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Multicomponent nanomaterials consisting of dense scintillating particles functionalized by or embedding optically active conjugated photosensitizers (PSs) for cytotoxic reactive oxygen species (ROS) have been proposed in the last decade as coadjuvant agents for radiotherapy of cancer. They have been designed to make scintillation-activated sensitizers for ROS production in an aqueous environment under exposure to ionizing radiations. However, a detailed understanding of the global energy partitioning process occurring during the scintillation is still missing, in particular regarding the role of the non-radiative energy transfer between the nanoscintillator and the conjugated moieties which is usually considered crucial for the activation of PSs and therefore pivotal to enhance the therapeutic effect. We investigate this mechanism in a series of PS-functionalized scintillating nanotubes where the non-radiative energy transfer yield has been tuned by control of the intermolecular distance between the nanotube and the conjugated system. The obtained results indicate that non-radiative energy transfer has a negligible effect on the ROS sensitization efficiency, thus opening the way to the development of different architectures for breakthrough radiotherapy coadjutants to be tested in clinics.

Garnet ceramic scintillators are a class of inorganic scintillation materials with excellent overall performance. The flexibility of cation substitution in different lattice positions leads to tunable and versatile properties and a wide range of applications. This paper starts with an overview of the development history of the inorganic scintillation materials, followed by a description of major preparation methods and characterization of garnet scintillation ceramics. Great progress obtained in recent years consisting in applying the band-gap and defect engineering strategies to the garnet scintillation ceramics is reviewed. Finally, the respective problems in the preparation and performance of multicomponent garnet single crystals and ceramics and the effective solutions are discussed. The garnet scintillation ceramics with the highest application potential are summarized, and the future development directions are proposed.

Optical, luminescence and scintillation characteristics were studied in garnet-type GAGG single-crystal scintillators grown by the Czochralski method and heavily doped with a cerium activator and a magnesium codopant at different concentrations. Emission quenching due to the formation of closely spaced Ce–Mg pairs accelerating the photoluminescence and scintillation decays down to a few nanoseconds and substantial suppression of slower decay components are observed. We show that despite a significant decrease in the scintillation yield, the coincidence time resolution and the afterglow, which are the most critically important parameters of fast scintillators, exhibited by the heavily doped GAGG:- Ce,Mg are superior to those in the state-of-the-art scintillators. Due to the peculiar feature of the GAGG host to tolerate extremely high cerium and magnesium concentrations while still maintaining a bulk single crystal form, this scintillator has a great potential for high-count-rate applications in high energy physics experiments and industries with harsh operational environments, where a lower light yield can be tolerated.

This manuscript summarizes last results on the development of composite luminescent materials based on the SCF and single crystals of simple and mixed garnet compounds obtained by the liquid-phase epitaxy growth method. Such composite materials can be applied as scintillating and thermoluminescent (TL) detectors for radiation monitoring of the mixed ionization fluxes, as well as the scintillation screens in the microimaging techniques. The film and crystal parts of composite detectors were fabricated from efficient scintillation / TL materials based on Ce3+, Pr3+ and Sc3+ doped Lu3Al5O12 garnets, as well as Ce3+ doped Gd3-xAxAl5-yGayO12 mixed garnets, where A = Lu or Tb; x = 0-1; y = 2-3 with significantly different scintillation decay or positions of the main peaks in their TL glow curves. This work also summarizes the results of optical study of films, crystals and epitaxial structures of these garnet compounds using absorption, cathodoluminescence and photoluminescence. The scintillation and TL properties of the developed materials under α- and β - particles and gamma-quanta excitations were studied as well. The most efficient variants of the composite scintillation and TL detectors for monitoring of composition of mixed beams of ionizing radiation were selected based on the results of this complex study.

