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0D organic metal halide hybrids (OMHHs) have recently emerged as a new generation of scintillation materials, due to their high luminescence quantum efficiency, sensitivity, stability, and cost‐effectiveness. While numerous 0D OMHH scintillators have been developed to date, most of them are based on solution grown single crystals that require time‐consuming synthesis and are limited in size. Here, high‐performance X‐ray scintillators based on facile solution processed 0D OMHH amorphous films are reported for the first time. By reacting triphenyl(9‐phenyl‐9H‐carbazol‐3‐yl) phosphonium bromide (TPPcarzBr) with manganese bromide (MnBr2), 0D (TPPcarz)₂MnBr₄ amorphous films can be prepared via solution processing with mild thermal annealing, which exhibits green photoluminescence with an emission maximum ≈517 nm and a photoluminescence quantum efficiency of ≈87%. The X‐ray scintillation of 0D (TPPcarz)₂MnBr₄ amorphous films is characterized to exhibit a light yield of 44600 photon MeV−1 and an outstanding linearity with a low limit of detection of 32.42 nGyairs−1 over a wide range of X‐ray dose rates. The versatile processability of 0D (TPPcarz)₂MnBr₄ is illustrated with remarkable recyclability, high cost‐effectiveness, and scalability for large‐scale production. By taking advantage of the amorphous nature of newly designed OMHHs, the approach opens up new opportunities for developing high‐performance, solution‐processable scintillators. [ABSTRACT FROM AUTHOR]

Scintillators have been widely used for high‐energy radiation imaging. It is in great demand and challenge to develop scintillator materials with fast decay time, high scintillation light yield, and low detection limit for high‐resolution imaging applications such as time‐of‐flight positron emission tomography. However, it is still a challenge to develop the ultrafast carrier dynamics to achieve 100% ultrafast decay time with high scintillation light yield. To meet the demand, a series of component‐tunable Cs2ZnCl4: x%Zr single crystals as promising ultrafast scintillators is successfully developed. With 8% of Zr‐dopant (Cs2ZnCl4: 8%Zr), the single crystal exhibits high light yield (28000 photons MeV−1) and low detection limit (51 nGy s−1) under X‐ray excitation. Photo‐induced transient absorption signals on sub‐nanosecond and nanosecond scales ensure almost 100% fast decay time (≈3 ns) in nanoseconds under γ‐ray excitation. In particular, the different radiative transition processes are achieved under ultraviolet and high‐energy radiation due to the tunable carrier dynamics from the shallow trapped state to the self‐trapped exciton (STE) state. [ABSTRACT FROM AUTHOR]

The current mainstream planar X‐ray imaging techniques face significant challenges for accurately capturing the internal structure of curved objects, since the variable distances between the curved objects and the flat‐panel scintillation screen cannot eliminate the distortion in X‐ray imaging. Though large‐area and transparent curved scintillation screens are much more desirable. Here, organic–inorganic hybrid Mn‐based single crystals ([CH3Ph3P]2MnX4, X = Cl, Br, I) exhibiting high photoluminescence quantum yield (PLQY) and low melting temperature have been employed to prepare transparent glass for X‐ray scintillation imaging application through a low‐temperature melting strategy. The [CH3Ph3P]2MnBr4‐glass shows high PLQY (47.8%), high‐resolution X‐ray imaging performance (12.3 lp mm−1), low limit of detection (25.33 nGy s−1), and impressive X‐ray irradiation stability (102 Gy). Furthermore, high‐contrast X‐ray imaging at a low dose (6.865 µGy per exposure, 14.5 times lower than the chest radiograph) is achieved. Based on the low glass transition temperature (Tg = 53.6 °C) and easy‐shapeable properties of [CH3Ph3P]2MnBr4‐glass scintillator, the large‐area curved scintillation screen with a series of sizes of Φ 2×4 – Φ 8×4 cm2 can be easily fabricated and show high X‐ray imaging quality. These findings provide a paradigm for future research in shapeable X‐ray scintillators, unlocking new possibilities for curved and 3D X‐ray imaging. [ABSTRACT FROM AUTHOR]

Ce‐doped Cs2LiLaBr6 (CLLB) scintillator crystals, known for their superior neutron/gamma dual‐mode detection capability and exceptional scintillation properties, have garnered significant attention for both fundamental science and practical applications. The role of Ce3+ cations as luminescent centers is pivotal, influencing the scintillation properties as their concentration varies. While the effects of Ce3+ concentration on scintillation performance are well‐documented, the ramifications for crystalline structure remain less explored. In this study, high‐quality CLLB:Ce single crystals are fabricated(atomic packing factor of maximum doped Ce is 0.04%) using the vertical Bridgman (VB) method and subsequently characterized their crystalline structure by neutron diffraction, X‐ray diffraction (XRD), and elemental analysis. The findings reveal a correlation between Ce3+ concentration and the crystal cell parameters, presenting intriguing deviations from Vegard's law. Such observations suggest the potential presence of alternative defects, potentially Li+ interstitials, in CLLB:Ce. This work offers critical insights for advancing the understanding and optimization of CLLB:Ce scintillators. [ABSTRACT FROM AUTHOR]

Background: A CZT (cadmium zinc telluride) PET (positron emission tomography) system is being developed at Stanford University. CZT has the promise of outperforming scintillator‐based systems in energy and spatial resolution but has relatively poor coincidence timing resolution. Purpose: To supplement GATE (GEANT 4 Application for Emission Tomography) simulations with charge transport and electronics modeling for a high‐resolution CZT PET system. Methods: A conventional GATE simulation was supplemented with electron‐hole transport modeling and experimentally measured single detector energy resolution to improve the system‐level understanding of a CZT high‐resolution PET system in development at Stanford University. The modeling used GATE hits data and applied charge transport in the crystal and RC‐CR processing of the simulated signals to model the electronics, including leading‐edge discriminators and peak pick‐off. Depth correction was also performed on the simulation data. Experimentally acquired data were used to determine energy resolution parameters and were compared to simulation data. Results: The distributions of the coincidence timing, anode energy, and cathode energy are consistent with experimental data. Numerically, the simulation achieved 153 ns FWHM coincidence time resolution (CTR), which is of the same order of magnitude as the raw 210 ns CTR previously found experimentally. Further, the anode energy resolution was found to be 5.9% FWHM (full width at half maximum) at 511 keV in the simulation, which is between the experimental value found for a single crystal of 3% and the value found for the dual‐panel setup of 8.02%, after depth correction. Conclusions: Developing this advanced simulation improves upon the limitations of GATE for modeling semiconductor PET systems and provides a means for deeper analysis of the coincidence timing resolution and other complementary electron‐hole dependent system parameters. [ABSTRACT FROM AUTHOR]

