Romanenko, Anton (2016)
Radiation damage produced by swift heavy ions in rare earth phosphates.
Technische Universität Darmstadt
Dissertation, Erstveröffentlichung
Kurzbeschreibung (Abstract)
This work is devoted to the study of radiation damage produced by swift heavy ions in rare earth phosphates, materials that are considered as perspective for radioactive waste storage. Single crystals of rare earth phosphates were exposed to 2.1 GeV gold (Au) and 1.5 GeV xenon (Xe) ions of and analyzed mainly by Raman spectroscopy. All phosphates were found almost completely amorphous after the irradiation by 2.1 GeV Au ions at a fluence of 10^13 ions/cm^2. Radiation-induced changes in the Raman spectra include the intensity decrease of all Raman bands accompanied by the appearance of broad humps and a reduction of the pronounced luminescence present in virgin samples. Analyzing the Raman peak intensities as a function of irradiation fluence allowed the calculation of the track radii for 2.1 GeV Au ions in several rare earth phosphates, which appear to be about 5.0 nm for all studied samples. Series of samples were studied to search for a trend of the track radius depending on the rare earth element (REE) cation. Among the monoclinic phosphates both Raman and small-angle X-ray scattering (SAXS) suggest no significant change of the track radius with increasing REE mass. In contrast, within the tetragonal phosphates Raman spectroscopy data suggests a possible slight decreasing trend of the track radius with the increase of REE atomic number. That finding, however, requires further investigation due to the low reliability of the qualitative Raman analysis. Detailed analysis of Raman spectra in HoPO4 showed the increase of peak width at the initial stage of the irradiation and subsequent decrease to a steady value at higher fluences. This observation suggested the existence of a defect halo around the amorphous tracks in HoPO4. Raman peaks were found to initially shift to lower wavenumbers with reversing this trend at the fluence of 5x10^11 for NdPO4 and 10^12 ions/cm^2 for HoPO4. At the next fluence steps peaks moved in the other direction, passed positions assigned for virgin materials and moved even further at the fluence step of 10^13 ions/cm^2. This study has also shown that variation of beam parameters could drastically affect material degradation. Increase of Au ion flux was shown to produce partial sample annealing, most likely due to macroscopic temperature increase. At the same time the increase of 1.5 GeV Xe ion beam pulse intensity was shown to invoke enhanced amorphization in comparison to beams of low pulse intensity.
Typ des Eintrags: | Dissertation | ||||
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Erschienen: | 2016 | ||||
Autor(en): | Romanenko, Anton | ||||
Art des Eintrags: | Erstveröffentlichung | ||||
Titel: | Radiation damage produced by swift heavy ions in rare earth phosphates | ||||
Sprache: | Englisch | ||||
Referenten: | Fujara, Prof. Dr. Franz ; Trautmann, Prof. Dr. Christina | ||||
Publikationsjahr: | 28 Juni 2016 | ||||
Ort: | Darmstadt | ||||
Datum der mündlichen Prüfung: | 18 Juli 2016 | ||||
URL / URN: | http://tuprints.ulb.tu-darmstadt.de/5995 | ||||
Kurzbeschreibung (Abstract): | This work is devoted to the study of radiation damage produced by swift heavy ions in rare earth phosphates, materials that are considered as perspective for radioactive waste storage. Single crystals of rare earth phosphates were exposed to 2.1 GeV gold (Au) and 1.5 GeV xenon (Xe) ions of and analyzed mainly by Raman spectroscopy. All phosphates were found almost completely amorphous after the irradiation by 2.1 GeV Au ions at a fluence of 10^13 ions/cm^2. Radiation-induced changes in the Raman spectra include the intensity decrease of all Raman bands accompanied by the appearance of broad humps and a reduction of the pronounced luminescence present in virgin samples. Analyzing the Raman peak intensities as a function of irradiation fluence allowed the calculation of the track radii for 2.1 GeV Au ions in several rare earth phosphates, which appear to be about 5.0 nm for all studied samples. Series of samples were studied to search for a trend of the track radius depending on the rare earth element (REE) cation. Among the monoclinic phosphates both Raman and small-angle X-ray scattering (SAXS) suggest no significant change of the track radius with increasing REE mass. In contrast, within the tetragonal phosphates Raman spectroscopy data suggests a possible slight decreasing trend of the track radius with the increase of REE atomic number. That finding, however, requires further investigation due to the low reliability of the qualitative Raman analysis. Detailed analysis of Raman spectra in HoPO4 showed the increase of peak width at the initial stage of the irradiation and subsequent decrease to a steady value at higher fluences. This observation suggested the existence of a defect halo around the amorphous tracks in HoPO4. Raman peaks were found to initially shift to lower wavenumbers with reversing this trend at the fluence of 5x10^11 for NdPO4 and 10^12 ions/cm^2 for HoPO4. At the next fluence steps peaks moved in the other direction, passed positions assigned for virgin materials and moved even further at the fluence step of 10^13 ions/cm^2. This study has also shown that variation of beam parameters could drastically affect material degradation. Increase of Au ion flux was shown to produce partial sample annealing, most likely due to macroscopic temperature increase. At the same time the increase of 1.5 GeV Xe ion beam pulse intensity was shown to invoke enhanced amorphization in comparison to beams of low pulse intensity. |
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URN: | urn:nbn:de:tuda-tuprints-59957 | ||||
Sachgruppe der Dewey Dezimalklassifikatin (DDC): | 500 Naturwissenschaften und Mathematik > 500 Naturwissenschaften 500 Naturwissenschaften und Mathematik > 530 Physik 500 Naturwissenschaften und Mathematik > 550 Geowissenschaften |
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Fachbereich(e)/-gebiet(e): | 05 Fachbereich Physik > Institut für Festkörperphysik (2021 umbenannt in Institut für Physik Kondensierter Materie (IPKM)) > Magnetische Kernresonanz 05 Fachbereich Physik > Institut für Festkörperphysik (2021 umbenannt in Institut für Physik Kondensierter Materie (IPKM)) 05 Fachbereich Physik |
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Hinterlegungsdatum: | 05 Mär 2017 20:55 | ||||
Letzte Änderung: | 05 Mär 2017 20:55 | ||||
PPN: | |||||
Referenten: | Fujara, Prof. Dr. Franz ; Trautmann, Prof. Dr. Christina | ||||
Datum der mündlichen Prüfung / Verteidigung / mdl. Prüfung: | 18 Juli 2016 | ||||
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