This manuscript summarizes recent results on the development of composite luminescent materials based on the single-crystalline films and single crystals of simple and mixed garnet compounds obtained by the liquid-phase epitaxy growth method. Such composite materials can be applied as scintillating and thermoluminescent (TL) detectors for radiation monitoring of mixed ionization fluxes, as well as scintillation screens in the microimaging techniques. The film and crystal parts of composite detectors were fabricated from efficient scintillation/TL materials based on Ce3+-, Pr3+-, and Sc3+-doped Lu3Al5O12 garnets, as well as Ce3+-doped Gd3−xAxAl5−yGayO12 mixed garnets, where A = Lu or Tb; x = 0–1; y = 2–3 with significantly different scintillation decay or positions of the main peaks in their TL glow curves. This work also summarizes the results of optical study of films, crystals, and epitaxial structures of these garnet compounds using absorption, cathodoluminescence, and photoluminescence. The scintillation and TL properties of the developed materials under α- and β-particles and γ-quanta excitations were studied as well. The most efficient variants of the composite scintillation and TL detectors for monitoring of composition of mixed beams of ionizing radiation were selected based on the results of this complex study.

After the discovery of a cross-luminescence (CL) in BaF2 in 1982, a large number of CL scintillators were investigated. However, no CL scintillator superior to BaF2 has been discovered, and the research of CL scintillators has subsided. Recent technological development in medical imaging and high-energy physics created a new demand for ultra-fast scintillators further supported by the development of UV-sensitive semiconductor photodetectors. As a consequence, renewed interest in CL scintillators appeared. To satisfy the requirements of fast timing applications high photo-detection efficiency, e. i. a good spectral match between the scintillator and photodetector must be achieved. Cesium-based ternary chlorides could provide a red-shift (∼1.5 eV) of CL towards the sensitive region of the photodetector (PMT or SiPM) while keeping light output and timing characteristics comparable to BaF2.

We report a breakthrough concept for a bulk single crystal as a heavy aluminum perovskite scintillator, where due to bandgap engineering by a balanced Gd admixture in a Lu cation sublattice, the scintillation performance dramatically increases. In an optimized composition of (Lu, Gd)AlO3:Ce (LuGdAP:Ce), the light yield approaches 21,000 phot/MeV, which is close to that of classical but much less dense YAP:Ce and 50% higher than the best LuYAP:Ce reported in the literature. Moreover, contrary to LuYAP:Ce, the LuGdAP host maintains a high effective atomic number close to that of LuAP:Ce (Zeff = 64.9), which is comparable to commercial LSO:Ce. An enormous decrease in afterglow on the millisecond time scale and acceleration in the rise time of the scintillation response further increase the application potential of the LuGdAP host. The related acceleration of the transfer stage in the scintillation mechanism due to diminishing electron trap depths is proven by thermally stimulated luminescence (TSL). Furthermore, we quantitatively characterize and model the energy transfer processes that are responsible for the change in the photoluminescence and scintillation decay kinetics of Ce3+ in the LuGdAP matrix. Such an innovative (Lu, Gd)AP:Ce scintillator will become competitive for use in applications that require heavy, fast, and high light yield bulk scintillators. The dependence of the afterglow in millisecond time scale and light yield (in the inset) on the Gd content in the GdxLu1-xAlO3 single crystal scintillator.

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.

The scintillation properties of novel type of composite scintillator based on Lu3Al5O12:Pr (LuAG:Pr) single crystalline film (SCF) and LuAG:Sc substrate grown by the liquid-phase epitaxy method are considered in this work. The registration of α-particles and γ-quanta in such types of composites occurs by means of separation of the scintillation decay kinetics of SCF and crystal parts, respectively. Namely, under excitation by α-particles of 241Am (5.5 MeV) source and γ-quanta of 137Cs (662 keV) source, the large differences in the respective scintillation decay kinetics and decay time values tα and tγ are observed for the LuAG:Pr SCF/LuAG:Sc SC composite scintillator with various film thicknesses. Furthermore, the best t γ/t α ratio above 4.5 is achieved for such types of epitaxial structure with SCF and substrate thicknesses of 17 μm and about 0.5 mm, respectively. The development types of composite scintillators can be successfully applied for simultaneous registration of α-particles and γ-quanta in the mixed radiation fluxes.

We have grown Ce-doped (La,Y)$_2$Si$_2$O$_7$ single crystal by micro-pulling-down method and investigated its optical and scintillation properties. We have successfully prepared the single crystal with (Ce$_{0.015}$La$_{0.600}$Y$_{0.385}$)$_2$Si$_2$O$_7$ composition. The observed thermal quenching process could be characterized by the quenching temperature (T50%) of 526 K and its activation energy was determined to be 0.62 eV. Further considering the thermal quenching factors, it was found that the thermal quenching was caused by at least the thermal ionization and maybe also by classical thermal quenching. The light output and scintillation decay time were evaluated to be ~12,000 photons/MeV and ~42 ns, respectively. These results indicate that (Ce$_{0.015}$La$_{0.600}$Y$_{0.385}$)$_2$Si$_2$O$_7$ has a great potential for application in scintillation materials.

