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Organic thermally activated delayed fluorescent (TADF) scintillators hold promising potential for applications in medical radiography and security detection, but the poor X‐ray absorption ability and inferior radioluminescence (RL) hampered their progression. Herein, the study has pioneered the development of high‐performance TADF Ag(I)‐based scintillators from M2X2(dppb)2 (M = Ag, Cu; X = Cl, Br, I) complexes with 1,2‐Bis(diphenylphosphino)benzene (dppb) ligand. In comparison with Cu(I) complexes, the Ag(I) series generally exhibited superior scintillation performance. Notably, Ag2Cl2(dppb)2 (Ag1) stands out with exceptionally high RL intensity (≈125% higher than that of CsI:Tl) and a low detection limit of 59.8 nGy s−1. The outstanding scintillation performance of Ag1 is primarily attributed to the synergistic effect of the high exciton utilization efficiency origin from a small singlet‐triplet energy gap, enhanced X‐ray absorption capacity by heavy atoms, and the high photoluminescence quantum yield (76.47% in ambient atmosphere). By fabricating a flexible film constructed with Ag1 submicron crystalline powders, a high spatial resolution of 25.0 lp mm−1 for X‐ray imaging is obtained. It offers new opportunities for utilizing TADF metal–organic complexes for highly efficient X‐ray scintillation and imaging. [ABSTRACT FROM AUTHOR]

Recently, all‐inorganic halide double perovskites (DPs) with a chemical formula of Cs2BIBIIIX6 have been emerging as a shinning star to be used in modern optoelectronic devices, due to their unique advantages such as environmentally friendly, high absorption coefficient, low trap densities, tunable bandgap, variable constituent elements and valences states through BI or BIII sites engineering. In this review, first, the impact of BI and BIII cation doping on the electronic structure and optical properties of Cs2BIBIIIX6 DPs are systematically overviewed, which cover several key issues including the interconversion between direct and indirect band gaps, the enhancement of light absorption, promotion of exciton localization, elucidation of energy transfer mechanisms, regulation of defect density and improvement in both stability and luminescence efficiency. Subsequently, state‐of‐the‐art research activities regarding their interesting optoelectronic device applications are systematically discussed, such as light‐emitting diodes, anticounterfeiting encryption, X‐ray scintillators, and optical thermometry. Finally, the existing difficulties, prospects, and research directions in this field are proposed. [ABSTRACT FROM AUTHOR]

First-principles calculations are carried out to investigate the effect of pressure (up to 40 GPa) on electronic, optical and elastic properties of the scintillator material calcium iodide, CaI2, by using Perdew–Burke–Ernzerh of generalized gradient approximation (PBE-GGA). The electronic band structure reveals an indirect band gap of 3.89 eV and a direct band gap of 4.35 eV for zero pressure. We have also calculated the pressure dependence of optical properties. The elastic constants and elastic moduli increase nonlinearly with pressure. Decreasing Pugh's ratio and increasing hardness with pressure indicate a cross-over from ductile to brittle nature at 5 GPa. Analyses of elastic properties show that CaI2 is mechanically stable up to the applied pressure of 40 GPa. The calculated light yield increases linearly with pressure yielding a pressure coefficient of 1327 ph/MeV per GPa due to the decreasing band gap. Light yield increases as much as 62% at 40 GPa. [ABSTRACT FROM AUTHOR]

A single crystal of Zn2Te3O8 (ZTO) was grown using the conventional Czochralski technique. TGA analysis showed that the melting point of ZTO is 681 °C, while it exhibits a structural phase transition at 621 °C. The powder X-ray diffraction analysis of ZTO confirmed that it possesses a single crystalline monoclinic structure with the C2/c space group. An indirect band gap of 3.75 eV was estimated for the ZTO crystal based on its absorption spectrum. The X-ray-induced luminescence of the grown crystal comprised a broad band peaking at 565 nm, which can be tentatively assigned to the self-trapped exciton emission from the (Te3O8)4− molecular complexes. The photoluminescence measured under 280 nm excitation showed a broad band luminescence peaking at about 600 nm, and its intensity was significantly enhanced upon cooling the crystal from 300 K to 10 K. The photoluminescence decay time under 280 nm excitation was shown to have two exponential components in the range from 10 K to 175 K, which became a single exponential upon further heating the crystal. Low scintillation light was observed at room temperature both under α- and β-particle excitations from 241Am and 90Sr sources, respectively. The scintillation light yield measured under β-particle excitation from the 90Sr source was enhanced by about five orders of magnitude at 10 K in comparison to that at 300 K. The scintillation light yield measured at 10 K under the same experimental conditions for ZTO in comparison with the well-known cryogenic scintillator Li2MoO4 (LMO) was shown to have four times higher scintillation light. A single-crystal ingot of ZTO was obtained for the first time; however, it had several cracks due to its phase transition. Notably, scintillation at low temperatures for a Te-based crystal was observed for the first time. These preliminary findings are very promising and show that ZTO will be a good candidate for cryogenic phonon scintillation detectors for the 0νββ decay search of 130Te. [ABSTRACT FROM AUTHOR]

The implementation of a density functional theory framework, specifically the full potential linearized augmented plane wave method, has been utilized to predict the electronic, structural, magnetic, and optical properties of Cs2LiCeBr6, a scintillating bromo-elpasolite material. The optimized lattice parameter "ao" is reported to be in reasonable accordance with the experimental value, and the lowest energy in the spin-polarized approach is observed. As per the Tran and Blaha modified Becke-Johnson potential approximation, the optimized results reveal that the band gap of the material is indirect at the momentum points from Γ-X. The calculated values for the band gap in the spin-up and down channels are 2.77 eV and 3.12 eV, respectively. The verification of ferromagnetic behavior is confirmed by the asymmetric densities of states in both spin schemes. Furthermore, based on the values of the band gap, the substance is classified as a ferromagnetic semiconductor. The optical properties are analyzed within the energy range spanning from 0 eV to 20 eV, and the Perdew-Burke-Ernzerhof generalized gradient approximation and the Tran and Blaha modified Becke-Johnson approximations are compared. The material being investigated demonstrates valuable characteristics, including absorption in the extreme ultraviolet range, reduced reflectivity, and elevated optical conductivity values. These properties make it suitable for various applications, including radiation detection in particle physics, medical instrument construction, security applications, and high-frequency devices that rely on ultraviolet radiation. [ABSTRACT FROM AUTHOR]

