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Luminescent nanoparticles are researched for their potential impact in medical science, but no materials approved for parenteral use have been available so far. To overcome this issue, we demonstrate that Eu3+-doped hafnium dioxide nanocrystals can be used as non-toxic, highly stable probes for cellular optical imaging and as radiosensitive materials for clinical treatment. Furthermore, viability and biocompatibility tests on artificially stressed cell cultures reveal their ability to buffer reactive oxygen species, proposing an anti-cytotoxic feature interesting for biomedical applications.

For the first time, hafnia (HfO2) nanoparticles have been produced by photochemical synthesis. The photochemical route has been proven to be scalable, affordable, and straightforward to create monoclinic HfO2 nanoparticles with a size of tens of nanometers. The exploitation of this route offers a chance to create large amounts of dense nanoparticles with reduced costs and time of production for future creation of large area composite scintillators for fast timing techniques. Specific annealing treatments from 450 °C to 1000 °C have been targeted to tune the structural and morphological properties and optimize the luminescence of the nanoparticles. Hafnia nanoparticles annealed at low temperature display an amorphous structure. After thermal treatment at 1000 °C, HfO2 nanoparticles crystallize into a monoclinic phase, as evidenced by thermal analyses and X-ray diffraction. Radioluminescence and photoluminescence of HfO2 have been investigated at room temperature and 77 K. The emission band of hafnia covers a range from 300 to 600 nm and it can be attributed to defects within the matrix. In particular, the highest radioluminescence intensity appears in the crystalline sample annealed at 1000 °C, thanks to the higher crystallinity degree and the reduction of non-radiative channels and quenching defects. Photoluminescence and scintillation decay have evidenced the presence of the fast decay in the nanosecond time range. Thus, due to their size, density, and spectroscopic and timing features, monoclinic hafnia nanoparticles obtained by photochemical synthesis are attractive for potential creation of large area scintillating composites. [ABSTRACT FROM AUTHOR]

Lutetium oxyorthosilicate Lu2SiO5 (LSO) and pyrosilicate Lu2Si2O7 (LPS) activated by Ce3+ or Pr3+ are known to be effective and fast scintillation materials for the detection of X-rays and γ-rays. Their performances can be further improved by co-doping with aliovalent ions. Herein, we investigate the Ce3+(Pr3+) → Ce4+(Pr4+) conversion and the formation of lattice defects stimulated by co-doping with Ca2+ and Al3+ in LSO and LPS powders prepared by the solid-state reaction process. The materials were studied by electron paramagnetic resonance (EPR), radioluminescence spectroscopy, and thermally stimulated luminescence (TSL), and scintillation decays were measured. EPR measurements of both LSO:Ce and LPS:Ce showed effective Ce3+ → Ce4+ conversions stimulated by Ca2+ co-doping, while the effect of Al3+ co-doping was less effective. In Pr-doped LSO and LPS, a similar Pr3+ → Pr4+ conversion was not detected by EPR, suggesting that the charge compensation of Al3+ and Ca2+ ions is realized via other impurities and/or lattice defects. X-ray irradiation of LPS creates hole centers attributed to a hole trapped in an oxygen ion in the neighborhood of Al3+ and Ca2+. These hole centers contribute to an intense TSL glow peak at 450–470 K. In contrast to LPS, only weak TSL peaks are detected in LSO and no hole centers are visible via EPR. The scintillation decay curves of both LSO and LPS show a bi-exponential decay with fast and slow component decay times of 10–13 ns and 30–36 ns, respectively. The decay time of the fast component shows a small (6–8%) decrease due to co-doping. [ABSTRACT FROM AUTHOR]

Conjugated BaI2:Eu (5 at.%) nanocrystalline particles were synthesized, decorated with golden nanoparticles (GNP). GNP demonstrated some hydrophilic effect, leading to the BaI2·H2O phase creation. The Eu2+ luminescence intensity was reduced according to the GNP content. This was due to the decreased number of Eu2+ ions in the BaI2, most probably, arising from the Au substitution for Ba competing with Eu. Moreover, the decay time of luminescence was decreased upon GNP content. This was explained by the moderation of negative charge in the GNP, leading to the repulsion with an electron in the excited Eu2+. [ABSTRACT FROM AUTHOR]

