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3. Crystal growth and optical properties of Ce-doped (La,Y)$_2$Si$_2$O$_7$ single crystal

Author

Horiai, Takahiko, Paterek, Juraj, Pejchal, Jan, Jarosova, Marketa, Rohlicek, Jan, Kurosawa, Shunsuke, Hanada, Takashi, Yoshino, Masao, Yamaji, Akihiro, Toyoda, Satoshi, Sato, Hiroki, Ohashi, Yuji, Kamada, Kei, Yokota, Yuui, Yoshikawa, Akira, and Nikl, Martin

Subjects
Physics - Optics, Condensed Matter - Materials Science
Abstract

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.

Published
2021
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6. Three-Layered Composite Scintillator Based on the Epitaxial Structures of YAG and LuAG Garnets Doped with Ce 3+ and Sc 3+ Impurities.

Author

Witkiewicz-Łukaszek, Sandra, Gorbenko, Vitalii, Zorenko, Tetiana, Pejchal, Jan, Mares, Jiri A., Kucerkova, Romana, Beitlerova, Alena, Nikl, Martin, Sidletskiy, Oleg, Winiecki, Janusz, D'Ambrosio, Carmelo, and Zorenko, Yuriy

Subjects
LIQUID phase epitaxy, LIQUID crystal films, IONIZING radiation, SINGLE crystals, SUBSTRATES (Materials science), SCINTILLATORS
Abstract

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]

Published
2024
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7. Two- and Three-Layered Composite Scintillators Based on the Ce3+-Doped GAGG and TbAG Garnets for the Simultaneous Registration of Various Types of Ionizing Radiation

Author

Syrotych, Yurii, Gorbenko, Vitaliy, Pejchal, Jan, Kucerkova, Romana, Mares, Jiri, Nikl, Martin, Kamada, Kei, Yoshikawa, Akira, Fedorov, Alexander, Sidleskiy, Oleg, Winiecki, Janusz, and Zorenko, Yuriy

Abstract

This work presents our most recent results in the development of composite scintillators using the liquid phase epitaxy growth method based on the single crystalline films and single crystals of garnet compounds for the radiation monitoring of different components of mixed ionization radiation fluxes. Such composite scintillators present two- and three-layered epitaxial structures consisting of two single crystalline films of Ce3+-doped garnets, namely, Gd3Al5–xGaxO12:Ce garnet with a Ga content of x= 1.75–2.25 as a first film layer and Tb3Al5O12:Ce garnet as a second film layer. As substrates, Gd3Al5–xGaxO12:Ce single crystals with fixed Ga concentrations x= 2.3, 2.5, and 3.0 were used. For the estimation of scintillation properties of the respective epitaxial structures (pulse height spectra, light yield, and scintillation decay kinetics), we have used three types of ionizing radiation: α-particles (239Pu), β-particles (90Sr + 90Y), and γ-quanta (137Cs).

Published
2024
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16. Development of a micro ORC power unit using digital prototyping methods

Author

Pejchal Jan and Kolář Petr

Subjects
Engineering (General). Civil engineering (General), TA1-2040
Abstract

The development of the prototype of the ORC micro turbine includes already in the design phase the creation of a digital prototype based on the use of computational simulations, especially the CFD flow program Simcenter STAR CCM +, strength and rotor-dynamic FEA analyses of system behaviour Simcenter 3D. This is followed by the optimization of the device by increasing its efficiency and improving the mechanical properties of the system. For this purpose, we used the optimization program HEEDS and the topological optimization method Simcenter 3D. This was followed by the production of a prototype, where 3D printing technology was used to produce turbine housing moulds and other components. A huge attention of this contribution is devoted to these additive production processes.

Published
2022
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36. Towards persistent phosphors deliberate design: study of La-Ga admixing in LuAG:Ce crystals to engineer elemental homogeneity and carriers trap depths

Author

Bartosiewicz, Karol, primary, Fritz, Verena, additional, Van der Heggen, David, additional, Szymanski, Damian, additional, Zeler, Justyna, additional, Yamaji, Akihiro, additional, Pejchal, Jan, additional, Kucerkova, Romana, additional, Beitlerová, Alena, additional, Kurosawa, Shunsuke, additional, Yoshikawa, Akira, additional, Smet, Philippe F, additional, Zych, Eugeniusz, additional, and Nikl, Martin, additional

Published
2023
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49. Towards deliberate design of persistent phosphors: a study of La–Ga admixing in LuAG:Ce crystals to engineer elemental homogeneity and carrier trap depths.

Author

Bartosiewicz, Karol, Fritz, Verena, Van der Heggen, David, Szymanski, Damian, Zeler, Justyna, Pejchal, Jan, Yamaji, Akihiro, Kucerkova, Romana, Beitlerova, Alena, Kurosawa, Shunsuke, Yoshikawa, Akira, Smet, Philippe F., Zych, Eugeniusz, and Nikl, Martin

Abstract

This research investigated the crystal chemical principles related to the incorporation of incompatible atoms into a garnet host lattice. These considerations might be used to guide and drive the design of new garnet compounds with novel properties. The strongly incompatible La atoms at the Lu sites of the Lu3Al2Ga3O12:Ce host lattice served as a research model. This study showed the possibility of designing material properties by exploiting atom mismatches in a crystal lattice. Lu3Al2Ga3O12:Ce0.075% crystals with increasing concentrations of La3+ ions were grown from the melt using the micro-pulling down method. The concentration of La3+ ions above 0.300 at% imposed physical and chemical boundary conditions on the crystallization process. The radial distributions of the chemical elements were studied as a function of the concentration of La3+ ions. It was revealed that La3+ codoping significantly reduced the cross-sectional fluctuation of the Ga and Al atoms. Persistent green-yellow luminescence due to the inter-configurational 5d → 4f transition of Ce3+ was observed after the blue-light excitation. The LuAGG:Ce0.075%,La0.015% phosphor showed long persistent luminescence for more than 14 h above 0.32 mcd m−2, the detection limit of a human eye. The thermoluminescence glow curves revealed that the addition of La3+ ions increased the concentration of traps. [ABSTRACT FROM AUTHOR]

Published
2023
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50. Charge Transfer and Charge Trapping Processes in Ca- or Al-Co-doped Lu 2 SiO 5 and Lu 2 Si 2 O 7 Scintillators Activated by Pr 3+ or Ce 3+ Ions.

Author

Laguta, Valentyn, Havlak, Lubomir, Babin, Vladimir, Barta, Jan, Pejchal, Jan, and Nikl, Martin

Subjects
CALCIUM ions, LUTETIUM compounds, SCINTILLATORS, ELECTRON paramagnetic resonance, CRYSTAL defects, RADIOLUMINESCENCE, CHARGE transfer, ION traps, IONS
Abstract

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]

Published
2023
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