The urgency for cost‐effective, high‐resolution, flexible X‐ray imaging detectors is generating great demand for scintillators with low‐temperature processability, high scintillation yield, and negligible afterglow. X‐ray imaging materials are currently dominated by inorganic scintillators in the form of rigid films and bulk crystals, which have inherent limitations including high‐temperature, complex synthesis, and considerable challenges toward advanced nonplanar imaging. Here, high‐performance and flexible X‐ray scintillators based on novel zero‐dimensional (0D) (BTPP)2MnX4 (BTPP = benzyltriphenylphosphonium; X = Cl, Br) halides are reported. They emit bright green light originating from the 4T1‐6A1 transition of Mn2+ under X‐ray excitation. In particular, (BTPP)2MnBr4 single crystals exhibit excellent air‐ and radiation‐stability, a high scintillation yield of 53 000 photons MeV−1, a low detection limit of 89.9 nGyair s−1, and an ultralow afterglow comparable to commercial Bi4Ge3O12 (BGO) single crystals. Moreover, the (BTPP)2MnCl4@polydimethylsiloxane (PDMS) flexible scintillation screens achieve a high spatial resolution of 14.1 lp mm−1 and realize high‐quality imaging results of nonplanar objects. This study demonstrates that the flexible scintillation screens based on low‐dimensional Mn(II) hybrid halides have significant potential for low‐dose and high‐resolution X‐ray imaging applications. [ABSTRACT FROM AUTHOR]

This article details work performed on the synthesis and characterization of an inorganic mixed‐cation double halide perovskite, Cs2Ag.6Na.4In.85Bi.15Cl6 (CANIBIC). Single crystals have been created via a hydrothermal reaction, milled into a powder, and pressed into pellets, while nanocrystals have been directly synthesized via mechanosynthesis. A computational model is constructed to predict the X‐ray diffraction pattern of CANIBIC; this model aligns very well with the X‐ray diffraction pattern measured for CANIBIC crystal powder. This model can therefore be developed in the future as a tool to predict lattice parameters and crystal structures of other novel double‐halide perovskites. Photoluminescence spectra obtained from each format show broad emission centered at 630 nm, as is typical for self‐trapped exciton emission; self‐trapped exciton emission is also confirmed by investigating photoluminescence intensity as a function of laser power. Nanocomposites are produced via the loading of nanocrystals of CANIBIC into PMMA. Although nanocomposite disks consisting of a small proportion of CANIBIC nanocrystals in PMMA have a smaller mass attenuation coefficient than a pressed pellet of CANIBIC, these disks have comparatively bright radioluminescence due to their optical transparency. These nanocomposite disks are therefore a particularly useful format for the practical use of the CANIBIC scintillator. [ABSTRACT FROM AUTHOR]

Metal‐halide perovskites have emerged as one of the most promising contenders for the next‐generation X‐ray scintillators on account of their large absorption coefficients, high light yields, and low‐cost fabrication. However, the existing X‐ray scintillators are plagued either by poor stability or high toxicity. Here, highly stable and flexible CsCu2I3@polymethyl methacrylate (PMMA) composite films are fabricated simply by a facile one‐step drop‐coating technique. Benefiting from the reasonable light yields (24 100 photons MeV−1), short photoluminescence decay time (207 ns), and flat surface, a low detection limit of 39 nGyair s−1 and a record‐high resolution of up to 25 lp mm−1 are demonstrated in these CsCu2I3@PMMA composite films. The X‐ray imaging tests show that the CsCu2I3@PMMA composite films display excellent properties in the dynamic and irregular objects imaging. In addition, the CsCu2I3@PMMA composite films exhibit a desirable endurance to the high‐energy X‐ray's irradiation and the water erosion (photoluminescence quantum yield remains up of 90% of its initial value even after submersion in water for 300 h). This work provides a potential to develop eco‐friendly and highly stable halide perovskite materials for high‐resolution X‐ray imaging. [ABSTRACT FROM AUTHOR]

Metal halide crystals are bright but hygroscopic scintillator materials that are widely used in X‐ray imaging and detectors. Precipitating them in situ in glass to form glass ceramics (GCs) scintillator offers an efficient avenue for large‐scale preparation, high spatial resolution, and excellent stability. However, precipitating a high fraction of metal halide nanocrystals in glass to maintain high light yield remains a challenge. Herein, an ionic‐covalent hybrid network strategy for constructing GCs scintillator with high crystallinity (up to ≈37%) of BaCl2: Eu2+ nanocrystals is presented. Experimental data and simulations of glass structure reveal that the Ba2+‐Cl− clustering promotes the high crystallization of BaCl2 nanocrystals. The ultralow phonon energy (≈200 cm−1) of BaCl2 nanocrystals and good Eu reduction effect enable high photoluminescence inter quantum efficiency (≈80.41%) in GC. GCs with varied crystallinity of BaCl2: Eu2+ nanocrystals demonstrate efficient radioluminescence and tunable scintillator performance. They either outperform Bi4Ge3O14 single crystal by over 132% steady‐state light yield or provide impressive X‐ray imaging resolutions of 20 lp mm−1. These findings provide a new design strategy for developing bright transparent GCs scintillators with a high fraction of metal halide nanocrystals for X‐ray high‐resolution imaging applications. [ABSTRACT FROM AUTHOR]

