Untersuchungen zum Kationentransport in Strontiumtitanat unter Berücksichtigung des Einflusses verschiedener Gitterdefekte
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Abstract
This dissertation investigates the transport properties of alkali ions in strontium titanate – an important representative of the oxide perovskite family – using the Charge Attachment Induced Transport (CAIT) method. In this approach, low-energy ions are deposited onto the sample surface, thereby inducing charge transport within the material. This technique not only enables the determination of electrical conductivities, but also the generation of characteristic transport profiles, which can subsequently be analyzed via Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS). The combination of CAIT and ToF-SIMS has thus proven to be a highly effective methodology.
In single-crystalline strontium titanate, well-defined, bimodal ion transport profiles were successfully produced and characterized. These profiles can be described as a superposition of two independent diffusion mechanisms, each with its own characteristic diffusion coefficient. A systematic investigation of their temperature dependence allowed, through Arrhenius evaluations, the derivation of corresponding activation energies. The mechanism with the higher activation energy was attributed to defect-mediated transport, likely dominated by vacancies, while the other mechanism was linked to diffusion via interstitial sites.
Since ion transport in crystalline solids generally relies on some form of lattice defect, the influence of specific types of defects on diffusion behavior was examined systematically. To this end, both grain boundaries (introduced through bicrystals) and targeted dopants were incorporated into the strontium titanate lattice.
Experiments on bicrystals revealed that, in addition to the two diffusion processes known from single crystals, a significantly faster transport mechanism occurs along the grain boundaries. Employing a regression method proposed by Mishin, it was possible to determine a notably higher diffusion coefficient for this grain-boundary-related mechanism.
Finally, niobium-doped strontium titanate single crystals were studied to understand the influence of doping on diffusion behavior. Potassium and rubidium ions were introduced into the doped material via CAIT experiments. Compared to undoped crystals, doping was found to reduce the activation energies required for potassium transport. Replacing potassium with rubidium increased one of the measured activation energies. For the other process, both ions exhibited similar and relatively low activation energies.
These findings were further complemented by additional experimental series, such as DC conductivity measurements, which are partially discussed in this work.
Overall, the presented results advance the understanding of ionic transport properties in oxide perovskites and open up new perspectives for the targeted control of ionic mobility through defect engineering.
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Contributors
Supervisor:
Weitzel, Karl-Michael
Dates
Issued: 2026-04-27
Relations
Is based on: https://doi.org/10.1002/admi.202400338Is based on: https://doi.org/10.1039/D5CP01917F
Faculty
FB15:Chemie
Language
de
Keywords
StrontiumtitanatIonentransportTransportmechanismenKorngrenzenGitterdefekteOxidische PerowskiteDiffusionCAITToF-SIMS
DFG-subjects
3.12-02 - Physikalische Chemie von Festkörpern und Oberflächen, Materialcharakterisierung
Funding
Funding Organisations:
Project Information:Deutsche Forschungsgemeinschaft. Grant Number: 428906592
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Bernzen, Janek: Untersuchungen zum Kationentransport in Strontiumtitanat unter Berücksichtigung des Einflusses verschiedener Gitterdefekte. : 2026-04-27. DOI: https://doi.org/10.17192/openumr/672.
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Except where otherwised noted, this item's license is described as Attribution 4.0 International