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With the rapid development of silicon-based light detectors with high detection efficiency and long-wavelength sensitivity, the development of near-infrared scintillation crystals has become a hotspot. Especially, the Sm2+ doped europium-based halide crystals exhibit excellent near-infrared luminescence properties. In this paper, Cs4 EuI6: Sm near-infrared scintillation crystals with a size of cm-level were successfully prepared by Bridgman method. The composition and structure were discussed by XRD, XPS and ICP-OES methods, indicating that the Sm2+ was introduced and has no obvious effect on the crystal structure of the matrix. Under ultraviolet and X-ray excitation, the crystal has two luminescence centers (Eu2+ and Sm2+), and the emission peaks are located at 450 and 840 nm, respectively, corresponding to the 5d→4f luminescence of Eu2+ and Sm2+. The decay time of Eu2+ and Sm2+ is at the level of microsecond under ultraviolet excitation. The results show that the emission wavelength gradually varies from blue to near infrared as Sm2+ doping concentration increased. The effects of Sm2+ concentration on the luminescence properties, Eu2+ -Sm2+ energy transfer and decay time of the crystals were also studied, which means that the luminescence properties can be tuned by adjusting the Sm2+ doping concentration. [ABSTRACT FROM AUTHOR]

To reduce the issue of tri-primary color reabsorption, a new approach for single-phase phosphors as light-emitting diodes (LEDs) has been recommended. The structures, morphology, photoluminescence, thermal stability, and luminescence mechanism of a variety of Ca3Bi (PO4)3 (CBPO): Ce3+/Dy3+ phosphors were investigated. XRD characterization showed that all CBPO samples were eulytite structures. Furthermore, the energy transfer process from Ce3+ to Dy3+ in CBPO is systematically investigated in this work, and the color of light can be adjusted by changing the ratio of doped ions. Under UV light, energy is transferred from Ce3+-Dy3+ mainly through quadrupole-quadrupole interactions in the CBPO host, and doping with different Dy3+ concentrations tunes the emission color from blue to white. The thermal stability of the CBPO: 0.04Ce3+, 0.08Dy3+ samples is outstanding, and the CIE coordinates of the samples after emission have little effect with temperature, while their emission intensity at 423 K is as strong as that at room temperature, reaching 90%. The above results indicate that this CBPO material has great potential as a white light phosphor under near-UV excitation at the optimized concentration of Ce3+ and Dy3+. [ABSTRACT FROM AUTHOR]

This research focuses on LPE growth, and the examination of the optical and photovoltaic properties of single crystalline film (SCF) phosphors based on Ce3+-doped Y3MgxSiyAl5−x−yO12 garnets with Mg and Si contents in x = 0–0.345 and y = 0–0.31 ranges. The absorbance, luminescence, scintillation, and photocurrent properties of Y3MgxSiyAl5−x−yO12:Ce SCFs were examined in comparison with Y3Al5O12:Ce (YAG:Ce) counterpart. Especially prepared YAG:Ce SCFs with a low (x, y < 0.1) concentration of Mg2+ and Mg2+–Si4+ codopants also showed a photocurrent that increased with rising Mg2+ and Si4+ concentrations. Mg2+ excess was systematically present in as-grown Y3MgxSiyAl5−x−yO12:Ce SCFs. The as-grown SCFs of these garnets under the excitation of α–particles had a low light yield (LY) and a fast scintillation response with a decay time in the ns range due to producing the Ce4+ ions as compensators for the Mg2+ excess. The Ce4+ dopant recharged to the Ce3+ state after SCF annealing at T > 1000 °C in a reducing atmosphere (95%N2 + 5%H2). Annealed SCF samples exhibited an LY of around 42% and similar scintillation decay kinetics to those of the YAG:Ce SCF counterpart. The photoluminescence studies of Y3MgxSiyAl5−x−yO12:Ce SCFs provide evidence for Ce3+ multicenter formation and the presence of an energy transfer between various Ce3+ multicenters. The Ce3+ multicenters possessed variable crystal field strengths in the nonequivalent dodecahedral sites of the garnet host due to the substitution of the octahedral positions by Mg2+ and the tetrahedral positions by Si4+. In comparison with YAG:Ce SCF, the Ce3+ luminescence spectra of Y3MgxSiyAl5−x−yO12:Ce SCFs greatly expanded in the red region. Using these beneficial trends of changes in the optical and photocurrent properties of Y3MgxSiyAl5−x−yO12:Ce garnets as a result of Mg2+ and Si4+ alloying, a new generation of SCF converters for white LEDs, photovoltaics, and scintillators could be developed. [ABSTRACT FROM AUTHOR]

Novel near-infrared (NIR) phosphors are in demand for light-emitting diode (LED) devices to extend their suitability for new applications and, in turn, support the sustainable and healthy development of the LED industry. The Cr3+ has been used as an activator in the development of new NIR phosphors. However, one main obstacle for the Cr3+-activated phosphors is the low luminescence efficiency due to the spin-forbidden d-d transition of Cr3+. The rare-earth (RE) huntite minerals that crystallize in the form of REM3(BO3)4 (M = Al, Sc, Cr, Fe, Ga) have a large family of members, including the rare-earth scandium borates of RESc3(BO3)4. Interestingly, in our research, we found that the luminescence efficiency of Cr3+ in the CeSc3(BO3)4 host, whose quantum yield was measured at 56%, is several times higher than that in GdSc3(BO3)4, TbSc3(BO3)4, and LuSc3(BO3)4 hosts. Hereby, the energy conversion and transfer in the luminescence of CeSc3(BO3)4:Cr3+ phosphor were examined. The Stokes shift of electron energy conversion within the Cr3+ 4T2g level for the emission at 818 nm and excitation at 625 nm in CeSc3(BO3)4 host was evaluated to be 3775.1 cm−1, and the super-large splitting energy of the 2F5/2 and 2F72 sub-states of the Ce3+ 4f1 state, about 3000 cm−1, was found in CeSc3(BO3)4 host. The typical electronic thermal vibration peaks were observed in the excitation spectra of CeSc3(BO3)4:Cr3+. On this basis, the smallest phonon energy, around 347.7 cm−1, of the CeSc3(BO3)4 host was estimated. Finally, the energy transfer that is responsible for the far higher photoluminescence of Cr3+ in CeSc3(BO3)4 than in other hosts was proven through the way of Ce3+ emission and Cr3+ reabsorption. [ABSTRACT FROM AUTHOR]