In this study, a new Cs4SrI6:Yb2+,Sm2+ near‐infrared (NIR) emitting scintillator was developed using sensitization strategy. It was found that Yb2+ sensitization significantly enhances the NIR radioluminescence (RL) of Sm2+, providing a new approach of designing highly emissive sensitized NIR scintillators. By studying the optical spectra and decay kinetics of Cs4SrI6:Yb2+,Sm2+, it was revealed that the energy transfer pathways involve both radiative and nonradiative processes. The gamma spectroscopy performance of Cs4SrI6:Yb2+,Sm2+ single crystals was studied by using the high‐quantum‐efficiency avalanche photodiode (APD) as the readout. Our results highlight the importance of using sensitization strategy of achieving NIR emitting scintillators and demonstrate the significant potential for radiation detection applications. [ABSTRACT FROM AUTHOR]

Low‐dimensional copper‐based halide single crystals are considered excellent scintillators for indirect X‐ray detection, but their potential in direct X‐ray detection has not been investigated. Herein, high‐quality pure Cs3Cu2I5 and Li‐doped Cs3Cu2I5:Li single crystals are grown by the Bridgman method. The Li+ dopant enhances the photoelectric properties of the Cs3Cu2I5 single crystal by extending the carrier lifetime, improving the carrier mobility from 6.49 to 9.52 cm2 V−1 s−1, and increasing the mobility‐lifetime (µτ) product from 1.4 × 10−4 to 2.9 × 10−4 cm2 V−1. The sensitive direct X‐ray detector with a vertical device configuration of Au/Cs3Cu2I5:Li single crystal/PCBM/Au is fabricated and demonstrated to have a high sensitivity of 831.1 µC Gyair−1 cm−2 and low detection limit of 34.8 nGyair s−1. Furthermore, the detector shows negligible baseline current drift and excellent stability upon X‐ray radiation. [ABSTRACT FROM AUTHOR]

Scintillators, which can convert high‐energy ionizing radiation (e.g., X‐ or γ‐rays) into ultraviolet‐visible light, have been widely applied in medical and industrial fields. Developing new scintillation materials with high performance and low cost is very desirable in order to address the growing application demands. Among them, single‐crystal scintillators of organic‐inorganic hybrid metal halides (OIMHs) have attracted much attention because of their excellent optical transparency, suppressed light scattering, and facile solution preparation methods. Herein, three new centimeter‐sized (2‐DMAP)2MnX4 (2‐DMAP+ = 2‐dimethylaminopyridinium, X = Cl, Br, I) single crystals with high crystal quality are synthesized via the solvent evaporation method. Benefiting from the high optical transparency and remarkable luminescence property, (2‐DMAP)2MnBr4 delivers a high X‐ray light yield of 22 000 photons MeV−1, a low limit of detection of 9.50 nGy s−1, and an excellent X‐ray imaging spatial resolution of 20–25 lp mm−1. Moreover, the regulation of single‐crystal thickness from 0.31 mm to 3.03 mm can be easily achieved via a simple solution post‐treatment method, which has a significant influence on the transmittance, spatial imaging resolution, and detection limit. This work demonstrates a promising single‐crystal scintillator for the application of high‐resolution X‐ray imaging with low preparation cost and tunable thickness. [ABSTRACT FROM AUTHOR]

Organic–inorganic halide perovskite single crystals (SCs) are promising materials for detecting ionizing radiation owing to their outstanding photoelectric conversion capability and inexpensive solution processability. However, the accuracy and stability of the detectors have been limited due to the charge traps and defects in SCs, especially when operated under high‐precision photon‐counting mode for energy spectrum acquisition. Here, we proposed a trap freezing deactivation route, which obviously suppressed dark current and noise by up to 97% and 92%, respectively. Furthermore, the bulk ion migration effect was essential for the ability to instantly self‐heal defects induced by radiation damage at temperatures down to −30°C. Consequently, the detector exhibits a record high energy resolution of 7.5% at 59.5 keV for 241Am γ‐ray source, which is the best solution‐processed semiconductor radiation detectors at the same energy range. In addition, the detector maintains over 90% of its initial performance after 9 months of storage when tested in the air. Our results will represent a revision of the paradigm that high‐spectral‐resolution and robust radiation detectors can only be realized with high temperature grown inorganic semiconductor single crystals. [ABSTRACT FROM AUTHOR]

Metal‐halide perovskites, especially for 3D halide perovskite single crystals (SCs), are emerging as the promising scintillators. However, the strong self‐absorption and low light yield of these perovskites restrict their practical applications. Quantum cutting can convert a high energy photon into multiple low energy photons, endowing a large Stokes shift and high photoluminescent quantum yield (PLQY). Here, this work reports a novel quantum cutting material, CsPbClxBr3−x:Yb3+ perovskite SCs, with the PLQY of 149% and a Stokes shift >550 nm, successfully conquering the issues of poor PLQY induced by the thermal quenching and the large self‐absorption in perovskite SCs. Benefiting from the extremely high PLQY and negligible self‐absorption effect, the first high‐performance quantum cutting scintillators based on CsPbClxBr3−x:Yb3+ perovskite SCs are developed, exhibiting high transmittance, large X‐ray absorption/conversion efficiency, outstanding light yield of ≈1.12 × 105 photons MeV−1, and a detection limit as low as 176.5 nGyair s−1. Finally, a single‐pixel X‐ray imaging is achieved by integrating CsPbCl3:Yb3+ SCs with silicon photomultiplier. This work sheds light on exploring highly competitive scintillators beyond the scope of traditional perovskites. [ABSTRACT FROM AUTHOR]

Organic–inorganic hybrid copper(I)‐based halides have attracted great interest in the field of optoelectronics due to their low cost, non‐toxicity, large Stokes shift, and high photoluminescence quantum yields (PLQYs). Here, bulk zero‐dimensional (0D) organic‐inorganic hybrid copper(I)‐based (R,S‐2‐mpip)2Cu2I6 (mpip = methylpiperazinium, C5H14N22+) single crystals have been grown with equal stoichiometric ratios of R‐ and S‐2‐mpip ligands by chirality–racemization strategy for the first time. Interestingly, (R,S‐2‐mpip)2Cu2I6 single crystals exhibit strong blue–green photoluminescence (PL) located at 520 nm with large Stokes shift of about 230 nm and high PLQY of about 65.96%, which originates from self‐trapped excitons (STEs). More importantly, (R,S‐2‐mpip)2Cu2I6 single crystals also exhibit the strong radioluminescence (RL) at 520 nm, the fast X‐ray scintillation response with a light yield of about 47 000 photon MeV−1 and low detection limit of 6.48 nGyairs−1 when exposed to X‐ray irradiation condition, which is superior to that of other copper(I) iodide‐based hybrids. Based on the excellent characteristics, X‐ray imaging systems based on (R,S‐2‐mpip)2Cu2I6 single crystals exhibit the clear images of "QFNU" logo and crystal symbol pattern. This work not only deepens the understandings of material design and fundamental properties of these racemate systems, but also provides guidance for the further applications in the multi‐functional optoelectronics. [ABSTRACT FROM AUTHOR]

