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Driven by the pursuit of optimizing the luminescent properties of garnet-based single crystals for X-ray imaging applications, this work reports on the successful synthesis and in-depth characterization of GYAGG crystals doped with Ce³⁺ or Tb³⁺ ions, and doubly-doped with both of them. Micro-pulling down synthesis yielded crystals with a single cubic phase confirmed by X-ray diffraction. Photoluminescence (PL) and radioluminescence (RL) measurements on Ce³⁺,Tb³⁺ co-doped GYAGG revealed bidirectional energy transfer processes. Characteristic broadband 5d 1 →4f emission of Ce³⁺ centers peaking at 530 nm and narrow 4f→4f emission lines of Tb³⁺ ions starting from 5D 4 level within 480–630 nm were observed. At higher doping levels, cross-relaxation in Tb³⁺ pairs resulted depleted 5D 3 state and only the emission from 5D 4 one was observed in the spectra. Analysis of PL decay characteristics corroborated the spectral observations, confirming progressively decreasing Ce³⁺ decay time (down to 40 ns at 15 % Tb3+) due to enhanced Ce³⁺→Tb³⁺ energy transfer. Similarly, the Tb³⁺ decay time accelerated by more than 60 % after the Ce³⁺ co-doping. Notably, co-doping with 0.5 % Ce³⁺ and 10–15 % Tb³⁺ doubled the luminescence intensity of RL spectra compared to 0.5 % Ce³⁺-doping alone, attributed to the increased density of emitting centers. • High-quality and crack-free GYAGG:Ce,Tb single crystals were successfully grown. • The photoluminescence spectra revealed Ce³⁺↔Tb³⁺ bidirectional energy transfer. • At lower Tb³⁺ doping (0.5 %), the bidirectional energy transfer was inefficient. • High Tb³⁺ doping (15 %) significantly enhanced energy transfer. • Co-doping yielded a two-fold radioluminescence intensity compared to sole doping. [ABSTRACT FROM AUTHOR]

We have developed Eu:BaFCl ceramics with translucency and investigated the optical and scintillation properties. The emission peaks appeared at around 365 and 390 nm in Eu:BaFCl translucent ceramics. Photoluminescence and scintillation decay time constants were approximately 0.5 and 6 μs, which was typical value s of Eu:BaFCl. The afterglow levels were 50–80 ppm, which was superior to commercial Tl:CsI assessed in the same setup. Under 137Cs γ-ray irradiation, the scintillation light yield of the 0.1, 0.5, and 1.0 % Eu:BaFCl were calculated to be 9,000, 16,000, and 13,000 ph/MeV, respectively. The light yield of our translucent ceramic samples was shown to be much higher than that of the Eu:BaFCl single crystal (883 ph/MeV). • Eu-doped (0.1, 0.5, and 1.0 %) BaFCl translucent ceramics were synthesized by the spark plasma sintering method. • Eu:BaFCl samples showed blue luminescence with the maximum peak at 390 nm in both the photoluminescence and X-ray-induced scintillation spectra. • The 0.5 % Eu:BaFCl sample showed the highest light yield (16,000 ph/MeV) under 137Cs γ-ray irradiation. [ABSTRACT FROM AUTHOR]

The photoluminescence and scintillation properties of n-bromophenethylammonium lead chloride ((n-BrPEA) 2 PbCl 4) (n = 4, 3, and 2) and phenethylammonium lead chloride ((PEA) 2 PbCl 4) have been investigated. All the samples showed broad emission peaks at 400–700 nm upon excitation by UV light or X-ray. The decay time constants of 8–28 ns were obtained which originated from the recombination of self-trapped exciton (STE) within inorganic layers. The afterglow levels at 20 ms after 2 ms of X-ray irradiation of (4-BrPEA) 2 PbCl 4 and (3-BrPEA) 2 PbCl 4 (76 and 55 ppm) were better than (PEA) 2 PbCl 4 (379 ppm). The light yield of (4-BrPEA) 2 PbCl 4 (3100 photons/5.5 MeV-α) was higher than (PEA) 2 PbCl 4 (1400 photons/5.5 MeV-α). • (BrC 6 H 4 C 2 H 4 NH 3) 2 PbCl 4 crystals were grown by the slow cooling method. • All the crystals showed the luminescence due to the recombination of the self-trapped excitons confined in inorganic layers. • The (4-BrC 6 H 4 C 2 H 4 NH 3) 2 PbCl 4 crystal showed the highest QY in the present crystals. • The light yields of the (4-BrC 6 H 4 C 2 H 4 NH 3) 2 PbCl 4 crystals surpassed that of the unsubstituted crystal. [ABSTRACT FROM AUTHOR]

Scintillators are of significance for X-ray excited luminescence (XEL) imaging from scientific research to medical diagnostics application. Rare earth fluoride nanocrystals possess distinctive luminescent properties originated from the abundant energy level of lanthanide activators, showing potential applications as next-generation scintillators. Herein, high Z atomic rare earth element lutetium was chosen to synthesized NaLuF 4 -based nanoscintillators by Tb doping. Core-shell structure was fabricated to further enhance the XEL emission intensity. The NaLuF 4 -based nanoscintillators was demonstrated more efficient XEL emission with 3-folds increase compared to NaYF 4 nanocrystals. NaLuF 4 nanocrystals with a 25 mol% Tb doping and an inert shell coating exhibited excellent scintillation performance with detection limit as low as to 57.05 nGy air s−1. X-ray imaging demonstrated a high spatial resolution of 10.5 lp mm−1 using a scintillator film made from as-prepared NaLuF 4 -based nanoscintillators. Finally, such NaLuF 4 -based scintillators film have been applied in X-ray imaging application for a chip and a biological specimen. This study proposed an effective strategy to enhance XEL for rare earth fluoride, providing the ability for high-quality X-ray imaging. • Enhanced luminescence of X-ray excitation nanocrystals were demonstrated by selecting NaLuF 4 -based and core-shell structure. • The nanoscintillators exhibited excellent X-ray scintillation performance, achieving efficient X-ray luminescence imaging. [ABSTRACT FROM AUTHOR]

X-ray Excited Optical Luminescence (XEOL) from rare earth doped whitlockite phosphates and silicate garnets [Ca 9 La(PO 4) 7 and Ca 9 Lu(PO 4) 7 , doped with 1 mol% Ce3+; Ca 3 Sc 2 Si 3 O 12, doped with 0.5 mol% Pr3+, 1 mol% Eu3+ and 1 mol% Tb3+], was obtained upon X-ray excitation with a tunable synchrotron light source. Excitation at photon energies across the M 5,4 -edge of the dopants reveals additional information not normally obtainable with conventional UV/visible or an X-ray line source (Al K α). It is found that despite the low concentration, photoluminescence yields excited with photon energy at the M 5,4 -edge of the rare-earth dopant can positively and negatively affect the overall energy transfer to the optical center. The implication of these observations is discussed. The application of XEOL in the investigation of X-ray scintillators is illustrated. [Display omitted] • X-ray Excited Optical Luminescence (XEOL) from rare earth doped phosphates and silicates is investigated. • Excitation at the M5,4-edge of the dopants reveals additional information not obtainable with UV/visible light. • Excitation at the M5,4-edge can positively and negatively affect the overall energy transfer to the optical channel. • The application of XEOL in the investigation of X-ray scintillators is illustrated. [ABSTRACT FROM AUTHOR]

