallium (Tl), we introduced cesium dopant into NaI. This is the first study for the NaI:Cs film excited by UV LED's ultraviolet C (273 nm, 4.54 eV). The luminescence spectra show two main peaks at 3.05 and 4.32/3.955 eV (for fused silica/B270 substrate), originating from the intrinsic defects and/or activator excited states and the intrinsic self-trapped excitons (STEs), respectively. In general, both Cs-doping and post-annealing processes enhance the luminescence performance of NaI films. [ABSTRACT FROM AUTHOR]

The luminescence and scintillation properties of Ce3+ doped alkali phosphate glasses 56P 2 O 5 :8Gd 2 O 3 :5Al 2 O 3 :1CeBr 3 :30XCl (PGAC:X, X = Li/Na/K/Rb/Cs) were studied for their potential applications in gamma and alpha detection. In the Fourier Transform Infrared Spectroscopy (FTIR), X-ray Luminescence (XRL), Photoluminescence (PL), and transmittance spectra, the red shift was found and explained by the concept of optical basicity. Broad Ce3+ emission and energy transfer from Gd3+ to Ce3+ were observed in XRL and PL measurements. Scintillation performance was studied by irradiating the samples under 137Cs gamma and 241Am alpha sources. The fast, intermediate, and slow decay components under gamma and alpha excitation were found around 30, 200 and 3000 ns, respectively. The decay time increased slightly from PGAC:Li to PGAC:Cs, indicating the less effective transition from Gd3+ to Ce3+. The alpha decay time was longer than the gamma decay time, revealing the Pulse Shape Discrimination (PSD) capability of the glasses for particle identification. The XRL intensity reduced significantly from PGAC:Li to PGAC:Cs samples did not reflect the scintillation tendency. By successfully detecting gamma and alpha scintillation signals, the scintillation performance of all samples was found to be similar. In general, all samples can be used for gamma and alpha detection. Using Rb+ or Cs+ ions is favorable in terms of high density and light yield, while Li+ ions enhance the transmittance and homogeneity. Furthermore, a correlation between P–O–H groups within the glass matrix and scintillation performance was also observed. [ABSTRACT FROM AUTHOR]

The production of scintillating ceramics can require the utilization of the phosphorus compounds at certain stages of 3D-printing, such as vat polymerization, applied for the formation of green bodies before sintering. The effect of phosphorus additive on the microstructure, optical, and scintillation parameters of Gd1.494Y1.494 Ce0.012Al2Ga3O12 (GYAGG:Ce) ceramics obtained by pressureless sintering at 1650 °C in an oxygen atmosphere was investigated for the first time. Phosphorus was introduced in the form of NH4H2PO4 into the initial hydroxycarbonate precipitate in a wide concentration range (from 0 to 0.6 wt.%). With increasing of phosphorus concentration, the density and the optical transmittance of garnet ceramics show a decrease, which is caused by an increase in the number of pores and inclusions. The light yield of fast scintillation, which is caused by Ce3+ ions, was found to be affected by the phosphorus additive as well. Moreover, an increase in phosphorescence intensity was recognized. [ABSTRACT FROM AUTHOR]

Organic–inorganic composite scintillators, demonstrating advantages of easy large-area preparation and a high detection efficiency, have shown enormous potential application prospects in radiation detection and imaging. In this study, bulk polystyrene (PS) composite scintillators were successfully prepared by embedding inorganic BaF2 particles with a loading amount of up to 80 wt% during the polymerization process of the plastic scintillator. The inorganic BaF2 particles were uniformly dispersed in the organic matrix. With the increase of the loading amounts of BaF2 particles, the X-ray-excited luminescence intensity of the PS-BaF2 composite scintillators was about eight times higher than that of the commercial pure plastic scintillator. The scintillation counts under the gamma ray (59.5 KeV) irradiation also showed that the detection efficiency was obviously enhanced by BaF2 particle loading. More importantly, their scintillation pulse retains the decay kinetics of the organic matrix without loading the slow-decay component of BaF2. This work provides a promising solution for the application of the PS-BaF2 composite scintillator in high-efficiency radiation detection and large-area imaging. [ABSTRACT FROM AUTHOR]