The implementation of a density functional theory framework, specifically the full potential linearized augmented plane wave method, has been utilized to predict the electronic, structural, magnetic, and optical properties of Cs2LiCeBr6, a scintillating bromo-elpasolite material. The optimized lattice parameter "ao" is reported to be in reasonable accordance with the experimental value, and the lowest energy in the spin-polarized approach is observed. As per the Tran and Blaha modified Becke-Johnson potential approximation, the optimized results reveal that the band gap of the material is indirect at the momentum points from Γ-X. The calculated values for the band gap in the spin-up and down channels are 2.77 eV and 3.12 eV, respectively. The verification of ferromagnetic behavior is confirmed by the asymmetric densities of states in both spin schemes. Furthermore, based on the values of the band gap, the substance is classified as a ferromagnetic semiconductor. The optical properties are analyzed within the energy range spanning from 0 eV to 20 eV, and the Perdew-Burke-Ernzerhof generalized gradient approximation and the Tran and Blaha modified Becke-Johnson approximations are compared. The material being investigated demonstrates valuable characteristics, including absorption in the extreme ultraviolet range, reduced reflectivity, and elevated optical conductivity values. These properties make it suitable for various applications, including radiation detection in particle physics, medical instrument construction, security applications, and high-frequency devices that rely on ultraviolet radiation. [ABSTRACT FROM AUTHOR]

CsCu2I3 crystal is a promising Cu-based halide material for scintillation detection. In this paper, Na+ ion-doped CsCu2I3 crystals with a size of ϕ12 mm × 50 mm were grown successfully using the vertical Bridgman method, and the properties were systematically investigated. CsCu2I3:Na crystals exhibit yellow light emission peaking at 575 nm and a large Stokes shift of 1.55 eV. Based on the results of the XRD and XPS, the Na+ was introduced successfully. The optical absorption spectra show that the band gap of CsCu2I3 crystals was narrowed when the Na+ was doped. The photoluminescence quantum efficiency (PLQY) is improved from 16.4% to 19.6%. Finally, the X-ray-induced afterglow, and scintillation (energy resolution, light yield and decay time) under a 137Cs source were measured and discussed. These results illustrate that CsCu2I3:Na crystals have potential applications in the radiation detection field. [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]

We investigated, using DFT calculations, the electronic, optical, polaron properties and estimate the upper light yield of Tl 2 ZrCl 6 material. The DFT calculations were performed with GGA+mBJ and GGA+mBJ+SOC approximations to obtain precise electronic, optical and polaron properties. The calculated results showed that Tl 2 ZrCl 6 has localized valence and narrow discrete conduction bands with many sharp peaks and low dispersion which reflects the heavier effective mass of electron at CBM, 4.63 m e , in comparison with that of hole at VBM, 1.05 m e . Indirect band gap energy of 4.30 eV was observed and which is close to the experimental value, 4.22 eV. Additionally, in the emission range, this material exhibited a high transmittance rate of around 90% which is an advantage of the scintillation properties. Following DFT calculations, polaron properties and also the temperature-dependence of polaron mobility and relaxation time were calculated by solving the Feynman polaron model, variationally, with the free-energies minimization. The obtained results showed that Tl 2 ZrCl 6 has a large electron (hole)-phonon coupling, α e = 8.55 ( α h = 4.1) , leading to large polaron mass, small relaxation time, high scattering rate and low electron (hole) mobility of 0.13 cm 2 V - 1 s - 1 (4.17 cm 2 V - 1 s - 1 ) at room-temperature. Such low mobility has a positive role only in the initial ionization track by increasing the recombination yield. Moreover, using the polaron and simple phenomenological models, the upper light yield was estimated to be 87,757 p h / M e V and 75,187 p h / M e V . Such findings could have important implications for understanding the scintillation behavior of this material to improve its performance as a potential scintillator for γ- and X-rays detection. [ABSTRACT FROM AUTHOR]

A bis‐heteroleptic Ru(II) complex, 1[PF6]2 of a benzimidazole substituted pyridyl‐1,2,3‐triazole ligand (BiPT) for highly selective luminescence turn‐on detection of hypochlorous acid (HOCl) is reported. Detection of HOCl is achieved by the Markovnikov addition of HOCl to the C=C bond of 1,2,3‐triazole and a successive highly specific C(sp2)‐H chlorination at the C5 position of 1,2,3‐triazole. The chlorination at C5 in 1,2,3‐triazole is supported by high‐resolution mass spectrometry and 1H NMR study. 1[PF6]2 shows high sensitivity towards HOCl in PBS buffer (pH 7.4) containing 5 % acetonitrile with a 37‐fold luminescence light‐up and a detection limit as low as 7.5 μM. HOCl mediated C(sp2)‐H chlorination increases the 3MC‐3MLCT energy gap as well as the population of the 3MLCT excited state and exhibits the radiative decay from the excited state of 1. The probe showed low cytotoxicity and efficiently permeated the cell membrane. The cell‐imaging experiments revealed rapid staining of the HeLa cells in the presence of exogenous HOCl. [ABSTRACT FROM AUTHOR]

The review is devoted to the analysis of the compositional disordering potential of the crystal matrix of a scintillator to improve its scintillation parameters. Technological capabilities to complicate crystal matrices both in anionic and cationic sublattices of a variety of compounds are examined. The effects of the disorder at nano-level on the landscape at the bottom of the conduction band, which is adjacent to the band gap, have been discussed. The ways to control the composition of polycationic compounds when creating precursors, the role of disorder in the anionic sublattice in alkali halide compounds, a positive role of Gd based matrices on scintillation properties, and the control of the heterovalent state of the activator by creation of disorder in silicates have been considered as well. The benefits of introducing a 3D printing method, which is prospective for the engineering and production of scintillators at the nanoscale level, have been manifested. [ABSTRACT FROM AUTHOR]

In this study, we investigate the halide perovskite material Cs 2 LiLuCl 6 using both density functional theory (DFT) and time-dependent density functional theory (TD-DFT) approaches. Our analysis focuses on the structural, electronic, and optical properties of the material, conducted with the Quantum Espresso code. In order to confirm the structural stability of the material, we performed various tests including analysis of elastic constants, formation energy, tolerance factor, and phonon dispersion. Employing the generalized gradient approximation (GGA) and GGA+U, we determine that the material behaves as an insulator with a direct band gap of 5.3042 eV and 5.4245 eV, respectively. Additionally, DFT+U calculations were performed to study the dielectric function, reflectivity, absorption coefficient, and refractive index, revealing a high transmittance rate exceeding 90%. Under ideal conditions, the upper light yield (LYsc) is estimated to be 75 411 ph/MeV and 73 739 ph/MeV for the DFT and DFT+U methods, respectively. These results, along with the presence of lithium in Cs 2 LiLuCl 6 , highlight its potential for use in scintillation-based thermal-neutron detection applications. • Cs2LiLuCl6 is stable in a cubic structure as shown by its formation energy and phonon data. • Cs2LiLuCl6 exhibits insulating behavior with a direct band gap. • The material has high UV emissivity, improving scintillation applications. • Cs2LiLuCl6 achieves 75,411 photons/MeV (DFT) and 73,739 photons/MeV (DFT+U). [ABSTRACT FROM AUTHOR]