This work is dedicated to investigation of the luminescent properties of the prospective photoconversion material based on the crystal of Ce3+ doped Ca 3 Sc 2 Si 3 O 12 (CSSG) garnet. The GSSG:Ce crystal was grown using the micro-pulling-down (μPD) method. The CSSG:Ce crystal exhibited an intensive photoluminescence (PL) emission band with two sub-bands peaked at 504 and 545 nm, corresponding to 5d-4f (2F 5/2;7/2) transitions. Furthermore, we have investigated also the formation of cerium multicenters in the GSSG:Ce crystal using analyses of the structure of Ce3+ photoluminescence emission and excitation spectra under excitation of the luminescence of this crystal by synchrotron radiation. The formation of Ce3+-multicenters in CSSG:Ce garnet is caused by the local inhomogeneity of the dodecahedral sites of garnet lattice due to localization of the hetero-valent Sc3+ and Si4+ cations in the octahedral and tetrahedral positions of the garnet host. The existence of Ce3+ multicenters resulted in a significant enhancement of the Ce3+ emission band in the red range and improving the performance of conventional YAG:Ce phosphor. The next task of our work was to evaluate the possibility of application of the GSSG:Ce crystal as a light phosphor-converter (pc) for white light-emitting diodes (WLEDs). In the frame of this task, we have successfully developed a prototype of WLED by employing the CSSG:Ce crystal as a phosphor-converter (pc) with blue 450 emitting LED as well as investigated the color characteristics of this pc-WLED. • Ca 3 Sc 2 Si 3 O 12 :Ce (CSSG:Ce) crystal was grown by micropulling down method. • Presence of two different Ce1 and Ce2 emission centers was detected CSSG:Ce crystals. • Luminescent properties and energy structure of F+ and F centers in CSSG host were studied. • Prototypes of a white LED based on CSSG:Ce phosphor and blue LED were developed. [ABSTRACT FROM AUTHOR]

Hexagonal-structure Mg 4 Ta 2 O 9 (MTO) powders doped by 0.25 at% RE (RE = La3+, Ce3+, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+, Tb3+, Dy3+, Ho3+, Er3+, Tm3 +, Yb3+, Lu3+, Y3+, Sc3+) were synthesized. All the rare earth-doped samples were checked by X-ray diffraction (XRD) and confirmed to be monophasic powders. Among them, Mg 4 Ta 2 O 9 doped by 0.25 at% Gd3+ and Sc3+ had higher X-ray excited luminescence (XEL) emission peak intensities, 3.05 and 2.79 times of MTO, respectively. The optimal concentrations of Gd3+ and Sc3+ were investigated based on XEL main emission peak intensity changing with the amount of dopants in the range of 0∼1.0 at%. The optimal XEL emission peak intensities were measured 3.32 and 3.09 times of MTO for MTO: 0.8 at% Gd3+ and MTO: 0.4 at% Sc3+, respectively. The photoluminescence (PL) emission peaks at around 370 nm correspond to two excitation peaks at 158 and 215 nm. The excitation peak at 158 nm is about 10 times more than that of at 215 nm in intensity. The emission spectra excited by vacuum ultraviolet light at 158 nm and ultraviolet light at 215 nm were investigated associated with scintillation emission mechanism. MTO: 0.8 at% Gd3+ and MTO: 0.4 at% Sc3+ show potential application in security inspection, industrial detection, etc. • Single-phase Mg 4 Ta 2 O 9 : 0.25 at% RE (RE = La3+, Ce3+, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+, Tb3+, Dy3+, Ho3+, Er3+, Tm3 +, Yb3+, Lu3+, Y3+, Sc3+) samples were synthesized. • Single-phase Mg 4 Ta 2 O 9 : x at% M (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0; M = Gd3+, Sc3+) samples were synthesized. • MTO: 0.8 at% Gd3+ among MTO: x at% Gd3+ and MTO: 0.4 at% Sc3+ among MTO: x at% Sc3+ have the highest excitation peaks at 158 and 215 nm. • MTO: 0.8 at% Gd3+ and MTO: 0.4 at% Sc3+ have highest relative main XEL emission peak intensities of 3.27 and 3.09 times of MTO, respectively. • The scintillation emission mechanism of improving XEL properties of Mg 4 Ta 2 O 9 scintillators by rare-earth doping is thoroughly analyzed. [ABSTRACT FROM AUTHOR]

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

The study of plastic scintillators with polyurethane (PU) matrix based on cycloaliphatic isocyanate 4,4′-methylenebis (cyclohexyl isocyanate) (H 12 MDI) and 2,5-diphenyloxazole (PPO) as a luminescence activator is presented. A number of samples with different PPO content amounting up to 20 wt% were synthesized and their optical and luminescence characteristics were investigated. Pure H 12 MDI – PU based polymer exhibits low optical density in the spectral region 350–500 nm characteristic of the PPO emission band. The PU sample loaded with 5 wt% PPO demonstrated a light yield of 1088 photons/MeV and ultrafast rise and decay time of few picoseconds and few nanoseconds, respectively. The estimated coincidence time resolution (CTR) value for a PU sample is 1.4 times smaller than that known for a commercial scintillator BC-422 available for ultrafast timing applications. • A new plastic polyurethane (PU) based scintillator has been synthesized. • The concentration of PPO dopant in the PU scintillator can reach up to 20 wt%. • The PU sample loaded with 5 wt% PPO has a light yield of 1088 photons/MeV. • The new PU scintillator has an ultrafast rise time. • The CTR of the new PU scintillator is 1.4 times smaller than that of BC-422. [ABSTRACT FROM AUTHOR]