Tb3+ doped sodium-gadolinium-aluminum-phosphate glass samples (PGNA) with chemical compositions 30Na 2 CO 3 :8Gd 2 O 3 :5Al 2 O 3: (57- x)P 2 O 5 : x Tb 4 O 7 (where x = 0 , 0.25, 0.5, 1.0, 2.0, 3.0, 4.0, and 5 mol. %) were manufactured by using adopting the conventional melt quenching technique. The PXRD study of the prepared samples was used to confirm the amorphous structure. FE-SEM, EDS, and FTIR studies were carried out to analyze the elemental and structural characteristics of synthesized glasses. The X-ray induced luminescence spectra were obtained at room temperature and the emission peak at 311 nm corresponding to Gd3+ transition was observed decreasing with the increase of Tb 4 O 7 concentrations, while emission peak intensities corresponding to Tb3+ electronic transitions increased with the concentrations of Tb 4 O 7. The results from the photoluminescence (PL) studies in the UV–Vis–NIR region showed the glasses emitting intense green light with the highest peak at 544 nm under excitations at 220, 272, and 311 nm. The PL emission intensities were found reasonably high under characteristic excitations of both Gd3+ and Tb3+, peaking at 380, 414, 437, 489, 544, 584, and 623 nm, which corresponding to 5D 3 → 7F 6, 5D 3 → 7F 5 , 5D 3 → 7F 4 , 5D 4 → 7F 6 , 5D 4 → 7F 5 , 5D 4 → 7F 5 , 5D 4 → 7F 4 , 5D 4 → 7F 3 transitions, respectively. The decay time of Tb3+ ions has been observed to decrease when the concentration of Tb 4 O 7 increases. The energy transfer from Gd3+ to Tb3+ was found increased with increasing of Tb3+ concentrations. The CIE 1931 chromaticity coordinates of Tb doped PGNA glasses were found to be in the green range, indicating a strong potential for green laser application. The results from X-ray imaging showed that Tb-doped glass scintillators promise of efficient and low-cost solution for X-ray imaging applications. • XRL spectra has the emission peak at 311 nm corresponding to 6P 7/2 → 8S 7/2 due to Gd3+ ion in the host. • Glasses emitting intense green light with highest peak at 544 nm under 220, 272, 311 nm excitations. • PL emission intensities found reasonably high for both Gd3+ and Tb3+ characteristic excitation. • CIE 1931 coordinates of glasses found in the green indentify potential for green laser application. • The Tb-doped glass promise of efficient and low-cost solution for X-ray imaging applications. [ABSTRACT FROM AUTHOR]

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]

Strontium phosphate (SrO–P 2 O 5 –Al 2 O 3 –Gd 2 O 3) glasses with 0.05, 0.1, 0.5, and 1 mol % CeO 2 were prepared by the conventional melt quenching technique. These glasses' luminescence, scintillation, and physical properties were measured and discussed in detail. The density, refractive index, and oxygen packing density of the studied glasses were increased with an increase in CeO 2 concentration. At lower concentrations of CeO 2 , the characteristic 310 nm emission from Gd3+ and broadband emission from Ce3+ ions were obtained under X-ray excitations. The intensity of both Gd3+ and Ce3+ emission bands under 270 nm Gd3+ excitations reduced with further increase in CeO 2 , showing the delayed energy transfer from Gd3+ to Ce3+ ions. The integrated X-ray-induced luminescence intensity of 0.5% CeO 2 glass was found to be 21% that of reference BGO crystal. For the lower concentration of CeO 2 , a slow decay time along with the fast Ce3+ decay was observed and disappears for higher CeO 2 concentrations. The fast luminescence decay in the range of 22 ns–30 ns was observed for all the PSAG:Ce glasses, which was attributed to the lifetime of the 4f-5d transition of the Ce3+ ions. The faster decay time and reasonable scintillation light suggest the application of these glasses for radiation detector applications. • Strontium phosphate glasses with various concentrations of CeO 2 are fabricated. • The density, refractive index, and OPD increased with CeO 2 concentrations. • Efficient energy transfer from Gd3+ to Ce3+ was confirmed from luminescence. • X-ray-induced scintillation light was found to be 21% that of BGO crystal. [ABSTRACT FROM AUTHOR]

Polystyrene film nanocomposites of 0.3mm thickness with embedded LaPO4-Pr nanoparticles (40 wt. %) have been synthesized. The luminescent and kinetic properties of these polystyrene composites with embedded LaPO4-Pr nanoparticles upon pulse X-ray excitation have been studied. The luminescence intensity of this polystyrene material significantly increases as it is loaded with inorganic LaPO4-Pr nanoparticles. Nanocomposite films reveal luminescence spectra typical for polystyrene activators (p-Terphenyl and POPOP) and two components of decay time kinetics of luminescence with 12 ns and 2.8 ns time constants, depending on nanoparticle sizes. The component with 12 ns decay constant arises due to the radiative transfer of the 5d-4f-emission of the Pr3+ ions in the LaPO4 nanoparticles to the polystyrene. The decay component with the time constant 2.8 ns originates from luminescence of polystyrene matrix excited by electrons emitted from nanoparticles due to the photoeffect. This nonradiative mechanism of energy transfer from nanoparticles to polystyrene matrices is determinative for nanoparticles, as their sizes are smaller than a mean free path of an electron. [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]

Dy3+-, Tb3+-activated, and Tb3+/Dy3+-coactivated oxyfluoride borogermanate scintillating glasses with the density of about 6.50 g/cm³ were successfully synthesized by a melt-quenching method. The structure and optical properties including transmittance, photoluminescence (excitation and emission spectra), photoluminescence decay, and X-ray excited luminescence (XEL) behaviors were studied in detail. Our results reveal that the energy transfer efficiency from Dy3+ to Tb3+ ions increases with an increase of Tb3+ concentration. The energy transfer mechanism is determined to be electric dipole–dipole interaction. However, the XEL intensity of Tb3+ decreases with the incorporation of sensitizer Dy3+ into borogermanate scintillating glass, which may result from the different mechanisms under ultraviolet light and X-ray excitation. [ABSTRACT FROM AUTHOR]