This study aims to determine the optimum composition of the CeBr1−xIx compound to achieve the maximum light output. It is based on calculations of the band energy structure of crystals, specifically taking into account the characteristics of the mutual location of local and band 5d states of the Ce3+ ions. The band energy structures for CeBr2I and CeBrI2 crystals were calculated using the projector augmented wave method. The valence band was found to be formed by the hybridized states of 4p Br and 5p I. The 4f states of Ce3+ are located in the energy forbidden band gap. The conduction band is formed by the localized 5d1 states, which are created by the interaction between the 5d states of Ce3+ and the 4f0 hole of the cerium ion. The higher-lying delocalized 5d2 states of Ce3+ correspond to the energy levels of the 5d states of Ce3+ in the field of the halide Cl0 (Br0) hole. The relative location of 5d1 and 5d2 bands determines the intensity of 5d–4f luminescence. The bottom of the conduction band is formed by localized 5d1 states in the CeBr2I crystal. The local character of the bottom of the conduction band in the CeBr2I crystal favors the formation of self-trapped Frenkel excitons. Transitions between the 5d1 and 4f states are responsible for 5d–4f exciton luminescence. In the CeBrI2 crystal, the conduction band is formed by mixing the localized 5d1 and delocalized 5d2 states, which leads to quenching the 5d–4f luminescence and a decrease in the light output despite the decrease in the forbidden band gap. CsBr2I is the optimum composition of the system to achieve the maximum light output. [ABSTRACT FROM AUTHOR]

The objective of this paper is to review the use of the thermoluminescence (TL) and optically stimulated luminescence (OSL) techniques as research tools in luminescence, particularly to detect the presence of trapping centers that can degrade the efficiency of scintillators, and shape the properties of persistent phosphors, storage phosphors and dosimeters. A brief review of the main analysis techniques is provided, followed by a discussion of their limitations. Examples of applications in which the TL or OSL analyses have provided useful information on the trapping and recombination of charges created by ionizing radiation is given. [ABSTRACT FROM AUTHOR]

To reduce the issue of tri-primary color reabsorption, a new approach for single-phase phosphors as light-emitting diodes (LEDs) has been recommended. The structures, morphology, photoluminescence, thermal stability, and luminescence mechanism of a variety of Ca3Bi (PO4)3 (CBPO): Ce3+/Dy3+ phosphors were investigated. XRD characterization showed that all CBPO samples were eulytite structures. Furthermore, the energy transfer process from Ce3+ to Dy3+ in CBPO is systematically investigated in this work, and the color of light can be adjusted by changing the ratio of doped ions. Under UV light, energy is transferred from Ce3+-Dy3+ mainly through quadrupole-quadrupole interactions in the CBPO host, and doping with different Dy3+ concentrations tunes the emission color from blue to white. The thermal stability of the CBPO: 0.04Ce3+, 0.08Dy3+ samples is outstanding, and the CIE coordinates of the samples after emission have little effect with temperature, while their emission intensity at 423 K is as strong as that at room temperature, reaching 90%. The above results indicate that this CBPO material has great potential as a white light phosphor under near-UV excitation at the optimized concentration of Ce3+ and Dy3+. [ABSTRACT FROM AUTHOR]

The luminescent Z-scan technique with time resolution is applied to the study of the luminescence properties of CH3NH3PbBr3 single crystals representative of the family of hybrid organic–inorganic lead perovskites successfully applied recently in photovoltaics and currently investigated as potential nanosecond scintillators. The third harmonic of Ti-sapphire laser (λ = 266 nm) with a pulse duration of 26 fs and 1 kHz frequency was applied for the luminescence excitation creating the charge carriers with the estimated density from 1017 to 1021 cm−3 in the temperature range from 13 to 300 K. Temperature and excitation density dependence of the luminescence yield and kinetics is interpreted with the consideration of the temperature-dependent binding of electrons and holes into excitons, a saturation of defects responsible for the non-radiative relaxation channel competing with exciton creation; absorption saturation resulting in the increased penetration depth of the excitation radiation and hence the increased contribution of the re-absorption. [ABSTRACT FROM AUTHOR]

Lutetium oxyorthosilicate Lu2SiO5 (LSO) and pyrosilicate Lu2Si2O7 (LPS) activated by Ce3+ or Pr3+ are known to be effective and fast scintillation materials for the detection of X-rays and γ-rays. Their performances can be further improved by co-doping with aliovalent ions. Herein, we investigate the Ce3+(Pr3+) → Ce4+(Pr4+) conversion and the formation of lattice defects stimulated by co-doping with Ca2+ and Al3+ in LSO and LPS powders prepared by the solid-state reaction process. The materials were studied by electron paramagnetic resonance (EPR), radioluminescence spectroscopy, and thermally stimulated luminescence (TSL), and scintillation decays were measured. EPR measurements of both LSO:Ce and LPS:Ce showed effective Ce3+ → Ce4+ conversions stimulated by Ca2+ co-doping, while the effect of Al3+ co-doping was less effective. In Pr-doped LSO and LPS, a similar Pr3+ → Pr4+ conversion was not detected by EPR, suggesting that the charge compensation of Al3+ and Ca2+ ions is realized via other impurities and/or lattice defects. X-ray irradiation of LPS creates hole centers attributed to a hole trapped in an oxygen ion in the neighborhood of Al3+ and Ca2+. These hole centers contribute to an intense TSL glow peak at 450–470 K. In contrast to LPS, only weak TSL peaks are detected in LSO and no hole centers are visible via EPR. The scintillation decay curves of both LSO and LPS show a bi-exponential decay with fast and slow component decay times of 10–13 ns and 30–36 ns, respectively. The decay time of the fast component shows a small (6–8%) decrease due to co-doping. [ABSTRACT FROM AUTHOR]