The luminescent properties of the single crystals of Ce3+ doped (Gd 1−x−y Lu x Y y) 3 Al 5 O 12 :Ce (x = 0.1; y = 1.5) and Gd 3 Ga x Al 5-x O 12 :Ce (x = 2.7) garnets (GLYAG:Ce and GGAG:Ce) were investigated in this work. Both crystals were grown by the micropulling down method. The conventional absorption and luminescence spectral measurements together with the luminescent spectroscopy under excitation by synchrotron radiation were performed to characterize the optical properties of crystals. It has been found that cumulative effects of reducing the ion radius from Gd3+ to Y3+ and Lu3+ in the dodecahedral sites of the garnets host and alloying of Al3+ ions in octahedral positions instead Ga3+ ions increases the crystal field strength and causes the respective redshift of the Ce3+ emission spectra in GLYAG:Ce crystals in comparison with GAGG:Ce garnet. The energy transfer from Gd3+ cations to Ce3+ has also been registered at the emission spectra and excitation spectra of both crystals. The energies of creation of the excitons bound with the Ce3+ ions in GLYAG:Ce and GAGG:Ce hosts were found to be equal to 6.415 ± 0.15 eV and 6.22 ± 0.15 eV, respectively. Both crystals show well-distinguished thermo- and optically stimulated luminescence (TSL and IR OSL) after α - and β -particle irradiation. Meanwhile, GAGG:Ce crystals show significantly higher TSL and IR OSL intensities (by 3–4 times) and faster OSL decay kinetics in comparison with GLYAG:Ce counterpart. • Gd 1.4 Lu 0.1 Y 1.5 Al 5 O 12 :Ce (GLYAG:Ce) and Gd 3 Ga 2.3 Al 2.7 O 12 :Ce (GAGG:Ce) garnet crystals were grown using the micro-pulling down method. • Luminescent properties of crystals were investigated using conventional spectral methods and synchrotron radiation excitation. • The energy of creation of the excitons bound with the Ce3+ ions in GLYAG:Ce and GAGG:Ce hosts was found. • Gd 1.4 Lu 0.1 Y 1.5 Al 5 O 12 :Ce and Gd 3 Ga 2.3 Al 2.7 O 12 :Ce crystals show well-distinguished TSL and IR OSL properties. • GAGG:Ce crystals show significantly higher TSL and IR OSL intensity and faster IR OSL decay kinetics in comparison with GLYAG:Ce counterpart. [ABSTRACT FROM AUTHOR]

We have designed a novel strategy to develop efficient X-ray-induced long afterglow luminescent materials. Eu3+ ions as electron receptors were chosen as trap creators and emitting centers and scintillator Bi 4 Ge 3 O 12 was regarded as the host to efficiently absorb X-ray. The obtained results showed that Bi 4 Ge 3 O 12 : Eu3+ can produce excellent x-ray induced red long afterglow luminescence which appeared at 589, 612, 655 and 705 nm corresponding to the 5D 0 →7F j (j = 1,2,3,4) transitions, respectively. The best afterglow performance was shown when the Eu3+ doping concentration was 0.5% at this time, and Bi 4 Ge 3 O 12 :Eu3+ also showed a strong afterglow under short-time X-ray excitation. The thermoluminescence results indicated the X-ray irradiation can produce massive secondary electrons and the abundant free electrons can easily induce Eu3+ ions to formed Eu2+* traps, which resulted in the excellent x-ray induced long afterglow luminescence of Bi 4 Ge 3 O 12 : Eu3+. Furthermore, the X-ray induced long afterglow red luminescence from Bi 4 Ge 3 O 12 :Eu3+ can persist for more than 5400 s, which still can be clearly observed by naked eyes even after 5400 s. All these results our designed strategy can realize the development of good X-ray induced long afterglow luminescent materials from scintillator to phosphor. • X-ray excited long afterglow material Bi 4 Ge 3 O 12 :Eu3+ shows red afterglow. • The transformation from scintillator to long afterglow material. • The Eu3+ to Eu2+ transition is responsible for the afterglow of Bi 4 Ge 3 O 12 :Eu3+. • A model is presented to clarify the afterglow mechanisms of Bi 4 Ge 3 O 12 :Eu3+. [ABSTRACT FROM AUTHOR]

Luminescence spectroscopic properties of lanthanide ions (Ce3+, Pr3+, Gd3+, Tb3+, and Dy3+) doped into Na 3 Y(BO 3) 2 were investigated upon UV-VUV excitation with synchrotron radiation. The positions of 4 f n–15 d state of Ce3+, Pr3+, Tb3+ and Dy3+ in host matrix Na 3 Y(BO 3) 2 were deduced according to the excitation spectra. Crystal-field depression D (A), an important parameter to predict the positions of the lowest 4 f n–15 d levels, was established on the basis of the 5 d levels of Ce3+ in Na 3 Y(BO 3) 2. Then, the average value of D (A) was obtained and further verified for 4 f n–15 d configurations of Pr3+, Tb3+ and Dy3+ in Na 3 Y(BO 3) 2. Finally, the lowest 4 f n–15 d levels of the other trivalent lanthanide ions in Na 3 Y(BO 3) 2 were predicted. The spectroscopic information on 4 f n–15 d levels of lanthanide ions in Na 3 Y(BO 3) 2 may provide new insights useful for designing of new efficient scintillators and WLED phosphors. [ABSTRACT FROM AUTHOR]

The luminescence and scintillation properties of SrI 2 single crystals doped with 5% Eu2+ and 0.05%, 0.2% and 0.5% Sm2+ are evaluated. X-ray excited and photoluminescence measurements show energy transfer from excited Eu2+ ions to Sm2+ ions. At a concentration of 0.5% Sm2+, the luminescence consists almost entirely of 740 nm emission from Sm2+ 5d-4f transitions. Co-doping SrI 2 :5% Eu2+ with Sm2+ provides a novel method to bypass the self-absorption problem encountered in large SrI 2 :Eu2+ crystals and, at the same time, provides a unique near-infrared emitting scintillator with a light yield of approximately 40,000 photons/MeV. [ABSTRACT FROM AUTHOR]

Abstract The work is dedicated to the investigation of the luminescent and scintillation properties of the LiLuP 4 O 12 :Ce tetraphosphate, as a new scintillation material. The LiLuP 4 O 12 :Ce polycrystalline samples were grown by the Micropulling down (MPD) method. Under e-beam excitation and excitation with energy above the band gap of host, the LiLuP 4 O 12 :Ce crystals possess very strong Ce3+ luminescence in the UV range in the bands peaked at 334 and 355 nm with a lifetime of 23 ns at room temperature. We have found that the scintillation light yield (LY) of polished plates prepared from MPD grown LiLuP 4 O 12 :Ce samples is relatively high and comparable with the LY of reference BGO crystal. Future improvement of the scintillation LY is expected at the optimization of the growth conditions of this compound. The energy structure of Ce3+ ions, related to the 4f-5d transitions of Ce3+ ions in the 3.7–25 eV range, was determined from the excitation and emission spectra of LiLuP 4 O 12 :Ce crystal under excitation by synchrotron radiation. We have also determined the energy of creation of excitons bound with Ce3+ ions and estimated the energy gap in LiLuP 4 O 12 host, which is equal to 8.5 and > 9.0 eV, respectively. [ABSTRACT FROM AUTHOR]