Excitation spectra (a) and emission spectra (b) of Ba 1.94 P 2 O 7 :0.04Dy3+, 0.02Ce3+ and Ba 1.96 P 2 O 7 :0.04Dy3+. After Dy3+ and Ce3+ are co-doped, Ba 2 P 2 O 7 :Dy3+, Ce3+ phosphors emit the enhanced characteristic blue and yellow emission of Dy3+ with nearly equal intensity under excitation at 323 nm, meaning Ce3+ co-doping increases the symmetry of Dy3+ site as well as the sensitizer. Simultaneously, energy transfer from Dy3+ to Ce3+ is found. [Display omitted] • Ba 2-x-y P 2 O 7 :xDy3+,yCe3+ phosphors were synthesized by calcining the precursor via chemical co-precipitation. • Ba 2 P 2 O 7 :Dy3+, Ce3+ phosphors exhibited the enhanced characteristic blue and yellow emission of Dy3+, and the energy transfer between Ce3+ and Dy3+ was discussed. • Ba 2 P 2 O 7 :Dy3+,Ce3+ phosphors displayed a good thermal stability with a remaining emission intensity of 78% at 250 ℃. In this paper, Ba 2-x-y P 2 O 7 :xDy3+,yCe3+ phosphors are synthesized by calcining the precursor via chemical co-precipitation. The phase structure, excitation and emission spectra, thermal stability, the chromatic performance of phosphors, and energy transfer from Ce3+ to Dy3+ are studied and discussed. The results indicate the samples keep a stable crystal structure as a high-temperature σ-Ba 2 P 2 O 7 phase with two different coordination of Ba2+ sites. Ba 2 P 2 O 7 :Dy3+ phosphors can be effectively excited by 349 nm n-UV light and emit 485 nm blue light and a relatively stronger yellow light peaking at 575 nm, corresponding to 4F 9/2 →6H 15/2 and 4F 9/2 →6H 13/2 transitions of Dy3+, implying that Dy3+ mainly occupies the non-inversion symmetric sites. By contrast, Ba 2 P 2 O 7 :Ce3+ phosphors exhibit a broadband of excitation peaking at 312 nm, and two symmetrical emission peaks at 336 nm and 359 nm from 5d1→4F 5/2 and 5d1→4F 7/2 transitions of Ce3+, showing Ce3+ should merely be presumed to occupy Ba1 site. After Dy3+ and Ce3+ are co-doped, Ba 2 P 2 O 7 :Dy3+, Ce3+ phosphors exhibit the enhanced characteristic blue and yellow emission of Dy3+ with nearly equal intensity under excitation at 323 nm, meaning Ce3+ co-doping increases the symmetry of Dy3+ site as well as the sensitizer. Simultaneously, energy transfer from Dy3+ to Ce3+ is found and discussed. The thermal stability of co-doped phosphors was characterized and briefly analyzed. The color coordinates of Ba 2 P 2 O 7 :Dy3+ phosphors fall in the yellow-green region near the white light, while the emission moves towards the blue-green region after the Ce3+ is co-doped. [ABSTRACT FROM AUTHOR]

Ce3+-doped dense glasses with high light yield (LY) are promising scintillators for use in high-energy particle physics research and radiation sensors for high-energy X- and γ- ray detection. In this work, Ce3+-doped (60-x)SiO 2 -xBaF 2 -20Al 2 O 3 -20Gd 2 O 3 oxyfluoride glasses have been prepared under a CO reducing atmosphere. Substitution of SiO 2 by BaF 2 has been made to increase the density, and the effects on luminescence and scintillation properties have been investigated. The amorphous nature of the prepared glass is confirmed by the XRD profile showing an absence of any diffraction peaks. The broad photoluminescence (PL) emission band of the Ce3+ 5d–4f transition in the 330–580 nm range is observed peaking around 385 nm and the PL decay is governed in the range of 46–53 ns decay time. The 10 mol% BaF 2 glass with density of 4.54 g/cm3 shows the highest LY value of 1590 photons/MeV and energy resolution of 16.5% in the pulse height spectrum of 662 keV γ rays, and the LY of 141 photons/MeV and energy resolution of 21.7% in the pulse height spectrum of 5.5 MeV α particles. • Ce3+-doped (60-x)SiO 2 -xBaF 2 -20Al 2 O 3 -20Gd 2 O 3 (x = 0–20) glasses were prepared under CO atmosphere. • XRD pattern confirms an amorphous nature of the prepared glass. • Gd3+ to Ce3+ energy transfer was observed in the prepared glasses. • Light yield of 1590 photons/MeV at 662 keV γ rays was obtained for 10 mol% BaF 2 containing glass. • Energy transport efficiency in scintillation process increases with increasing BaF 2 content. [ABSTRACT FROM AUTHOR]

In this study, we fabricated Cs 3 ScCl 6 crystals doped with different concentrations of Ce and investigated their luminescence properties. In both the photoluminescence (PL) and scintillation spectra, emission bands attributable to Ce3+ 5d–4f transition were observed. The PL temporal profiles revealed decay time constants of ~35 ns, which are typical values for Ce3+ 5d–4f transition. In the scintillation temporal profiles, two decay components were observed. The fast and slow components could be attributed to Ce3+ 5d–4f luminescence and self-trapped excitons (STEs) or a slow energy transfer from STEs to Ce3+, respectively. The maximum light yield was 9200 photons/MeV for a Ce concentration of 0.5 mol%. [ABSTRACT FROM AUTHOR]

