Search

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]

The development of Eu2+-activated oxide materials with high efficiency, fast decay and narrow bandwidth emission in the visible region is still challenging for the field of luminescence and scintillation applications. Generally, Eu2+ in oxide hosts can emit intense and broad 5d-4f emission in the visible region, but efficient emitting with stable bivalence of Eu is rare in inorganic oxide system. In this work, a series of ASL:Eu2+ (Sr 1-x La x Mg x Al 12-x O 19) powder samples with various La, Mg doping ratios were designed and synthesized to modulate the UV or X-ray excited luminescence properties, including redshift, quantum yield, and decaying lifetime. Moreover, an ASL:Eu2+ crystal with the optimal ratio x = 1/3 was grown, its scintillation performance was compared with standard Bi 4 Ge 3 O 12 crystal sample and evaluated in detail. These results indicate that the ASL:Eu2+ crystal is potential scintillator as a kind of X-ray detection and provide a reference for the further development of high-performance Eu-activated oxide scintillation materials. • The La, Mg dopants in SrAl 12 O 19 host promotes the red shift of Eu2+ emission under UV excitation. • The ASL:Eu2+ shows the self-trapped excitons radiation in XEL spectra. • The light yield of the as-grown ASL:Eu2+ crystal was determine to be 111.6 p.e./MeV. [ABSTRACT FROM AUTHOR]

We have developed LiAlO 2 nanoparticle-loaded polystyrene-based plastic scintillators for neutron detection and evaluated the neutron detection properties. The size of LiAlO 2 nanoparticles was ∼150 nm. The distribution of nanoparticles in the plastic scintillator was uniform in the horizontal direction but non-uniform in the vertical direction. The emission peak was observed around 420 nm in the scintillation spectra and is attributed to1,4-Bis[2-(5-phenyloxazolyl)] benzene (POPOP) included as an organic phosphor. The 10 wt% LiAlO 2 nanoparticle-loaded plastic scintillators containing 22 wt% 2,5-Diphenyloxazole (DPO-POPOP (the molar ratio of 80:1) had the highest light yield of 1600 photons/neutron, which is significantly higher than that of a commercially available 10B-loaded plastic scintillators (BC-454) having a light yield of 800 photons/neutron. • We developed LiAlO 2 nanoparticle-loaded plastic scintillators for neutron detection. • The light yield of 1600 photons/neutron was achieved. • The size of LiAlO 2 nanoparticles was ∼150 nm. [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]

Zero-dimensional (0D) hybrid indium halides have recently received great attention for their potential as X-ray scintillators due to their non-toxicity, superior optical properties and exceptional stability. However, most indium halides suffer from low emission efficiency, resulting in inferior performance. Herein, we demonstrate that a small amount of Sb3+ doping can greatly enhance the photoluminescence efficiency of a 0D hybrid indium chloride, DMA 4 InCl 7. The pristine crystals exhibit weak self-trapped exciton (STE) emission centered at 620 nm with a low quantum yield of 11%. After Sb3+ doping, the STE emission efficiency can be greatly increased to 91%. The spectroscopic experiments and theoretical calculations indicate the efficient energy transfer from excited Sb3+ ions to the emitting STE state of the host is responsible for the substantial increase in emission efficiency. Furthermore, we find the energy transfer efficiency is related to the distance between dopants and [InCl 6 ]3- units. The strong STE emission endows the doped samples with desirable X-ray scintillation performance, with a high light yield of 23500 photons/MeV and a low detection limit of 175 nGy air ·s−1. [Display omitted] • Sb3+ doping increases the STE emission efficiency of DMA 4 InCl 7 from 11% to 91%. • The energy transfer from Sb3+ to the STE state leads to the enhanced emission. • The energy transfer efficiency is related to the Sb–In distance within lattice. • Sb3+ doped DMA 4 InCl 7 exhibits great X-ray scintillation properties. [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]

