Exploring solid state reaction pathways with IN SITU methods

我们的材料发现计划侧重于磁性材料、离子导体和光催化剂。我们强调了固态制备方法对这些材料的发现和改性的重要性。对固态反应途径的深入研究为改变扩展结构、控制氧化状态和捕获亚稳态和中间结构提供了机会。感兴趣的体系范围从过渡金属氧化物、氧氯化物到硫代氯化物。这些系统允许将陶瓷的磁性和电性作为其结构的函数来合理化。材料的性能强烈地依赖于固态结构，因此可靠地确定固态晶体结构是至关重要的。粉末X射线和中子衍射是研究这些相的特别有力的方法。衍射仪和分析软件的最新进展使实时跟踪固态反应成为可能。用原位粉末X射线衍射法研究了过渡金属氧化物如钒酸盐和具有锆石、钙钛矿、方铅矿、缺陷萤石和焦绿石结构的钒氧化物在相形成、还原和氧化过程中的固相反应途径。现场实验有助于提高我们对固相合成方法的认识，有助于优化固相合成方法。我们还研究了稀土过渡金属硫属四氯化物作为低维磁性的模型化合物。在氧氯化物中，由于阴离子有序，通过各向异性的磁交换路径形成了低维顺磁亚晶格。所研究的体系包括具有有序和无序阴离子晶格的氧氯化物和硫氯化物，以及代表单一阴离子晶格的过渡金属氧化物。这些模型系统提供了评估阴离子有序对扩展固体中磁交换相互作用的影响的机会。我们还研究了氧化物的结晶学相变。该研究计划将大型合成成分与物理性质的研究相结合，以确定固体中的结构-性质关系

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