The fact that the scheelite based compounds are of high technological importance in the area of scintillator and optoelectronics, makes their detailed photophysical study relevant not only for fundamental material science but also in tailoring their optical properties for advanced applications. With this view, we have carried out a very systematic study on near infra‐red (NIR) emitting Nd3+ doped CaWO4, SrWO4, and BaWO4 compounds. Light emitting efficiency in AWO4:Nd3+ is governed strongly by radiative/nonradiative properties, host‐dopant energy transfer (HDET) efficiency and defect density. We have used photoluminescence, positron annihilation, and photoacoustic (PA) spectroscopy to study the factors effecting light emission. These scheelites are known to exhibit self activated luminescence in visible region due to charge transfer within the tungstate group and wavelength maxima exhibited red shift as we move from Ca→Sr→Ba. This can provide a new strategy to achieve spectral tunability in AWO4 scheelite by changing A2+ ionic radius. The fractional intensity in the green region is least in the case of SrWO4 samples suggesting that the oxygen vacancy density is minimal in case of SrWO4 which is well‐supported by the positron annihilation lifetime spectroscopy (PALS). Based on our studies, we found that the HDET was highly efficient in CaWO4:Nd3+ and minimal in BaWO4:Nd3+ which get's reflected in photoluminescence intensity. Emission lifetimes are shorter in CaWO4 and highest in SrWO4 host which are in sync with positron annihilation lifetime values. Based on our results of PALS, it was found that CaWO4:Nd3+ has the highest concentration of defects i.e. cation vacancies; so larger is the probability of nonradiative signals and hence higher PA intensity from it. [ABSTRACT FROM AUTHOR]

Luminescence excitation spectra of BaBrI single crystals doped by divalent lanthanide ions are studied using synchrotron radiation excitations from the MAX IV 1.5 GeV storage ring. The energy of the edge and the formation of core cation exciton as well as the energy threshold of the multiplications of electronic excitations is found. It was clearly established the energy transfer from intrinsic luminescence centers to Sm2+ and Eu2+ ions. [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]

X-ray luminescence from CdTe nanoparticles is observed when CdTe nanoparticles are encapsulated into BaFBr:Eu2+ phosphors. In contrast, negligible x-ray luminescence is observed from the unencapsulated nanoparticles, either in solution or in solid form. The origin of the x-ray luminescence is attributed to the effective energy transfer from Eu2+ ions to CdTe nanoparticles in the nanocomposite materials. The x-ray luminescence of these nanocomposites is dose dependent and the emission wavelength is size adjustable which may allow use as a type of dosimeter for both in vitro and in vivo applications. [ABSTRACT FROM AUTHOR]

Time-resolved luminescence of YAG-Ce (150 ppm) fiber crystal with Mg co-doping was studied under pulsed X-ray excitation and γ-rays (Cs 662 keV). The initial part of decay kinetics under X-ray excitation is faster than for direct cerium excitation (63 ns). Decay kinetics is also characterized by the presence of slow components with at least two characteristic times longer than Ce3+ radiation time. The slowest one which dominates for t > 500 ns in YAG-Ce without Mg co-doping practically vanishes for samples with 50 ppm co-doping. Decay kinetics under γ-rays are characterized by slower rise time than that under X-rays. These properties can be explained by competition of energy transfer and energy losses in track regions. The distribution of excitations in tracks produced by X-rays differs from that in tracks produced by γ-rays, since the energy of primary electron after γ-quantum conversion is much higher than after X-ray absorption. The stopping power for energetic electrons decreases with increase of electron energy, and therefore the density distribution after X-ray conversion is shifted to higher densities, Therefore, the acceleration of recombination and quenching of excitations is more prominent under X-ray excitation. Specific role of Ce4+ induced by Mg co-doping is also discussed in the paper. • Samples YAG-Ce,Mg grown by micro-pulling-down were studied under X-ray and γ-rays. • Luminescence decay becomes faster with increase of Mg concentration. • Slow component vanishes for samples with 50 ppm Mg co-doping. • Decay kinetics under γ-rays show rise part and is slower than under X-rays. • The difference is explained using of the excitation densities distribution in track. [ABSTRACT FROM AUTHOR]

Abstract In this study, the Gd3+-substituted yttrium aluminum perovskite epitaxial films activated by Ce3+ ions, (YGd)AlO 3 :Ce3+ with Gd content 0–44%, were prepared by liquid phase epitaxy technique and their optical, luminescence, and scintillation properties were studied. The results showed that films with Gd content below 20% had greater photoluminescence and radioluminescence intensities. For higher Gd concentrations, the Ce3+ emission gradually decreased and the Ce3+ decays were accelerated. The model of bidirectional non-radiative energy transfer between Gd3+ and Ce3+ ions and energy migration over the Gd3+ sublattice is suggested and the processes responsible for the observed effects are discussed. Highlights • (GdY)AlO 3 :Ce3+ perovskite scintillators were characterized. • Bidirectional Gd3+-Ce3+ energy transfer in GdYAP:Ce perovskite was proposed. • Gd co-doped YAlO 3 :Ce3+,Gd3+ perovskite films were prepared by liquid phase epitaxy. [ABSTRACT FROM AUTHOR]

Photoluminescence and thermally stimulated luminescence of Gd 3 (Ga,Al) 5 O 12 :Ce single crystals and epitaxial films co-doped with different concentrations of Mg 2+ ions are investigated in the 77–500 K temperature range under excitation in the 4f - 5d 1 and 4f - 5d 2 absorption bands of Ce 3+ ions. Influence of Mg 2+ ions on the photoluminescence intensity, spectrum, decay kinetics, temperature dependence of the photoluminescence intensity, and the activation energy of luminescence thermal quenching is observed. Co-doping with Mg 2+ is shown to result in a drastic reduction of the afterglow and thermally stimulated luminescence and in a strong shortening of the afterglow decay kinetics. It influences also defects creation spectra and the activation energy of the photostimulated defects creation. The Mg 2+ - induced changes in the characteristics of the Gd 3 (Ga,Al) 5 O 12 :Ce, Mg single crystals and epitaxial films are found to be strongly different, and possible reasons of these differences are discussed. [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]