0.05, 0.1, 0.5, and 1% Nd-doped CsI single crystals were synthesized by the vertical Bridgman-Stockbarger method, and the photoluminescence and scintillation properties were evaluated. Under X-ray irradiation, two emission peaks were observed at 310 and 430 nm ascribed to on- and off-center configuration self-trapped excitons, respectively. In near-infrared regions, sharp peaks were observed at 900, 1080, and 1350 nm due to 4F 3/2 -4I 9/2 , 4F 3/2 -4I 11/2 , and 4F 3/2 -4I 13/2 transitions of Nd3+, respectively. Dose rate response functions had good linearity in the range of 0.06–6 Gy/h in all the samples, and the 0.5% Nd-doped sample showed the highest intensity among all the samples. • Photoluminescence and scintillation properties of Nd-doped CsI were evaluated. • Under X-ray irradiation, three peaks were observed at 900, 1080, and 1350 nm due to 4F 3/2 -4I 9/2 , 4F 3/2 -4I 11/2 , and 4F 3/2 -4I 13/2 transitions of Nd3+. • Dose rate response functions had good linearity in the range of 0.06–6 Gy/h in all the samples, and the 0.5% Nd-doped sample showed the highest intensity among all the samples. [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]

Scintillators have been commercialized as radiation detectors in several practical applications. However, fabrication of commercial inorganic crystal scintillators is time-consuming and expensive. Herein, we report inorganic glass scintillators for gamma and X-ray detection based on phosphate glasses, with alkali and alkali earth metals in the host and Ce3+ ions as emission centers. Unlike inorganic crystals, inorganic glasses have industrial advantages owing to their low cost and ease of fabrication, which facilitate the large-scale production of scintillators. Previously studied inorganic glass scintillators for gamma and X-ray detection exhibited low light yields compared to inorganic crystal scintillators. In contrast, our glass exhibits a high light yield of 3200 photons/MeV. This light yield is higher than that of previously reported glasses, whose light yields are less than several hundred photons/MeV in most cases and approximately 2000 photons/MeV as the highest value. In addition, this glass has a relatively high density of 3.33 g/cm3 and a fast scintillation decay of approximately 30 ns, which is attributed to the 5d–4f transition of Ce3+ ions acting as emission centers. These properties are suitable for gamma and X-ray detection and this glass has the potential to expand the practical applications of inorganic glass scintillators. • We fabricated a phosphate glass scintillator for gamma- and X-ray detection. • This glass exhibited a high light yield of 3200 photons/MeV. • This glass has the potential to expand applications of glass scintillators. [ABSTRACT FROM AUTHOR]

A statistical model based on the condition of thermal and diffusive equilibrium between the conduction electrons and the electrons in the excited 5d 1 level of Ce3+ is presented. Using this model, we find the probability for an excited Ce3+ ion to be thermally ionized leading to an electron in the conduction band. The density of conduction electrons is then calculated over a wide range of temperatures and excitation densities. The observed quenching of emission at high temperature in Ce-doped YAG with low Ce concentrations is also investigated within this model. It is shown that the experimentally-observed nonradiative losses in this phosphor can be reasonably simulated assuming losses occur via nonradiative decay from the conduction band to the Ce3+ ground state. • We present a model of thermal ionization in YAG:Ce leading to conduction electrons. • The density of conduction electrons in YAG:Ce is calculated. • Conduction electron trapping by Ce4+ explains losses in YAG:Ce at high temperatures. • Discrepancy between activation energy and ionization energy is explained. [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]