[Display omitted] • Growth of a crack-free, optical transparent, and large-size trans -stilbene (TSB) single crystal using novel vaporized purification method is reported. • The crystal also exhibits strong blue emission (380 nm) in photoluminescence and emission at 387 nm under X-ray radiation in radioluminescence spectroscopy. • The scintillation decay time is calculated to be 6 ns under 137Cs gamma source. • The figure of merit of 2,4 indicates its potential significance in fast neutron detection with efficient PSD property. The paper reports the successful growth of large, crack-free trans -stilbene (TSB) single crystals using an in-house developed vertical Bridgman setup. The material purification involved a novel vaporized method at 130 °C. Parameters like furnace setup and ampoule's cone angle were optimized during the growth process. The Powder XRD pattern confirms the phase of material and crystallinity. The crystal exhibited high transmittance (78 %) in the visible region, with an optical band gap of 3.4 eV. Photoluminescence study indicated strong blue emission at 380 nm, with radioluminescence spectroscopy showing emissions at 387 nm under X-ray radiation. The crystal exhibited a scintillation decay time of 6 ns under 137Cs gamma source, highlighting its fast decay and efficient PSD property with a figure of merit of 2.24 for fast neutron detection applications. [ABSTRACT FROM AUTHOR]

Intrinsic defects are known to greatly affect the structural and electronic properties of scintillators thereby impacting performance when these materials are in operation. In order to overcome this effect, an understanding of the defect process is required for the design of more stable materials. Here we employed density functional theory calculations and the PBE0 hybrid functional to study the structural, electronic,defect process and optical properties of Bi 4 Ge 3 O 12 (BGO), a well know material used as scintillator. We examined possible intrinsic defects and calculated their formation energy and their impact on the properties that affect the scintillation process. Furthermore, we investigated the effect and role of rare earth element (REE = Nd, Pr, Ce and Tm) doping on the properties of the BGO system. While the PBE functional underestimated the band gap, the PBE0 was found to adequately describe the electronic properties of the system. Out of all the defects types considered, it was found that Bi Ge antisite is the most favourable defect. Analysis of the effect of this defect on the electronic properties of BGO revealed an opening of ingap states within the valence band. This observation suggests that the Bi 3 + could be a charge trapping defect in BGO. We found that the calculated dopant substitution formation energy increases with increase in the size of the dopant and it turns out that the formation of O vacancy is easier in doped systems irrespective of the size of the dopant. We analyzed the optical spectra and noted variations in different regions of the photon energy spectra. [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]

Fluorescent Ag-doped ZnS nanoparticles have been prepared and used as scintillators for detecting ionizing radiation. Results demonstrate a linear relationship between emitted luminescence and the fluence of alpha particles. These results suggest that Ag-doped ZnS nanoparticles alone could be used as solid scintillators for specific environmental and medical applications. This study deals with the investigation of some physical characteristics of hydrothermal synthesized Ag-doped ZnS nanoparticles (NPs) using different techniques. XRD analysis clear that the prepared materials have a cubic phase. Direct energy gap has been investigated using Diffuse Reflectance Spectroscopy (DRS) and well-known Kubelka–Munk function (F(R)). The energy gap is equal to 3.47 eV. Also, for PL decay, the time constant observed for decay at 480 nm is 130.6 ns for fast component and 2611.4 ns for slow component. For studding the performance of the scintillation materials, a charged particle irradiation system was designed and constructed to examine the response of a commercial and native ZnS scintillator for alpha particles. Also, Pulse height spectrum of alpha particles and gamma rays has been investigated. Enhancing the PL emission of doped ZnS is one of the paper's achievements. [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]

Cadmium tungstate crystals have attracted much attention because of its excellent scintillation performance. The existence of oxygen vacancies will reduce the luminous efficiency of the crystal, extend its luminous decay time and reduce light resolution of the crystal. However, the luminescence mechanism of the oxygen vacancies is not clear yet. Here, the optical properties of cadmium tungstate crystal with oxygen vacancies have been studied based on the Density Functional Theory (DFT). We calculated the defect formation energies of oxygen vacancies with three different charges (0, +1, +2), and corrected the band gap to make it more accurate. We obtained the absorption and emission peaks of the F center and F+ center for two different types of oxygen vacancies. The calculated absorption peaks of the F center of V OI and F+ center of V OII at 3.04 eV and 3.59 eV respectively, which are close to the experimental results (3.1 eV (400 nm) and 3.5 eV (350 nm)). So we speculate that these two obvious absorption peaks are caused by oxygen vacancies. [ABSTRACT FROM AUTHOR]

• BGSOs with different Si/Ge ratio are successfully grown by Bridgman technique. • The scintillation properties of BGSOs with different Si/Ge ratio are investigated. • Si/Ge–O and Bi–O interactions play a critical role in the band gap of BGSO. • BGSO shows great potential for application in dual readout calorimeters. Bismuth silicate-germanate (Bi 4 Ge 3x Si 3(1-x) O 12) crystals are successfully grown with the modified Bridgman technique. The X-ray diffraction, transmittance spectra, radioluminescence spectra and scintillation properties of these crystals are investigated at different ratios of Ge and Si. Furthermore, the XEL peaks of BGSO crystals exhibit a red-shift with the increase of Ge content. Meanwhile, the light yield and energy resolution of crystals represent obviously variation with changing of Ge and Si contents in the crystal. Density-functional theory (DFT) calculations were performed for energy band structure and geometry optimizations of Bi 4 Ge 2.4 Si 0.6 O 12 crystal. The calculated energy band of BGSO crystal is 3.957 eV, which is different from that of BSO and BGO crystals. The results of DOS and PDOS calculated by CASTEP package reveal that Si/Ge–O and Bi–O interactions play a critical role in the band gap of BGSO crystal. [ABSTRACT FROM AUTHOR]