The aim of the current report is to fabricate Eu 3+ -doped glasses with the chemical composition of 50Li 2 O-15Gd 2 O 3 -5Bi 2 O 3 -(30-x)B 2 O 3 -xEu 2 O 3 (where x = 0.5, 1.0, 1.5, 2.0 and 2.5 mol%), with the help of conventional melt quenching technique. The fabricated glasses have been studied with help of physical, structural and luminescence properties for application of LEDs. The structural properties were investigated by XRD and FTIR spectra. Physical properties have been measured. Direct and indirect optical energy band gap (E g ) have been calculated and found to be increasing with Eu 2 O 3 concentration. Luminescence spectra have been observed from photo and radioluminescence spectra and found in good agreement with each other, however the concentration quenching was not determined for the samples. The high-covalence and asymmetric nature was confirmed from Photoluminescence emission and RL emission transition as well as from the higher values of luminescence intensity ratio. The JO parameters have been found for the better performance of lasing materials. The lifetime's data have been found to be decreasing from 1.64 to 1.50 ms, which is the confirmation of energy transfer in Eu 3+ ions through cross relaxations. From the calculated properties it has been suggested that the present glass samples might be good for red-light emitting devices. [ABSTRACT FROM AUTHOR]

Crystalline materials containing tungsten and europium ions are frequently used as scintillators because tungsten complexes show a high absorption cross section for high energy radiation and efficient energy transfer to europium ions, which relax radiatively in the visible spectral range according to the 5 D 0 → 7 F 2 transition. However, this intra-configurational transition is forbidden on spin and parity and, consequently, shows a slow decay rate (hundreds of microseconds to milliseconds). In order to use this kind of materials in high repetition rate processes, faster luminescence decays are required. A set of Eu 2-x Dy x (WO 4 ) 3 solid solutions has been synthesized. Rietveld refinement of X-ray diffraction patterns has been performed in order to determine the crystalline structure of the samples and particularly the distance between rare earth cations. The morphology and composition was characterized with scanning electron microscopy combined with energy-dispersive X-ray spectroscopy. Optical absorption, emission spectra and decay rates have been systematically measured to analyze the luminescent properties of the materials. Cross-relaxation processes between Eu 3+ and Dy 3+ ions are responsible of the reduction of the 5 D 0 decay rate. The average lifetime of the Eu 3+ 5 D 0 excited state can be decreased in the range of one order of magnitude. However, the 5 D 0 → 7 F 2 emission intensity decreases in the same range too. Nevertheless, the proposed strategy of Eu 3+ 5 D 0 lifetime reduction can be of interest for those opto-electronic detection applications, which are not limited by sensitivity but by time resolution, such as it occurs in many cases for high energy-high repetition rate photon pulses. [ABSTRACT FROM AUTHOR]

Ce3+,Pr3+-codoped SiO2-Al2O3-B2O3-Gd2O3 glasses (SABG:Ce,Pr) were prepared by melt quenching under a CO reducing atmosphere. Luminescence properties were investigated under UV and X-ray excitations. A dominant emission band at 430 nm belonging to the Ce3+:5d1 → 4f transition was observed in the photo- and radio-luminescence spectra. The energy transfer occurs from this Ce3+ band toward the 3PJ levels of Pr3+ with an efficiency of up to 24%, followed by the reduction of integrated luminescence intensity with an increasing Pr3+ concentration. This result is attributed to the increase in the reabsorption of Ce3+ luminescence and the non-radiative energy transfer toward the 3PJ levels of Pr3+. The cross-relaxation process within the Pr3+ pairs can further diminish the total luminescence yield at high Pr3+ concentrations. The integral scintillation efficiency and light yield measurements were carried out and compared to the reference Bi4Ge3O12 (BGO) crystal. [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]

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]

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]

Gd3+ and Dy3+-doped borate glasses are considered attractive candidates for white light emission. In this work, the samples, developed by the melt-quenching route, contain a mixture of Gd3+ and Dy3+ with known molar compositions. The determined physical parameters indicate structural changes. Information regarding the Judd-Ofelt (JO) intensity parameters and spectral radiative features, calculated from absorption spectra and emission properties, respectively, are obtained. Excitation and photoluminescence characteristics of the developed samples are found. The energy transfer (ET) efficiency from Gd3+ → Dy3+ is determined by considering their emission intensities and lifetime. The quantum efficiency (QE) of glasses is evaluated. Inokuti –Hirayama (IH) model shows that the Dy3+ → luminescence center ET is dominated by dipole-dipole coulomb interaction. Due to the excitation of more secondary electrons, the X-ray luminescence shows an intense emission pattern. Furthermore, we find the integral scintillation efficiency to be 8.4% of the commercial BGO scintillator crystal for the 10 mol% Gd 2 O 3 -doped glass. Commission International deI'Eclairage (CIE) color coordinates and color correlated temperature (CCT) show the suitability of tested samples for white-light applications. • Synthesized 20Li 2 O 3 –30SrO-(49-x)B 2 O 3 -xGd 2 O 3 -1Dy 2 O 3 glasses with Gd3+ as sensitizer and Dy3+ as activator via melt quenching technique. • PL emission spectra showed reduced Gd3+ luminescence evidenced energy transfer. • CIE and CCT confirmed cool white emission. [ABSTRACT FROM AUTHOR]

A novel NIR emitting scintillator with 825 nm was developed by doping Sm2+ in Cs 4 Eu(Br,I) 6 crystal. The single crystals of Cs 4 Eu(Br,I) 6 :Sm were successfully grown by the Bridgman method. The crystal structure and valence state was approved by XRD and XPS methods. The luminescence properties and energy transfer were systematically investigated. The energy transfer mechanism is variable for different Sm2+ concentration. The PL decay profiles show that the Sm2+-related emission has fast decay of nanosecond. The proportion of fast decay can be tunable by adjusting Sm2+ doped concentration. The Sm2+ doped europium -host material will have a potential application for unclear detection as near-infrared (NIR) scintillators. • The novel NIR emitting Cs 4 Eu(Br,I) 6 :Sm scintillation crystals were successfully grown by the Bridgman method and the luminescence properties is tunable. • The proportion of nonradiative energy transfer from Eu2+ to Sm2+ was improved and the PLQY of Sm2+-related is up to 42.1%. • The fast decay time component of Sm2+ (50 ns) is up to 31.8% for Cs 4 Eu(Br,I) 6 : 3 mol%Sm crystal. • The proposed Sm2+ doped europium -host material principle is an effective method to develop near-infrared (NIR) scintillators for nuclear radiation detection. [ABSTRACT FROM AUTHOR]

