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The role and effect of stable Ce^4+ centers in Ce-doped LuAG single crystal scintillator is further studied by means of measurements of several optical, luminescence and scintillation characteristics. Two LuAG:Ce single crystal samples are compared: in one of them the dominating Ce^4 + center is stabilized by high concentration Mg^2+ codoping while the other one shows only the presence of stable Ce^3 + center. Tailored (Eu, Mg)–doped LuAG single crystal is also prepared to test the presence and thermal stability of hole traps in the host which affect the timing characteristics of Ce^4+ scintillation cycle, namely its restoration back to 4+ charge state in last step of the cycle. EPR experiment was also employed at Mg- and (Eu, Mg) doped LuAG samples and the signature of the O^ - hole center stabilized by Mg^2 + ion was clearly obtained. [ABSTRACT FROM AUTHOR]

Ce-doped lutetium aluminum garnet Lu 3 Al 5 O 12 (LuAG) nanoceramics were fabricated at 1600 °C and 1700 °C by spark-plasma sintering (SPS) method from nano-powders prepared by radiation synthesis. Both undoped and Ce-doped LuAG ceramic samples were also prepared from the nano-powders at 1700 °C with significantly increased pre-heating rate. The backscattered electron images revealed large amount of pores in all the Ce-doped samples causing their significant opacity. On the other hand, very large grains and no pores were revealed in the undoped sample, which was the only transparent one. The radioluminescence measurements revealed superior overall scintillation efficiency of the samples sintered at the temperature 1700 °C, and their defect emission in the UV region was ascribed to oxygen-vacancy-related defects such as F + centers. The photoluminescence decay of the defect emission was characterized by an extremely fast decay time of a few nanoseconds. Influence of sintering procedure and subsequent annealing on the luminescence and scintillation properties is discussed. [ABSTRACT FROM AUTHOR]

The Nd-doped, Gd-doped and doubly Nd, Gd-codoped BaLu 1.2 Y 0.8 F 8 (BaLuYF) and LuF 3 single crystals were grown by a micro-pulling-down method. Their photoluminescence, radioluminescence and alpha-ray-excited pulse-height spectra were studied in the vacuum-ultra-violet (VUV) region to confirm their possible application as fast VUV scintillators. Complementary photoluminescence measurements in the ultra-violet/visible spectral region were performed as well. The possibility of scintillation performance improvement by Gd codoping was tested. The overall scintillation efficiency of BaLuYF:Nd1% was comparable to that of the LaF 3 :Nd8% reference sample and only slight improvement was observed after Gd1% codoping. The positive effect of Gd codoping was confirmed for higher dopant concentrations. This was explained by an energy transfer from the high-energy Gd 3+ 4f 2 G(0) 7/2 level to the Nd 3+ 5d state. On the other hand, pulse-height spectra showed degradation of the light yield under alpha-ray excitation, which was explained by introduction of slow components due to Gd codoping. On the other hand, no positive effect of Gd codoping was found for the overall scintillation efficiency of Nd-doped LuF 3 , despite the same energy transfer process was confirmed. Slight improvement of the light yield under alpha-ray excitation was confirmed. [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]

Abstract Ce:(Gd,La) 2 Si 2 O 7 (Ce:La-GPS) and Al co-doped Ce:(Gd,La) 2 Si 2 O 7 (Al,Ce:La-GPS) single crystals were grown by the micro-pulling-down method to improve the mechanical, optical and scintillation properties. In a tensile test, the maximum strain and stress values in the stress-strain curve of the Al,Ce:La-GPS single crystal compared to the Ce:La-GPS single crystal and the result suggests that there is a possibility of the improvement on the mechanical property by Al co-doping. In addition, the light yield of the La-GPS single crystal under γ-ray irradiation was slightly increased and the decay time was accelerated by the Al co-doping. Highlights • Al co-doped Ce:La-GPS single crystals were grown by the μ-PD method. • It is a possibility that Al co-doping improves the mechanical property of the La-GPS. • Emission peaks originated from 5 d-4f transitions of the Ce3+ ion were observed. • The light yield under γ-ray irradiation was slightly increased by Al co-doping. • Scintillation decay times were accelerated by Al co-doping. [ABSTRACT FROM AUTHOR]

The In-doped LiCaAlF 6 [In:LiCAF] single crystals were grown by the micro-pulling-down (μ-PD) method, and the phases, chemical compositions, transmittance and radioluminescence spectra were investigated. All the grown crystals showed high transparency and single phase of LiCAF without visible cracks and inclusions except for the end part of In2%:LiCAF crystal which included the impurity phase. In the radioluminescence spectra of the In:LiCAF crystals under X-ray irradiation, the emission peak around 750 nm was revealed. [ABSTRACT FROM AUTHOR]

Monovalent Li + codoped Lu 3 Al 5 O 12 :Ce (LuAG:Ce) optical ceramics were fabricated by solid state reaction method and further optimized by an air-annealing process. Optical absorption, radioluminescence spectra and scintillation properties such as light yield, scintillation decay times and afterglow were measured and compared with those of the Li + free LuAG:Ce ceramic and the commercial LuAG:Ce single crystal samples. Positive effect of Li + codopant consists mainly in the significant increase of scintillation light yield, acceleration of scintillation decay as well as the decrease of afterglow intensity. With 0.3% Li codoping, the obtained LuAG:Ce,Li ceramic displays a light yield of ∼29200 ph/MeV at 10 μs shaping time, higher than that of the LuAG:Ce single crystal and optical ceramic scintillators ever reported. The partial conversion of the stable Ce 3+ to Ce 4+ centers and the shallow and deep traps effect suppression by the Li + codoping are discussed. [ABSTRACT FROM AUTHOR]

Lead halide perovskite nanocrystals of the formula CsPbBr3 have recently been identified as potential time taggers in scintillating heterostructures for time-of-flight positron emission tomography (TOF-PET) imaging thanks to their ultrafast decay kinetics. This study investigates the potential of this material experimentally. We fabricated CsPbBr3 thin films on scintillating GGAG:Ce (Gd2.985Ce0.015Ga2.7Al2.3O12) wafer as a model structure for the future sampling detector geometry. We focused this study on the radioluminescence (RL) response of this composite material. We compare the results of two spin-coating methods, namely the static and the dynamic process, for the thin film preparation. We demonstrated enhanced RL intensity of both CsPbBr3 and GGAG:Ce scintillating constituents of a composite material. This synergic effect arises in both the RL spectra and decays, including decays in the short time window (50 ns). Consequently, this study confirms the applicability of CsPbBr3 nanocrystals as efficient time taggers for ultrafast timing applications, such as TOF-PET. [ABSTRACT FROM AUTHOR]