All‐inorganic halide perovskites appear as a promising class of scintillators for radiation detection applications due to their excellent optoelectronic properties. Herein, a self‐activated perovskite CsEuBr3 single crystal is developed as an efficient X‐ and γ‐ray scintillator. Single crystals of CsEuBr3 are grown by the Bridgman method. The phase structure, stability, photophysics properties, and scintillation performance of CsEuBr3 single crystals are studied. Under X‐ray irradiation, its emission peaks at 445 and 510 nm, associated with Eu2+ 5d–4f and defect‐related emission, respectively, are studied. Under 137Cs gamma irradiation, it has a decent light yield of 22 000 ± 2000 photons MeV−1 and an energy resolution of 6.2 ± 0.4% at 662 keV with a scintillation decay of 510 ns. [ABSTRACT FROM AUTHOR]

X‐Ray‐induced luminescence behavior of Si/Ge‐doped GaN single crystals is observed and analyzed in combination with undoped GaN. Similarities between radioluminescence (RL) and photoluminescence (PL) indicate an analogous physical process. Under X‐Ray irradiation, the gallium nitride (GaN) single crystals doped with Si/Ge elements intensely emit tunable visible light ranging from 1.8 to 2.2 eV, and an ultraviolet (UV) emission of ≈3.3 eV is aroused by the intrinsic direct band‐edge transition of GaN. Due to the difference in the physical properties of excitation source and the self‐absorption effect, the UV signal in RL has a dramatic reduction (especially for undoped GaN) and redshift, which is also considered to be the obvious difference between the two spectra. RL results obtained herein along with PL demonstrate that the visible luminescence of Si/Ge‐doped GaN is mainly attributed to DAP or/and e‐A recombination, which is supported by density functional theory (DFT) calculations. [ABSTRACT FROM AUTHOR]

Anti‐counterfeiting has become a serious issue around the global world; fluorescence‐based tags are praised for the low‐cost and facile decryption process. However, the high‐level anti‐counterfeiting application requires incorporating multifunctional luminescent materials with response to different excitation sources. Herein, a dimeric Cu(I)‐halide‐clusters‐assembled single‐crystal (AEP)2Cu2I6·2I·2H2O (AEP = N‐aminoethylpiperazinium) concerning a high down‐conversion photoluminescence quantum yield (PLQY) value of near unity is reported (λex = 305 nm), which can also be activated by the near‐infrared light and X‐ray. The ultrafast spectroscopy and density functional theory calculations reveal that the broad‐band emission originates from the recombination of self‐trapped excitons. Remarkably, the high PLQY and excellent attenuation capability for X‐ray confers an outstanding light yield of 55 650 photons MeV−1 to (AEP)2Cu2I6·2I·2H2O, which is 5.25 times higher than the standard bismuth germaniumoxide scintillator. Such multi‐light‐stimulus response endows (AEP)2Cu2I6·2I·2H2O with great application potential in anti‐counterfeiting, solid‐state lighting devices, and digital radiography. [ABSTRACT FROM AUTHOR]

Corundum (α‐Al2O3) is a technologically important material and, in particular, widely used in optical applications such as luminescent radiation dosimeters, cryogenic scintillators, and is being considered as a promising candidate for windows in future fusion reactors. Its optical and mechanical properties are controlled by the presence of radiation‐induced (in particular, by fast neutrons) defects. Herein, the thermal stability and recombination kinetics of primary anion Frenkel defects—the F and F+ electronic centers and oxygen interstitials—in fast‐neutron‐irradiated α‐Al2O3 single crystals are analyzed. Theory is developed considering the formation of both neutral and charged oxygen Frenkel defect pairs; defect migration, interaction and recombination. Based on ab initio calculations and new theoretical kinetics analysis, for the first time, a coexistence is demonstrated, in comparable concentrations, of two interstitial types—neutral O atoms and negatively charged O− ions (with attributed optical absorption band maxima at 6.5 eV and 5.6 eV, respectively); and their diffusion parameters, necessary for the prediction of secondary defect‐induced reactions and defect/material thermal stability, are obtained. [ABSTRACT FROM AUTHOR]

Low‐dimensional organic–inorganic hybrids have emerged as promising X‐ray scintillators due to efficient radioluminescence properties. Herein, stable and efficient X‐ray scintillator based on 0D (C40H38P2)MnBr4 hybrid single crystals grown by a facile solution‐processing method is reported. Its crystal structure is determined to be triclinic with P1¯ space group. It has good stability against moisture and irradiation. (C40H38P2)MnBr4 with tetrahedrally coordinated Mn2+ exhibits green emission peaking at 518 nm originating from d–d 4T1→6A1 transition of Mn2+ ion with a high photoluminescence quantum yield (PLQY) of 74.2%. Under X‐ray excitation, it shows high scintillation yield of 32 000 photons MeV−1, a decent detection limit of 288 nGyair s−1, and a low afterglow comparable to that of Bi4Ge3O12 (BGO). [ABSTRACT FROM AUTHOR]