Luminescence clusters composed of organic ligands and metals have gained significant interests as scintillators owing to their great potential in high X-ray absorption, customizable radioluminescence, and solution processability at low temperatures. However, X-ray luminescence efficiency in clusters is primarily governed by the competition between radiative states from organic ligands and nonradiative cluster-centered charge transfer. Here we report that a class of Cu4I4 cubes exhibit highly emissive radioluminescence in response to X-ray irradiation through functionalizing biphosphine ligands with acridine. Mechanistic studies show that these clusters can efficiently absorb radiation ionization to generate electron-hole pairs and transfer them to ligands during thermalization for efficient radioluminescence through precise control over intramolecular charge transfer. Our experimental results indicate that copper/iodine-to-ligand and intraligand charge transfer states are predominant in radiative processes. We demonstrate that photoluminescence and electroluminescence quantum efficiencies of the clusters reach 95% and 25.6%, with the assistance of external triplet-to-singlet conversion by a thermally activated delayed fluorescence matrix. We further show the utility of the Cu4I4 scintillators in achieving a lowest X-ray detection limit of 77 nGy s−1 and a high X-ray imaging resolution of 12 line pairs per millimeter. Our study offers insights into universal luminescent mechanism and ligand engineering of cluster scintillators. X-ray luminescence efficiency of copper halide clusters is limited by nonradiative charge transfer. Here, Zhang et al. report highly emissive radioluminescence of Cu4I4 cubes by functionalizing biphosphine ligands with acridine, unlocking the potential use as low-cost and eco-friendly scintillators. [ABSTRACT FROM AUTHOR]

Gallium nitride is a wide-direct-bandgap semiconductor suitable for the creation of modern optoelectronic devices and radiation tolerant detectors. However, formation of dislocations is inevitable in MOCVD GaN materials. Dislocations serve as accumulators of point defects within space charge regions covering cores of dislocations. Space charge regions also may act as local volumes of enhanced non-radiative recombination, deteriorating the photoluminescence efficiency. Surface etching has appeared to be an efficient means to increase the photoluminescence yield from MOCVD GaN materials. This work aimed to improve the scintillation characteristics of MOCVD GaN by a wet etching method. An additional blue photo-luminescence (B-PL) band peaking at 2.7–2.9 eV and related to dislocations was discovered. This B-PL band intensity appeared to be dependent on wet etching exposure. The intensity of the B-PL was considerably enhanced when recorded at rather low temperatures. This finding resembles PL thermal quenching of B-PL centers. The mechanisms of scintillation intensity and spectrum variations were examined by coordinating the complementary photo-ionization and PL spectroscopy techniques. Analysis of dislocation etch pits was additionally performed by scanning techniques, such as confocal and atomic force microscopy. It was proved that this blue luminescence band, which peaked at 2.7–2.9 eV, is related to point defects those decorate dislocation cores. It was shown that the intensity of this blue PL band was increased due to enhancement of light extraction efficiency, dependent on the surface area of either single etch-pit or total etched crystal surface. [ABSTRACT FROM AUTHOR]

Synthesis in the radiation field is a promising direction for the development of materials transformation processes, especially those differing in melting temperature. It has been established that the synthesis of yttrium–aluminum ceramics from yttrium oxides and aluminum metals in the region of a powerful high-energy electron flux is realized in 1 s, without any manifestations that facilitate synthesis, with high productivity. It is assumed that the high rate and efficiency of synthesis are due to processes that are realized with the formation of radicals, short-lived defects formed during the decay of electronic excitations. This article presents descriptions of the energy-transferring processes of an electron stream with energies of 1.4, 2.0, and 2.5 MeV to the initial radiation (mixture) for the production of YAG:Ce ceramics. YAG:Ce (Y3Al5O12:Ce) ceramics samples in the field of electron flux of different energies and power densities were synthesized. The results of a study of the dependence of the morphology, crystal structure, and luminescence properties of the resulting ceramics on the synthesis modes, electron energy, and electron flux power are presented. [ABSTRACT FROM AUTHOR]