Abstract Eu3+ doped tellurite scintillating glasses were prepared by the conventional melt-quenching method. The physical and luminescent properties of glasses were investigated by DTA, density, transmittance spectra, photoluminescence spectra, and X-ray excited luminescence (XEL) spectra. The densities of the glasses are in the range from 5.89 g/cm3 to 6.05 g/cm3. The glasses exhibit intense red emissions upon 393 nm light and X-ray excitations. The maximum integral XEL intensity of the glasses is about 6% of that of commercial Bi 4 Ge 3 O 12 (BGO) scintillating crystal. The results reveal that Eu3+ doped tellurite glass could be a scintillator candidate used in X-ray detection field. [ABSTRACT FROM AUTHOR]

Abstract The glass phosphor thermoluminescence (TL) properties of zinc borate silica (ZBS:45ZnO-45B 2 O 3 –10SiO 2) doped with various concentrations of Cu 2 O and then co-doped with various SnO 2 was analyzed. The doped sample with 0.005% Cu 2 O concentration and co-doped with 0.1 mol% SnO 2 have a higher TL response among the other concentrations for a delivered dose 50 Gy of Cobalt-60 gamma radiation. The obtained glow curve from the optimum doped and co-doped samples with 0.005% Cu 2 O and 0.1 mol% SnO 2 concentrations are simple with single glow peak. The annealing procedure and heating rate are determined for both optimum samples. TL response within the dose range of 0.5–100 Gy, minimum detectable dose, reproducibility and fading are investigated. Based on analyses of glow curve, linearity, reproducibility, dose threshold, thermal fading, optical bleaching and activation energy frequency factor, the glass with co-doped 0.1 mol% SnO 2 found to be suitable as a thermoluminescence dosimeter. [ABSTRACT FROM AUTHOR]

Microstructural and luminescent properties of lithium lanthanum phosphate LiLaP 4 O 12 (LiLaPO), undoped and doped with trivalent rare earth (RE 3+ , RE = Ce, Eu, and Tb) ions, were studied. LiLaPO powders were synthesized by sol-gel method assisted by polyvinyl alcohol (PVA). The structural phase analysis was confirmed by X-ray powder diffraction (XRD). Scintillator properties were investigated to evaluate the luminescent response of the material under excitation with X-rays. The scintillation efficiency of the doped samples were compared to the one measured for a known BGO scintillator and it was shown that Tb-doped LiLaPO showed efficiency 30% higher than the BGO one. The chromaticity diagram was obtained from radioluminescent (RL) measurements. The stability of the RL response was investigated during long term X-ray exposure. The results showed that the RL efficiency of the LiLaPO increased almost by 40%, for the Ce-doped sample, and almost 25%, for Eu and Tb-doped samples, as the exposure time increased. This behavior was attributed to the presence of the deep trapping centers that trap charge carriers during the first stage of the irradiation, with a subsequent release of the trapped charges increasing the probability of the electron-hole pair recombination as a function of the time. Time-resolved RL was carried out to investigate the luminescent decay time for doped samples and, for Ce-doped samples, a fast decay component with luminescent decay time of 17 ns dominates. Typical millisecond decay components with decay time constants of 3.12 ms and 5.17 ms were observed for Tb 3+ and Eu 3+ -doped LiLaPO, respectively. Additionally, a slow component with decay time constant of 31.3 ms was also found for Eu 3+ -doped LiLaPO and this component was attributed to the existence very shallow traps in the material. [ABSTRACT FROM AUTHOR]

This paper reports the effects of Au codoping on the scintillation and optical properties of BaBrCl:Eu single crystals grown by the Bridgman-Stockbarger method. The study, performed by varying both Eu and Au concentrations, demonstrates the highly effective role of Au codoping for improving the scintillation light output for all the considered europium concentrations. These, up to trifold, improvements are accompanied by a substantial reduction in the long scintillation decay tails, and in the thermo- and optically stimulated luminescence intensities with respect to crystals doped only with Eu. The role of Au ions is discussed based on these experimental results. [ABSTRACT FROM AUTHOR]

The synthesis of efficient nano-scintillators is of great significance for the development of X-ray imaging and other applications. Here, X-ray excited afterglow rare earth nanoparticles β-NaLuF 4 :Gd3+/Tb3+ are investigated. The X-ray-induced luminescence intensity and afterglow duration of NaLuF 4 :Gd3+/Tb3+ nanoparticles are effectively improved by Ca2+ doping. The optimal luminescence and afterglow performance are achieved when Ca2+ doping ratio reaches 10%. The change of crystal field symmetry is the main reason for the improvement of luminescence performance. According to the thermoluminescence curve, it is proved that Ca2+ doping increases the trap concentration and further enhances the afterglow. This study provides the research basis for the application of persistent luminescence materials in biomedical and other fields. • NaLuF 4 :Ca2+/Gd3+/Tb3+ nanoparticles were synthesized by solvothermal method. • The X-ray induced luminescence of NaLuF 4 :Ca2+/Gd3+/Tb3+ NPs were improved by Ca2+ doping. • Afterglow properties were improved after 10% Ca2+ ions doping. [ABSTRACT FROM AUTHOR]

LiAlO 2 can be considered as a good candidate for neutron scintillator host matrix due to the high Li content and high energy deposit of reaction of 6 Li isotope with neutron. Low density (2.75 g/cm 3 ) is of advantage to achieve low sensitivity of background gamma radiation in mixed radiation fields. Ti-doped LiAlO 2 shows relatively high neutron light yield comparable to that of the Li-glass standard neutron scintillator. At room temperature the Ti 4+ charge transfer (CT) luminescence at 375 nm with the 2.5 µs decay time is the leading emission process. Besides the CT luminescence host emission at shorter wavelengths (350 nm), defect-related emission at 440 nm and impurity Fe 3+ luminescence at 740 nm are observed. Their emission spectra, excitation spectra and decay kinetics including temperature dependences were studied. Luminescence mechanism in the material and interplay between the luminescence processes are discussed together with possible role of nonstoichiometry and Mg codoping. [ABSTRACT FROM AUTHOR]

This paper deals with the study of 1-phenyl-3-(2,4,6-trimethyl-phenyl)-2-pyrazoline, 2,2´,7,7´-tetrakis(N,N-diphenyl-amino)-9,9´-spirobifluorene, 2-(4-biphenylyl)−6-phenylbenzoxazole and 9,9´-bifluorenyl as possible replacements of the existing and most widely used luminophore (2.5-diphenyloxazole (PPO)) in contemporary scintillators. The study is focused on the determination of emission wavelength, concentration optimization, the influence of the wavelength shifters POPOP and bis -MSB. In addition, the response to alpha and beta radiation were measured, in particular, the pulse length index (PLI) was determined. Finally, yet importantly, the effect of emulsifiers on the shape of the spectrum and the solubility of the aqueous phase was tested. The results obtained were compared with the commercially available Aqualight scintillation cocktail. [ABSTRACT FROM AUTHOR]