Low‐dimensional perovskite halides have shown a great potential as X‐ray detection materials because of efficient exciton emissions originating from strongly spatially localized charge carriers. Nonetheless, most of them have a scintillation yield far below their theoretical limits. Here, it is found that the harvesting efficiency of produced charge carriers can be significantly enhanced via a small amount of In+ doping in these highly localized structures. A bright and sensitive zero‐dimensional Cs3Cu2I5:In+ halide with efficient and tunable dual emission is reported. The radioluminescence emission of Cs3Cu2I5:In+ crystals under X‐ray excitation consists of a self‐trapped exciton emission at 460 nm and an In+‐related emission at 620 nm at room temperature. In+ doping enhances the photoluminescence quantum efficiency (PLQY) of Cs3Cu2I5 from 68.1% to 88.4%. Benefiting from the higher PLQY, Cs3Cu2I5:In+ can achieve an excellent X‐ray detection limit of 96.2 nGyair s−1, and a superior scintillation yield of 53 000 photons per MeV, which is comparable to commercial CsI:Tl single crystals. As a result, a remarkable X‐ray imaging resolution of 18 line pairs mm–1 is demonstrated, which is so far a record resolution for single crystal perovskite‐based flat‐panel detectors. These results highlight the importance of efficient harvesting of carriers (and excitons) in low‐dimensional perovskites for radiation detection applications. [ABSTRACT FROM AUTHOR]

Europium-doped lutetium oxide (Lu2O3:Eu) single crystal is grown by vertical Bridgman method for the first time. Correlated measurements of X-ray diffraction, X-ray fluorescence spectra, optical transmittance, photoluminescence excitation, photoluminescence (PL), PL decay, and X-ray excited luminescence (XEL) spectra are performed. The transmittance of about 80% above 300 nm indicates that the crystal is of good optical quality. By measuring actual Eu3+ concentration, the effective segregation coefficient of Eu3+ in the Lu2O3:Eu crystal is calculated to be 0.75. In the PL spectrum, the dominant emission peaks at 612 and 630 nm originate from the 5D0→7F2 transitions of Eu3+ in C2 site. It is worth mentioning that several emission peaks between 575 and 605 nm mainly ascribe to the transitions of different 5D0 levels to the split 7F1 levels of Eu(C2) or Eu(C3i). PL decay spectra indicate the decay time of 612 nm emission can be determined about 1.0 ms. The decay curve of 582.6 nm emission can be fitted into triple components, and the 5.3 and 1.4 ms components are attributed to Eu3+(C3i) and Eu3+(C2), respectively. The XEL strongest emission of Lu2O3:Eu sample is around 612 nm with a bright red luminescence that matches silicon photodetectors sensitivity. [ABSTRACT FROM AUTHOR]

Lithium iodides are very efficient single‐crystal scintillators for thermal neutron detection. Doping with silver, as activator ions, has shown to improve its limitation of discriminating gamma background by introducing pulse shape discrimination ability. To improve the scintillation performance, single crystals of LiI:Ag, codoped with different concentration of Sr ions, are grown and characterized in details. A systematic investigation of radioluminescence, thermoluminescence, and scintillation properties along with the decay kinetics provides better understanding about the role of defect structure in scintillation mechanism. The extra charge, provided by Sr2+ ions, is found to alter the defect structure with relative reduction of the contribution from the deeper trap centers in comparison with the shallow traps. Consequently, it leads to a significant improvement of light yield quenching under higher excitation density of charged particle irradiation. The 0.1% Sr codoped crystals provide a better discrimination ability of neutron and gamma radiations for simultaneous detection. [ABSTRACT FROM AUTHOR]

The luminescent property of 2D perovskite materials promotes their applications in light emitting diodes, phosphor powders, and scintillators. Recently, an interesting extrinsic low‐energy broadband luminescence is hotly investigated. However, the understanding of such emissions is still at the early stage. In this study, based on a modified solvent evaporation method, centimeter‐size (BDA)PbI4 (BDA = NH3C4H8NH32+) single crystals are grown which, besides the band–band emission, show a large Stokes‐shifted broadband luminescence. We find such emission can be effectively excited by sub‐gap photons and conclude defects‐induced shallow traps are the corresponding luminescence centers. Density functional theory (DFT) calculations indicate that in‐plane iodine vacancies can introduce shallow electron traps in the band gap and give rise to the broadband emission. [ABSTRACT FROM AUTHOR]

The high‐profile candidacy of low‐dimensional metal‐halide single crystals as promising light emitters originates from the intriguing emission properties (e.g., extremely broad luminescence spectra, large Stokes shift, high color rendition), which have enabled the recent great achievements on their application in lighting, artificial illumination, and scintillators. Among the family of low‐dimensional metal‐halide single crystals, zero‐dimensional (0D) materials have been featured in the lowest dimensionality, and as a consequence, strongest quantum confinement, softest lattice, and strongest electron–phonon coupling have been further translated into near‐unity photoluminescence (PL) efficiency with broadband emission. However, as far as it is known, 0D structures are significantly underexplored. Herein, an overview is provided on recent advances of 0D metal‐halide single crystals, with a focus on comprehensive understanding and insightful perspectives behind the photophysical mechanism. Additionally, the challenges and future opportunities currently faced by 0D bulk metal halides are discussed in order to provide a roadmap for the future development of novel materials with versatile optical properties suited for practical applications. [ABSTRACT FROM AUTHOR]

Single crystal scintillators have become one of the most common materials used in technologies that use radiation detectors. Unfortunately, as technology demands improved detectors, research into better single crystal scintillators has nearly reached its limit. Ceramics provide many benefits over single crystal scintillators and have emerged as a promising new production process. Recent research into ceramic scintillators has mostly dealt with oxides as they are relatively easy to handle and are typically non‐hygroscopic. Among single crystal scintillators, a trend has emerged indicating that the addition of halide ions into the crystal structure improves the light yield and energy resolution of the scintillation material but also tends to make the material hygroscopic and in some cases intrinsically radioactive. Little research is devoted to the investigation of undoped halide ceramic scintillators. Transparent halide Cs2HfCl6 ceramics are developed by hot uniaxial pressing, and the scintillation properties are compared to that of its single crystal counterpart. The energy resolution of the ceramic is found to be 6.4% at 662 keV. The initial results indicate that ceramic scintillators are a viable alternative and a promising new direction in scintillator material technology. [ABSTRACT FROM AUTHOR]