Understanding of host-to-impurity energy transfer process is crucial for the development of efficient and fast response scintillator materials. In this work, Pr3+ doped Na 3 LuSi 3 O 9 (NLS) double salt silicate has been successfully synthesized using a high temperature solid-state reaction method and further comprehensively characterized by means of XRD measurements, crystal structure refinement, luminescence spectroscopic and time-domain study upon VUV-UV and X-ray synchrotron excitation, and thermally stimulated luminescence (TSL) study. Based on these results a model of host to Pr3+ 4 f 15 d 1 and 4 f 2 has been proposed. It has been demonstrated that NLS:Pr3+ has a good potential for fast response scintillator applications due to the presence of an efficient energy transfer from host electronic excitations to Pr3+ 4 f 15 d 1 states. The Pr3+ 4 f 15 d 1→4 f 2 emission reveals a good thermal stability and is characterized by a lifetime of about 16 ns. Upon pulse X-ray excitation the main fast decay component is accompanied by slower one with lifetime of about 64 ns that is ascribed to the presence of shallow traps which retrap carriers and cause appearance of delayed recombination. Parameters for the corresponding traps have been calculated based on the TSL glow curve analysis. • Pr3+ doped Na 3 LuSi 3 O 9 double salt silicate was synthesized by solid-state reaction method. • Thermally stable luminescence from Pr3+ 4 f 15 d 1 with life time of ∼16 ns was observed. • Efficient energy transfer from host to Pr3+ 4 f 15 d 1 is explained by electron-hole recombination at Pr3+ • 5 types of traps with domination of shallow ones was determined by TSL measurements. • Na 3 LuSi 3 O 9 :Pr3+ was found to be promising for fast response scintillator applications. [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]

Improving the spatial resolution of X-ray imaging is one of the main directions of scintillation screen research. Herein, a structured Cs 3 Cu 2 I 5 scintillation screen based on oxidized silicon micropore array template was developed. A feasible method was explored to solve the problems such as the preparation of oxidized silicon micropore array template with micron-period structure and the compact filling of Cs 3 Cu 2 I 5 scintillator into the template. The X-ray imaging resolution using the structured Cs 3 Cu 2 I 5 scintillation screen reaches 113 lp/mm attributing to the light guide and optical isolation of the template pore walls. The results of detective quantum efficiency, the X-ray imaging photographs of a micro-resolution plate and a small zebrafish show that the image quality using the structured screen is excellent. Meanwhile, the developed Cs 3 Cu 2 I 5 scintillation screen exhibits good radiation resistance, which can keep the light output basically unchanged when the radiation dose is up to 43.2 Gy. The screen also exhibits good luminescence stability compared to Cs 3 Cu 2 I 5 itself due to the protection of the template. These indicate that the structured Cs 3 Cu 2 I 5 scintillation screen has a good application prospect in high-resolution X-ray imaging. • A structured Cs 3 Cu 2 I 5 scintillation screen based on oxidized silicon micropore array template was first developed by melt-injection method. • High spatial resolution (113 lp/mm) and good detective quantum efficiency were achieved in X-ray imaging. • The structured Cs 3 Cu 2 I 5 screen exhibited good radiation resistance and luminescence stability. [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]

Bulk glass scintillators, which process the advantages of low cost, cheap elaboration, excellent transparency and high uniformly, have garnered great attention for X-ray imaging application. Cu+-doped oxyfluoride glass scintillators were designed and elaborated by using Al powder as reducing agent. The relationship of X-ray excited luminescence (XEL) of Cu+-doped glasses with doping concentration of Cu+ and the addition of Al content were investigated by the response surface methodology to get the optimal glass. The optimal glass scintillator shows high transmittance (90.0% at visible region), short lifetime (42.9 μs), high absorption efficiency (93.0% at 290 nm) and good internal quantum yield (75.2%). Excitedly, the integrated XEL intensity of optimal sample is 141% of that of Bi 4 Ge 3 O 12 crystal. And its spatial resolution reaches 20 lp/mm for X-ray imaging. Above results illustrate the potential application of Cu+-doped oxyfluoride glass scintillators in X-ray imaging filed. • Cu+ -doped oxyfluoride glass scintillators with excellent properties were designed. • The optimal doping contents of Cu+ and Al powders were perfectly solved by RSM. • The highest internal quantum yield is 75.2% and absorption efficiency is 93%. • The XEL intensity of SACA1 was 141% of that of BGO commercial scintillator. • The spatial resolution of SACA1 is 20 lp/mm for X-ray imaging. [ABSTRACT FROM AUTHOR]

