•Optical properties of YAG crystals grown under different conditions are compared.•Carbon admixture with the concentration up to 0.01 wt% in YAGMo crystals grown under reducing conditions is found.•A ...procedure of YAGMo irreversible bleaching in the 200–1100 nm range by heat treatment is proposed.
Optical properties of YAG crystals grown and annealed under different atmosphere conditions have been compared. Simultaneously we have registered the surface composition of crystals and content of basic admixtures in the crystals grown under the reducing conditions. Unlike YAG grown under weakly oxidizing conditions in Ir crucibles and bleached under oxidizing annealing, YAGMo crystals grown in Mo crucibles under reducing Ar + CO atmosphere can be bleached by both oxidizing and reducing thermal annealing. The bleaching of YAGMo is not reversed by further annealing under any available conditions. Mechanisms of this phenomenon have been discussed, including a possible role of admixtures in elimination of color centers in YAG grown under the reducing conditions.
•Eu concentration dependences of SrI2:Eu properties are analyzed.•Energy resolution better 4% sustains even at Eu concentration as low as 0.3 at%.•Scintillation properties of SrI2:Eu do not depend on ...growth method (Czochralski or Bridgman).
SrI2:Eu crystals with the activator content of 0.1–5.5% were grown by the Bridgman-Stockbarger technique. The dependences of light yield, energy resolution, optical and luminescent properties on the Eu concentration have been studied. It has been shown that with a decrease in the amount of activator to 0.3% Eu, the energy resolution at 662 keV remains below 4%. The light yield gradually diminishes with decreasing Eu concentration. This makes it possible to revise the required amount of the expensive activator for growing high performance SrI2:Eu crystals. Scintillation parameters of crystals grown by the Czochralski and Bridgman-Stockbarger technique have been compared.
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•OSL properties of Gd3GaxAl5−xO12:Ce crystals with various Ga content x = 2.3–3 were studied after IR stimulation.•OSL signal of GAGG crystal with x = 2.5 is the highest and ...comparable with conventional commercial phosphors.•Correlation between OSL and TL properties of GAGG:Ce crystals was analyzed.
In this study, the infrared optically-stimulated luminescence (IR-OSL) of single crystals of Ce3+ doped Gd3(GaxAl5−x)O12 mixed garnet with Ga content x = 2.5, 2.7, 3 was investigated for the first time. It was demonstrated that infrared stimulation of these crystals previously exposed to beta radiation produces a strong luminescence signal comparable with conventional OSL phosphors. The intensity of the IR-OSL highly depends on Ga content, reaching maximum for x = 2.5. The IR-OSL decay curves are multicomponent, with predominant fast components with the decay time around 1 s. The relation between IR-OSL and thermoluminescence was also studied. It was found that the most intense fast components of IR-OSL decay are related to the low-temperature peaks in thermoluminescence glow curves occurring at the temperature range 78–96 °C. The observed high intensity of the IR-OSL signal creates perspectives for possible applications of Gd3(GaxAl5−x)O12 mixed garnet crystals for passive radiation measurements and dosimetry.
Growth technologies of oxide crystals in W/Mo crucibles have been developed as a low-cost alternative to conventional processes involving Ir crucibles. Carbon-containing atmosphere needed to protect ...crucibles from oxidation leads to the introduction of carbon into the crystal lattice and creation of carbon-related defects, which affect the scintillation performance. Meanwhile, a search for fast scintillators for the new generation of positron-emission tomographs and high-energy physics experiments at colliders is under way. Codoping with divalent cations has become an efficient way to suppress long components of scintillation decay in Ce-doped scintillators. This work addresses Y 3 Al 5 O 12 (YAG) crystals codoped with carbon, cerium activator, and divalent cations. Optical and scintillation properties of YAG:Ce,C,<inline-formula> <tex-math notation="LaTeX">\text{A}^{2+} </tex-math></inline-formula> crystals (A = Ca<inline-formula> <tex-math notation="LaTeX">^{2+} </tex-math></inline-formula>, Mg<inline-formula> <tex-math notation="LaTeX">^{2+} </tex-math></inline-formula>, Ba<inline-formula> <tex-math notation="LaTeX">^{2+} </tex-math></inline-formula>, Sr<inline-formula> <tex-math notation="LaTeX">^{2+} </tex-math></inline-formula>) are systematically studied. Among all the studied garnet compounds, YAG:Ce,C,Ca<inline-formula> <tex-math notation="LaTeX">^{2+} </tex-math></inline-formula> crystals demonstrated the fastest scintillation decay times, which are promising for the mentioned applications. Mechanisms of scintillation process in the studied materials are discussed. The Ce<inline-formula> <tex-math notation="LaTeX">^{3+} </tex-math></inline-formula>/Ca<inline-formula> <tex-math notation="LaTeX">^{2+} </tex-math></inline-formula> ratio in YAG:Ce,C,Ca<inline-formula> <tex-math notation="LaTeX">^{2+} </tex-math></inline-formula> was optimized to minimize slow components in scintillation decay.
Undoped and Ce3+-doped Lu3Al5O12 (LuAG) fibers were grown to evaluate their potential use in new particle physics experiments, such as dual-readout calorimeters. The choice of grown crystals was made ...to detect scintillation (doped LuAG) and Cherenkov radiation (undoped LuAG). Growth conditions for obtaining fibers with improved quality were found based on measurements of attenuation length of the fibers and cathodoluminescence measurements. The effect of annealing on attenuation length for LuAG and LuAG:Ce was also studied. In addition, we also evaluated a possibility to substitute LuAG by the cheaper mixed and (Lu,Y)3Al5O12 (LuYAG:Ce) fibers.
•Undoped and Ce-doped LuAG fibers were grown by micro-pulling down technique.•Substitution of Lu3+ by Y3+ in (Lu1−xYx)3Al5O12 fibers improve Ce distribution.•Annealing of Ce-doped LuAG fibers improve the light propagation through the fibers.•Attenuation length over 1m can be achieved in LuAG:Ce after thermal annealing.
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.
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