The influence of Mo on the electronic states and crystalline structure, as well as morphology, phase composition, luminescence, and defects in ZnO rods grown as free-standing nanoparticles, was studied using a variety of experimental techniques. Mo has almost no influence on the luminescence of the grown ZnO particles, whereas shallow donors are strongly affected in ZnO rods. Annealing in air causes exciton and defect-related bands to drop upon Mo doping level. The increase of the Mo doping level from 20 to 30% leads to the creation of dominating molybdates. This leads to a concomitant drop in the number of formed ZnO nanorods. [ABSTRACT FROM AUTHOR]

Erbium-doped Y3Al5O12 (YAG) single crystals grown using the micro-pulling-down technique were investigated. Three Er concentrations were chosen: 0.1, 0.3 and 1 at%. Er3+ electron paramagnetic resonance (EPR) spectra were measured in the ground and first excited states. The corresponding g tensors and 167Er hyperfine interaction were changing upon Er content indicating moderation of the Er-O bond length and/or Er local surrounding. Photoluminescence (PL) and radioluminescence (RL) spectra were complex, consisting of strongly overlapped typical Er3+ transitions. In addition, there were other broad PL band (3.1 eV) and RL band (3.95 eV) attributed to the F+ center and yttrium substituting for aluminum (YAl), respectively. The X-ray excited decay kinetics exhibited a decrease of the decay time of the YAl from hundreds of nanoseconds to nanoseconds upon Er doping level. This is discussed and explained considering EPR data. [ABSTRACT FROM AUTHOR]

Nanorods of erbium-doped zinc oxide (ZnO:Er) were fabricated using a hydrothermal method. One batch was prepared with and another one without constant ultraviolet (UV) irradiation applied during the growth. The nanorods were free-standing (FS) as well as deposited onto a fused silica glass substrate (GS). The goal was to study the atomistic aspects influencing the charge transport of ZnO nanoparticles, especially considering the differences between the FS and GS samples. We focused on the excitons; the intrinsic defects, such as zinc interstitials, zinc vacancies, and related shallow donors; and the conduction electrons. UV irradiation was applied for the first time during the ZnO:Er nanorod growth. This led to almost total exciton and zinc vacancy luminescence reduction, and the number of shallow donors was strongly suppressed in the GS samples. The effect was much less pronounced in the FS rods. Moreover, the exciton emission remained unchanged there. At the same time, the Er3+ content was decreased in the FS particles grown under constant UV irradiation while Er3+ was not detected in the GS particles at all. These phenomena are explained. [ABSTRACT FROM AUTHOR]

The glass‐ceramics (GC) of gadolinium aluminum gallium garnets with the expected composition of Gd3Al3Ga2O12:Ce and Gd3Al3Ga2O12:Ce,Be (GAGG:Ce and GAGG:Ce,Be, respectively) are fabricated by crystallization from the Gd2O3–Al2O3–Ga2O3–CeO2–SiO2–BeO (Gd:Ga:Al ratio is close to 3:2:3) glasses. The influence of Be2+ co‐doping (including doping level) on the luminescent properties of the GAGG is demonstrated. In particular, Be co‐doping results in the suppression of the Ce3+‐related radioluminescence (RL) and as a consequence, the light yield is lowered as well. The conclusion is made that Be2+ creates effective electron or hole trapping centers. [ABSTRACT FROM AUTHOR]

