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Luminescence spectroscopy of impurities in fast oxide scintillators
Kučerková, Romana ; Kučera, Miroslav (advisor) ; Mareš, Jiří A. (referee)
In the present work we studied the dependence on concentration gallium ion in single crystal LGAG: Pr a LuAG: Pr, prepared by ,,micro-pulling down,, method (-PD) at Tohoku University in Sendai, Japan. -PD method allows growing a single crystal using small amount of row material, typically less than 1 g, in time period of one day because of very high growth speed up to 20mm/min. Scintillation materials are necessary for a number of applications (e.g. medicine), in which high spatial resolution is required. The aim of this work was to measure luminescence and scintillation characteristics of the Pr3+ doped -PD grown Lu3Al5O12 single crystal host. The absorption, photo- and radioluminescence spectra and both photoluminescence and scintillation decay curves were measured. The photoluminescence decay curves was single-exponetial characterized by a lifetime around 17ns. Slow components were present in the scintillation decay curves. This is a consequence of retrapping of the charge carriers on electron traps connected with the anti-site defects, which are generally present in Czochralski od -PD grown aluminium garnets. On the other hand, they are completely supressed in the liquid-phase-epitaxy grown single crystalline films due to lower growth temperature. Excitation spectra of the 5d-4f luminescence completely...
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Novel thin scintillation films for 2D imaging screens
Hanuš, Martin ; Kučera, Miroslav (advisor) ; Mareš, Jiří A. (referee)
In this work we studied properties of Ce doped garnet scintillator layers (CexLu3-xAl5O12, CexY3-xAl5O12). They were prepared by liquid phase epitaxy. Studied materials show fast response, high quantum efficiency and good chemical and mechanical stability. Thus they are ideal for use in devices for 2D imaging. We measured absorption, excitation and emission spectra and kinetics of luminescence. Aim was to compare properties of grown layers with properties of single crystals grown by Czochralski method. We looked for the impact of melt compounds to measured layer properties. We also tried to determine optimal amount of Ce in layer. We used flux PbO - B2O3 and flux BaO - BaF2 - B2O3. In those fluxes we succeeded to grow garnet layers at temperatures as low as 1000řC. This lead to less intrinsic defects in crystalic lattice of layer in comparison to single crystals grown by Czochralski method (1900řC). Our layers were from 1 to 30 mm thick with higher concentration of Ce than singlecrystal. Due to higher concentration of impurities in layers grown from PbO - B2O3 flux we grown layers from BaO - BaF2 - B2O3 flux too. Flux BaO - BaF2 - B2O3 leaves less impurities in layers.
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Luminescence properties of phosphors for highpower LED applications
Rejman, Martin ; Nikl, Martin (advisor) ; Mareš, Jiří A. (referee) ; Nejezchleb, Karel (referee)
For selected YAG:Ce sample the temperature dependent absorbtion and emission spectra were measured and used to simulate white LED behavior. Various CIE-xy dependencies were observed. Sample surface scaterring parameters were calibrated using a custom-made automated goniospektrometer, which provided measured data with fine accuracy. Finally, the measured data were used to construct a Geant4 simulation to optimize two light devices for output intensity and target CIE-xy coordinates. Powered by TCPDF (www.tcpdf.org)
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Optical properties of thin film scintillators
Onderišinová, Zuzana ; Kučera, Miroslav (advisor) ; Mareš, Jiří A. (referee)
In the present work we studied Pr, Sc co-doped and Eu-doped Lu3Al5O12 thin epitaxial garnet layers prepared by liquid phase epitaxy (LPE) on Y3Al5O12 (YAG) and Lu3Al5O12 (LuAG) single crystalline substrates. In the process of growth BaO - BaF2 - B203 (Pr, Sc co - doped layers) and PbO - B2O3 (Eu - doped layers) fluxes were used. These materials are considered perspective scintillators with high density, fast scintillation response, high quantum e fficiency and good chemical and mechanical stability. They are used in a number of applications in which high spatial resolution is required. The absorption, emission and excitation spectra of experimental samples were measured and investigated. Our attention was focused especially on the study of infuence of Sc3+ ions on the emission properties of Pr3+ ions in epitaxial layers which mutually contain various amounts of concentrations of dopants. The Sc3+ ions do not show any radiative transitions in visible and UV spectral regions, but they increase the scintillation response of Pr3+ ions. This phenomenon is caused by overlappig of the Sc-related emission around 275 nm with the 4f-5d absorption band of Pr3+ centers. By measurement of radioluminescence this energy transfer from Sc3+ to Pr3+ activator centres was con firmed.