Large‐sized Gd3Al2.3Ga2.7O12:Ce single crystals are grown by the Czochralski method. The distribution of Al and Ga at octahedral (oct‐, 6‐oxygen‐coordinated) and tetrahedral (tet‐, 4‐oxygen‐coordinated) sites in the crystal is studied. Rietveld refinement is used to analyze the site occupation of Al and Ga. The results show that Ga ions with a larger radius than Al ions prefer to occupy the more compact tetrahedral sites. Density functional theory calculations show that the energy for a Ga ion at the tetrahedral site is lower than that at the octahedral site in the Gd3Al5O12 crystal, whereas the case for Al occupation in the Gd3Ga5O12 crystal is opposite. Slater rules are used to estimate the effective charge number of different ions, and the distribution of coordination ions around the octahedral and tetrahedral sites is analyzed. Then, the interaction between ions is simplified and the repulsive energy between Al/Ga and the coordination ions is calculated, which could provide reasonable understanding on the abnormal occupation. In addition, the occupation of Sc in Gd/Y garnet systems is also discussed using this method. [ABSTRACT FROM AUTHOR]

Low‐dimensional halide perovskites with excellent luminescent properties have become leading candidates for optoelectronic and radiation‐detection applications. In this work, Tl cation is incorporated into 0D perovskite Cs3Cu2I5 host and an ultrabright and efficient scintillator is developed for X‐ray and γ‐ray detection. The Tl‐doped Cs3Cu2I5 crystals exhibit a high photoluminescence quantum efficiency of 79.2%. The radioluminescence emission of Cs3Cu2I5:Tl crystal under X‐ray excitation consists of a self‐trapped exciton emission at 440 nm and a Tl‐related emission at 510 nm at room temperature. With optimized Tl doping, the Cs3Cu2I5 not only demonstrates about five‐times enhanced steady‐state scintillation yield up to 150 000 photons/MeV and an improvement of X‐ray detection limit from 103.6 to 66.3 nGy s−1, but also maintains an extremely low afterglow of 0.17% at 10 ms after X‐ray cut‐off. The Cs3Cu2I5:Tl also possess a remarkable energy resolution of 3.4% at 662 keV and an ultrahigh light yield of 87 000 photons/MeV under 137Cs γ‐ray radiation. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study is to perform three‐dimensional (3D) source position reconstruction by combining in vivo dosimetry measurements from two independent detector systems. Methods: Time‐resolved dosimetry was performed in a water phantom during HDR brachytherapy irradiation with 192Ir source using two detector systems. The first was based on three plastic scintillator detectors and the second on a single inorganic crystal (CsI:Tl). Brachytherapy treatments were simulated in water under TG‐43U1 conditions, including a HDR prostate plan. Treatment needles were placed in distances covering a range of source movement of 120 mm around the detectors. The distance from each dwell position to each scintillator was determined based on the measured dose rates. The three distances given by the mPSD were recalculated to a position along the catheter (z) and a distance radially away from the mPSD (xy) for each dwell position (a circumference around the mPSD). The source x, y, and z coordinates were derived from the intersection of the mPSD's circumference with the sphere around the ISD based on the distance to this detector. We evaluated the accuracy of the source position reconstruction as a function of the distance to the source, the most likely location for detector positioning within a prostate volume, as well as the capacity to detect positioning errors. Results: Approximately 4000 source dwell positions were tracked for eight different HDR plans. An intersection of the mPSD torus and the ISD sphere was observed in 77.2% of the dwell positions, assuming no uncertainty in the dose rate determined distance. This increased to 100% if 1σ search regions were added. However, only 73(96)% of the expected dwell positions were found within the intersection band for 1(2) σ uncertainties. The agreement between the source's reconstructed and expected positions was within 3 mm for a range of distances to the source up to 50 mm. The experiments on a HDR prostate plan, showed that by having at least one of the detectors located in the middle of the prostate volume, reduces the measurement deviations considerably compared to scenarios where the detectors were located outside of the prostate volume. The analysis showed a detection probability that, in most cases, is far from the random detection threshold. Errors of 1(2) mm can be detected in ranges of 5–25 (25–50) mm from the source, with a true detection probability rate higher than 80%, while the false probability rate is kept below 20%. Conclusions: By combining two detector responses, we enabled the determination of the absolute source coordinates. The combination of the mPSD and the ISD in vivo dosimetry constitutes a promising alternative for real‐time 3D source tracking in HDR brachytherapy. [ABSTRACT FROM AUTHOR]

Herein, optical‐quality single crystals of yttrium aluminum garnet (YAG):Ce,Ca,Li are grown by the vertical Bridgman method. Substitution and charge compensation mechanisms of Li+ are considered based on optical absorption in as‐grown and γ‐ray‐irradiated single crystals and their luminescence decay and rise time under X‐ray excitation. The measurements are conducted on single crystals with impurity concentrations varying over a wide range. A suitable combination of Ca and Li concentration is able to control the cerium valence, which plays a major role in the time response under ionizing radiation. [ABSTRACT FROM AUTHOR]

Low‐dimensional halide perovskites with highly efficient luminescent properties have attracted huge attention in optoelectronic and radiation detection applications in recent years. Herein, a highly efficient 0D Cs3Cu2I5 perovskite crystal is presented for X‐ray and γ‐ray detection that can be easily grown from the melt by the Bridgman method. The crystal structure of Cs3Cu2I5 belongs to an orthorhombic system with a space group of Pnma. The Cs3Cu2I5 crystal is nonhygroscopic and self‐absorption free due to a large Stokes shift of 120 nm originated from its self‐trapped exciton emission. Its scintillation emission centers at 440 nm with a principal decay time of 967 ns. The Cs3Cu2I5 crystal not only demonstrates a high scintillation yield of about 32 000 photons MeV−1 and an extremely low afterglow of 0.03% at 10 ms under X‐ray radiation, but also possesses a high light yield of 29 000 photons MeV−1 with an excellent energy resolution of 3.4% at 662 keV under γ‐ray radiation. [ABSTRACT FROM AUTHOR]

This research deals with a novel approach for the self‐flux growth of Tb3Al5O12:Ce single crystal using the micro‐pulling‐down method. The self‐flux method enables the fabrication of the crystals with excellent photoconversion and scintillation properties. Tb3Al5O12:Ce (TbAG:Ce) efficiently converts the blue light‐emitting diode (LED) radiation into bright white light. The gradual change of crystal thicknesses (0.2–1 mm) allows for tuning white light temperature from cold to neutral white. The scintillation response is comparable with that of a high‐quality single crystalline film counterpart with a light yield value of around 4500 photons MeV−1 under α particle excitation from 239 Pu radioisotope. This is the highest value obtained for the TbAG:Ce crystal yet. [ABSTRACT FROM AUTHOR]