Micron/sub-micron hard X-ray imaging is an important development direction of X-ray detection technology. Scintillation screens with excellent X-ray stopping power and high light output are desired to obtain good imaging quality. Europium-doped lutetium oxide (Lu 2 O 3 :Eu) film with micro-columnar structure is an ideal candidate for this application. In this study, micro-columnar structured Lu 2 O 3 :Eu films were prepared on quartz glass substrates by laser chemical vapor deposition (LCVD) method. The influences of preparation conditions on structure and morphology properties of films were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Photoluminescence and scintillation properties of the films, including photoluminescence excitation (PLE), photoluminescence (PL), PL decay, X-ray excitation luminescence (XEL), and afterglow curves, were recorded. The relationships between structure, morphology, luminescence properties of films, and preparation conditions were investigated and discussed as well. The preparation conditions include laser power, oxygen flow rate, and precursor evaporation temperature. In addition, dual-layer Lu 2 O 3 :Eu film was prepared for the first time by just turning off the laser. [ABSTRACT FROM AUTHOR]

The study deals with the use of different amounts of MgO or tetraethyl orthosilicate (C 8 H 20 O 4 Si, TEOS), from 0.04 wt %, 0.06 wt %, 0.08 wt %, 0.4 wt %, 0.6 wt % to 0.8 wt %, respectively, as additional sintering aids during the vacuum sintering of transparent Ce3+ doped Y 3 Al 5 O 12 (Ce:YAG) ceramics to investigate their effect on microstructure and luminescence properties. A comparative study was carried out by using X - ray diffraction, scanning electron microscopy/energy dispersive X - ray spectroscopy, optical and photo-luminesce spectra, as well as electroluminescent spectra. The dominant garnet phase was obtained even when adding 0.8 wt % of MgO or TEOS, while adding MgO led to finer average grain size (∼ 5 - 10 μm) and more homogenous distribution compared to TEOS (∼ 20 - 25 μm) in Ce:YAG ceramics. Adding a large amount of MgO was found to result in the segregation of MgO in Ce:YAG ceramics, while an excess of TEOS led to the segregation of Al 2 O 3. A strong absorption peak at 308 nm was observed in Ce:YAG ceramics with MgO sintering aids, which was ascribed to the existence of Ce4+ induced by a charge compensation effect of Mg2+. The optimum transmittance reached 80% @ 800 nm in Ce:YAG ceramics when adding 0.6 wt % TEOS, which also exhibited a maximum luminous efficacy of 106 lm/W. Si4+ was experimentally proved to have a better optimization effect on luminous efficacy compared to Mg2+. • MgO or TEOS (C 8 H 20 O 4 Si) was added as additional sintering aids in a wide amount range. • MgO proves to have distinct inhibit effect on the grain growth. • Better luminous efficacy were observed in ceramics with TEOS additives. [ABSTRACT FROM AUTHOR]

Thin luminescent films of the organometallic complex of lithium 8-hydroxyquinolate Liq on glass substrates were fabricated by capillary deposition and lithography. The spectral-luminescent properties of the obtained film structures were investigated. The film surface was analyzed. The light yield and the kinetics of scintillation emission of the obtained film structures are estimated. [ABSTRACT FROM AUTHOR]

This research focuses on LPE growth, and the examination of the optical and photovoltaic properties of single crystalline film (SCF) phosphors based on Ce3+-doped Y3MgxSiyAl5−x−yO12 garnets with Mg and Si contents in x = 0–0.345 and y = 0–0.31 ranges. The absorbance, luminescence, scintillation, and photocurrent properties of Y3MgxSiyAl5−x−yO12:Ce SCFs were examined in comparison with Y3Al5O12:Ce (YAG:Ce) counterpart. Especially prepared YAG:Ce SCFs with a low (x, y < 0.1) concentration of Mg2+ and Mg2+–Si4+ codopants also showed a photocurrent that increased with rising Mg2+ and Si4+ concentrations. Mg2+ excess was systematically present in as-grown Y3MgxSiyAl5−x−yO12:Ce SCFs. The as-grown SCFs of these garnets under the excitation of α–particles had a low light yield (LY) and a fast scintillation response with a decay time in the ns range due to producing the Ce4+ ions as compensators for the Mg2+ excess. The Ce4+ dopant recharged to the Ce3+ state after SCF annealing at T > 1000 °C in a reducing atmosphere (95%N2 + 5%H2). Annealed SCF samples exhibited an LY of around 42% and similar scintillation decay kinetics to those of the YAG:Ce SCF counterpart. The photoluminescence studies of Y3MgxSiyAl5−x−yO12:Ce SCFs provide evidence for Ce3+ multicenter formation and the presence of an energy transfer between various Ce3+ multicenters. The Ce3+ multicenters possessed variable crystal field strengths in the nonequivalent dodecahedral sites of the garnet host due to the substitution of the octahedral positions by Mg2+ and the tetrahedral positions by Si4+. In comparison with YAG:Ce SCF, the Ce3+ luminescence spectra of Y3MgxSiyAl5−x−yO12:Ce SCFs greatly expanded in the red region. Using these beneficial trends of changes in the optical and photocurrent properties of Y3MgxSiyAl5−x−yO12:Ce garnets as a result of Mg2+ and Si4+ alloying, a new generation of SCF converters for white LEDs, photovoltaics, and scintillators could be developed. [ABSTRACT FROM AUTHOR]

