Spektroskopische Untersuchungen oxidischer Funktionsmaterialien (English shop)

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Owing to their physical properties, functional materials are found in numerous everyday components. A total of three oxide systems were investigated:

BaTiO3-δ is used in technology on account of its ferroelectric, dielectric and piezoelectric properties, for example in the manufacture of capacitors, PTC thermistors (PTCR effect) and ceramic transducers (MLCC). Sustained loading in electronic components can lead to a degradation process (reduction) of the material, resulting in losses in performance and/or a shortened service life. One aim of this work was therefore to investigate this process by means of optical and ESR spectroscopy in order to contribute to a fundamental understanding of the behaviour of this material.

The system Zn1-xMxO1-ySy (M = Mn, Co) is discussed as a candidate for the class of Diluted Magnetic Semiconductors (DMS), which, as a new storage material, could replace the materials currently used in storage media. Here the information is stored directly in the spin of the electrons, which leads to a markedly increased writing and reading speed. A further possible application is its use as a colour pigment. The incorporation of the transition metal ions into the host material was investigated using optical, fluorescence and ESR spectroscopy.

Mullite (Al4+2xSi2-2xO10-x) is used because of its high temperature stability for heat-protection claddings (including the heat shield on the Space Shuttle) and as a catalyst support. The structure of mullite permits the incorporation of numerous transition metal ions, e.g. Mn2+, Fe3+, Cr3+, Ti4+, V3+ and V4+. Depending on the transition metal ion, different sites in the crystal lattice can be occupied. This was investigated using the example of chromium(III) ions, which can be employed as a local probe for optical and ESR spectroscopy.