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Luminescence properties of phosphors for highpower LED applications
Rejman, Martin ; Nikl, Martin (advisor) ; Mareš, Jiří A. (referee) ; Nejezchleb, Karel (referee)
For selected YAG:Ce sample the temperature dependent absorbtion and emission spectra were measured and used to simulate white LED behavior. Various CIE-xy dependencies were observed. Sample surface scaterring parameters were calibrated using a custom-made automated goniospektrometer, which provided measured data with fine accuracy. Finally, the measured data were used to construct a Geant4 simulation to optimize two light devices for output intensity and target CIE-xy coordinates. Powered by TCPDF (www.tcpdf.org)
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Optical properties of thin film scintillators
Onderišinová, Zuzana ; Kučera, Miroslav (advisor) ; Mareš, Jiří A. (referee)
In the present work we studied Pr, Sc co-doped and Eu-doped Lu3Al5O12 thin epitaxial garnet layers prepared by liquid phase epitaxy (LPE) on Y3Al5O12 (YAG) and Lu3Al5O12 (LuAG) single crystalline substrates. In the process of growth BaO - BaF2 - B203 (Pr, Sc co - doped layers) and PbO - B2O3 (Eu - doped layers) fluxes were used. These materials are considered perspective scintillators with high density, fast scintillation response, high quantum e fficiency and good chemical and mechanical stability. They are used in a number of applications in which high spatial resolution is required. The absorption, emission and excitation spectra of experimental samples were measured and investigated. Our attention was focused especially on the study of infuence of Sc3+ ions on the emission properties of Pr3+ ions in epitaxial layers which mutually contain various amounts of concentrations of dopants. The Sc3+ ions do not show any radiative transitions in visible and UV spectral regions, but they increase the scintillation response of Pr3+ ions. This phenomenon is caused by overlappig of the Sc-related emission around 275 nm with the 4f-5d absorption band of Pr3+ centers. By measurement of radioluminescence this energy transfer from Sc3+ to Pr3+ activator centres was con firmed.
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Luminescence spectroscopy of impurities in fast oxide scintillators
Kučerková, Romana ; Kučera, Miroslav (advisor) ; Mareš, Jiří A. (referee)
In the present work we studied the dependence on concentration gallium ion in single crystal LGAG: Pr a LuAG: Pr, prepared by ,,micro-pulling down,, method (-PD) at Tohoku University in Sendai, Japan. -PD method allows growing a single crystal using small amount of row material, typically less than 1 g, in time period of one day because of very high growth speed up to 20mm/min. Scintillation materials are necessary for a number of applications (e.g. medicine), in which high spatial resolution is required. The aim of this work was to measure luminescence and scintillation characteristics of the Pr3+ doped -PD grown Lu3Al5O12 single crystal host. The absorption, photo- and radioluminescence spectra and both photoluminescence and scintillation decay curves were measured. The photoluminescence decay curves was single-exponetial characterized by a lifetime around 17ns. Slow components were present in the scintillation decay curves. This is a consequence of retrapping of the charge carriers on electron traps connected with the anti-site defects, which are generally present in Czochralski od -PD grown aluminium garnets. On the other hand, they are completely supressed in the liquid-phase-epitaxy grown single crystalline films due to lower growth temperature. Excitation spectra of the 5d-4f luminescence completely...
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Novel thin scintillation films for 2D imaging screens
Hanuš, Martin ; Kučera, Miroslav (advisor) ; Mareš, Jiří A. (referee)
In this work we studied properties of Ce doped garnet scintillator layers (CexLu3-xAl5O12, CexY3-xAl5O12). They were prepared by liquid phase epitaxy. Studied materials show fast response, high quantum efficiency and good chemical and mechanical stability. Thus they are ideal for use in devices for 2D imaging. We measured absorption, excitation and emission spectra and kinetics of luminescence. Aim was to compare properties of grown layers with properties of single crystals grown by Czochralski method. We looked for the impact of melt compounds to measured layer properties. We also tried to determine optimal amount of Ce in layer. We used flux PbO - B2O3 and flux BaO - BaF2 - B2O3. In those fluxes we succeeded to grow garnet layers at temperatures as low as 1000řC. This lead to less intrinsic defects in crystalic lattice of layer in comparison to single crystals grown by Czochralski method (1900řC). Our layers were from 1 to 30 mm thick with higher concentration of Ce than singlecrystal. Due to higher concentration of impurities in layers grown from PbO - B2O3 flux we grown layers from BaO - BaF2 - B2O3 flux too. Flux BaO - BaF2 - B2O3 leaves less impurities in layers.
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Influence of Sc.sup.3+./sup. doping on Pr.sup.3+./sup. emission in epitaxial scintillation garnet layers
Hanuš, M. ; Kučera, M. ; Nikl, Martin ; Nitsch, Karel ; Průša, Petr ; Mareš, Jiří A. ; Onderišinová, Z.
Yttrium (Y3Al5O12) and lutetium (Lu3Al5O12) aluminium garnets doped by rare earths such as Ce, Eu, Pr, are considered as very good scintillation materials. The garnets have chemical, mechanical, and radiation stability superior to most of scintillation materials and light yield is high, thus they are often used as scintillation screens.
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