Heat treatment is needed to increase the luminescence intensity of ZnO:Ga particles, but it comes at the cost of higher particle agglomeration. Higher agglomeration results in low transparency of scintillating powder when embedded in a matrix and constitutes one of the biggest disadvantages, besides low light yield and low stopping power, of ZnO:Ga powder. Limiting ZnO:Ga particle size is therefore a key step in order to prepare highly luminescent and transparent composites with prospects for optical applications. In this work, SiO2 coating was successfully used to improve luminescence intensity or limitation of crystallite size growth during further annealing. Furthermore, ZnO:Ga and ZnO:Ga-SiO2 core–shells were embedded in a polystyrene matrix.

Electron and hole trapping is studied in the ${\mathrm{Ce}}^{3+}$- and ${\mathrm{Pr}}^{3+}$-doped ${\mathrm{Lu}}_{2}{\mathrm{Si}}_{2}{\mathrm{O}}_{7}$ scintillation single crystals (LPS:$\mathrm{Ce}$ and LPS:$\mathrm{Pr}$) by electron paramagnetic resonance (EPR). Detailed EPR measurements of the x-ray irradiated LPS crystals reveal that holes generated by irradiation are predominantly trapped at oxygen lattice ions creating ${\mathrm{O}}^{\ensuremath{-}}$ centers. The same x-ray irradiation creates also electron-type centers, which are attributed to ${\mathrm{Lu}}^{2+}$ ions, where the trapped electron at the Lu lattice ion is stabilized by a nearby defect, such as the oxygen vacancy and ${\mathrm{Ir}}^{3+}$ impurity ion. Both the hole and electron centers can be thus considered as a bound small polaron, which makes the charge trapping in a scintillation mechanism quite competitive. The hole ${\mathrm{O}}^{\ensuremath{-}}$ and electron ${\mathrm{Lu}}^{2+}$ centers show thermal stability well above room temperature. Thermal decays of their concentrations correlate well with the appearance of the thermally stimulated luminescence glow peaks at 470--550 K. The presence of the same intrinsic traps in the $\mathrm{Ce}\text{\ensuremath{-}}$ and $\mathrm{Pr}$-doped LPS crystals suggests that the difference in the light yield of these crystals is an intrinsic property of the ${\mathrm{Ce}}^{3+}$ and ${\mathrm{Pr}}^{3+}$ activator centers in the LPS lattice. An origin of charge traps in this pyrosilicate structure and their role in the scintillation mechanism is compared with the results previously described in the literature on orthosilicates.

Bi-doped compounds recently became the subject of an extensive research due to their possible applications as scintillator and phosphor materials. The oxides co-doped with Bi3+ and trivalent rare-earth ions were proposed as prospective phosphors for white light-emitting diodes and quantum cutting down-converting materials applicable for enhancement of silicon solar cells. Luminescence characteristics of different Bi3+-doped materials were found to be strongly different and ascribed to electronic transitions from the excited levels of a Bi3+ ion to its ground state, charge-transfer transitions, Bi3+ dimers or clusters, radiative decay of Bi3+-related localized or trapped excitons, etc. In this review, we compare the characteristics of the Bi3+-related luminescence in various compounds; discuss the possible origin of the corresponding luminescence centers as well as the processes resulting in their luminescence; consider the phenomenological models proposed to describe the excited-state dynamics of the Bi3+-related centers and determine the structure and parameters of their relaxed excited states; address an influence of different interactions (e.g., spin-orbit, electron-phonon, hyperfine) as well as the Bi3+ ion charge and volume compensating defects on the luminescence characteristics. The Bi-related luminescence arising from lower charge states (namely, Bi2+, Bi+, Bi0) is also reviewed.