Ce:Cs 2 LiYCl 6 (CLYC) crystal is a marketable halide inorganic scintillator with very high light yield, excellent energy resolution and pulse-shape discrimination between gamma rays and thermal neutrons. Although the scintillation performance of Ce:Cs 2 LiLaCl 6 (CLLC) crystal is better than CLYC crystal, the promising application was restricted by the crystal growth difficulties. To utilize the advantage of La 3+ halide, research on the growth of Ce:Cs 2 LiLa x Y 1-x Cl 6 (0 < x ≤ 0.4) crystals were undertaken. The Ce:Cs 2 LiLa x Y 1-x Cl 6 with x = 0.05, 0.1, 0.2 and 0.4 were grown by the vertical Bridgman technique, and transparent Ce:Cs 2 LiLa 0.1 Y 0.9 Cl 6 samples were successfully obtained. The crystal structure and composition of the as-grown crystals were characterized by powder x-ray diffraction patterns. The luminescence and scintillation properties of the mixed elpasolites Ce:Cs 2 LiLa x Y 1-x Cl 6 (0 < x ≤ 0.4) crystals were also investigated. Finally, it was found that Ce:Cs 2 LiLa 0.1 Y 0.9 Cl 6 is a very promising gamma-rays and thermal neutrons scintillator with relatively high optical quality grown from vertical Bridgman method, acceptable energy resolution and relatively fast decay time. [ABSTRACT FROM AUTHOR]

Composite films of CdWO 4 embedded in polystyrene have been prepared and characterized through microtomography, photoluminescence and X-ray excited optical luminescence. CdWO 4 scintillator powder was successfully produced via microwave-assisted hydrothermal method using oxide precursors. With the control of synthesis pH, CdWO 4 wolframite structure was obtained at temperatures as low as 100 °C for reaction time of 1 h. Surface modification of CdWO 4 particles by stearic acid promoted good dispersion of scintillator nanoparticles within the polymeric matrix. The composites have been prepared with 220 µm or 440 µm thickness and CdWO 4 /PS mass ratios of 10% and 20%. Optical measurements show the characteristic CdWO 4 emission in the blue region as well as PS luminescence due to PPO, POPOP and PTO organic impurities. Under X-ray excitation, the light output was proportional to the increase of scintillator content and sample thickness. The emission intensity varied for each film face irradiated, being the most homogeneous condition achieved for the composite of 440 µm and CdWO 4 /PS = 10%. [ABSTRACT FROM AUTHOR]

Cathodoluminescence yield of hot intraband luminescence (IBL) under ∼100 keV pulsed electron excitation was evaluated in several halide and oxide compounds. Its values lie in the range of 5–35 ph/MeV, which is in accordance with the general assumptions on the mechanism of IBL. The expected inverse correlation between the IBL yield and highest phonon energies was found for binary compounds, therefore the IBL yield dependence on charge carrier thermalisation rate was experimentally confirmed. Consequently, CsI was found to have the highest IBL yield (33 ph/MeV) compared to other studied crystals due to its lowest phonon energy among them. The studied sample of pure CsI shows both cathodoluminescence and scintillation yields significantly higher than the value frequently cited earlier (2000 ph/MeV), pointing out that its intrinsic scintillation properties might be currently underestimated. CsI shows good coincidence time resolution (CTR) up to 110 ps FWHM in a TOF-PET-like geometry, which surpasses all the materials studied so far except the much more expensive scintillators from the lutetium-yttrium silicates family (CTR values up to 73 ps). Therefore, CsI can be considered as a promising material for low-cost TOF-PET machines. For complex (ternary) compounds the phonon energies and IBL yield are not noticeably correlated, and the highest spectral yield (at 2.5 eV) among the studied compounds is shown by Na 2 Mo 2 O 7 . [ABSTRACT FROM AUTHOR]

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

(Pr x Y 0.9 La 0.1 ) 2 O 3 (x = 0.05, 1, 5) transparent ceramics were fabricated by conventional ceramic processing. The absorption, emission spectra excited by ultraviolet and X-ray as well as the excitation spectra have been investigated as a function of the Pr 3+ concentration. The emission under ultraviolet excitation shows the ability of Pr 3+ to downconvert ultraviolet light to blue emission. The strong excitation band at 430–520 nm is in good agreement with the emissions of InGaN blue chips (λ em = 450–470 nm), which can be efficiently excited by the 470 nm light and generate bright red emission at around 630 nm. The radioluminescence spectra demonstrate the possible application of Pr 3+ : (Y 0.9 La 0.1 ) 2 O 3 in scintillator. In addition, the concentration quenching observed in the case of the P1 and P5 ceramics leads us to conclude that an optimum Pr 3+ concentration to generate the best luminescence properties is achievable. Given overall luminescence properties, the low Pr 3+ content (0.5 mol%) doped (Y 0.9 La 0.1 ) 2 O 3 transparent ceramic is a potential candidate for the applications in the ultraviolet-based and InGaN blue chip based white light-emitting diodes, as well as the scintillators. [ABSTRACT FROM AUTHOR]

In this paper, the effects of some synthesis parameters such as type and concentration of primary and secondary dopants, temperature and time of polymerization on luminescence properties of a vinyltoluene based plastic scintillator are investigated. Thermal polymerization was used to polymerize the samples. After synthesizing, the samples were cut into dimensions of 2.5 cm diameter by 1 cm thickness and were evaluated compared to the commercial sample BC-400. The results of gamma-ray spectroscopy under cobalt-60 and cesium-137 sources as well as photoluminescence spectroscopy showed that some synthesized plastic scintillators have a higher light yield with respect to commercial one. The measurements showed that the increase of dopant larger than optimum concentration degraded the performance of plastic scintillator due to concentration quenching. It was also found that pre-treatment at the temperature of 78 °C led to about 6% light yield loss compared to direct treatment at 160 °C, due to more non-uniform structure acquired during former treatment which might attenuate the efficient transfer of energy. [ABSTRACT FROM AUTHOR]

The work is necessitated by search for new materials to detect ionizing radiation. The rare-earth doped ternary alkali earth-halide systems are promising scintillators showing high efficiency and energy resolution. Some aspects of crystal growth and data on the structural and luminescence properties of BaBrI and BaClI doped with low concentrations of Eu 2 + ions are reported. The crystals are grown by the vertical Bridgman method in sealed quartz ampoule. New crystallographic data for BaClI single crystal obtained by single crystal X-ray diffraction are presented. Emission, excitation and optical absorption spectra as well as luminescence decay kinetics are studied under excitation by X-ray, vacuum ultraviolet and ultraviolet radiation. The energies of first 4f-5d transition in Eu 2 + and band gaps of the crystals are obtained. The electronic band structure of the crystals are calculated using density functional theory as implemented in Vienna Ab initio Simulation Package. Calculated band gap energies are in accordance with the experimental estimates. The energy gaps between the valence band maximum and occupied Eu 2 + 4f levels in BaBrI and BaClI are suggested. In addition, vacuum referred binding energy diagram of lanthanide levels is constructed using the chemical shift model. [ABSTRACT FROM AUTHOR]