An emerging prospect of solution-processed organic–inorganic hybrid halide perovskites is promising for next generation x-ray imaging applications. Herein, the optical and x-ray scintillation properties of lead-free two-dimensional perovskite crystals are reported, i.e. X2MnCl4 (X = PEA, PPA). At room temperature (RT), the photoluminescence (PL) spectra of both crystals show a peak around 600 nm with the lifetime between 3 and 4 µs, making them applicable for scintillator in x-ray imaging applications. Materials with a small electronic band gap of about 2 eV may allow a good promise for high-light-yield scintillators. On the other hand, x-ray luminescence (XL) measurements for both crystals show no spectra at RT, while those at 10 K exhibit the similar features observed in PL spectra. Temperature-dependent XL intensities reveal thermal quenching behaviour with activation energies between 40 and 54 meV. Thermoluminescence (TL) and glow curves in both crystals show residual luminescence background as slow as 1648 s and some deep traps with energies as large as 190 meV. Thermal quenching and TL measurements of both crystals are the opposite of those of PEA2PbCl4 crystals. Although some properties may not be beneficial for scintillators, the small differences of scintillation properties in both crystals may provide direction for the new designs of high-light-yield lead-free perovskite single crystal scintillators. [ABSTRACT FROM AUTHOR]

The scintillation response of LaBr3:Ce scintillation crystals was studied as function of temperature and Ce concentration with synchrotron X-rays between 9 keV and 100 keV. The results were analyzed using the theory of carrier transport in wide band gap semiconductors to gain new insights into charge carrier generation, diffusion, and capture mechanisms. Their influence on the efficiency of energy transfer and conversion from X-ray or γ-ray photon to optical photons and therefore on the energy resolution of lanthanum halide scintillators was studied. From this, we will propose that scattering of carriers by both the lattice phonons and by ionized impurities are key processes determining the temperature dependence of carrier mobility and ultimately the scintillation efficiency and energy resolution. When assuming about 100 ppm ionized impurity concentration in 0.2% Ce3+ doped LaBr3, mobilities are such that we can reproduce the observed temperature dependence of the energy resolution, and in particular, the minimum in resolution near room temperature is reproduced. [ABSTRACT FROM AUTHOR]

This article outlines the main results of a research and development cooperation between Philips Research Eindhoven; Peter the Great St. Petersburg Polytechnic University; Ioffe Institute, St. Petersburg; Utrecht University; and Philips Healthcare. It reviews the properties of garnet ceramics in the (Lu,Gd)3(Ga,Al)5O12:Ce system for medical imaging, especially time-of-flight positron emission tomography (PET). Thermally stimulated luminescence (TSL) peaks are attributed to impurities, verified by intentional codoping of samples. A lately developed method allows extraction of carrier lifetimes, thermal trap depths, and frequency factors from TSL and afterglow measurements. A detailed analysis reveals the presence of a distribution of trap depths, allowing a more accurate afterglow modeling. Activation energies of thermal ionization and trap depths obtained from TSL show the influence of Ga/Al substitution on thermal quenching and on trap position. The resulting nonmonotonic dependence of the conduction band edge with Ga content in (Lu,Gd) garnets is consistent with earlier predictions. Shallow traps determine both signal decay and short-term afterglow. The impact of signal height, rise, and decay times on coincidence resolving time and further on PET image quality is described by analytical models. [ABSTRACT FROM AUTHOR]

The scintillation, luminescence and optical properties of the multicomponent Gd 3 Sc 2 Ga (2+x) Al (1-x) O 12 :Ce (x = 0, 0.25, 0.5, 0.75, 1), Gd 2.957 Sc 1.905 Ga (2.138+x) Al (1-x) O 12 :Ce (x = 0, 1) and the (200, 1000, 5000 ppm) Mg2+ co-doped Gd 3 Sc 2 Ga 2.75 Al 0.25 O 12 :Ce single crystals grown by the μ-PD method were characterized. Scintillation decay kinetics and light yield were correlated with the sum of the content of Ga and Sc in the host. While the Ga-admixed GSAG:Ce composition exhibited higher scintillation efficiency compared to pure GSAG:Ce, it also showed very high afterglow, due to an intense delayed electron-hole recombination at Ce3+ centres. This was supported by the calculated activation energy obtained from the temperature dependence of photoluminescence decay times. Codoping with Mg2+ significantly improved afterglow compared to pure GSAG:Ce, however, at the expense of light yield. • Ga-admixed GSAG:Ce single crystals were grown by μ-PD method. • Scintillation and luminescence properties were investigated. • Ga/Sc content strongly influences the band gap and scintillation efficiency. • High afterglow is explained by the delayed electron-hole recombination at Ce3+. • Co-doping by Mg2+ results in enhanced scintillation performance. [ABSTRACT FROM AUTHOR]

Bismuth silicate (Bi 4 Si 3 O 12 , BSO) crystal is considered as a promising candidate for fabricating dual-readout calorimeters. Ta 2 O 5 doped BSO crystals were successfully grown by the modified vertical Bridgman method. The crystals possessed about 80% transmittance in the region of 350–800 nm with an absorption edge at about 280 nm. The emission and excitation spectra only showed a wide band which could be ascribed to the typical peaks of Bi3+. The light yield of BSO crystals could be improved effectively by doping Ta 2 O 5 , and the optimized concentration was about 1 mol%, dramatically improving the light output to about 150% of pure BSO crystals. Both the experimental results and theoretical calculations showed that doping Ta5+ ion could reduce the band gap and effectively enhance the light absorption, which was beneficial to generate more electron-hole pairs and promote its emission and light yield. Ta5+ ion is an effective candidate among the transition metal ions for improving the light output of BSO crystals. [Display omitted] • Ta 2 O 5 : BSO crystals with 25 mm diameter and 80 mm length were successfully grown by the modified vertical Bridgman method. • It was showed that Ta5+ improves the light yield of BSO to about 150% of the pure one. • Ta5+ introduces defect levels in the band gap of BSO, which is beneficial to promote the emission and light yield. [ABSTRACT FROM AUTHOR]