The present work reports results of the electron paramagnetic resonance (EPR), optical absorption, radio- and photoluminescence (RL and PL) complex study of the Lu2Si2O7:Pr and Lu2Si2O7:Ce pyrosilicate crystals. In both crystals, the EPR spectra demonstrate the presence of characteristic signals originating from the Yb3+, Er3+, Nd3+, Dy3+, Gd3+ and V3+ ions existing in the material as uncontrolled impurities. The corresponding spectra (except for Gd3+) have been analysed in detail and g- and hyperfine tensors are determined for all these ions for the first time in the lutetium pyrosilicate lattice. Optical absorption, RL and PL measurements in the Lu2Si2O7:Pr crystal have shown only the characteristic Pr3+ transitions. In addition, the Pr3+- Pr3+ energy transfer was observed and confirmed experimentally.

The ${F}^{+}$ center consisting of an electron trapped at an oxygen vacancy (${V}_{\mathrm{O}}$) was investigated in oxygen deficient ${\mathrm{Y}}_{3}{\mathrm{Al}}_{5}{\mathrm{O}}_{12}$ (YAG) garnet crystals by electron paramagnetic resonance (EPR) techniques. The measurements were performed in the wide temperature interval 5--450 K and the frequency range 9.4--350 GHz using both the conventional continuous-wave and pulse EPR experiments. Pulse electron-nuclear double resonance was applied to resolve the hyperfine interaction of the trapped electron with surrounding nuclei. The measurements show that at low temperatures, $Tl50$ K, the EPR spectrum of the ${F}^{+}$ center is anisotropic with $g$ factors in the range 1.999--1.988 and originates from three magnetically inequivalent positions of the center in a garnet lattice. As the temperature increases, the EPR spectrum becomes isotropic suggesting a motional averaging of the anisotropy due to motion of the ${F}^{+}$-center electron between neighboring oxygen vacancies. With further increase of temperature up to $T$ g 200 K, we observed delocalization of the ${F}^{+}$-center electron into the conduction band with the activation energy about 0.4--0.5 eV that resulted in substantial narrowing of the EPR spectral line with simultaneous change of its shape from Gaussian to Lorentzian due to disappearance of the Fermi contact hyperfine field at $^{27}\mathrm{Al}$ and $^{89}\mathrm{Y}$ nuclei. Such temperature behavior of the ${F}^{+}$-center electron in YAG is completely similar to behavior of a donor electron in a semiconductor. Our findings are further supported by measurements of the conductivity and dielectric properties. In particular, these data show that the electrons in the conduction band are not homogeneously distributed in the crystal: There are highly conductive regions separated by poorly conductive dielectric layers. This leads to the so-called Maxwell-Wagner dielectric relaxation with huge apparent dielectric constant at low frequencies. This paper reports an observation of a donorlike behavior of an ${F}^{+}$ center in wide band-gap insulating crystals.

Single crystals of LiCaAlF6, undoped, Eu-doped and Na co-doped, were studied by electron paramagnetic resonance, radioluminescence and thermally stimulated luminescence techniques applied in a correlated manner. The undoped samples exposed to X-ray irradiation featured two hole-like charge trapping centers which were attributed to the perturbed F 2 − pseudomolecular ion and O− (as a result of the contact with air). Their trap depths (Et) and frequency factors (f0) were determined as follows: E t Perturbed F 2 − = 1.1 ± 0.1 eV , E t ( O − ) = 1.7 ± 0.1 eV , f 0 Perturbed F 2 − = f 0 O − ~ 10 13 s − 1 , respectively. Annealing in air caused the appearance of another defect, a new electron-like center as well. It was found that the europium dominating charge state is 2 + in the LiCaAlF6:Eu,Na samples, however, some amount of the Eu3+ is also present. Moreover, there were two Eu2+ centers: the dominating Eu 1 2 + = Eu Ca 2 + and the low-content Eu 2 2 + = Eu Li 2 + . The amount of the latter is easily governed by the sodium admixture while the former is insensitive to the Na co-doping. The Eu and Na co-doping affected the defects distribution and incorporation in the LiCaAlF6 host. Thermally stimulated luminescence yielded up to 8 peaks within the 100–600 K temperature range in glow curves of the undoped and doped crystals signalizing the presence of deep trapping states in the bandgaps. Along with the obvious degradation of the crystal surface in air by creation of new trapping centers this can contribute to the decreased light yield and downgrade of timing characteristics.