Hot intraband luminescence (IBL) was observed under excitation by high-power (120 keV, 10 A/cm 2 ) pulsed electron beam, low-energy (10 keV) and low-current (2 μA) continuous electron beam as well as pulsed x-rays. Thus, the fundamental possibility of IBL excitation by x-rays was confirmed, and for most studied materials the absence of the dependence of IBL spectral shape on excitation energy was revealed. For the first time, the intraband luminescence was monitored under low-power excitation, which confirmed the absence of a power threshold of its mechanism and completely ruled out the role of excitation density effects in IBL formation. The data obtained allow the prediction that the IBL can be excited by single photons of 511-keV energy, which is required for enhancing scintillation time resolution in TOF-PET. [ABSTRACT FROM AUTHOR]

Very low amount of Eu and alkali metal (Na, K, Rb and Cs) co-doped LiCaAlF 6 crystal scintillators were prepared by using the micro-pulling down method to investigate the origin of the light yield enhancement and the fast luminescence of LiCaAlF 6 -based scintillators. In X-ray and α-ray induced scintillation spectra, the host and Eu 2+ 5d-4f transition emission appeared around 300–500 nm as a broad shape and 370 nm as a sharp line, respectively. At a synchrotron facility (UVSOR), the excitation spectra under vacuum ultra violet (VUV) photons excitation were investigated, and the results confirmed new excitation bands around 80–90 nm as well as the band gap of LiCaAlF 6 (~113 nm). Fast luminescence with the lifetime of few ns was confirmed in K, Rb and Cs doped samples under VUV and X-ray excitations. The detector property was tested, and K co-doping improves the pulse shape discrimination performance. [ABSTRACT FROM AUTHOR]

The study of optical and photoluminescence properties of codoped Lu 2 SiO 5 :Ce, Yb single crystals was performed using conventional spectroscopy as well as time-resolved spectroscopy under excitation by pulsed synchrotron radiation. It was shown that the quenching of cerium luminescence is due to the nonradiative energy transfer from Ce3+ to Yb3+ ions. It was confirmed also that such energy transfer is not cooperative process. According to the constructed vacuum referred binding energy diagram the possible mechanism of quenching of cerium luminescence is the metal-to-metal electron transfer from Ce3+ to Yb3+. • The formation of luminescence properties of LSO:Ce,Yb crystals were studied at UV-VUV excitation. • The nonradiative energy transfer from the cerium to ytterbium has been shown. • The energy transfer mechanism is not cooperative. • Vacuum referred binding energy diagram for Lu 2 SiO 5 :Ce,Yb was constructed. [ABSTRACT FROM AUTHOR]

A good quality Zr:GdTaO 4 single crystal with an 8.84 g/cm3 density, higher than the well-known dense scintillator PbWO 4 , was successfully synthesized by the Czochalski method for the first time. The effective segregation coefficient of Zr in Zr:GdTaO 4 is 0.288. The light yield and the energy resolution of Zr:GdTaO 4 are approximately the same as GdTaO 4. The scintillation decay time of Zr:GdTaO 4 contains a fast decay of 9.51 ns, close to the fast scintillator PbWO 4 , and a slow decay of 755.61 ns, which is much faster than that of GdTaO 4 whose fast decay time is 101.82 ns and slow decay time is 3290.52 ns. With Zr4+ doping, the photoluminescence band of GdTaO 4 is blueshifted and the traps are shallowed, which may help accelerate the scintillation decay. As far as we know, the Zr:GdTaO 4 single crystal is the densest scintillator with a less than 10 ns scintillation decay time, which can be used in electromagnetic calorimeters. • A Zr:GdTaO 4 single crystal with an 8.84 g/cm3 density was first synthesized. • Zr:GdTaO 4 crystal contains a fast scintillation decay of 9.51 ns, close to PbWO 4. • Blueshifted luminescence band and shallowed trap accelerate the scintillation decay. [ABSTRACT FROM AUTHOR]

Luminescent nanopowders of single (Y 3 Al 5 O 12 :Ce 3+ ) and multicomponent (Lu 2 Gd 1 Al 5 O 12 :Ce 3+ ) garnets were synthesized by the solvothermal method in a high pressure autoclave. The synthesis conditions were optimized with respect to morphological and photoluminescence properties. Optimized conditions allow to synthesize well-dispersed nanoparticles with a size of some 30 nm. Concentration quenching of the Ce 3+ emission as well as luminescence quenching by surface states of nanoparticles were found and discussed. [ABSTRACT FROM AUTHOR]

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

The X-ray luminescence and scintillation properties of undoped ZnTe crystal were investigated as function of temperature down to T<10 K. The luminescence of ZnTe is quenched at room temperature, but below 150 K the crystal exhibits emission at 575 nm with characteristic recombination decay kinetics. The emission is attributed to the radiative annihilation of electrons captured at the shallow levels of impurities or defects with holes trapped by Zn vacancies. The temperature dependence of scintillation light output of ZnTe was studied. It was found that at excitation with α-particles the light output of undoped ZnTe is 117±20% of a reference CaWO 4 crystal measured under the same experimental conditions. It is concluded that undoped zinc telluride is a promising scintillator for cryogenic application, particularly for the cryogenic search for neutrinoless double beta decay (0νDBD) of 130 Te. [ABSTRACT FROM AUTHOR]

We report on the efficient photoluminescence (PL) and radioluminescence (RL) of the PbI 2 nanoclusters (NCLs), which are naturally formed in the nanostructured Pb 1-X Cd x I 2 alloys (X=0.70). Here, we carried out the studies of the nature of radiative recombination processes in the NCLs of various sizes by measuring PL temperature evolution. Our results indicate that at low temperatures the PL is mainly caused by exciton emission and recombination of donor-acceptor pairs, generated in volume of large NCLs. The broad bands, which are associated with the deep intrinsic surface states, including self-trapped excitons (STEs), are dominant in the PL spectra at higher temperature (>100 K). Our work shows that the nature of emission, associated with RL bands is analogous to that for PL bands. It was shown that the investigated nanostructured material is strongly radiation-resistant. Thus, the Pb 1-X Cd X I 2 alloys can be considered as new effective layered semiconductor nanostructured materials which can be suitable for the elaboration of perspective semiconductor scintillators. These nanomaterials have promising prospects for applications in new generations of devices for biomedical diagnostics and industrial imaging applications. [ABSTRACT FROM AUTHOR]