Full-visible-spectrum white light-emitting diodes (LEDs) with ultrahigh color rendering index (CRI), which are capable of offering a light source that mimics natural sunlight, have great application potentials in healthy lighting, high-resolution displays, and plant growth lighting. However, cyan gap in the 480–520 nm wavelength range is commonly existed in the emission spectra of traditional phosphor-converted white LEDs, and thus it is urgent to develop high-performance cyan-emitting phosphors to close this spectral gap for realizing full-visible-spectrum LED lighting. Herein, we demonstrate a new efficient cyan-green-emitting Ce3+-activated CaY 2 ZrGaAl 3 O 12 garnet phosphor for near-ultraviolet (near-UV) pumped full-visible-spectrum warm-white LEDs. The CaY 2 ZrGaAl 3 O 12 :Ce3+ cyan-green phosphor has a cubic structure with the space group Ia 3 ‾ d and lattice parameters of a = b = c = 12.39645(8) Å and V = 1886.08(6) Å3. Ce3+ doping concentration dependent luminescence properties have been studied, and the highest emission intensity is obtained at 1 mol%. The optimal CaY 2 ZrGaAl 3 O 12 :1%Ce3+ sample shows a broad excitation band in the 300–490 nm wavelength range with peak at 409 nm due to the 4f→5d transition of Ce3+ ions. Upon 409 nm excitation, CaY 2 ZrGaAl 3 O 12 :1%Ce3+ produces a wide cyan-green emission band in the 425–750 nm spectral range with a peak at 514 nm and a full width at half-maximum of 110 nm owing to the 5d→4f transition of Ce3+ ions, and the corresponding CIE color coordinates and internal quantum efficiency are determined to be (0.2802, 0.4856) and 56%, respectively. Furthermore, the resulting CaY 2 ZrGaAl 3 O 12 :1%Ce3+ phosphor exhibits good thermal stability, and its emission intensity at 423 K is about 58% of that at 303 K. Finally, a white LED device is fabricated by employing a 395 nm near-UV chip with the phosphor blend of commercial BaMgAl 10 O 17 :Eu2+ blue phosphor, as-prepared CaY 2 ZrGaAl 3 O 12 :1%Ce3+ cyan-green phosphor, commercial (Ba,Sr) 2 SiO 4 :Eu2+ green phosphor and commercial CaAlSiN 3 :Eu2+ red phosphor, which exhibits a bright full-spectrum warm-white light with low color correlated temperature of 3334 K and ultrahigh CRI values (Ra = 97, R9 = 95.3, R12 = 90.1) for 20 mA driving current. This work provides a new perspective in designing luminescent materials for high-color-quality full-visible-spectrum LED lighting. [Display omitted] • A bright cyan-green emission (peak: 514 nm; FWHM: 110 nm) is observed. • IQE is 56%. • Full-spectrum LED lighting with high CRI (Ra = 97, R9 = 95.3, R12 = 90.1) is realized. [ABSTRACT FROM AUTHOR]

Due to recent development in detector technology, photon-counting computed tomography (PCCT) has become a rapidly emerging medical imaging technology. Current PCCT systems rely on the direct conversion of X-ray photons into charge pulses, using CdTe, CZT, or Si semiconductor detectors. Indirect detection using ultrafast scintillators coupled to silicon photomultipliers (SiPM) offers a potentially more straightforward and cost-effective alternative. In this work a new 2D perovskite scintillator, benzylamonium lead bromide (BZA) 2 PbBr 4 , is experimentally characterised as function of temperature. The material exhibits a 4.2 ns decay time under X-ray excitation at room temperature and a light yield of 3700 photons/MeV. The simulation tool developed by Van der Sar et al. was used to model the pulse trains produced by a SiPM-based (BZA) 2 PbBr 4 detector. The fast decay time of (BZA) 2 PbBr 4 results in outstanding count-rate performance as well as very low statistical fluctuations in the simulated pulses. These features of (BZA) 2 PbBr 4 , combined with its cost-effective synthesis make (BZA) 2 PbBr 4 very promising for PCCT. • PCCT systems using ultrafast scintillators and SiPMs a straight forward and cost-effective alternative to direct detection. • Solution grown 2D perovskites are an interesting and versatile class of materials for specific scintillation applications. • The short life time of (BZA)2PbBr4 results in outstanding count-rate performance and low statistical fluctuations. [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]