Pioneered by our group, thallium (Tl)‐based inorganic halide single‐crystals are potential new scintillators. Most of these scintillators exhibit excellent scintillation performance, including peak emission between 370 and 450 nm, good energy resolutions, high light yield (more than 50 000 ph MeV‐1) and fast decay‐time (less than 40 ns). In addition, these scintillators demonstrate good pulse shape discrimination capability. The grown pure crystals show strong luminescence and high light yields due to the presence of Tl ion in the host lattice. Thanks to the high Z‐number and density of the Tl, the grown scintillators have high density (ρ > 4 g cm−3) and high effective Z‐number (Zeff ≥ 60). Being hygroscopic, like other halide scintillators, these single crystals are grown by the Bridgman technique. It is expected that the discovered scintillators will perform better than most commercial scintillators used in different applications. Significant improvement in the scintillation properties are achieved with the modification of the crystal growth procedure of the grown scintillators. Preliminary results revealed that these scintillators are very promising from an application point of view, while further investigations are underway for the enhancement of the present scintillators as well as for the discovery of new compounds of this family. [ABSTRACT FROM AUTHOR]

Li+ codoping of Gd3(Ga, Al)5O12:Ce (GGAG:Ce) single crystals induces the acceleration of scintillation decay time. However, its effect on the scintillation properties of GGAG:Ce remains poorly understood. Herein, the relationship between Ce/Li concentration and scintillation properties is investigated. GGAG crystals with a range of Ce and Li concentrations are grown by the Czochralski method and the scintillation decay and light output of GGAG:Ce, Li are measured. The results show comparable or improved performance compared with conventional scintillators. In optical absorption and photoluminescence (PL) measurements, the conversion of the stable Ce3+ to Ce4+ is not observed in a clear manner in GGAG:Ce samples with variable Li concentration. Instead, some defect‐related absorption seems to appear. Temperature dependence of PL decay for samples with variable Ce concentration is also evaluated. A shift of the luminescence quenching temperature is observed for GGAG samples with >0.2% Ce. [ABSTRACT FROM AUTHOR]

Herein, the development of phosphor‐converted white light‐emitting diodes (pc‐WLED) and scintillators based on the crystals of Ce3+‐doped multicomponent garnets, grown by the micro‐pulling‐down (MPD) method is studied. The combined technique of the "bandgap engineering" and "positioning of Ce3+ 5d‐levels" is applied to the crystals of Gd3−xLuxAl5−yGayO12 (x = 0–1.5 and y = 2–3) mixed garnets for improving their color‐rending properties in pc‐WLEDs application as well as their scintillation figure of merit. The absorption, cathodoluminescence, photoluminescence, photoconversion (PC), and also the scintillation light yield and scintillation decay time measurements under excitation by α‐particles of 239Pu radioisotope are used for the characterization of the crystals. Among all the investigated garnet compounds, the best photoconverting properties are observed in Gd3−1.5Lu0−1.5Al5−yGayO12:Ce crystals at x = 0–1.5 and y = 2.5–3. Meanwhile, the best scintillation characteristics are found in Gd3−xLuxAl5−yGayO12 crystals at x = 0–1.5 and y = 2–2.5. [ABSTRACT FROM AUTHOR]

Indirect detection of X‐rays using single‐crystal scintillators is a common approach for high‐resolution X‐ray imaging. With the high X‐ray flux available from synchrotron sources and recent advances in high‐speed visible‐light cameras, these measurements are increasingly used to obtain time‐resolved images of dynamic phenomena. The X‐ray flux on the scintillator must, in many cases, be limited to avoid thermal damage and failure of the scintillator, which in turn limits the obtainable light levels from the scintillator. In this study, a transient one‐dimensional numerical simulation of the temperature and stresses within three common scintillator crystals (YAG, LuAG and LSO) used for high‐speed X‐ray imaging is presented. Various conditions of thermal loading and convective cooling are also presented. Numerical simulations have been performed in order to understand thermal loading of three common X‐ray scintillator materials. [ABSTRACT FROM AUTHOR]

Time‐resolved spectroscopic study of the photoluminescence response to femtosecond pulse excitation and free carrier absorption at different wavelengths, thermally stimulated luminescence measurements and investigation of differential absorption are applied to amend the available data on excitation transfer in GAGG:Ce scintillators, and an electronic energy‐level diagram in this single crystal is suggested to explain the influence of codoping with divalent Mg on luminescence kinetics and light yield. The conclusions are generalized by comparison of the influence of aliovalent doping in garnets (GAGG:Ce) and oxyorthosilicates (LSO:Ce and YSO:Ce). In both cases, the codoping facilitates the energy transfer to radiative Ce3+ centers, while the light yield is increased in the LYSO:Ce system but reduced in GAGG:Ce. [ABSTRACT FROM AUTHOR]

Single crystals of new scintillation materials ACaBr3:Eu2+ (A = K, Rb) were grown using the Bridgman-Stockbarger method. The luminescence spectra of RbCa1-xEuxBr3 crystals include a single band with a maximum which position shifts from 433 to 443 nm with the increase of mole fraction of Eu2+ from 0.005 to 0.08. The decay of the scintillation pulse can be described using single component and the decay time rises towards concentration of Eu2+ in crystals from 2.70 μs (x = 0.03) to 3.14 μs (x = 0.05). The relative light yield achieves 77 per cent vs. NaI:Tl for RbCa0.92Eu0.08Cl3 sample and the energy resolution is 8.2%. Comparing with the K-based analogs RbCa1-xEuxBr3 materials are more stable and they are considerably brighter scintillators than CsCa1-xEuxBr3. [ABSTRACT FROM AUTHOR]