Cesium lead bromide (CsPbBr 3 , CPB) powder formed by micro-, nanocrystals (MC, NC) and quantum dots (QD) was synthesized as free-standing and polystyrene covered. Luminescence was multicomponent, in general, ranging from below 1.9 eV up to about 2.6 eV. The ultrafast decay kinetics exhibited strong decay time component with the value of 260 ps. Electron paramagnetic resonance (EPR) revealed surface defects like O 2 − and some spin transitions most likely originating from some complex defect, supposedly F-V k (H) dimer center under the constant ultraviolet (UV) light irradiation at the temperature T = 10 K. The thermal release of the electrons from the O 2 − center was correlated with the 117 K thermally stimulated luminescence (TSL) peak. Coating with polystyrene resulted in the about doubly increased decay time of luminescence. The O 2 − and F-V k (H) EPR resonances were not observed as well. The TSL peak which might be ascribed to the O 2 − was not clearly detected anymore. The glow curve was composed of one very broad peak typical for the amorphous materials. At the same time, the polystyrene prevented the MCs creation. The existence of charge/energy transfer between the CPB and polystyrene due to the chemical bonding was assumed and confirmed also by calculations. [Display omitted] • EPR, TSL and RL study of charge trapping and luminescence in CsPbBr 3. • Charge/energy transfer was detected. • O 2 − -related electron trapping center was revealed in these crystals. • TSL peak was correlated to the release of electrons from the O 2 − surface center. • Complex bromine vacancy-related charge trapping center was observed. [ABSTRACT FROM AUTHOR]

The scintillation characteristics of Lu0.8Gd2.2 (Al5–xGax)O12:Ce,Mg (x = 2.6 and 3) single crystals grown by the micropulling down method are investigated. The light yield of 27600 photons/MeV obtained for Lu0.8Gd2.2Al2Ga3O12:Ce,Mg is higher than that of 25 400 photons/MeV obtained for Lu0.8Gd2.2Al2.4Ga2.6O12:Ce,Mg. The photoluminescence and scintillation decays measured at room temperature (RT) for Lu0.8Gd2.2Al2Ga3O12:Ce,Mg are faster than those for Lu0.8Gd2.2Al2.4Ga2.6O12:Ce,Mg. Temperature dependence of radioluminescence (RL) intensity indicates a lower quenching temperature for Lu0.8Gd2.2Al2Ga3O12:Ce,Mg. Coincidence time resolution of a Lu0.8Gd2.2Al2Ga3O12:Ce,Mg detector in coincidence experiment with a BaF2 detector was measured to be 410 ps. The afterglow and thermally stimulated luminescence (TSL) characteristics below RT are also measured. [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]

We have investigated Li 4 SiO 4 scintillation crystals for their possible application in neutron detection due to high Li content and low density of 2.35 g/cm 3 . The micro-pulling-down method employing the Ir crucible and afterheater was optimized for crystal growth of Li 4 SiO 4 taking into account the Li evaporation. To grow high-quality crack-free single crystals, the heating power was increased to establish milder temperature gradient, thicker meniscus, smaller crystal diameter and resulting smaller stress in the as-grown crystals. The undoped, Ti-, Cr-, and Al- doped crystals were prepared and studied. Radioluminescence measurements under X-ray excitation showed quite high overall scintillation efficiency of the Ti-doped sample reaching as high as 250% of that of Bi 4 Ge 3 O 12 reference scintillator. The emission spectrum was dominated by one broad band peaking at 350 nm related to Ti 4+ impurity. Reasonable light yield of 10000 photons/neutron was found. However, its long decay time of 54 μs might be a limitation especially for high counting rate applications. The overall scintillation efficiency of the Cr 3+ sample was much lower and the spectrum shows one broad peak at 463 nm which does not correspond to Cr 3+ luminescence. The radioluminescence spectrum of the Al-doped sample resembled to that of the Ti-doped one, just its magnitude is considerably lower, which was explained by Ti contamination. Peculiarities and optimization of crystal growth and a preliminary sketch of luminescence mechanisms and dopant incorporation are discussed. [ABSTRACT FROM AUTHOR]