In this paper, we have successfully demonstrated that the directional control of the light output of the scintillator can be achieved by mixed-scale microstructures which integrate photonic crystals on the wavelength scale and microlens arrays on the micrometer scale. Compared to the reference sample, the mixed-scale microstructures can enhance the light output of the scintillator by 3.07-fold at the emergence angle of 35°. This enhancement in the light output exhibits both azimuthal angle and wavelength dependence. Our hybrid simulation and experimental characterization explain the physical mechanism behind the enhanced directional light output. This method holds potential for application in radiation detection systems and other light-emitting devices requiring directional light output. • Mixed-scale microstructures control directional light output of scintillators. • Soft X-ray interference lithography can prepare mixed-scale microstructures. • Directional light output is beneficial for the radiation detection system. [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]

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]

Since Helium-3 shortage announcement, organic scintillators play a major role in neutron detection. Our laboratory decided to focus on plastic scintillators and their ability to discriminate fast neutrons from gamma rays. In this work, we highlight the influence of the secondary fluorophore in lab-made plastic scintillators. The secondary fluorophore is generally added in the scintillating mixture to shift the emission wavelength towards the transparency domain of the material to improve its attenuation length. Thus, it is considered as a harmless molecule and is barely seen as a key criterion that could enhance the performances of the organic scintillator. In our work, we demonstrate that this molecule, even added at a small concentration (typically in the range 0.02–0.2 wt%), directly impacts the neutron/gamma discrimination ability of plastics. Not only the secondary fluorophore plays a role in self-absorption of the scintillating material, but also the couple it creates with the primary fluorophore has to be carefully chosen, as some specific triplet energy transfers between the two fluorophores can influence the neutron/gamma discrimination abilities of the plastic scintillator. Aside from classical photophysical inconveniences such as self-absorption or diffusion, the possibility that the whole, bulk material was heterogeneous in a photochemical point of view was also checked. Thus, various samples were cut from bulk monoliths and their pulse shape discrimination compared with the parent scintillator in terms of Figure of Merit and light output. • Fast neutrons/gamma discrimination efficiency is usually reduced when the volume of a plastic scintillator is increased. • This effect is studied, first in a morphologically way, then chemically and photophysically. • The secondaray fluorophore has an essential role in the discrimination process. [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]

LuI 3 :Ce is considered to be a candidate scintillator in radiation detectors for high energy physics and nuclear medicine due to high light yield. However, slow decay induced by energy transfer from self-trapped excitons on intrinsic defects to Ce limits the time resolution of detectors. The effect of Li, Cu, Mg, and Zn doping on tuning the intrinsic defects in LuI 3 are investigated using first-principles calculations. The thermodynamic levels introduced by the Lu interstitials and the I vacancies turn out to match emission energies of the self-trapped excitons. The cation interstitials enhance the formation energies of the Lu interstitials and I vacancies because of charge balance. Importantly, Mg doping is demonstrated to effectively suppress the Lu interstitials and the I vacancies in LuI 3 [ABSTRACT FROM AUTHOR]

