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In this study, we propose novel three-layer composite scintillators designed for the simultaneous detection of different ionizing radiation components. These scintillators are based on epitaxial structures of LuAG and YAG garnets, doped with Ce3+ and Sc3+ ions. Samples of these composite scintillators, containing YAG:Ce and LuAG:Ce single crystalline films with different thicknesses and LuAG:Sc single crystal substrates, were grown using the liquid phase epitaxy method from melt solutions based on PbO-B2O3 fluxes. The scintillation properties of the proposed composites, YAG:Ce film/LuAG:Sc film/LuAG:Ce crystal and YAG:Ce film/LuAG:Ce film/LuAG:Sc crystal, were investigated under excitation by radiation with α-particles from a 239Pu source, β-particles from 90Sr sources and γ-rays from a 137Cs source. Considering the properties of the mentioned composite scintillators, special attention was paid to the ability of simultaneous separation of the different components of mixed ionizing radiation containing the mentioned particles and quanta using scintillation decay kinetics. The differences in scintillation decay curves under α- and β-particle and γ-ray excitations were characterized using figure of merit (FOM) values at various scintillation decay intensity levels (1/e, 0.1, 0.05, 0.01). [ABSTRACT FROM AUTHOR]

In this study, Ce3+-doped Lu3Al5O12 garnet (LuAG) crystal detectors, with a density of ρ = 6 g/cm3 and an effective atomic number Zeff = 62, are proposed as promising materials for radiotherapy applications. This type of detector demonstrates excellent uniformity of structural and optical properties, high thermoluminescence (TL) light yield, optimal position of main TL glow peaks at temperatures around 245–295 °C, and high radiation stability. The set of TL detectors made from LuAG:Ce single crystal was used to evaluate the uniformity of dose and energy spectra of X-ray radiation from a clinical accelerator with 6 MV and 15 MV beams at the Department of Medical Physics, Oncology Center in Bydgoszcz, Poland, and γ-rays from a 60Co source at the National Institute of Oncology in Warsaw. The LuAG:Ce crystal detectors demonstrated highly promising results for registering X-ray radiation from accelerators with both 6 MV and 15 MV electron beams, as well as γ-rays from a 60Co source with energies of 1.17 and 1.33 MeV. [ABSTRACT FROM AUTHOR]

The SC‐YAG:Tb@YAG:Pr‐SCF composite epitaxial structure consisting of a 1 mm thick single crystal substrate of YAG:Tb garnet and a thin (9 µm) single crystalline film of YAG:Pr garnet is fabricated, and its luminescent properties are examined toward luminescence thermometry. The possibility to efficiently excite, individually or simultaneously, the Tb3+ and Pr3+ dopants by their intense allowed 4f→5d transitions is executed to reach relative thermal sensitivity higher than 1% K−1 over the range of temperatures as wide as 100–625 K and above 0.5% K−1 over 13–650 K. The obtained results demonstrate that using intra‐ and inter‐configurational emission transitions of Pr3+ and other lanthanides makes it possible to design wide‐range luminescence thermometers with high sensitivity spanning the entire operating limits. [ABSTRACT FROM AUTHOR]