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

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

[Display omitted] • Electron and hole trapping centers were observed in the molybdenum doped zinc oxide rods. • Electron trapping centers were mostly molybdenum-based. • Holes were trapped at oxygen complexes. • Exciton- and defect-related emission bands appear suppressed after X-ray irradiation. • Zinc vacancies participated in the charge trapping processes. Peculiarities of the point defects creation under X-ray irradiation and the influence of Mo doping in ZnO powders of nano- and microrods fabricated by the hydrothermal growth method (as-grown and annealed in air) were studied in detail. Correlated experiments of X-ray diffraction, X-ray photoelectron spectroscopy, electron paramagnetic resonance, photo- and radioluminescence as well as thermally stimulated luminescence allowed us to trace the effect of the molybdenum inclusion on the phase purity of synthesized materials and the role of Mo in the creation of X-ray induced point defects. Oxygen-based hole trapping centers (most probably involving interstitial oxygen) as well as Mo5+-based electron trapping centers were observed and their thermal stabilities were studied. Some amount of the hole trapping centers seemed to be directly connected with the creation of Mo5+. Zinc vacancies and the Mo5+ centers up to some extent were assumed to act as recombination centers for the holes released from the hole trapping centers. The X-ray irradiation also affects the luminescence properties of the ZnO:Mo samples – the intensity of the luminescence bands in general becomes weaker. [ABSTRACT FROM AUTHOR]

CsPbBr3 nanocrystals have been identified as a highly promising material for various optoelectronic applications. However, they tend to coexist with Cs4PbBr6 phase when the reaction conditions are not controlled carefully. It is therefore imperative to understand how the presence of this phase affects the luminescence performance of CsPbBr3 nanocrystals. We synthesized a mixed CsPbBr3-Cs4PbBr6 sample, and compared its photo- and radioluminescence properties, including timing characteristics, to the performance of pure CsPbBr3 nanocrystals. The possibility of energy transfer between the two phases was also explored. We demonstrated that the presence of Cs4PbBr6 causes significant drop in radioluminescence intensity of CsPbBr3 nanocrystals, which can limit possible future applications of Cs4PbBr6-CsPbBr3 mixtures or composites as scintillation detectors. [ABSTRACT FROM AUTHOR]

The influence of the Mg 2+ codoping and annealing in the air on the scintillation and luminescence characteristics of Pr-doped lutetium-aluminum garnet crystals (LuAG) was studied to find a possible positive effect of Pr 4+ . The overall scintillation efficiency under X-ray excitation of the annealed Pr- doped samples decreased with increasing Mg concentration. This was explained by increased overlap of the Pr 3+ 5d-4f emission with the charge-transfer (CT) absorption band of the Pr 4+ ion stabilized by Mg 2+ . This absorption caused even greater decrease of the light yield, as the light is collected from the whole sample volume in the pulse-height spectrum measurement. Electron centers based on oxygen vacancies (F + centers) which can have negative influence on scintillation mechanism were revealed by the electron paramagnetic resonance (EPR) experiments. The O - hole center was detected as well and the temperature dependences of the EPR spectra showed that its thermal stability was decreased by Mg codoping. Negligible changes in the decay time of Pr 3+ 5d-4f photoluminescence exclude the non-radiative energy transfer from relaxed 5d 1 excited state of Pr 3+ towards CT absorption transition of Pr 4+ and suggest that simple reabsorption of the emitted light takes place. Unlike for the Ce-doped analogs, promoting the Pr 3+ luminescence center to the tetravalent state by divalent ion co-doping and air annealing did not improve scintillation properties of Pr-doped LuAG. [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]

Luminescence and scintillation properties of Lu 2 YAl 2.5 Ga 2.5 O 12 :Ce,Mg (0.02, 0.05 %) garnet crystals grown by the micro-pulling down method were investigated. The onset temperature for luminescence quenching at ∼365 K is determined from the temperature dependence of photoluminescence decay time. At room temperature, the Mg (0.05 %) sample exhibits high integral scintillation efficiency of ∼445 % of BGO crystal, light yield value of 23,500 photons/MeV, and fast scintillation decay times of 20 ns (15 %) + 54 ns (85 %). The higher radioluminescence intensity of the Mg (0.05 %) sample correlates with an appearance of its lower themally-stimulated luminescence intensity in 77–500 K range. • Luminescence and scintillation properties of Lu 2 YAl 2.5 Ga 2.5 O 12 :Ce,Mg (Mg = 0.02 %, 0.05 %) crystals are investigated. • Both crystals show onset of luminescence quenching at 365 K. • Lu 2 YAl 2.5 Ga 2.5 O 12 :Ce,0.05%Mg shows light yield of 23,500 photons/MeV. • Lu 2 YAl 2.5 Ga 2.5 O 12 :Ce,0.05%Mg shows scintillation decay time of 20 ns (14 %) + 54 ns (86 %). • Thermoluminescence characteristics are investigated. [ABSTRACT FROM AUTHOR]