Abstract In this review, modern insights into the synthesis and fundamental optical properties as well as applications of divalent lanthanides as spectral energy converters are discussed, which have especially evolved within the last two decades. An emphasis is put on the state-of-the-art knowledge about the luminescence of other divalent lanthanides than the most commonly applied representative Eu2+ and what special features in their luminescence arises due to the different number of 4f n electrons. In particular, the luminescence of Sm2+, Tm2+, Yb2+ and the less stable ions Nd2+ and Dy2+ will be regarded. A broad overview over the synthetic approaches to inorganic compounds based on divalent lanthanide ions will be conveyed as well and shall demonstrate the fascinating developments in the field of inorganic solid-state chemistry of the lanthanides. Besides their fundamental optical properties, also applications of the presented divalent lanthanide activators are discussed. Sm2+ is a well-known temperature and pressure sensor due to its interconvertible 4f‐4f and 5d-4f transitions. Moreover, nanocrystalline BaFCl:Sm2+ has an appreciable potential as novel X-ray storage phosphor. Tm2+ is interesting for upconversion in photovoltaic and lasing applications, whereas Yb2+ in halides may be a promising alternative to Eu2+ for scintillation materials and phosphors for light-emitting diodes (LEDs). Nd2+ and Dy2+ are currently emerging as novel near infrared (NIR)-absorbing and emitting activators that might become interesting as lasing ions. The spectroscopy of these unusual lanthanide ions provides many non-trivial features due to the excited two-open shell 4fn-15d1 configuration overlapping with the excited 4f n levels. Finally, a perspective for future developments will be given. [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 Defect, doping and particle size play important roles on the optical performance of nanophosphors. In this study, undoped La 2 Zr 2 O 7 NPs (LZO) displayed multicolor emission under UV irradiation due to the presence of ionized oxygen vacancies in the band gap. In addition, we explored the effect of particle size of La 2 Zr 2 O 7 :Eu3+ (LZOE) NPs on their structure, surface area, photoluminescence, radioluminescence, lifetime and quantum yield. There is progressive decrease in luminescence output and quantum yield as the coprecipitation pH is raised to prepare the single-source precursors for the molten salt synthesis of the NPs. Under X-ray irradiation, the LZOE NPs emit red light highlighting their potential as X-ray scintillator. We explained the experimental observations based on surface defect analogy. The experimentally obtained emission in violet-blue and red optical regions is correlated to defect related emission. High asymmetry ratio suggested low symmetric environment of Eu3+ ions in the LZO host and the occupancy of Eu3+ ions is more favorable at LaO 8 site compared to ZrO 6 site. Emission spectra of the LZOE also showed favorable host to dopant (Eu3+) energy transfer. This work provides a clear picture of making highly efficient red phosphor and X-ray scintillator for applications in optoelectronics and X-ray induced theranostics. Graphical abstract fx1 [ABSTRACT FROM AUTHOR]

Abstract RE 2 O 3 :1%Eu (RE=Lu, Y, Sc) single crystals were grown by the optical floating zone method. Correlated measurements of afterglow curves, thermoluminescence, photoluminescence decay, and radioluminescence curves were performed. It is found that the afterglow intensity of Sc 2 O 3 :Eu is much lower than the other two compounds and Y 2 O 3 :Eu presents a slightly lower afterglow intensity than Lu 2 O 3 :Eu. It is discussed in the light of the influence of trap states and site preference in the RE 2 O 3 :Eu. The afterglow difference between Sc 2 O 3 :Eu and other two compounds mainly comes from the disappearance of Schottky defect in Sc 2 O 3 :Eu. Meanwhile the afterglow difference between Y 2 O 3 :Eu and Lu 2 O 3 :Eu probably ascribes to the lower S 6 site ratio in Y 2 O 3 :Eu. Their photoluminescence and other radioluminescence properties were also measured and compared. [ABSTRACT FROM AUTHOR]