The physical, electronic and optical properties of Barium halides have been investigated by both experimental and theoretical approaches. The First Principle electronic structure and optical properties were calculated by DFT formalism using Full Potential Linearized Augmented Plane Wave plus local orbitals (FP-LAPW + lo) implementing different appropriate exchange-correlation functionals in WIEN2k code at various applied volumetric pressure up to 50 GPa. All the properties of these halides were analyzed and compared using their cation-anion radii ratio and ionicity. Except BaF 2 , the other three halides show ionic to covalent transformation at 50 GPa applied pressure. Both experimental and theoretical results compare reasonably well. The scintillation efficiency of these three halides was found to be directly proportional to their ionicity or band gap. • Study of physical, electronic and optical properties of Barium halides by experimental and theoretical approaches. • All the properties of the halides were analyzed and compared using their cation-anion radii ratio and ionicity. • The direct type band gap of the three halides decrease with pressure at least till 50 GPa. • Observed ionic to covalent transformation at 50 GPa applied pressure. • Experimental and theoretical results match reasonably well. [ABSTRACT FROM AUTHOR]

Abstract Cerium doped lutetium aluminum garnet single crystal has been drawing great research interest of scientists due to its superior performance in scintillation material for high energy particle detection. However, the problem about slow components in the scintillation response restricts the further improving. Here, we utilize the "band-gap engineering" strategy that the admixture of Ga3+ in Lu 3 Al 5 O 12 can lower the conduction band edge and bury shallow traps, and get the Ce3+ doped Lu 3 Ga 3 Al 2 O 12 scintillation ceramics sintered in the oxygen atmosphere and hot isostatic pressing post-treated. The luminescence and scintillation properties are investigated. A shortened dominant decay time and the presence of some second slower components in the photoluminescence decays prove that the admixture of Ga3+ in Lu 3 Al 5 O 12 can lower the conduction band edge and consequently also the ionization barrier for Ce3+ emission from 5d 1 level. Meanwhile, the Ce:Lu 3 Ga 3 Al 2 O 12 ceramic sample shows good steady-state scintillation efficiency under the X-ray excitation. Furthermore, it performs excellent in terms of the fast-to-slow emission ratio in scintillation response with a LY 0.5μs /LY 6μs values ratio up to 92%. Highlights • Ce:Lu 3 Ga 3 Al 2 O 12 scintillation ceramics were fabricated by oxygen sintering with hot isostatic pressing. • Ce:Lu 3 Ga 3 Al 2 O 12 ceramics show the excellent steady state scintillation efficiency under the X-ray excitation。. • Light yield of Ce:Lu 3 Ga 3 Al 2 O 12 scintillation ceramics reaches ∼19500 ph/MeV under 137Cs-ray irradiation. [ABSTRACT FROM AUTHOR]

The ZnS nanoparticles activated with various concentrations of Ag and co-activated with Cl ions were synthesized hydrothermally and sintered under controlled environment at 960 °C. The transition from cubic to hexagonal phase and presence of some fraction of ZnO were detected with powders X-rays diffraction (PXRD) and confirmed by energy dispersive X-rays (EDX) analysis as well. An increase in particle sized from ∼450 nm to ∼700 nm was observed with increase in Ag doping concentration in the synthesized ZnS nanoparticles. The optical band gap was found lower for the synthesized ZnS nanoparticles as compared to the reported optical band gap for ZnS, which can be assigned to defect states. Emission bands peaking at ∼2.68 eV and 2.35 eV were observed due to the characteristics ZnS, and ZnO luminescence, respectively. A significant improvement in the emission intensity by about 2.3 orders of magnitude with increase in Ag doping concentration were observed as compared to pristine ZnS nanoparticles. For the samples having higher concentrations of O atoms the quenching in luminescence intensity were found which can be assigned to the trapping of charge carriers by O defects states. The scintillation light yield enhanced with increase in Ag doping concentration and showed similar quenching behavior as observed for photoluminescence. A faster decay time response with suppression of afterglow were observed for ZnS nanoparticles as compared to commercial micron size ZnS phosphors. • Different phase formation in ZnS nanoparticles and its effect are studied. • The presence of O in ZnS nanoparticles are confirmed. • The luminescence and scintillation light yield enhanced with Ag doping. • For the ZnS nanoparticles faster decay time with low afterglow were observed. [ABSTRACT FROM AUTHOR]

Ce-doped (Gd, La)2Si2O7 (Ce:La-GPS) scintillator was found to have a good light output of around 40 000 photons/MeV, while some other parameters have not been determined so far. In order to clarify the cause for such a high light yield, some physical parameters have been estimated in this paper. The bandgap energy of Ce:La-GPS was evaluated to be over 7.13 ± 0.03 eV for (Gd0.75, La0.25)2Si2O7. Although Ce:La-GPS had wider bandgap compared with the other oxide scintillators, its light output was larger than values for some other scintillators. Since quantum yield of Ce:La-GPS was as high as around 0.8, the product of transfer efficiency and electron–hole pair generation efficiency was estimated to be around 0.9, which was higher than for the other scintillators. Thus, Ce:La-GPS was suggested to have high the product of transfer efficiency and/or electron–hole pair generation efficiency. [ABSTRACT FROM AUTHOR]

The paper addresses the recent progress in study of light yield behavior in scintillators based on solid solutions (mixed crystals), which are among the brightest known scintillators. Following the prior work [O. Sidletskiy et al., Phys. Status Solidi A 2014, 211, 2384], the extended phenomenological analysis of the correlations between light yield behavior and physical properties of mixed crystals (band gaps of the components, ionic radii, and atomic weights of the substitutional atoms) is carried out. The trend to light yield enhancement is notable in systems with the substitution of atoms in two non‐equivalent crystallographic sites in the lattice leading to formation of planes and columns enriched with one of the substitutional atoms. This evidences an important role of nanoscale spatial inhomogeneity (domains or clusters) in scintillation process in mixed scintillators. A roadmap of search for new bright scintillators is proposed basing on the established trends. [ABSTRACT FROM AUTHOR]