The scintillation characteristics of Gd 3 Al 2 Ga 3 O 12 :Ce, Li (GAGG:Ce,Li) and Gd 3 Al 2 Ga 3 O 12 :Ce, Mg (GAGG:Ce,Mg) single crystals were compared. Radioluminescence spectra and photoluminescence decay curves were measured at various temperatures between 77 and 500 K to investigate the thermal luminescence quenching. At 662 keV γ rays, the LY value of 35,400 photons/MeV and energy resolution of 6.9% obtained for GAGG:Ce, Li are superior to those of 24,200 photons/MeV and 9.5% for GAGG:Ce,Mg. Scintillation decays are approximated by a double exponentials with a fast principal decay component of 47 ns (83%) for GAGG:Ce, Mg and 90 ns (86%) for GAGG:Ce,Li. Coincidence time resolution of 282 ps obtained for GAGG:Ce, Mg is better than that of 389 ps for GAGG:Ce,Li. GAGG:Ce, Mg shows a much lower afterglow and thermally stimulated luminescence intensity with respect to GAGG:Ce,Li. • Scintillation properties of Li+ and Mg2+ -codoped Gd 3 Al 2 Ga 3 O 12 :Ce are compared. • Gd 3 Al 2 Ga 3 O 12 :Ce, Mg exhibits better timing performance. • Gd 3 Al 2 Ga 3 O 12 :Ce, Mg shows lower afterglow and TSL intensity. • Gd 3 Al 2 Ga 3 O 12 :Ce, Li exhibits high light yield and good energy resolution. [ABSTRACT FROM AUTHOR]

Cerium doped gadolinium gallium aluminum garnet (Gd 3 Al 3 Ga 2 O 12 , GAGG) was synthesized in the glass ceramics form by the crystallization from Gd 2 O 3 –Al 2 O 3 –Ga 2 O 3 –SiO 2 –CeO 2 glass in the following weight proportion: 101 : 26: 47 : 25: 1. The spatial distribution and incorporation of Ce into the GAGG ceramic grains as well as the luminescence and scintillation performance are studied carrying out correlated experiments of photo-, radio- and cathodoluminescence including decay kinetics as well as energy dispersive X-ray spectroscopy combined with scanning electron microscopy. Optical absorption features were investigated using photothermal deflection spectroscopy. Cerium stays within the material mostly in the Ce3+ charge state. Its distribution in the bulk of the sample exhibits irregular trend indicating the tendency to coalesce in the middle. • The GAGG:Ce glass nanoceramics was fabricated. • Spatial distribution of Ce3+ in the batch of the glass nanoceramics was observed. • Hole trapping processes affect the luminescence in GAGG:Ce glass nanoceramics. [ABSTRACT FROM AUTHOR]

Optical and scintillation characteristics of Mg2+-codoped Lu 2 Y(Al 5-x Ga x)O 12 :Ce (x = 2, 3) multicomponent garnet crystals grown by the micro-pulling down method were investigated. At RT, the shortening of scintillation decay time and a decrease of light yield (LY) value measured for a higher Ga containing samples can be explained by thermal ionization of the Ce3+ 5d 1 excited state. At 662 keV γ-rays, Lu 2 YAl 3 Ga 2 O 12 : Ce, 0.05%Mg exhibits high LY value of 29,000 ph/MeV along with scintillation decay times of 50 ns (86%) + 73 ns (14%). Co-doping with larger Mg2+ content leads to a decrease of LY value, scintillation decay time, and afterglow level. Radioluminescence quenching observed at low temperature region in correlation with large thermoluminescence peaks can be caused by trapping of electrons at intrinsic shallow traps. • Luminescence and scintillation properties of Lu 2 Y(Al 5-x Ga x)O 12 :Ce,Mg (x = 2, 3) crystals are investigated. • Temperature dependencies of photo-and radioluminescence are presented. • Lu 2 YAl 3 Ga 2 O 12 :Ce,0.05%Mg shows high light yield of 29,000 photons/MeV. • Lu 2 YAl 3 Ga 2 O 12 :Ce,0.05%Mg shows quenching temperature at 435 K due to thermal ionization. • Afterglow and thermoluminescence characteristics are investigated. [ABSTRACT FROM AUTHOR]