Photoluminescence, thermally stimulated luminescence (TSL) and EPR characteristics of the Ce3+-doped single crystals of multicomponent Y1Lu2GaxAl5-xO12 and Lu3GaxAl5-xO12 garnets with different Ga contents (x = 0, 1, 2, 3, 4, 5) excited in the Ce3+-related absorption bands are investigated in the 9–500 K temperature range. The distribution of Ga3+ and Al3+ ions in the crystal lattice is determined by the NMR method. The relative number of Ga3+ ions in the tetrahedral crystal lattice sites, the maxima positions of the TSL glow curve peaks and the corresponding trap depths are found to decrease linearly with the increasing Ga content. At the same time, the reduction of the activation energy Ea of the TSL glow curve peaks creation under irradiation in the 4f–5d1 absorption band of Ce3+ is strongly nonlinear. To explain this effect, the suggestion is made that Ea is the energy distance between the excited 5d1 level of Ce3+ and a defect level located between the 5d1 level and the bottom of the conduction band and arising from the Ga3+ ion perturbed by the nearest neighboring Ce3+ ion. The electrons thermally released from the excited Ce3+ ions are suggested to be trapped at the perturbed Ga3+ ions resulting in the appearance of electron Ga2+ centers. In spite of the fact that the paramagnetic Ga2+ ions were not detected by EPR, the process described above has been found for Fe3+ impurity ions, namely, the electron transfer from the 5d1 excited level of Ce3+ to Fe3+ is directly detected by EPR.

Non-linear absorption spectroscopy in pump and probe configuration has been used to test the population of non-equilibrium carriers in Ce-doped Y$_{3}$Al$_{5}$O_${12}$ (YAG), Lu3Al5O12 (LuAG), and Gd3AlxGa(5-x)O12 (GAGG) crystals with and without codoping by Mg2+ ions. A faster rise time of the induced optical density has been observed in all crystals codoped with Mg with respect to that in Mg-free samples. A significant difference in the time evolution of the differential optical density in GAGG with respect to YAG and LuAG crystals has also been measured. In both GAGG:Ce and GAGG:Ce,Mg an absorption band with maximum in the blue-green range and a decay time of 1.4 ps is present. This band is due to the absorption by free electrons before they are trapped or re-captured by Ce3+ ions. A broad absorption band in the yellow-red region with very short rise time and a decay time longer than 150 ps has been observed in all the Ce-doped garnets under study and can be attributed to the absorption from the Ce3+ excited states.

Ternary sulfides ALnS2 (A = Alkaline Metal, Ln = rare-earth element) doped with the Eu2+ ions are characterized by a very wide range of tunability of the Eu2+ emission maxima with the host’s chemical composition. In the present work, a detailed analysis of the structural properties of these materials was performed. It was shown that their lattice constants can easily be expressed as the linear functions of the ionic radii and electronegativities of the constituting elements. As a further step, the relations between the structural properties of the hosts and optical properties of the Eu2+ dopant were analyzed. It was demonstrated that the position of the Eu2+ emission maxima is a linear function of the so-called hexagonality ratio c/a, where c and a are the lattice constants of the rhombohedral ternary sulfides. The obtained results can be used as helpful guides for manufacturing Eu2+-doped ternary sulfides with desired emission properties with high potential for white LEDs applications.

A comprehensive study of the optical, radioluminescence and scintillation properties of both the Lu3+ rich and Lu3+ deficient non-stoichiometric Lu3+xAG:Ce,Mg (Lu3+xAl5O12:Ce,Mg, x = −4, −1, +1 and +4 at.%) ceramics are performed, completed further by the microstructure and defects characterization. Small deviation from the stoichiometric composition as well as Mg2+ codoping plays a crucial role in ceramic transparency, radioluminescence intensity and the timing characteristics of scintillation response. The LuAl antisite defects could be suppressed efficiently by controlling Lu3+ content below stoichiometry of LuAG host. MgO (Mg2+ ions) as effective sintering aids, can improve both the optical quality and scintillation performance (light yield, scintillation decay times and the ratio of fast decay components). We generally discuss the composition dependence of defects and properties tailoring. We also performed the systematic comparative study with the stoichiometric LuAG:Ce,Mg ceramic and the commercial BGO and LuAG:Ce single crystals.

