Exploring solid state reaction pathways with IN SITU methods

我们的材料发现项目侧重于磁性材料、离子导体和光催化剂。我们强调固态制备方法对这些材料的发现和修饰的重要性。对固态反应途径的深入研究为改变扩展结构、控制氧化态、捕获亚稳和中间结构提供了机会。感兴趣的系统范围从过渡金属氧化物、氧氯化物到硫氯化物。这些系统允许将陶瓷的磁性和电子特性作为其结构的功能进行合理化。材料的性能在很大程度上取决于固体结构，因此可靠地确定晶体固体结构至关重要。粉末x射线和中子衍射是研究这些相的特别有效的方法。衍射仪器和分析软件的最新进展允许实时跟踪固体反应。利用原位粉末x射线衍射，我们研究了过渡金属氧化物（如钒酸盐和钒酸盐）与锆石、钙钛矿、璧长石、缺陷萤石和焦绿石结构的相形成、还原和氧化过程中的固相反应途径。原位实验将提高我们的认识，并将有助于优化固态合成方法。我们还研究了稀土过渡金属硫族氯化物作为低维磁性模型化合物。在氯氧化物中，通过阴离子有序的各向异性磁交换路径形成低维顺磁亚晶格。所研究的体系包括有序和无序阴离子晶格的氯氧化物和硫氯化物，以及代表单阴离子晶格的过渡金属氧化物。这些模型系统提供了一个机会来评估阴离子排序对扩展固体中磁交换相互作用的影响。我们还研究了氧化物中的晶体相变。该研究计划将大型合成成分与物理性质调查相结合，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