In 2 Si 2 O 7 is a known indium-based scintillator with fast ultraviolet photoluminescence. Unfortunately the emission only can be detected below 200 K. the poor thermal stability limits its application at room temperature. In this work, the luminescence improvement of In 2 Si 2 O 7 was realized by F − -ions doping in the lattices. The ceramic phosphors were via typical solid-state reaction method. The pure crystalline phase with thortveirite-type structure was confirmed by X-ray diffraction (XRD) Rietveld refinements. The photoluminescence (PL) emission and excitation spectra together with the luminescence thermal stability were tested. The fluorescence decay curves CIE emission Stokes shifts were measured. The ceramic samples could present blue luminescence with maximum wavelength at about 340 nm under the excitation of UV light or high energy X-ray irradiation. The pure sample only presents luminescence below 200 K, however, the F-doping can be greatly enhance the luminescence thermal stability. The F-doped In 2 Si 2 O 7 could present emission signals with fast decay lifetime of 850 ns at room temperature. The luminescence transitions from the In 3+ -O 2− charge transfer (CT) were discussed on the structure properties. [ABSTRACT FROM AUTHOR]

In this work, density, optical, photoluminescence and x-ray scintillation properties of calcium gadolinium silicoborate glass (CaO:Gd 2 O 3 :SiO 2 :B 2 O 3 ) have been investigated. Glasses were prepared by the conventional melt quenching technique. The results show that the density of glass increased with increasing of Sm 2 O 3 . The optical spectra of glass shows eleven discrete absorption bands at 360, 373, 403, 475, 944, 1077, 1225, 1368, 1468, 1520 and 1586 nm which are due to the transitions of 6 H 5/2 to 4 D 3/2 , 6 P 7/2 , 6 P 3/2 , 4 I 11/2 , 6 F 11/2 , 6 F 9/2 , 6 F 7/2 , 6 F 5/2 , 6 F 3/2 , 6 H 15/2 and 6 F 1/2 , respectively. The emission spectra were observed and assigned to 312, 563, 600, 646 and 703 nm by excitation at 275 nm. The emission intensity of Sm 3+ increased with increasing of Sm 2 O 3 concentration until 0.25 mol%, while decay time decrease with increasing of Sm 2 O 3 content. For results of the radioluminescence (RL), they perform four emission peaks with the strongest emission at 598 nm. Glass doped with 0.35 mol% Sm 2 O 3 show the highest RL emission. The integral scintillation efficiency of 0.35 mol% Sm 2 O 3 doped glass was determined as 25% of commercial BGO scintillator crystal. [ABSTRACT FROM AUTHOR]

Lutetium aluminum garnet nanopowders doped with Pr in concentration range 0.1–10 at% prepared via photo-induced synthesis were studied in this work. The preparation and luminescence properties of these high-density materials are reported, featuring fast response and high scintillation efficiency. Prepared samples were characterized using several analytical methods to determine the structure of the prepared materials and their luminescent properties, which are discussed and compared with analogous bulk material (single crystal). [ABSTRACT FROM AUTHOR]

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

The development of multifunctional nanocrystals has attracted growing interest lately in the biological and medical sciences. Herein, the dual-mode luminescence properties and optical thermometric performances of Tm3+, Yb3+: Gd 2 Zr 2 O 7 nanocrystals synthesized by a facile hydrothermal method are investigated systematically. Upon 980 nm excitation, the upconversion (UC) luminescence spectra of the obtained samples consist of blue (485 nm), red (655 and 681 nm), and near-infrared (785 nm) emission bands of Tm3+ ions. Diversely, the X-ray excited luminescence (XEL) spectra contain a strong ultraviolet (UV) emission from Gd3+ ions (314 nm), a weak defect-related emission band (400–600 nm), and several tiny emissions from Tm3+ ions. To realize the optical thermometry in the biological window, the luminescence intensity ratio (LIR) between 3F 2,3 → 3H 6 (681 nm) and 1G 4 →3F 4 (655 nm) transitions is employed for temperature sensing, giving high absolute and relative sensing sensitivities (S a-max = ∼1064 × 10−4 K−1, S r-max = ∼2.32%K−1). Therefore, the present Tm3+, Yb3+: Gd 2 Zr 2 O 7 nanocrystals could be useful in optical thermometry, photodynamic therapy, and X-ray imaging. • Dual-mode luminescence and thermometric properties of Tm3+/Yb3+: Gd 2 Zr 2 O 7 are studied. • UCL spectra consist of blue, red and NIR emissions of Tm3+ upon 980 nm excitation. • UV emission from Gd3+ is predominant under X-ray excitation. • LIR of 681 nm–655 nm shows high sensing sensitivity with S r-max of 2.32% K−1. • Tm3+/Yb3+: Gd 2 Zr 2 O 7 could be used for optical thermometry and photodynamic therapy. [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]

Developing efficient strategies to fabricate planar photoluminescence scintillators is of great importance to explore X-ray detectors with new platform. Rare-earth (RE) doped Lu 2 O 3 thin films are successfully fabricated by mild aqueous phase electrochemical deposition on ITO/glass substrates with low-temperature post-annealing treatment. The as-prepared Lu 2 O 3 :RE3+ (RE = Eu, Tb and Tm) thin films exhibit steerable thickness, high transparency in the visible-NIR range, and low transmittance at UV band mainly due to the oxygen-metal (O2--RE3+) charge transfer processes and the 4f-4f transitions of the RE3+. The Lu 2 O 3 :RE3+ thin films emit intense red, green and blue (RGB) photoluminescence, which mainly correspond to the 5D 0 -7F 2 transition of Eu3+, 5D 4 -7F 5 transition of Tb3+ and 1G 4 -3H 6 transition of Tm3+ respectively. Moreover, the transparent Lu 2 O 3 :RE3+ thin films also exhibit high sensitivity and linearity luminescence to the X-ray stimulation in a dose rate from 30 to 160 mGy s−1. This rapid and energy-saving synthesis show high efficiency to fabricate rare-earth doped thin-film with a tunable optical performance for optoelectrical application in the fields of solar light concentrators, agricultural light conversion thin films, biosensors, photodetectors and especially the X-ray detectors. [Display omitted] • The thickness of Lu 2 O 3 :RE3+ (RE = Eu, Tb and Tm) films prepared by electrodeposition is controllable. • The thin films exhibit high transparency at Visible-NIR band. • The Lu 2 O 3 :RE3+ thin films emit intense RGB photoluminescence upon UV light excitation. • The Lu 2 O 3 :RE3+ thin films exhibit high sensitivity and linearity to the X-ray. [ABSTRACT FROM AUTHOR]

The Tm-doped MgAl 2 O 4 single crystals were synthesized by using Xe arc lamps-equipped floating zone furnace. The synthesized crystals exhibited luminescence due to the 4f-4f transitions of Tm3+ in photoluminescence (PL), scintillation, and thermally stimulated luminescence (TSL). In all of PL, scintillation, and TSL, the 0.5% Tm-doped crystal showed the highest luminescence intensity. In TSL dose response functions, the 0.5% Tm-doped crystal showed sensitivity from X-ray irradiation with 0.1 mGy. In addition, we measured linear energy transfer (LET) dependence on TSL glow curve of the crystal and X-ray imaging test taken by TSL. We revealed the spatial resolution of the crystal was 100 μm. • We have characterized the photoluminescence, scintillation, and dosimetric properties of Tm-doped MgAl 2 O 4 single crystals. • All the crystals showed luminescence properties due to Tm3+ ion. • We revealed possibility of Tm-doped MgAl 2 O 4 crystal for personal dosimetry, 2D dosimetry, and heavy ion beam measurement. [ABSTRACT FROM AUTHOR]

