Browsing by Author "Drechsler, Felix"

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GRK 2802: Dislocation-induced local symmetry reduction in single-crystal KNbO3 observed by Raman spectroscopy
(Technische Universität Bergakademie Freiberg, 2026-01-12) Drechsler, Felix; Himcinschi, Cameliu; Preuß, Oliver; Fang, Xufei; Kortus, Jens
In recent years, dislocation-tuned functionalized ceramics have become one of the focal points of modern materials research due to their outstanding properties. These range from improved electrical conductivity and ferroelectric properties to dislocation-enhanced toughening and superconductivity, caused by local strain fields. The aim of this work is to investigate the dislocation-induced structural changes in single-crystal KNbO3 by micro-Raman spectroscopy. Dislocation-rich regions with tailored densities have been generated using the Brinell indenter scratching method. The influence of the dislocations on the single-crystal structure can be observed in the Raman spectra. The activation of additional Raman modes is observed, which does not occur in regions of low dislocation density. This observation is confirmed by DFT calculations of vibrational modes and is attributed to a reduction in the crystal symmetry due to increased defect densities in plastically deformed KNbO3. In addition, an increase in compressive stress at higher dislocation densities can be demonstrated by a blueshift in Raman mode positions.
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GRK 2802: Raman Spectroscopic Identi cation of Oxide Phases in a Cor- roded MgO-Steel Composite Anode Used in Aluminum Molten Salt Electrolysis
(Technische Universität Bergakademie Freiberg, 2026-03-04) Drechsler, Felix; Yaroshevskyi, Serhii; Adamczyk, Alexander; Mehdizadehlima, Mahnaz; Richter, Julia; Himcinschi, Cameliu; Rafaja, David; Charitos, Alexandros; Aneziris, Christos G.; Kortus, Jens
This study presents the post-mortem phase characterization of a metal ceramic composite anode composed of 316L stainless steel and recycled MgO, sourced from spent refractory lining bricks, employed in aluminium molten salt electrolysis. The analysis focused on the immersed section of the anode, where direct exposure to the molten Na-cryolite melt promotes the formation of corrosion products. Raman spectroscopy was applied as a structural characterization technique, providing phase information that complements the morphological and elemental analyses obtained from SEM EDX measurements. Due to its high spatial resolution, micro-Raman spectroscopy enabled the identi cation of local phases within the corrosion layer and the determination of their depth-dependent distribution. The local chemical analysis revealed an outer Fe O-rich layer penetrating several tens of micrometers into the material, followed by a Fe Al O-containing zone. Raman spectroscopy identi ed the Fe O layer as magnetite (Fe3O4) and the inner layer as hercynite (FeAl2O4), with a transition region consisting of Al-doped Fe3O4. The results demonstrate the applicability of Raman spectroscopy for identifying corrosion products to provide contributions to the corrosion mechanisms of MgO-steel anodes under electrolytic conditions.