The electronic structures and exciton properties of HgI 2 , CH 3 NH 3 HgI 3 and (CH 3 NH 3) 2 HgI 4 are reported. Compared with HgI 2 , organic-inorganic hybrids CH 3 NH 3 HgI 3 and (CH 3 NH 3) 2 HgI 4 have lower dimension and higher band gap, which show significant excitonic properties. The effective masses of electrons and holes of these three materials were predicted by their energy band structures. Their exciton binding energy at room temperature therein was calculated to be 13.77, 166.81, and 256.00 meV, respectively. HgI 2 has low exciton binding energy that cannot exist stably, while CH 3 NH 3 HgI 3 and (CH 3 NH 3) 2 HgI 4 have strong charge localization and high exciton binding energy. In addition, the UV–vis diffuse reflectance spectra reveal the presence of exciton absorption in CH 3 NH 3 HgI 3 and (CH 3 NH 3) 2 HgI 4 , and the exciton energy levels is confirmed by combining the diffuse reflectance spectra with its exciton binding energy. Importantly, the exciton luminescence peaks of CH 3 NH 3 HgI 3 and (CH 3 NH 3) 2 HgI 4 were observed at 468 nm and 419 nm in their photoluminescence spectra at room temperature, respectively. This indicates that CH 3 NH 3 HgI 3 and (CH 3 NH 3) 2 HgI 4 have strong exciton properties and are potential candidates for high-light-yield scintillators and light-emitter applications. • The exciton binding energy of HgI 2 , CH 3 NH 3 HgI 3 and (CH 3 NH 3) 2 HgI 4 are 13.77, 166.81, and 256.00 meV, respectively. • The exciton energy level was confirmed by combining the diffuse reflectance spectra with its exciton binding energy. • The exciton luminescence peaks of CH 3 NH 3 HgI 3 and (CH 3 NH 3) 2 HgI 4 were observed at 468 nm and 419 nm. [ABSTRACT FROM AUTHOR]

The short-wavelength sub-nanosecond luminescence in BaF 2 material, discovered in the early 80s, gave a new direction to research into fast scintillators and phosphors. In contrast to 'typical' luminescence occurring within the forbidden band gap, the new type of emission was due to transitions between the upper core and valence bands. Thus it was named core-valence luminescence (CVL); the terms cross-luminescence and Auger-free luminescence have also been used. Given its unusual nature, this new luminescence process has attracted considerable interest in the field of condensed matter physics. During the sequent decades (till the end of the previous century) CVL has been experimentally observed in several dozen compounds and the conditions for detecting CVL have been established. Interest in this kind of luminescence increased in recent years due to the emergence of new methods of crystal synthesis, the development of high-speed solid-state photodetectors, and the construction of unique modern set-ups using synchrotron radiation. This paper analyzes the numerous studies of CVL, obtained mainly over the past decade. Experimental and theoretical data on this topic are considered in detail. Special attention is given to new results on scintillation characteristics of BaF 2 in the form of single crystals, ceramics, nanoparticles, and composites. The features of CVL in binary and ternary compounds are discussed. Some Cs- and Ba-based ternary halides show relatively high light yields and represent promising fast scintillators. The prospects of using materials with CVL as fast scintillators for time-of-flight positron emission tomography and other applications are deliberated. • Overview of recent theoretical and experimental findings on Core Valence luminescence. • Most attractive CVL crystals for ultrafast scintillator applications analyzed. • Prospects for future studies and underexplored CVL materials listed. [ABSTRACT FROM AUTHOR]

• Structure reports of newly synthesized 4-fluoro phenyl derivative of 4-methyl piperidine (FPMPM) and Hirshfeld surface analysis. • Comparative vibrational analysis of molecules using FT-IR and FT-Raman spectral vibration modes. • The prompt fluorescence decay of 3.72 (2) and 2.85 (1) ns are promising material to act as an optical imaging fluorophores. • The F substituent possesses high hydrophobicity and lipophilicity, mitigating bacterial activity. • The moderate H...Cl and C H...π interactions allow for incredible antifungal activity of the Cl analogue. A new fluoro derivative of 4-methyl piperidine (FPMPM) was synthesized by Scholten-Baumann condensation reaction, and the crystal structure was elucidated using single-crystal X-ray diffraction intensities. The molecules are arranged in monoclinic P 2 1 / n symmetry allowing for a dihedral angle of 36.76 (8)° observed between the mean plane of the benzene ring and the mean plane of the piperidine chair. Essentially projected non-bonded interactions were corroborated through Hirshfeld surface analysis. Predominant H...H and long-ranged halogen interactions packed with weak dispersion forces suggest the sizeable hydrophobic surface area. The chloro analogue (CPMPM) of FPMPM was compared for its FT-IR and FT-Raman spectra displaying their characteristic vibration modes of the functional groups. The bandgaps of 2.82 and 3.97 eV in FPMPM and CPMPM divulged by the Tauc's plots of UV–vis spectral data are concomitant with the optical band gaps disclosed by photoluminescence spectra. A longer delayed fluorescence lifetime of 31.5(8) and 33.1(1) ns with relatively high contribution confirmed the intermediate triplet state in the materials. The fast, prompt fluorescence decay of 3.72 (2) and 2.85 (1) ns in FPMPM and CPMPM with 54 (1) and 69 (1) % percent fractional contribution are promising shreds of evidence for the materials to act as an optical imaging fluorophore and an imminent scintillating material at moderate temperatures. Relatively moderate values of nonlinear susceptibility (3.44 and 3.85) × 10−6 (e. s. u.) and positive nonlinear absorption coefficient with z-scan measurements supported thermal concave lensing behavior and reverse saturable absorption in both the materials. Thermogravimetry coupled with Differential Scanning Calorimetry (DSC) declares the moderately low melting point (70.4 and 107 °C) for the material, FPMPM, and CPMPM, respectively. The F substituent in FPMPM possesses high hydrophobicity and lipophilicity, mitigating antibacterial activity, while moderate H...F and C-H...π interactions allow for susceptible antimicrobial activities. CPMPM exhibits robust antifungal activity against Trichoderma with reference to amphotericin-B. The antioxidant scavenging property is reflected by relatively high proton reactivity sites in FPMPM and hence relatively low % DPPH activity in CPMPM. [Display omitted] [ABSTRACT FROM AUTHOR]

We synthesized the 0.1, 0.5, 1.0, and 1.5% Ce-doped mullite single crystals by the floating zone method and evaluated their photoluminescence (PL) and thermally stimulated luminescence (TSL) properties. The single-phase orthorhombic structure was confirmed in all the samples from powder X-ray diffraction patterns. The transmittance spectra of all the samples showed the absorption related to the 4f-5d transitions of Ce3+ ions and optical band gap of mullite. The Ce-doped mullite single crystals had the PL attributed to the 5d-4f transitions of Ce3+ ions. In TSL properties, TSL glow curves had the glow peaks at 250 and 370 °C, and TSL spectra heated at 250 and 370 °C had the peak at around 390 nm owing to the Ce3+ ions. TSL dose response functions showed linear response from 0.01 mGy to 10 Gy for the 1.0% Ce-doped mullite single crystal and from 0.1 mGy to 10 Gy for the 0.1, 0.5, and 1.5% Ce-doped ones. The 1.0% Ce-doped mullite single crystal could be used multiple times for dosimetry. In addition, the TSL intensity of the 1.0% Ce-doped mullite single crystal after 7 days from X-ray irradiation was about 82.4% from immediately one after X-ray irradiation. • We have synthesized Ce-doped Al 4 SiO 8 single crystals by floating zone method. • We have characterized the photoluminescence, and thermally stimulated luminescence. • All the samples showed luminescence properties due to the 5d-4f transitions of Ce3+. • The lower detection limit of the 1.0% Ce-doped Al 4 SiO 8 single crystals was better than those of a part of commercial dosimeters. [ABSTRACT FROM AUTHOR]