Y 3 Al 5 O 12 :Ce (YAG:Ce) polycrystalline ceramics with 0.1 and 0.3 mol% Ce substituting for Y were fabricated by laser sintering and characterized in their microstructure, luminescence, thermoluminescence and scintillation in comparison to a single crystal. The polycrystalline ceramics had cubic single crystallographic phase and relative densities of 97 ± 1 and 99 ± 1% for the 0.1 and 0.3 mol% Ce concentrations, respectively. The combined results of attenuated total reflection Fourier transform infrared (ATR FTIR) spectroscopy and photoluminescence measurements showed the polycrystalline ceramics fabricated by laser sintering to contain a higher level of structural disorder than the single crystal. The consequent broadening of the luminescence bands caused enhanced self-absorption in the polycrystalline ceramics. Radioluminescence (RL) under X-ray excitation, optical transmission and photoluminescence measurements revealed the presence of numerous types of point defects, including F centers, F+ centers/perturbed F+ centers and Y Al anti-sites. A detailed investigation of the thermoluminescence of YAG:Ce was executed using different methods and a complex behavior deviating from the first order kinetics mechanism was observed. The scintillation response of the polycrystalline ceramics was evaluated under low energy γ-ray irradiation. • Detailed comparison between laser-sintered ceramic and single crystal YAG:Ce. • Comprehensive thermoluminescence analysis. • Ceramics have higher level of structural disorder and shallower traps. [ABSTRACT FROM AUTHOR]

Fast energy transfer from Yb2+ to Sm2+ is a requirement when using Yb2+ as a sensitiser for Sm2+ emission for near-infrared scintillator applications. This cannot be achieved through dipole-dipole interactions due to the spin-forbidden nature of the involved Yb2+ transition, making the rate of energy transfer too slow for application. This work explores whether exploiting the exchange interaction by increasing the Yb2+ concentration to 99% is an effective way to increase the rate at which energy is transferred from Yb2+ to Sm2+. The scintillation characteristics of CsYbBr 3 :1%Sm, CsYbI 3 :1%Sm and YbCl 2 :1%Sm single crystals were studied through 137Cs excited pulse height spectra, X-ray excited decay and X-ray excited luminescence spectra. An energy resolution of 7% and a light yield of 30,000 ph/MeV was achieved with CsYbI 3 :1%Sm. Photoluminescence spectroscopy and decay studies were performed to study the band structure and relaxation dynamics. • Energy transfer from Yb2+ to Sm2+ happens on a subnanosecond timescale. • Detection of 20,000 photons in the 662 keV photopeak for CsYbI 3 :1%Sm. • A 7% energy resolution was achieved with CsYbI 3 :1%Sm. • Sm2+ emission intensity of all samples is stable between 78 K and 700 K. [ABSTRACT FROM AUTHOR]

In the present paper, physical, structural, optical and luminescence properties of Sm3+ activated scintillating glasses with variation in Bi 2 O 3 concentration have been studied. The amorphous nature of the glass samples was ascertained by the presence of a broad hump in XRD spectra. FTIR examinations advocated that Bi 2 O 3 exists primarily as [BiO 6 ] units and BO 4 units enhanced with surging bismuth oxide content. The values of density increase continuously with the addition of Bi 2 O 3 , whereas V m first decreases till 25 mol% Bi 2 O 3 content, after that it is found to increase. Optical characterization of samples affirms strong sensitivity towards the absorbance of UV–visible radiation. Among the prepared samples, 35 mol% of Bi 2 O 3 doped glass showed the lowest bandgap, high refractive index and Urbach energy. Also, it contains more localized states that confirm its suitability as a protection material from UV radiation. PL results reveal the strong emission occurs at 562, 598, 644, 704 nm wavelength and Bi15 glass exhibits maximum intensity in both excitation and emission spectrum. The intense emission peak originated from 4G 5/2 → 6H 7/2 transition centered at 600 nm in XRL which discloses the scintillation properties of the material. The CIE chromaticity diagram demonstrated the emission located in the reddish-orange region, which suggests prepared glasses could be useful for reddish-orange laser and LED. Thus, 15 mol% Bi 2 O 3 doped glass becomes more efficient for the use of scintillators in high-energy physics experiments. • Al 2 O 3 -B 2 O 3 -Bi 2 O 3 -Sm 2 O 3 borate glass samples were fabricated using melt quenching technique. • Bi 2 O 3 acts as a modifier at low concentration and acts as a glass former at higher concentration. • Steepness parameter confirmed the formation of the localized state till Bi25. • PL and XRL have measured for the prepared glass samples. • Bi15 glass has better emission, CIE colour and CCT value than other existing glasses. [ABSTRACT FROM AUTHOR]

Hafnium-based materials are attractive for a scintillator owing to their high density and effective atomic number. In this study, single crystals of Ce-doped calcium hafnate perovskite (Ce:CaHfO 3) were synthesized from a Ca-rich composition, and photoluminescence (PL) and scintillation properties were investigated. The X-ray diffraction patterns revealed that the synthesized single crystals were a single phase of CaHfO 3. The Ce:CaHfO 3 exhibited blue luminescence at 430 nm and fast decay due to the 5d–4f transition of Ce3+ in both PL and scintillation. From the measurement of pulse height spectra under 137Cs irradiation, the highest light yield of 7800 photons/MeV was observed in the 3% Ce:CaHfO 3. • Single crystals of Ce-doped calcium hafnate perovskite (Ce:CaHfO 3) were successfully synthesized from a Ca-rich composition. • Ce:CaHfO 3 exhibited blue luminescence and fast decay due to the 5d–4f transition of Ce3+ in both PL and scintillation. • The light yield of 7800 photons/MeV was observed in the 3% Ce:CaHfO 3 under 137Cs gamma-ray irradiation. [ABSTRACT FROM AUTHOR]

Intraband luminescence (IBL) is a prompt emission originating from the radiative intraband transitions of charge carriers during thermalisation. Despite its low intensity, IBL can hopefully enhance scintillation time resolution, for instance, in positron emission tomography. The continuous and structureless spectrum of IBL spans over the whole transparency region of a material. Exploiting a wide spectral sensitivity range of our instrumentation (0.77–10.6 eV), we have discovered a strong rise of IBL spectral yield in the NIR region in all studied compounds, which could not be explained within the available theoretical models of IBL. We have developed a new model attributing the NIR rise of the IBL spectrum to the phonon-assisted electron transitions within a single parabolic energy band, which yields a fair correspondence to our experimental data. [ABSTRACT FROM AUTHOR]