This work investigates the physical, optical, luminescence, and scintillation properties of borosilicate glasses doped with different concentrations of Gd 2 O 3 and Dy 2 O 3. All glasses were prepared by the melt quenching technique. The density and molar volume value increase as the Gd 2 O 3 and Dy 2 O 3 content increases. Dy3+ in glasses absorb photons in visible light and near-infrared regions, confirmed by the absorption spectra. The emission spectra of glasses show two strong peaks at 575 nm (4F 9/2 →6H 13/2) and 481 nm (4F 9/2 →6H 15/2) under Gd3+, direct Dy3+ and X-ray excitation. The integral scintillation efficiency of 1.50Dy:12.5Gd is 7.22%, compared with BGO crystal. The luminescence of glass can be tuned for different shades of white emission by selecting the excitation source such as photon with 275 nm, 387 nm and X-ray, respectively. The developed glasses are the potential for tunable emitting and scintillation material applications. [ABSTRACT FROM AUTHOR]

The moisture sensitivity of LuI 3 :Ce,Hf and luminescent properties of undoped LuI 3 and LuI 3 :M (M=Ce 3+ , Tb 3+ , Dy 3+ ) powders were investigated. The possibility of improving the air and moisture stability of LuI 3 :Ce by Hf doping was tested. It was proven that the Hf contribution to the LuI 3 :Ce stability is very limited and is insignificant to render LuI 3 :Ce scintillator powders suitable for applications. Photoluminescence results of LuI 3 without dopants added on purpose showed luminescence due to a plurality of rare-earth elements׳ impurities. Two types of self-trapped luminescence were found. Energy transfer between host lattice, self-trapped excitons and rare-earth ions was investigated. [ABSTRACT FROM AUTHOR]

Multicomponent garnets (Y 3− x Gd x Al 5− y Ga y O 12 ) doped with Ce 3+ ions are promising scintillators with a high density, fast response time and high light yield. To deepen the knowledge about the transfer stage of scintillation mechanism we discuss the energy migration and energy transfer processes in the set of undoped and Ce 3+ activated multicomponent garnet single crystals. Temperature dependence of Gd 3+ emission intensities as well as decay kinetics in Y 3− x Gd x Al 5− y Ga y O 12 ( x , y =1,2,3) crystals point to the Gd 3+ →Gd 3+ nonradiative energy migration, which is diffusion limited. Concentration quenching of Gd 3+ emission occurs by energy migration to accidental impurities and/or structure defects. Temperature dependence of photoluminescence emission intensities and decay time measurements of Gd 3+ as well as Ce 3+ ions in Gd 3 Ga 3 Al 2 O 12 :Ce 3+ single crystal reveal nonradiative energy transfer Gd 3+ →Ce 3+ (including migration through Gd 3+ sublattice) which is responsible for slow Ce 3+ fluorescence decay component. [ABSTRACT FROM AUTHOR]

Gd 3+ -, Tb 3+ /Gd 3+ -coactivated oxyfluoride borogermanate scintillating glasses with the density of about 6.35–6.61 g/cm 3 were prepared by a melt-quenching method. The luminescent and energy transfer properties were studied by transmittance, photoluminescence and X-ray excited luminescence (XEL) spectra. The total content of rare-earth oxide and fluoride is as high as 49 mol% in oxyfluoride borogermanate glasses, which are necessary to ensure their density up to 6.61 g/cm 3 . Energy transfer efficiency and mechanism from Gd 3+ to Tb 3+ were determined, and the corresponding critical distances for both Gd 3+ –Tb 3+ and Tb 3+ –Tb 3+ ion pairs were calculated, respectively. The optimal concentration of Tb 3+ ions in dense oxyfluoride borogermanate glasses excited by both ultraviolet light and X-ray excitation were also determined. The integral scintillation efficiency of Tb 3+ -activated borogermanate scintillating glass was found to be about 26.9% of the standard Bi 4 Ge 3 O 12 (BGO) scintillating crystal. [ABSTRACT FROM AUTHOR]

Silicate oxyfluoride scintillating glasses doped Tb 3 + with different concentrations were prepared by a melt-quenching method. The detailed analyses of photoluminescence spectra and luminescence decay curve testified that the Gd 3 + indeed transfers their energy to Tb 3 + via phonon assistant electric dipole–dipole interaction. The evaluated energy transfer efficiency from Gd 3 + to Tb 3 + increases gradually with increasing the Tb 2 O 3 content and reaches 99% when the content of Tb 2 O 3 exceeds 5 mol%. Due to the more efficient energy transfer from Gd 3 + to Tb 3 + and higher doping concentration of Tb 3 + , the intensity of green emission originated from 5 D 4 → 7 F J reaching the maximum when the content of Tb 2 O 3 is 6 mol%. Meanwhile, a strong 5 D 3 luminescence quenching happens due to the cross-relaxation process. Under X-ray excitation, the intensity of 542 nm emission in our glass doped with 6 mol% of Tb 2 O 3 shows 5.2 times stronger than that of 500 nm emission in the commercial Bi 4 Ge 3 O 12 (BGO) crystal, the integral scintillation efficiency is about 68% of the BGO crystal, which is much useful for reducing radiative dose to obtain high-resolution X-ray imaging. [ABSTRACT FROM AUTHOR]

The nature of luminescence centers in NaI:Eu scintillation crystals was studied in a wide excitation energy and temperature ranges. Radio- and photoluminescence spectra and TSL curves were measured for crystals with varied activator concentrations. Two main narrow luminescence bands at 2.8 eV (center I) and 2.6 eV (center II) were found at 10 К. Center I dominates for low Eu concentration (<0.07%). Increase of activator content leads to suppression of center I emission and enhancement of center II. Presence of oxygen containing impurities in heavily doped crystals is due to high hygroscopicity of the NaI matrix and EuI 2 dopant. Analysis of emission and thermoluminescence features allows justifying the role of anion impurities (oxygen/hydroxyl ions) in formation of activator center II, which is responsible for scintillation efficiency of NaI:Eu crystals at room temperature. [ABSTRACT FROM AUTHOR]