Monovalent Li+ codoped Lu3Al5O12:Ce (LuAG:Ce) optical ceramics were fabricated by solid state reaction method and further optimized by an air-annealing process. Optical absorption, radioluminescence spectra and scintillation properties such as light yield, scintillation decay times and afterglow were measured and compared with those of the Li+ free LuAG:Ce ceramic and the commercial LuAG:Ce single crystal samples. Positive effect of Li+ codopant consists mainly in the significant increase of scintillation light yield, acceleration of scintillation decay as well as the decrease of afterglow intensity. With 0.3% Li codoping, the obtained LuAG:Ce,Li ceramic displays a light yield of ∼29200 ph/MeV at 10 μs shaping time, higher than that of the LuAG:Ce single crystal and optical ceramic scintillators ever reported. The partial conversion of the stable Ce3+ to Ce4+ centers and the shallow and deep traps effect suppression by the Li+ codoping are discussed.

Lu3-xAl5O12:Ce optical ceramics (Lu(3-x)AG:Ce, x = 1, 2, 3 and 4 at.%, respectively) with Lu3+ compositions ranging from 1 to 4 at.% below stoichiometry content were fabricated by solid state reaction method and further optimized by an air-annealing process. The effect of Lu3+ deficiency on the optical, luminescence and scintillation properties of such a non-stoichiometric Lu3-xAl5O12:Ce ceramics was investigated. Significant influence in the material densification was found leading to strong changes in the transparency, radioluminescence (RL) and scintillation response of these ceramics. Within the range of 1 4 at.% Lu3+ deficiency, Lu-Al antisite defects were suppressed effectively and the Lu(3-x)AG:Ce ceramics displayed an extremely high RL intensity which reaches similar to 4 times higher than that of the latest commercial LuAG:Ce single crystals while its transparency deteriorated. The microstructure, presence of foreign phases and charge traps acting in scintillation mechanism were also Characterized by means of SEM, back scattered electron imaging and thermoluminescence techniques, respectively. (C) 2016 Elsevier B.V. All rights reserved.

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.

The 3 in. size Ce1%:Gd 3 Al 2 Ga 3 O 12 single crystals were prepared by the Czochralski (Cz) method. Optical constants were measured. Chemical composition analysis and uniformity of scintillation decay and light yield along growth direction were evaluated. The timing resolution measurement for a pair of 3 mm×3 mm×3 mm size Ce:GAGG scintillator crystals was performed using Si-PMs.

International audience; A set of multicomponent sulfide-based phosphors of general formula ARES2: 0.05% Eu, where A represents any combination of Rb, K, Na and RE is any combination of La, Gd, Lu and Y, was synthesized in the form of transparent hexagonal crystalline platelets by inorganic reaction under the flow of H2S gas. X-ray diffraction and X-ray fluorescence were employed to investigate their structural properties and intrinsic chemical composition. Optical properties connected to the Eu2+ emission center present in these sulfidic hosts, including photoluminescence excitation and emission spectra as well as the overall emission spectra of circadian light source, were measured by means of luminescence spectroscopy using either PMT or CCD as detection elements. Electron paramagnetic resonance (EPR) was utilized in order to understand the mechanism of the Eu2+ ions incorporation into the ARES2 structure. Important parameters connected to phosphors to be used in solid state white LED technology, such as x,y coordinates in the CIE color space, color correlated temperature (CCT), color rendering index (CRI) and color quality scale (CQS) were calculated from the experimentally obtained emission spectra. Application potential of given phosphors in solid state lighting technology was discussed thoroughly.

The microstructures and optical properties of Ce,Mg:Lu3Al5O12 scintillator ceramics are investigated with particular focus on the effect of postannealing in air from 1000 to 1450°C. The formation of Al2O3 clusters after annealing above 1300°C is evidenced by scanning electron microscopy. The presence of this secondary phase is tentatively explained by the occurrence of Ce and Mg evaporation, proved by inductive coupled plasma optical emission spectrometry measurements, followed by defect diffusion and clustering during high temperature annealing. Meanwhile, optical investigations including absorption, X-ray induced luminescence, light yield, scintillation decay, and thermoluminescence prove the positive role of post-annealing that leads to a brighter and faster scintillation emission. This behavior is associated to the removal of oxygen vacancies occurring during such treatments. In parallel, the partial conversion of Ce3+ ions into Ce4+ is also observed as a consequence of annealings and the role of Ce4+ ions in the scintillation process is discussed