Organic single crystals (OSCs) have ideal qualities (well defined structure and morphology, lack of grain boundaries, high purity, 3D long range order, good electronic transport properties) for several technological applications, in particular as key components for electronic devices. It is only recently that OSCs have been considered as ionizing radiation detectors, and the latest developments in this field are here reported. In the first section, various methods for OSC growth are described, with emphasis on cost-effective, solution-based approaches capable of delivering large volume, well performing crystals. The second section is focused on the use of solution-grown OSCs as scintillators (i.e., as high energy photon to UV-vis photon conversion), highlighting the ability of cm-scale OSCs to effectively detect neutrons and to carry out neutrons-gamma pulse-shape discrimination tasks. Finally, the third section describes the use of semiconducting, solution-grown OSCs as effective solid state direct detectors (i.e., directly converting high energy photons into charge carriers), evidencing extremely promising performances in terms of operability in environmental conditions (i.e., no need for encapsulation), radiation hardness, linear response and low operating voltage. [ABSTRACT FROM AUTHOR]

A novel approach is reported to minimize various defect centers in Ce doped Gd3Ga3Al2O12 single crystals to improve the scintillation properties. The crystals of Gd3Ga3Al2O12 codoped with 0.2 at% Ce and B (GGAG:Ce,B) have been grown in air and argon ambient using the Czochralski technique. The scintillation light output of crystals grown in Ar ambient was significantly increased after annealing the crystals in air. The measured light output of 60000 ph/MeV for annealed crystals is the highest value reported among this class of materials. As a consequence, the energy resolution at 662 keV gamma-rays from a 137Cs source was improved from 8% for the crystals grown in air to 6% for crystals grown in Ar and subsequently annealed in air. Further, the thermal quenching energy of photoluminescence (PL) emission was increased to be 470 meV for the annealed crystals. The thermoluminescence (TL) measurements suggest that the crystals grown in Ar ambient and post-growth annealed in air may have a lesser concentration of trap centers which subsequently lead to the improvement in optical and scintillation properties leading to a superior detector performance. (© 2015 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

In this review, the major achievements and research and development (R&D) trends from the last decade in the field of single crystal scintillator materials are described. Two material families are included, namely, those of halide and oxide compounds. In most cases, the host crystals are doped with Ce3+, Pr3+ or Eu2+ rare earth ions. Their spin‐ and parity‐allowed 5d–4f transitions enable a rapid scintillation response, on the order of tens to hundreds of nanoseconds. Technological recipes, extended characterization by means of optical and magnetic spectroscopies, and theoretical studies are described. The latter provide further support to experimental results and provide a better understanding of the host electronic band structure, energy levels of specific defects, and the emission centers themselves. Applications in medical imaging and dosimetry, security measures, high‐energy physics and the high‐tech industry, in which X(γ)‐rays or particle beams are used and monitored, are recognized as the main driving factor for R&D activities in this field. [ABSTRACT FROM AUTHOR]

The influence of different activator impurities on the scintillation yield of alkali halides has been investigated as a function of temperature. Luminescence spectra of pure and activated CsI and NaI scintillation crystals were measured under X-ray and VUV excitation at temperatures from 10 to 300 K. In indium- and thallium-doped crystals activator centers can capture electrons. Along with self-trapping of holes at low temperatures, electron capture by the dopant results in energy storage. This leads to a significant decrease of luminescence yield. In Eu-doped NaI and CsI crystals activator centers capture a hole first. In this way, at low temperatures electrons recombine either with self-trapped holes (yielding STE emission), or with holes trapped by the activator (giving rise to Eu emission band). No energy loss at low temperature is evident in CsI:Eu and NaI:Eu crystals. [ABSTRACT FROM AUTHOR]

Summary An examination of the backscattered electron imaging status in environmental scanning electron microscopy is presented with particular attention to the testing and use of cerium doped yttrium aluminium garnet and yttrium aluminium perovskite scintillation detectors. A comparison is made with plastic scintillating backscattered electron detectors used previously (Nuclear Enterprises type NE102A scintillator). Semi-disk, strip and wedge shapes of these materials have been tested in conjunction with various light-guide geometries. These systems have been combined with two different types of photomultipliers, which also play a critical role in the total detector efficiency. The advantage of increased light output from the monocrystal materials is gained only if matched with suitable light-guides and photomultipliers. The associated problems are discussed and proposals for further work are made for the construction of most efficient backscattered electron detectors in the environmental scanning electron microscope. [ABSTRACT FROM AUTHOR]

Commercially available Lu2SiO5:Ce (LSO:Ce) scintillators for the nuclear medical imaging applications, such as positron electron tomography (PET), normally have a light yield of 30 000–32 000 photons/MeV and a scintillation decay time of 43–45 ns. We demonstrate a simultaneous improvement of light yield and decay time of LSO:Ce single crystal scintillators with lithium codoping. Li codoping significantly enhances the light yield of LSO:Ce from 32 500 to 39 000 photons/MeV, shortens the scintillation decay time from 45.4 to 42.1 ns, and reduces the room temperature afterglow by around one order of magnitude. The physical insights on the role of Li codopants in scintillation mechanism are provided by studying cerium oxidation state, luminescence properties of cerium activator centers, defect structure, and preferential occupation of lithium ions. The improved light yield and afterglow are explained in terms of the dissociation of spatially correlated oxygen vacancies (VO) and Ce centers or the suppression of VO formation, allowing a more efficient electron migration to Ce centers. We attribute the decay time shortening upon Li+ codoping to the reduction of slow Ce2 emissions via a non‐radiative energy transfer from six‐coordinated Ce2 to seven‐coordinated Ce1 centers. This letter reports a simultaneous improvement of light yield, decay time, and afterglow of Lu2SiO5:Ce3+ scintillation detectors by Li+ codoping. Analysis reveals the non‐conversion of stable Ce3+ to Ce4+ upon Li codoping, and the critical role of Li site occupancy on the suppression of oxygen vacancies. This strategy is also expected to be extended to other oxide scintillators. [ABSTRACT FROM AUTHOR]

Organic single crystals (OSCs) have only recently been considered for applications as ionizing radiation detectors, both as scintillators and as solid state direct detectors. On page 2276, B. Fraboni and co‐workers review the latest developments in this field, discussing the specificall relevant properties of OSCs as well as the most effective and convenient methods for their growth. [ABSTRACT FROM AUTHOR]