Ce-doped 20CsBr-20BaBr2-60ZnBr2 glasses were synthesized by the conventional melt quenching method, and their photoluminescence (PL) and scintillation properties were investigated. In the PL and scintillation spectra, all the Ce-doped glasses showed broad emissions due to the 5d-4f transitions of Ce3+ ions. Under 241Am α-rays, the light yield of 0.05% Ce-doped glass was 40 photons/5.5 MeV-α. [ABSTRACT FROM AUTHOR]

We synthesized 20Lu2O3-30Ga2O3-50SiO2 glasses doped with various concentrations of Sn using a floating zone furnace equipped with Xe arc lamps. The samples showed a luminescence band around 450 nm in both photoluminescence (PL) and scintillation spectra. The origin of the luminescence was ascribed to the T1-S0 transition of Sn2+ on the basis of the luminescence wavelength and PL decay time constant. The highest scintillation intensity and PL quantum yield were observed from the 1% Sn-doped sample. The afterglow level tended to decrease with increasing Sn doping, and the afterglow levels of the 1 and 3% Sn-doped samples were comparable to that of the conventional Tl-doped CsI scintillator. The optimal concentration of Sn for the glass was estimated to be 1%. [ABSTRACT FROM AUTHOR]

A comparative study on the radioluminescence properties of Ce-doped SrAl2O4 single crystal and translucent ceramic was performed. The transmittance of the synthesized ceramic is 20-30% in the visible region. Both samples exhibit photo- and radioluminescence with a broad emission peaking at 380 nm. The decay curves are fitted by a single exponential decay function with decay time constants of 30-50 ns, consistent with the typical value of the emission for the 5d-4f transitions of Ce3+. From the pulse height spectra measured under 241Am γ-ray (59.5 keV) irradiation, the scintillation light yields are 17000 ph/MeV for the single crystal and 6100 ph/MeV for the synthesized ceramic. The scintillation light yield and afterglow of the present samples show a negative correlation. [ABSTRACT FROM AUTHOR]

Ce:(MgxCa1-x)HfO3 (x = 0.5, 2.5, 5, and 10%) single crystals were successfully grown by the floating zone method, and their photoluminescence (PL) and scintillation properties were investigated. A broad luminescence band with a maximum at 430 nm was observed in both the PL and scintillation spectra. The PL quantum yield (QY) improved with the substitution of Mg, and the PL QY of Ce:(MgxCa1-x)HfO3 reached 50%. Fast decay due to the 5d-4f transition of Ce3+ was observed for both the PL and scintillation. Ce:(MgxCa1-x)HfO3 (x = 5%) showed the highest light yield of ~9500 photons/MeV among the synthesized samples, and this value is higher than that of common X- and gamma-ray detection scintillators such as Bi4Ge3O12 and Ce:Gd2SiO5 single crystals. [ABSTRACT FROM AUTHOR]