Abstract Eu2+-doped mixed halide scintillators, CsSrBrI 2 , CsCaBrI 2 and CsSrClBr 2 were studied for gamma-ray spectroscopy applications. We grew Ø13 mm single crystals via the vertical Bridgman method using a self-seeded technique and investigated physical and scintillation properties. Single crystal X-ray diffraction and thermal analysis reveal that CsSrBrI 2 and CsSrClBr 2 have orthorhombic crystal structures and melt congruently at 611 °C and 752 °C, respectively, while CsCaBrI 2 has a cubic structure and melts congruently at 671 °C. All three compounds have the typical Eu2+ 5d – 4 f single-peak emission centered between 445 and 462 nm with a scintillation decay time of a few microseconds. The optimal Eu2+ concentration to maximize the scintillation light yield was determined to be ~7–10%. All three mixed scintillators have an improved energy resolution compared to the non-mixed CsSrI 3 :Eu, CsCaI 3 :Eu and CsSrBr 3 :Eu. The best performing scintillator is CsSrBrI 2 :Eu 7% with light yield of 65,300 ph/MeV and energy resolution of 3.4% at 662 keV. Excellent proportional response for a wide range of gamma-ray energies was measured for all three scintillators. Highlights • Ø13 mm single crystals of CsSrBrI 2 :Eu, CsCaBrI 2 :Eu and CsSrClBr 2 :Eu were grown via the Bridgman technique. • The crystal structures of CsSrBrI 2 , CsSrClBr 2 and CsCaBrI 2 were determined. • The energy resolution of all three mixed scintillators was below 4.0% at 662 keV. • CsSrBrI 2 :Eu 7% has scintillation light yield of 65,300 ph/MeV and energy resolution of 3.4% at 662 keV. [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]

In our effort to develop a new kind of detector for low-energy, low-rate energy deposition events we have investigated the cathodo- and radioluminescence of Ho:YAG and Ho:YLF single crystals in an extended wavelength range from 200 nm to 2200 nm. The emission spectra of both crystals show a much more intense emission in the infrared range than in the visible one. We estimate an infrared light yield of several tens of photons/keV when exciting the crystals with X-rays of energy ≈ 30 keV. The main reason of this high value is due to the Ho 3+ ions energy levels scheme that allows efficient cross relaxation processes to occur even at low dopant concentration. [ABSTRACT FROM AUTHOR]

We investigate the hydrothermal growth of zinc oxide (ZnO) nanorods to realize their potential scintillator applications. Vertically aligned ZnO nanorods were successfully fabricated on seeded silicon (Si) substrates at a relatively low temperature of 85 °C using different hexamethylenetetramine [(CH 2 ) 6 N 4 , HMTA] and zinc acetate dihydrate [Zn(CH 3 COO) 2 ·2H 2 O, ZnAc] concentration ratios. Varying the precursor concentration ratio affects the nanorod dimensions which, in turn, influence the apparent densities and observed emissions. But regardless of the HMTA and ZnAc concentration ratio used, the fabricated nanorods exhibit well-defined morphologies, hexagonal crystal structure, preferential c -axis orientation, and 24–120-ps ultraviolet (UV) emissions. With these excellent structural and optical properties, the hydrothermal-grown ZnO nanorods are suggested to be used as scintillator materials which offer not only fast scintillation response but also high spatial resolution for future radiation detectors. [ABSTRACT FROM AUTHOR]

This work describes the relation between crystallite size and scintillation properties of Eu 3+ -doped yttrium oxide. Nanocrystalline Y 2 O 3 :Eu 3+ 1.0 mol% powders were prepared by Pechini method and thermal treated at 700–1100 °C. The thermal treatment temperature has influence on the crystallite sizes of Y 2 O 3 :Eu 3+ nanocrystals and, consequently, on the structural and electronic defects concentration, which contributes to nonradiative recombination routes in scintillation materials. This relationship between the crystallite sizes and scintillation properties was investigated by X-ray diffraction and X-ray excited optical luminescence measurements. [ABSTRACT FROM AUTHOR]