Results of spectroscopic studies at ambient and high pressures of a LuAlO 3 :Ce3+ (LuAP:Ce) single crystalline film (SCF) as well as LuAP:Ce and YAlO 3 :Ce (YAP:Ce) single crystals are reported. Room temperature absorption measurements of the single crystals in the vacuum UV region allowed establishing the bandgap energies of 7.63 eV for YAP and 7.86 eV for LuAP, with an assumption of the direct band-gaps. Luminescence of Ce3+ in LuAP and YAP bulk crystals was measured as a function of temperature from 6 K up to 873 K. Temperature quenching of the Ce3+ luminescence in YAP:Ce was observed above 650 K, which is related to the location of the lowest Ce3+ 5d level at 1.27 eV below the conduction band minimum. No temperature quenching occurred in LuAP:Ce up to 873 K, mostly due to the lower energy of the 4f levels with respect to the valence band maximum. The barycenter energies and splittings of Ce3+ 5d states in YAP and LuAP at room temperature were precisely established. Theoretical calculations of the Ce3+ 5d states energy structure under pressure revealed a discrepancy between the obtained experimental results and the prediction of Dorenbos' theoretical model. The discrepancy can be removed if instead of the 5d state of the free Ce3+ ion the bandgap of the compound is taken as reference energy for the red-shift of the 5d level. This hypothesis also allows us to take into account the pressure-induced increase of the bandgap energy, expected for the studied compounds. Pressure dependences of LuAP:Ce luminescence spectra suggest that a certain type of phase transition occurs above 15 GPa. • Bandgap energies of YAP and LuAP from vacuum UV absorption spectra. • Position of Ce3+ levels in the band gap of YAP and LuAP. • High-pressure phase transition of LuAP, high-pressure luminescence of Ce3+ in YAP and LuAP. [ABSTRACT FROM AUTHOR]

Radioluminescence spectra at temperatures ranging from 10 to 320 K and low temperature thermoluminescence glow curves of BaY 2 F 8 :Ce and BaY 2 F 8 :Nd scintillator crystals have been investigated. In both materials the intensities of the excitonic and the activator ion’s emission at X-ray excitation vary with temperature, anticorrelating with each other, which provides valuable information on the host-to-ion energy transfer. Detailed thermoluminescence studies, in turn, prove the existence of charge traps, which introduce quasi-continuous distributions of energy levels into the bandgap. [ABSTRACT FROM AUTHOR]

Nonequilibrium carrier dynamics in the scintillators prospective for fast timing in high energy physics and medical imaging applications was studied. The time-resolved free carrier absorption investigation was carried out to study the dynamics of nonequilibrium carriers in wide-band-gap scintillation materials: self-activated led tungstate (PbWO 4 , PWO) ant two garnet crystals, GAGG:Ce and YAGG:Ce. It was shown that free electrons appear in the conduction band of PWO and YAGG:Ce crystals within a sub-picosecond time scale, while the free holes in GAGG:Ce appear due to delocalization from Gd 3+ ground states to the valence band within a few picoseconds after short-pulse excitation. The influence of Gd ions on the nonequilibrium carrier dynamics is discussed on the base of comparison the results of the free carrier absorption in GAGG:Ce containing gadolinium and in YAGG without Gd in the host lattice. [ABSTRACT FROM AUTHOR]

The structural and luminescent properties of perspective scintillating Zn x Mg 1-x WO 4 mixed crystals were studied. The following characteristics were found to depend linearly on x value: the energy of several vibrational modes detected by Raman spectroscopy, the bandgap width deduced from the shift of the excitation spectrum onset of a self-trapped exciton (STE) emission, the position of thermally stimulated luminescence peaks. It is also shown that the thermal stability of the STE luminescence decreases gradually when x decreases. These data indicate that each Zn x Mg 1-x WO 4 mixed crystal is not a mixture of two constituents, but possesses its original crystalline structure, as well as optical and luminescent properties. [ABSTRACT FROM AUTHOR]

We investigated the scintillation and dosimeter properties of yttria stabilized zirconia (YSZ, Y 2 O 3 –ZrO 2 ) crystal. It showed 70–80% in-line transmittance at wavelength longer than 300 nm. Under excitations around the bandgap energy, several intense photoluminescence (PL) emission peaks appeared at 450, 550, 570 and 600 nm, and the PL decay time constants were 5.5 and 20.7 ns. In the X-ray induced scintillation spectrum, an intense emission peak around 450 nm was observed, and the scintillation decay time constants were 14.4 and 169.8 ns. After irradiations with X-rays, thermally stimulated luminescence (TSL) glow peaks appeared at 100, 200 and 450 °C. Also, after X-ray irradiations, optically stimulated luminescence (OSL) was detected around 500 nm with 650 nm stimulation. [ABSTRACT FROM AUTHOR]

The BaBr 2 films grown by vacuum thermal evaporation prefer three different completely ( hkl ) oriented growth at different growth parameters and each orientation develops strain due to residual stress. The optical absorption indicates a direct type band gap for these films. The band gap of each ( hkl ) orientation varies linearly with its uniaxial strain. The three ( hkl ) orientations show band gap anisotropy (2.94–4.25 eV). The negative (for (101) and (111)) and positive (for (013)) pressure coefficients of band gap are attributed to the strain in Br–Br and Ba–Br bonds along [ hkl ] respectively. The average pressure coefficient of band gap of all three orientations found to be significantly smaller than that calculated by volumetric pressure dependence. [ABSTRACT FROM AUTHOR]