In this work, three sets of single crystalline films (SCF) of Al2O3:Mn sapphire, YAlO3:Mn perovskite (YAP:Mn), and Y3Al5O12:Mn garnet (YAG:Mn), with a nominal Mn content of 0.1%, 1%, and 10 atomic percent (at.%) in the melt-solutions, were crystallized by the liquid phase epitaxy (LPE) method onto sapphire, YAP and YAG substrates, respectively. We have also calculated the average segregation coefficient of Mn ions for Al2O3:Mn, YAP:Mn and YAG:Mn SCFs with Mn content in the melt-solution in the 0.1–10% concentration range, which was equal to 0.1, 0.14 and 0.2, respectively. The main goal of the conducted research was the spectroscopic determination of the preferable valence states of manganese ions which were realized in the SCFs of sapphire, perovskite and garnet depending on the Mn content. For this purpose, the absorption, cathodoluminescence (CL), photoluminescence (PL) emission/excitation spectra and PL decay kinetics of Al2O3:Mn, YAP:Mn and YAG:Mn SCFs with different Mn concentrations were studied. Based on the CL and PL spectra, we showed that Mn ions, depending on the Mn content in the melt-solution, are incorporated in Al2O3:Mn, YAP:Mn and YAG:Mn SCFs in the different charged states and are located in the different crystallographic positions of the mentioned oxide lattices. We have observed the presence of the luminescence of Mn4+, Mn3+ and Mn2+ valence states of manganese ions in CL spectra in all SCFs under study with 0.1 and 1% Mn concentrations. Namely, the Mn4+ ion valence state with the main sharp emission bands peaked at 642 and 672 nm, related to the 2E → 4A2 transitions, was found in the luminescence spectra of the all studied Al2O3:Mn SCFs. The luminescence of the Mn2+ valence state was found only in YAP:Mn and YAG:Mn SCFs, grown from melt solution with 1% Mn content, in the emission bands peaked at 525 and 560 nm, respectively, related to the 4T1 → 6A1 transitions. The PL and CL spectra of YAP:Mn and YAG:Mn SCFs with the Mn content in the 0.1–1% range show that the main valence state of manganese ions in these films is Mn3+ with the main emission bands peaking at 655 and 608 nm, respectively, related to the 1T2 → 5E transitions. Meanwhile, higher than 1% Mn content in the melt solution causes a strong concentration quenching of luminescence of all Mn centers in Al2O3:Mn, YAP:Mn and YAG:Mn SCFs. [ABSTRACT FROM AUTHOR]

Ce3+ doped Al2O3-YAG eutectics were successfully grown by the horizontal directional crystallization method. The crystallization rate of eutectic growth was changed in the 1–7.5 mm/h range at a growth temperature of 1835 ℃. The microstructure of eutectic samples was investigated using scanning electron microscopy and X-ray microtomography. The intrinsic morphology of eutectic represents the stripe-like channel structure with a random distribution of the garnet Y3Al5O12 (YAG) and Al2O3 (sapphire) phases. The content of these phases in the stripes changes in the 52.9–55.3% and 46.1–47.1% ratios, respectively, depending on the growth rate of the crystallization of the eutectic samples. The luminescent properties of the eutectic demonstrated the dominant Ce3+ luminescence in the garnet phase. The luminescence of the Ce3+ ions in Al2O3 has also been observed and the effective energy transfer processes between Ce3+ ions in the Al2O3 and YAG garnet phases were revealed under high-energy excitation and excitation in the UV Ce3+ absorption bands of sapphire. The phosphor conversion properties and the color characteristics (Al2O3-YAG):Ce eutectic with different thicknesses were investigated under excitation by a blue LED. We have also tested the prototypes of white LEDs, prepared using a blue 450 nm LED chip and (Al2O3-YAG):Ce eutectic photoconverters with 0.15 to 1 mm thicknesses. The results of the tests are promising and can be used for the creation of photoconverters for high-power white LEDs. [ABSTRACT FROM AUTHOR]

Sesquioxides of lanthanides, yttrium, and scandium are promising hosts for laser and scintillation materials; however, the crystallization of such compounds is complicated by very high melting temperatures, as well as polymorph transitions. This work reports for the first time the growth of Y2O3 and Y2−xScxO3 crystals by the Vertical Gradient Freezing method from tungsten crucibles, proposing an alternative to extremely expensive rhenium and iridium crucibles. Translucent Y2O3 samples are obtained, and their luminescent and scintillation parameters are evaluated. The main issues of Y2O3 crystallization under the proposed conditions are discussed, as well as ways of enhancing the crystal quality. Finally, polymorph transitions are avoided by decreasing the average radius of the rare earth cation by Y3+/Sc3+ substitution, providing transparent Y2−xScxO3 crystals with a cubic structure. [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]

In this study, the infrared optically stimulated luminescence (IRSL) of single crystals of Ce3+ doped yttrium aluminum garnet (YAG) was investigated for the first time. It was found that infrared stimulation of these crystals, following previous exposure to beta radiation, produces a strong luminescence signal. The highest luminescence efficiency was exhibited by the YAG crystal with 0.1% of Ce. With this crystal, it was possible to measure as low doses as 0.1 mGy. Moreover, IRSL is mainly related to the TL peak at a relatively high temperature of c.a. 175 °C, which leads to quite good stability of the signal in time. These properties create good prospects for potential applications of YAG:Ce in dosimetric radiation measurements [ABSTRACT FROM AUTHOR]