Novel near-infrared (NIR) phosphors are in demand for light-emitting diode (LED) devices to extend their suitability for new applications and, in turn, support the sustainable and healthy development of the LED industry. The Cr3+ has been used as an activator in the development of new NIR phosphors. However, one main obstacle for the Cr3+-activated phosphors is the low luminescence efficiency due to the spin-forbidden d-d transition of Cr3+. The rare-earth (RE) huntite minerals that crystallize in the form of REM3(BO3)4 (M = Al, Sc, Cr, Fe, Ga) have a large family of members, including the rare-earth scandium borates of RESc3(BO3)4. Interestingly, in our research, we found that the luminescence efficiency of Cr3+ in the CeSc3(BO3)4 host, whose quantum yield was measured at 56%, is several times higher than that in GdSc3(BO3)4, TbSc3(BO3)4, and LuSc3(BO3)4 hosts. Hereby, the energy conversion and transfer in the luminescence of CeSc3(BO3)4:Cr3+ phosphor were examined. The Stokes shift of electron energy conversion within the Cr3+ 4T2g level for the emission at 818 nm and excitation at 625 nm in CeSc3(BO3)4 host was evaluated to be 3775.1 cm−1, and the super-large splitting energy of the 2F5/2 and 2F72 sub-states of the Ce3+ 4f1 state, about 3000 cm−1, was found in CeSc3(BO3)4 host. The typical electronic thermal vibration peaks were observed in the excitation spectra of CeSc3(BO3)4:Cr3+. On this basis, the smallest phonon energy, around 347.7 cm−1, of the CeSc3(BO3)4 host was estimated. Finally, the energy transfer that is responsible for the far higher photoluminescence of Cr3+ in CeSc3(BO3)4 than in other hosts was proven through the way of Ce3+ emission and Cr3+ reabsorption. [ABSTRACT FROM AUTHOR]

This research revealed the response of Ga and Al sublattices to the incorporation of mismatching substituents in Gd3Al2Ga3O12:Ce single crystals. Incompatible in size and charge, Li+ and Mg2+ substituents violated configurational entropy. This led to lattice distortion and triggered structural rearrangements. The radial fluctuation of the Ga and Al elements was proven by multi-elemental energy-dispersive X-ray spectroscopy mapping and elemental composition analysis. Further evidence was observed by the shift of the exciton creation energy toward higher energy in the vacuum ultraviolet excitation spectra recorded with synchrotron radiation. In the Li+ and Mg2+ co-doped samples, the crystal core was depleted with Ga atoms and enriched with Al elements. The crystal rim showed the opposite behavior. The change in thermoluminescence peak positions revealed a different mechanism for the formation of localized traps. As a result, Li+ co-doping slightly improved the light yield value, but at the same time decelerated the scintillation decay time. On the contrary, Mg2+ co-doping markedly diminished scintillation parameters. [ABSTRACT FROM AUTHOR]

Pr3+ doped high density germanate glasses were prepared by the melt-quenching method. The physical and luminescent properties were investigated. The glass containing BaF 2 represented maximum phonon energy of 810 cm−1, and the glass density was greater than 6 g/cm3. The glass exhibited good radiation resistance under 2 h of X-ray irradiation. Intense blue, green emissions and weak red emissions were observed when the glass was excited by X-ray, and the blue fluorescence lifetimes were in the range of 9.15–12.59 μs The results show that Pr3+ doped germanate glass could be a potential scintillating material in the field of X-ray detection for fast events. [ABSTRACT FROM AUTHOR]

In this study, the infrared optically stimulated luminescence (IRSL) of single crystals of Ce3+ doped yttrium aluminum garnet (YAG) was investigated for the first time. It was found that infrared stimulation of these crystals, following previous exposure to beta radiation, produces a strong luminescence signal. The highest luminescence efficiency was exhibited by the YAG crystal with 0.1% of Ce. With this crystal, it was possible to measure as low doses as 0.1 mGy. Moreover, IRSL is mainly related to the TL peak at a relatively high temperature of c.a. 175 °C, which leads to quite good stability of the signal in time. These properties create good prospects for potential applications of YAG:Ce in dosimetric radiation measurements [ABSTRACT FROM AUTHOR]

In this paper, we have investigated characteristics of ultraviolet and visible radiation generated by the 2.7 MeV electrons. It is shown that the Cherenkov radiation (ChR) intensity predominates over scintillations including wavelength shifting and cathodoluminescence quenching in pure poly(methylmethacrylate) (PMMA) for such electron energy. To separate ChR and scintillations, we measured emission spectra and orientation dependence of the PMMA samples and compared with GEANT4 model taking into account only ChR mechanism. [ABSTRACT FROM AUTHOR]

In recent years, Cs2ZnCl4 crystal has become an ideal substrate for various functional doped ions due to its large bandgap, showing potential in photodetectors and scintillators. In practical application, the intrinsic defect luminescence of bulk crystals has an important effect on the photoelectrical properties. In this work, Ø12 mm × 90 mm Cs2ZnCl4 single crystal was grown by the vertical Bridgman method. The theoretical bandgap, state density distribution, and refractive index curve of the crystal were obtained by first-principles calculation of the structure data. The luminescence properties of the crystal were characterized, including photoluminescence spectrum and radioluminescence spectrum. The temperature-dependent photoluminescence spectrum of the crystal was studied, and the luminescence process of the defects in the crystal was analyzed by the experimental results. [ABSTRACT FROM AUTHOR]