In this paper, Dy 2 O 3 , Tb 4 O 7 singly doped and Dy 2 O 3 /Tb 4 O 7 -codoped borogermanate-tellurite glasses for radiation application were synthesized by a melt-quenching method. The density of developed glasses exceeds 5.0 g/cm3, which is the fundamental requirement of dense scintillators in the application fields of medical imaging and high-energy physics engineering. The optical properties of these glass scintillators were systematically studied by transmittance, photoluminescence (PL) and X-ray excited luminescence (XEL) spectra, together with the corresponding photoluminescence dynamic process. The transmittance results reveal that the transmittance rate of all glasses can reach at the vicinity of 80%. The optimal content of Dy 2 O 3 and Tb 4 O 7 for both PL and XEL intensity were determined under ultraviolet light and X-ray excitation, respectively. The energy transfer occurred from Dy3+ to Tb3+ ions were demonstrated, and the energy transfer efficiency from Dy3+ to Tb3+ ions is observed to increase with higherTb 4 O 7 content. The scintillation efficiency of Dy3+, Tb3+doped, and Dy3+/Tb3+ co-doped borogermanate-tellurite scintillating glasses is about 10.45%, 41.38%, and 38.73% of the standard Bi 4 Ge 3 O 12 (BGO) crystal, respectively. • The efficient energy transfer from Dy3+ to Tb3+ ions in borogermanate-tellurite glasses were revealed. • The optimal concentration of Tb3+, Dy3+, and Dy3+/Tb3+were found to be 7 mol%, 1 mol%, and 1 mol%/4 mol%, respectively. • Dy3+, Tb3+ singly doped, Dy3+/Tb3+ codoped borogermanate-tellurite glasses with density of 5.0 g/cm3. • The XEL intensity of 4 mol% Tb3+ green light is expectedly observed to decrease about 6.4% after the addition of 1 mol% Dy3+ ion. • The scintillation efficiency of Dy3+, Tb3+ doped, and Dy3+/Tb3+ codoped glasses is about 10.45%, 41.38%, and 38.73% of the standard BGO crystal, respectively. [ABSTRACT FROM AUTHOR]

Lanarkite type Pb 2 MoO 5 single crystals were grown using low temperature gradient Czochralski technique and their optical and luminescent properties were studied. The luminescence band at 590–600 nm was observed under UV and X-ray excitations and ascribed to emission of self-trapped excitons. The band is thermally quenched at T > 15 K with the activation energy of process, E act = 11 meV. The measurements of thermostimulated luminescence demonstrated the presence of shallow traps, which adversely influence the energy transfer to the emission centers. [ABSTRACT FROM AUTHOR]

The Nd-doped and Er-doped LuF 3 single crystals were grown by the micro-pulling-down method to study their scintillation properties in the vacuum-ultraviolet (VUV) region. The doubly Nd–Er codoped single crystal was grown to study possibility of scintillation performance improvement by energy transfer from Er 3+ to Nd 3+ ions. The LiF flux was to avoid phase transition below melting temperature. The 1%Nd-doped sample showed the highest overall scintillation efficiency under X-ray excitation which was 7 times as high as that of the LaF 3 :Nd 8% standard. The leading Nd 3+ 5d–4f emission was situated at 176 nm, while the Er 3+ 5d–4f emission for Er-doped samples was observed at 163 nm, which better matches the sensitivity of some VUV-sensitive photodetectors. The optimum Er concentration was determined to be around 1–3 mol%. No Er 3+ 5d–4f emission was observed for the doubly Er,Nd-codoped sample due to energy transfer from the Er 3+ to Nd 3+ ions. Slight improvement of the light yield was observed in the doubly-doped sample with respect to the Nd-only doped one. [ABSTRACT FROM AUTHOR]

The spectra and decay of luminescence in scintillation glass of the LiO-BO-PO-CaF system doped by Gd, Gd/Ce, Gd/Pr, Tb, Tb/Ce, and Tb/Eu have been investigated. The technology of synthesis has been described and the evolution of luminescence spectra relative to the electron excitation pulse has been studied. The presence of the buildup stage in the kinetics of terbium ions luminescence was revealed in the bands at 380 and 490 nm. The existence of interaction between ions (Gd and Ce, Tb and Ce, Tb and Eu) has been established. The estimation of the scintillation efficiency of glass with rare earth ions (REIs) has been performed. [ABSTRACT FROM AUTHOR]

Novel Lu 2 WO 6 :Eu 3+ films with excellent luminescence performance were successfully prepared by Pechini method for the first time and characterized with X-ray diffraction (XRD), micro X-ray fluorescence imaging (μ-XRF), atomic force microscope (AFM), and X-ray excited luminescence (XEL), etc. Eu 3+ -doped films emitted strong red light peak wavelength at 612 nm under both UV light or X-ray excitation. The optimal annealing temperature and Eu 3+ -doped concentration are around 950 °C and 10 mol%, respectively. In addition, luminescence mechanism associated with Eu 3+ site occupation and possible energy transfer of Lu 2 WO 6 :Eu 3+ films have also been proposed. The optimized thin film shows great potential for applications as a candidate for X-ray imaging due to its high density, suitable emission wavelength and high light yield. [ABSTRACT FROM AUTHOR]

Absorption, excitation and emission spectra of cadmium fluoride crystals doped with rare-earth ions were investigated. In contrast to alkaline-earth fluorides the absorption spectra due to 4f - 5d transitions of Ce^3+, Pr^3+ and Tb^3+ ions are broadened. No 5d-4f emissions were observed. These prove that 5d(eg) levels of rare earth ions lie in conduction band of CdF2 crystal. Emission spectra of Tb^3+ show the group of 4f-4f ^5D4-^{7}F_j lines in contrast to other alkaline-earth fluorides where emission due to ^5D3-^{7}F_j transitions is also observed. The absence of the emission is due to position of ^5D3 level within condution band. Among the all measured crystals doped with impurity ions (Pr, Nd, Eu, Ho, Tb, Tm, Yb, Ga, In or Mn), the CdF2 doped with Pr^3+, Tb^3+, or Mn^2+ ions have the highest light outputs under x-ray excitation. [ABSTRACT FROM PUBLISHER]