The optical and scintillation properties of Ce 3+ -doped YGd 2 Al 5− x Ga x O 12 ( x =2,3,4) single crystals were investigated. With increasing Ga content in the garnet host, the 5d 1 absorption and emission bands shift toward higher energy due to the decrease in the crystal field splitting of the 5d levels. Temperature dependences of absorption and emission spectra and of photoluminescence decays of both prompt and delayed components were measured. Light yield (LY) and its dependence on an amplifier shaping time were measured under excitation with γ-rays. High LY value of 38,000 photons/MeV was obtained for a YGd 2 Al 2 Ga 3 O 12 :Ce sample. Scintillation decay was measured with an extended dynamical and temporal scale under the nanosecond-pulsed soft X-ray excitation. The relative content of the fastest component in the scintillation response increases with increasing Ga content. [ABSTRACT FROM AUTHOR]

Mg2+-codoped Y 0.6 Gd 2.4 Al 2 Ga 3 O 12 :Ce (YGAGG:Ce,Mg) single crystal was grown by the Czochralski method and its luminescence and scintillation properties were investigated. Temperature dependence of radioluminescence (RL) yield and photoluminescence (PL) decay time was measured, and activation energy of thermal ionization process was determined from temperature-dependent PL decay time measurement. YGAGG:Ce,Mg exhibited high X-ray excited RL yield almost 5 times higher than BGO reference scintillator. Its light yield of 41,500 ph/MeV and scintillation decay times of 12 ns (2%) + 52 ns (65%) + 207 ns (33%) were measured under excitation with 662 keV γ rays from 137Cs source. Afterglow and thermally stimulated luminescence characteristics are also investigated. • Luminescence and scintillation properties of Y 0.6 Gd 2.4 Al 2 Ga 3 O 12 :Ce,Mg crystal are investigated. • Temperature dependence of photo-and radioluminescence are presented. • Y 0.6 Gd 2.4 Al 2 Ga 3 O 12 :Ce,Mg shows high light yield of 41,500 photons/MeV. • Luminescence quenching above RT can be caused by thermal ionization. • Afterglow and thermoluminescence characteristics are investigated. [ABSTRACT FROM AUTHOR]

Luminescence and scintillation characteristics of Mg2+-codoped (Lu x Gd 3-x)Al 2.4 Ga 2.6 O 12 :Ce (x = 0.2–0.8) garnet crystals grown by the micro-pulling down method are investigated. The Ce3+ 5d 1 → 4f luminescence is blue-shifted with increasing Lu content due to the decrease in crystal field splitting of the 5 d levels. With increasing Lu content, the shortening of scintillation decay time accompanied with a decrease of LY value as measured at room temperature can be explained by thermal ionization of the Ce3+ 5d 1 excited state. Co-doping with Mg2+ results in the shortening of scintillation decay time, the reduction of LY value and afterglow intensity. At low temperature the radioluminescence quenching is observed in correlation with large thermoluminescence peaks, which can be attributed to the localization of electrons at intrinsic shallow traps. • Luminescence and scintillation of (Lu,Gd) 3 Al 2.4 Ga 2.6 O 12 :Ce, Mg crystals are investigated. • Temperature dependence of photo-and radioluminescence are presented. • Luminescence quenching above RT can be caused by thermal ionization. • Afterglow and low-temperature TL characteristics are investigated. [ABSTRACT FROM AUTHOR]