In the present article, the influence of the activator concentration and impurity content of raw materials on the luminescence and scintillation properties of Li2CaSiO4 was studied. Polycrystalline powder material was obtained by the sol–gel method. It was shown that europium had limited solubility in the host lattice with a limiting concentration proximate to 0.014 formula units. The maximum intensity of photoluminescence was observed with a divalent europium concentration of 0.002 formula units; the light yield under alpha-particle excitation was measured to be 21,600 photons/MeV for ~200 μm of coating, and under neutron excitation, it was calculated to be 103,800 photons/n, the scintillation kinetics was characterized by an effective decay time of 157 ns. These properties and the transparency in the visible spectrum make it possible to produce scintillation screens with a coating of Li2CaSiO4 for detecting neutrons, alpha particles and low-energy beta radiation. The low Zeff (~15) of this compound makes it less sensitive to gamma rays. The 480 nm blue emission peak makes this material compatible with most commercial PMT photocathodes, CCD cameras and silicon photomultipliers, which have a maximum quantum efficiency in the blue–green spectral region. [ABSTRACT FROM AUTHOR]

The ability of a scintillator to absorb and convert the high-energy X-ray photons to low-energy visible photons is crucial for the application of X-ray in medical tests, security checks and scientific research. However, traditional scintillation crystals are synthesized by complex preparation process with high cost, hindering the wide development in practical applications. Here, Tb3+ doped sodium silicate glass, which exhibits remarkable scintillation property and recoverability to X-ray irradiation, was successfully prepared by an exercisable melt-quenching method. The obtained scintillator shows intense radioluminescence, which is about 1.5 times higher than that of the reference of Bi 4 Ge 3 O 12. The damaged glass to X-ray irradiation can be returned to the original state after heat treatment again, indicating excellent recovery. Moreover, the scintillator displays wonderful thermal stability with the fluorescence intensity at 573 K still remaining 96% at room temperature. These results demonstrate that the obtained scintillating glass has potential application towards the real world. [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]

The effect of CeF3 concentration and γ-irradiation on the physical, optical and luminescence properties of Gd2O3–B2O3–CeF3 glasses were studied in this work. Before irradiation, the addition of CeF3 in glass degraded the network connectivity observed from FTIR and possibly created the non-bridging oxygen (NBO) in glass structure. This NBO caused the reduction of Ce3+/Ce4+ ratio in XANES, the red-shift in transmission spectra and the raise of refractive index with addition of CeF3 content. Such red-shift also was influenced by 4f–5d transition of Ce3+ dopant. This ion generated the strongest photoluminescence (PL) and radioluminescence (RL) in 0.3 mol% CeF3-doped glass with nanoseconds decay time. The irradiation with γ-rays damaged the glass structure, broke the chemical bonds, and created color center in the glass network. The non-bridging oxygen hole center (NBOHC), that absorbed photons in the visible light region, caused the darkening, color change and increment of refractive index. These irradiation effects on glass were mitigated by the addition of CeF3 that the electron donation of Ce3+ decreased the number of NBOHC. The Ce3+/Ce4+ ratio in most glasses after irradiation then reduced compared to them before irradiation, resulting to the decrease in PL and RL intensity. Our results confirm that CeF3 can enhance the radiation hardness of glass and the 0.3 mol% CeF3-doped glass is a promising glass scintillator. [ABSTRACT FROM AUTHOR]

A special group of luminescence materials are scintillators for thermal neutron detection. Due to the properties of neutrons (contrary to e.g. electrons or gamma photons), a different approach has to be utilized—the high content of atoms with the sufficient absorption cross‐section toward neutrons and lower material density are needed. This work pursues a basic study of LiSrBO3 and LiSr4(BO3)3 doped with cerium or europium—materials promising as thermal neutron scintillators. These borates exhibit promising properties such as the high content of lithium and boron, suitable density, and proper environment for luminescent ions. Radioluminescence of these ceramic borates doped with cerium and europium was examined and promising samples were further characterized by photoluminescence spectroscopy and radioluminescence and photoluminescence kinetics measurement. The radioluminescence study of these borates is published for the first time. Cerium‐doped borates, in particular, exhibit a very promising response to an X‐ray excitation. [ABSTRACT FROM AUTHOR]