Sodium decatungstoeuropate, Na 9 [Eu(W 5 O 18 ) 2 ]·14H 2 O, is a promising material to convert X-ray into visible light. In this work, temperature and exposure time-dependent scintillation of the Na 9 [Eu(W 5 O 18 ) 2 ]·14H 2 O sample under X-ray excitation were evaluated. Light emission intensity decreases along with X-ray exposure time, probably due to electronic defects at (W 5 O 18 ) 6- groups, leading to a lower efficiency of the LMCT (O→W) process, which is determinant in the scintillation mechanism of this material. After X-ray exposition, there is a partial recovery of the initial emission intensity, indicating that defects created are reversible. With temperature increasing, changes in the emission spectra evidence the decreasing of the local symmetry around the Eu 3+ ions, caused by reticular vibration and dehydration process. The luminescence intensity dependence with temperature suggests the possibility to use this material as molecular thermometer in two different temperatures ranges. [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]

Undoped and Ce-doped Sr 2 Al 2 SiO 7 bulk crystals with different concentrations of Ce were synthesized by the floating zone method. Under X-ray irradiation, the both undoped and Ce-doped samples show scintillation with broad emission with decay time constants of approximately 30 and 300 ns. By utilizing photoluminescence (PL) techniques, we attributed the origin of the former emission component is due to the 5d-4f transitions of Ce 3+ while the one of the latter emission is due the host. The scintillation afterglow levels depends on the concentration of Ce and are on an order of ppm. From the pulse height spectrum measured under 241 Am 59.5 keV γ-ray irradiation, the 0.3% Ce-doped Sr 2 Al 2 SiO 7 crystal was revealed to show the absolute scintillation light yield of 1100 ph/MeV, which is the highest among the present samples. In addition, the Ce-doped samples show TL properties with a glow peak at 250 °C and a shoulder around 130 °C. [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]

A self-activated Cs 4 YbI 6 single crystal was grown by the vertical Bridgman method. Crystal structure refinements verified the phase purity and the trigonal crystal system with a space group of R 3 ̅ c. By using differential scanning calorimetry, the melting and crystallization points were determined to be 550 and 510 °C, respectively. Luminescence and scintillation properties were systematically studied. Upon ultraviolet light (360 nm) excitation, the Cs 4 YbI 6 crystal exhibits bluish-green emission centered at 450 and 480 nm due to spin-allowed and spin-forbidden transitions of Yb 2+ activators. The lifetimes of the corresponding emission bands at room temperature are tens and hundreds of nanoseconds, respectively. X-ray excited radioluminescence spectrum is dominated by the spin-forbidden transition of Yb 2+ at 480 nm. The absolute light yield is 2700 ± 200 photons/MeV with a principal scintillation decay time of 33 ns. The physical explanation for the low light yield observed is proposed from experimental and theoretical insights. [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]

Undoped and Ce-doped Ca 2 Al 2 SiO 7 single crystals with different Ce concentrations were prepared by the floating zone method. From the X-ray diffraction patterns, we confirmed that all the grown crystals have no impurity phases. The undoped sample shows scintillation induced by X-rays, and the spectrum consists of two broad emission bands peaking at 350 and 400 nm. The decay curve appeared to consist of only single exponential decay with the decay constant of 51 ns. In contrast, Ce-doped samples show a broad scintillation peaking around 400 nm, in which the decay curve consists of two exponential decay functions with the decay times of approximately 30 and 100 ns. From the pulse height spectra measured using the present samples under 241 Am 59.5 keV γ-ray irradiation, we confirmed that the 0.3% Ce-doped sample exhibits the highest absolute scintillation light yield of 16,000 ph/MeV. The samples also exhibit thermoluminescence (TL). The glow curves appear to have a broad feature with the peak temperature from 100 to 500 °C for undoped and from 50 to 400 °C for Ce-doped samples. Among the present samples, the 0.3% Ce-doped sample shows the highest sensitivity, and a linear response to the irradiation dose was confirmed in the dose range of 0.01–100 mGy. [ABSTRACT FROM AUTHOR]