Three types of acrylates with the fluorenyl group were selected for the purpose of enhancing 3D-printed plastic scintillators. The mechanical and optical characteristics of all the selected monomers were investigated, and optical absorbance and band gap energy were measured and compared to the standard monomers of styrene, PMMA, and vinyltolune. By measurement of light output for the 3D-printed plastic scintillators, an increase in light output correlating with an increase in the number of benzene rings per molecule weight was observed in the results of all the selected acrylates. The analysis of Raman spectroscopy revealed a linear dependence (R 2 = 0.9599) of light output on the Raman intensities at 3070 cm−1. In the use of ethoxylated bisphenol fluorene diacrylate (OPPEA 40%), the best mechanical and optical performance of the 3D-printed plastic scintillator was found to 72% transmission, maximum emission wavelength 470 nm, hardness 84 Shore-D, and light output 5300 photons/MeV. • Properties of bisphenol fluorine diacrylates were characterized for 3D-printing • Ethoxylated bisphenol fluorine diacrylate is the promising monomer for 3D-printing. • Scintillation light output was increased with the number of benzene rings. • Linear dependence between the number of benzene rings and Raman intensities. [ABSTRACT FROM AUTHOR]

Inorganic phosphors based on rare earth elements are commonly used as scintillation materials due to their high chemical and radiation resistance. In this work, we study gadolinium oxyselenide as a new phosphor material. The work describes a facile synthesis method for Gd 2 O 2 Se. Single crystal structure of this compound was determined for the first time: sp.gr. P ¯3 m 1 with a ​= ​3.8911(4) Å and c ​= ​6.8829(8) Å. Gd 2 O 2 Se is stable in the inert atmosphere and melts at 2075 ​± ​20 ​°C. This material is also stable when heated in air up to 720 ​°C. with the following oxidation and weight increase. This mass increase can be explained by the oxidation of Se2− to Se4+. Further temperature increase above 952°С leads to a sharp mass loss and the final mass of sample corresponds to full oxidation of Gd 2 O 2 Se to gadolinium oxide. The band gap of the material was estimated to be 3.6 ​eV. Photoluminescence spectrum for Gd 2 O 2 Se:Tb3+ shows the characteristic transitions in Tb3+ ion with the most intense green emission that corresponds 5D 4 → 7F J transitions. [Display omitted] • A powder of Gd 2 O 2 Se was obtained and the single crystal structure was determined: sp.gr. P ¯3 m 1, a ​= ​3.89Å, c ​= ​6.88 Å. • The melting point was found to be 2075 ​± ​20 ​°C. High air stability for this compound was demonstrated up to 720 ​°C. • The estimated value of the band gap is 3.6 ​eV. The photoluminescence of the Tb3+ doped sample was investigated. [ABSTRACT FROM AUTHOR]

Full-potential linearized augmented plane wave method has been used to study the cross luminescence of halide scintillators. The electronic structure and optical properties of alkali halides such as CsMgCl 3 , CsCaCl 3 , and CsSrCl 3 are presented. One of the major criteria for the cross luminescence to happen is the energy difference between valence band and next deeper core valence band being lesser when compared to energy gap of the compound, so that radiative electronic transition may occur between core valence band and valence band which might lead to fast scintillation. We found this criterion to be satisfied in these compounds leading to cross luminescence. The presence of high energy peaks in the absorption spectra indicates the creation of holes in the core valence band, which is an essential criterion for the occurrence of cross luminescence. The electronic structure, and optical properties studies clearly indicate CsMgCl 3 , CsCaCl 3 , and CsSrCl 3 to be cross luminescence materials comparable to CsCl which is one of the well known fast scintillators. In addition, CsMgCl 3 is found to be better among the studied compounds with optical isotropy though the compound is structurally anisotropic. [ABSTRACT FROM AUTHOR]

We synthesized a fast scintillation material based on a ternary halide crystal, CsCaCl 3 , which is known to exhibit Auger-free luminescence (AFL) under core-level excitation. We characterized its luminescence properties using vacuum ultraviolet (VUV) light for excitation. We observed a broad AFL band centered at approximately 300 nm for the core hole excitation, with a decay time of 2.3 ns. In addition to AFL, we observed several luminescence bands for interband and sub-band-gap excitation. The scintillation light yield was estimated to be 410 photons/MeV. We observed a fast scintillation component due to the AFL having a decay time constant of 2.3 ns. This fast component accounts for 58% of the total scintillation. These results indicate that a fast scintillation material was successfully fabricated, employing AFL as the luminescence mechanism based on a ternary halide crystal. [ABSTRACT FROM AUTHOR]

Highlights: [•] A new methodology to produce Ca2Al2SiO7 nanoparticles was proposed. [•] The Ca2Al2SiO7 optical band gap was estimated via diffuse reflectance. [•] The energy levels of the Ce3+ 5d1 and Mn2+ 3d5 excited states were estimated in Ca2Al2SiO7 matrix. [ABSTRACT FROM AUTHOR]

Highlights: [•] The influence of Gd3+–Ga3+ admixture on the luminescent mechanism was studied. [•] The promising composition for scintillation application was achieved. [•] Energy transfer from Gd3+ to Ce3+ was corroborated. [•] Band gap engineering and energy level positioning strategies were discussed. [•] The luminescence behaviors varying with electronic structures were demonstrated. [ABSTRACT FROM AUTHOR]

• The optical constants of Lu 2 O 3 single crystals covering the UV–VIS–NIR spectral region are firstly investigated • The bandgap energy 5.541 ± 0.004 eV of Lu 2 O 3 single crystal is derived experimentally • Large-size and damage-free Lu 2 O 3 single crystal is obtained by chemical mechanical polishing Lu 2 O 3 has attracted widespread attention in high-power lasers, scintillators, and semiconductors due to its high thermal conductivity, high stability, and large band gap. Due to the limitations of the growth process, high-precision characterization of polished quality and optical properties for large-size Lu 2 O 3 single crystal is extremely scarce, which hinders the design and optimization of optics based on Lu 2 O 3. In this study, we design a systematic machining scheme for large-size Lu 2 O 3 single crystal thick chip to obtain polished crystal with virtually no surface and subsurface damage. The surface/subsurface quality was evaluated utilizing optical profilometer, scanning electron microscope, and transmission electron microscope. Variable-angle spectroscopic ellipsometer was employed to measure the optical constants over wide spectral region (210–1690 nm), removing the lack of optical constants of Lu 2 O 3 single crystal in the ultraviolet region. The band gap is analyzed based on the optical constants results. The consistency of the measured data with the relevant literature verifies the reliability and accuracy of the measurement method along with the data. The surface/subsurface damage inspection method provides an effective approach for ultra-precision machining mechanism research and process optimization of Lu 2 O 3 and other hard and brittle materials. The band gap and the optical constants in wide spectral region provide critical fundamental data for the design and performance optimization of related optics. [ABSTRACT FROM AUTHOR]