Photoluminescence, X-ray excited radioluminescence and photoelectron yield characteristics were studied in multicomponent GdGaYAG:Ce and GdGaLuAG:Ce garnet films grown by liquid phase epitaxy. Nonradiative energy transfer from \Gd^3+ to activator \Ce^3+ ions was evidenced. At low Gd doping, < \5\%, two virtually independent emission centers coexist, which compete for intensity: \Ce^3+ with fast 5d-4f emission and \Gd^3+ with slow 4f-4f emission. At higher Gd concentrations, the \Ce^3+ emission retrieves intensity due to the energy transferred from \Gd^3+ donors. At Gd concentration \sim \50\% and above, the \Gd^3+ emission is suppressed due to energy migration and transfer to \Ce^3+ centers. In these samples, the host emission is also completely quenched and the best scintillator performance is achieved. Contrary to melt-grown crystals, no positive role of Ga substitution was found in epitaxial films. [ABSTRACT FROM PUBLISHER]

Highlights: [•] Ce3+-doped dense scintillating glasses containing Gd2O3 and Lu2O3 were prepared. [•] Increasing the concentration of Gd2O3 and Lu2O3 can increase the light yields. [•] The highest light emission intensity excited by X-ray is 87% of BGO. [•] The decay time constants are in the range of 30–40ns. [•] The energy transfer from Gd3+ to Ce3+ plays an important role in the glasses. [ABSTRACT FROM AUTHOR]

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

We prepared Tb3+-doped Gd2O3-based oxide glasses by high-temperature melting method and presented their density and optical characterization including transmission, emission and excitation spectra. Dependence of density and luminescence properties on the concentration of Tb3+ and Gd2O3 was also analyzed. The results show that rising Tb3+ ions concentrations would lead to the reduction of distance between Tb3+ ions, the increase of probabilities of energy resonate-transfer and a stronger luminous intensity. In addition, a high Gd2O3 concentration was beneficial to improve the glass samples density, but exerting a negative effect on Tb3+ ions and decreasing the luminous intensity of Tb3+ ions. [ABSTRACT FROM AUTHOR]

Abstract: The work is dedicated to the development of scintillating screens based on the single crystalline films (SCF) of Ce,Tb doped Lu-based silicates, perovskites and garnets grown by the liquid phase epitaxy method. We confirm in this work the presence of the Ce → Tb energy transfer in LSO and LuAP hosts. We also show that in Ce–Tb doped LuAG SCF, the effective Tb → Ce energy transfer is observed. This results in increasing the light yield of the luminescence of double doped LuAG:Ce,Tb SCF up to 25–30% with respect to single Ce doped (Y,Lu)AG SCF counterparts at optimal ratio of Ce/Tb ions. [Copyright &y& Elsevier]

The feasiblity of using Yb2+ as a scintillation sensitiser for CsBa 2 I 5 :Sm2+ near-infrared scintillators has been assessed. CsBa 2 I 5 samples with concentrations ranging from 0.3% to 2% Yb2+ and 0–1% Sm2+ have been studied. The scintillation properties have been determined and the dynamics of the scintillation mechanism have been studied through photoluminescence measurements. Radiationless energy transfer between Yb2+ ions plays a key role in increasing the ratio between the spin-forbidden and spin-allowed emission with increasing Yb2+ concentration in samples where Yb2+ is the only dopant. In samples co-doped with Sm2+, the Yb2+ 4 f 13 [ F 2 7 / 2 ] 5d 1 [LS] and 4 f 13 [ F 2 7 / 2 ] 5d 1 [HS] states both serve as donor states for radiationless energy transfer to Sm2+ with a rate of energy transfer that is inversely proportional to the luminescence lifetime the respective donor states. At a Sm2+ concentration of 1%, 85% of the Yb2+ excitations are transferred to Sm2+ through radiationless energy transfer. Almost all of the remaining Yb2+ emission is reabsorbed by Sm2+, resulting in nearly complete energy transfer. • The ratio of Yb2+ spin-allowed to spin-forbidden emission is shown to depend on the Yb2+ concentration. • When CsBa 2 I 5 :Yb2+ is co-doped with 0.5% Sm2+, almost exclusively Sm2+ emission is detected. • Energy transfer from Yb2+ to Sm2+ mainly takes place through radiationless energy transfer. • Energy is transferred from both emissive states of Yb2+ with rates inversely proportional to their luminescence lifetime. [ABSTRACT FROM AUTHOR]

Abstract: Lu3Al5O12:Ce3+ (LuAG:Ce) is a scintillator with a fast response time. The light yield is lower than theoretically expected and to increase the light yield co-doping with Pr3+ is investigated. To better understand the energy flow to the Ce3+ ion, first low temperature emission and excitation spectra of Pr3+ doped LuAG were investigated, allowing the accurate determination of the zero-phonon lines for the 5d states of Pr3+ in LuAG and the temperature dependent energy transfer from the Self Trapped Exciton to Pr3+. In addition VUV excitation and soft X-ray excited emission spectra of the co-doped LuAG:Ce,Pr were studied. The results show that energy transfer from Pr3+ to Ce3+ occurs but it is followed by back transfer to the 4f states of Pr3+. [Copyright &y& Elsevier]

Results of investigation of energy transfer mechanism in SrF2 crystals doped with Pr^3+ ions are presented. Temperature dependences of 5d-4f and exciton emission in this material under X-ray excitation, and thermostimulated luminescence (TSL) in temperature range 80–300 K are studied. It has been established that in SrF2-Pr^3+ crystals the consecutive electron-hole capture mechanism of energy transfer takes place. Also we found that hole centers made a contribution to energy transfer from primary electrons and holes to Pr^3+ ions. [ABSTRACT FROM PUBLISHER]

Emission and excitation spectra of CaF_2, SrF_2, BaF_2 doped with Nd^3+, Sm^3+, Ho^3+, Er^3+, Tm^3+ excited by vacuum ultraviolet photons or by x-rays were studied. Decay times of the Nd^3+ emission near 180 nm at 7 K were 17.7, 15.3, 12.3 ns in CaF_2, SrF_2, BaF_2 respectively. 4f^n-1 5d^1-4f^n luminescence bands were found at 170–200 nm for Sm^3+ ions and at 140–190 nm for Ho^3+. [ABSTRACT FROM PUBLISHER]