Exploring solid state reaction pathways with IN SITU methods

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Our materials discovery program focuses on magnetic materials, ion conductors and photocatalysts. We emphasize the importance of solid state preparation methods for the discovery and modification of these materials. The in-depth investigations of solid state reaction pathways provides opportunities to alter extended structures, control oxidation states and trap metastable and intermediate structures. Systems of interest range from transition metal oxides, oxychlorides to sulfychlorides. These systems permit rationalizing magnetic and electronic properties in ceramics as a function of their structures. Materials' properties strongly depend on solid state structures, it is therefore crucial to reliably determine crystalline solid state structures. Powder X-ray and neutron diffraction are particularly powerful methods for the investigation of these phases. The recent progress in diffraction instrumentation and analysis software allows to follow solid state reactions in real-time. Using in-situ powder X-ray diffraction we are investigating solid state reaction pathways during phase formation, reduction and oxidation of transition metal oxides such as vanadates and vanadites with zircon, perovskite, bixbyite, defect fluorite and pyrochlore structures. In-situ experiments will improve our understanding and will aid the optimization of solid state synthesis methods. We also investigate rare-earth transition metal chalcogenidechlorides as model compounds for low-dimensional magnetism. In oxychlorides low-dimensional paramagnetic sublattices are formed by means of anisotropic magnetic exchange paths due to anion ordering. Systems under investigation encompass oxychlorides and sulfychlorides with ordered and disordered anion lattices as well as transition metal oxides representing single anion lattices. These model systems provide an opportunity to evaluate the impact of anion ordering on magnetic exchange interactions in extended solids. We also investigate crystallographic phase transitions in oxides. The research program combines a large synthetic component with the investigation of physical properties in order to identify structure-property relations in solids