Temperature dependence of the luminescence characteristics of Lu1.84Y0.16SiO5:Ce (LYSO:Ce) scintillator was investigated under x-ray excitation. The luminescence decay time, light yield, radioluminescence (RL) spectra, spatial resolution, and luminescence homogeneity from 300 to 550 K are experimentally examined with multiple x-ray facilities. The results show that the decay time and light output of the LYSO:Ce scintillator will decrease from 42 to 1.89 ns and from 32 000 to 1120 photons/MeV with a temperature increase from 300 to 550 K, respectively. The RL spectrum experiments demonstrate that the spectrum peak will move from 414 to 426 nm when adjusting the temperature from 300 to 550 K. The spatial resolution experiments show that the spatial resolution is hardly affected and can reach as high as 2.5 lp/mm when increasing the temperature from 300 to 550 K, and the luminescence homogeneity remains unchanged with increase in temperature. The experimental results provide important information for the radiation imaging application of the LYSO:Ce scintillator. [ABSTRACT FROM AUTHOR]

Radiodiagnostic technologies are powerful tools for preventing diseases and monitoring the condition of patients. Medicine and sectors such as industry and research all use this inspection methodology. This field demands innovative and more sophisticated systems and materials for improving resolution and sensitivity, leading to a faster, reliable, and safe diagnosis. In this study, a large characterization of gadolinium oxysulfide (Gd2O2S) scintillator screens for imaging applications has been carried out. Seven scintillator samples were doped with praseodymium (Pr3+), terbium (Tb3+) activators and co-doped with praseodymium, cerium, and fluorine (Gd2O2S:Pr,Ce,F). The sample screens were prepared in the laboratory in the form of high packing density screens, following the methodology used in screen sample preparation in infrared spectroscopy and luminescence. Parameters such as quantum detection efficiency (QDE), energy absorption efficiency (EAE), and absolute luminescence efficiency (ALE) were evaluated. In parallel, a structural characterization was performed, via XRD and SEM analysis, for quality control purposes as well as for correlation with optical properties. Spatial resolution properties were experimentally evaluated via the Modulation Transfer Function. Results were compared with published data about Gd2O2S:Pr,Ce,F screens produced with a standard method of a sedimentation technique. In particular, the ALE rose with the X-ray tube voltage up to 100 kVp, while among the different dopants, Gd2O2S:Pr exhibited the highest ALE value. When comparing screens with different thicknesses, a linear trend for the ALE value was not observed; the highest ALE value was measured for the 0.57 mm thick Gd2O2S:Pr,Ce,F sample, while the best MTF values were found in the thinner Gd2O2S:Pr,Ce,F screen with 0.38 mm thickness. [ABSTRACT FROM AUTHOR]

Recent surge in additive manufacturing efforts demonstrate stereolithography as a promising technique for fabricating glass materials due to the high speed and scalability of the process. However, little efforts have been devoted to manufacture borosilicate glass by the stereolithographic process. One of the challenges is that its relatively low softening temperatures could interfere with the thermal post-printing process and introduce poor fidelity and structure instability. Here, we report on the first demonstration of stereolithographic manufacturing of cerium-doped (Ce-doped) (<10%) and undoped borosilicate glass which was enabled by a multi-step post thermal processing. The optical properties of the printed glass depend on thermal processing parameters (temperature, time, and environment) and can be readily tuned and optimized for a wide range of applications. The printed amorphous glass shows good structural stability with band gap of 3 eV, Urbach energy of 0.75 eV and refractive index of 2.14 for 8% Ce-doped glass, respectively. These results indicate Ce-doped glass fabricated by stereolithography is suitable for scintillator applications and that additive manufacturing could be promising for borosilicate glass fabrication. [ABSTRACT FROM AUTHOR]

X-ray luminescence tomography (XLT) detects X-ray scintillators contrast agents using a focused or collimated X-ray beam to provide high spatial resolution excitation through thick tissue. The approach requires bright nanophosphors that are either synthesized or purchased. However, currently available commercial nanophosphors are mostly composed of a polydisperse mixture of several micro- to nano-sized particles that are unsuitable for biomedical imaging applications because of their size and aggregated form. Here, we demonstrate a fast and robust method to obtain uniform nano to submicron phosphor particles from a commercial source of polydisperse Eu- and Tb-doped Gd2O2S particles by separating the smaller particles present using gravitational and centrifugal sedimentation. In contrast to ball milling for 15–60 min, which drastically degraded the particles' brightness while reducing their size, our sedimentation method enabled the extraction of comparatively bright nanophosphors (≈100–300 nm in size) with a luminescence intensity of ≈10–20% of the several micron particles in the sample. Moreover, if scale up for higher yielding is required, the sedimentation process can be accelerated using fixed-angle and/or swinging bucket rotating centrifugation. Finally, after separation and characterization, nano and submicron phosphors were suspended and imaged through 5 mm thick porcine tissue using our in-house-built scanning X-ray induced luminescence chemical imaging (XELCI) system. [ABSTRACT FROM AUTHOR]