Stucture property relations in anion ordered phases

材料化学在很大程度上依赖于对结构的可靠测定。晶体材料最好用衍射法进行研究。在过去的十年中，粉末衍射方法得到了显著的改进，由于高分辨率的衍射仪和先进的数据分析工具，现在是可靠的方法，几乎接近单晶衍射实验的性能。利用各种还原、惰性和氧化气氛进行的高温衍射实验使我们现在能够以极好的时间分辨率跟踪固态反应。这些实验将提高我们对固相反应的理解，从而使优化固相合成方法成为可能。稀土过渡金属氧氯酸盐和还原稀土过渡金属氧化物被作为低维磁性亚晶格的模型化合物。由于不同的阴离子，通过各向异性的磁交换路径实现了低维顺磁亚晶格。所研究的体系将具有有序和无序阴离子晶格的混合阴离子(氧氯化物)与单一阴离子晶格(氧化物)相结合。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。用衍射法和差热分析法研究了晶体的相变。该研究项目有大量的合成成分，并结合物理性质的调查。主体物理性质和结构细节将被关联，以试图识别结构-性质关系。

Materials chemistry depends to a large extent on reliable determination of structures. Crystalline materials are best investigated by diffraction methods. Powder diffraction methods have been improved significantly during the last decade and due to high-resolution diffractometers and advanced data analysis tools are now reliable methods, almost approaching the performance of single crystal diffraction experiments. High temperature diffraction experiments using a variety of reducing, inert and oxidizing atmospheres permit us now to follow solid state reactions with excellent time resolution. These experiments will improve our understanding of solid state reactions and thus will permit to optimize solid state synthesis methods. Rare-earth transition metal oxychloride and reduced rare-earth transition metal oxides are targeted as model compounds for low-dimensional magnetic sublattices. Low-dimensional paramagnetic sublattices are being realized by means of anisotropic magnetic exchange paths due to different anions. The systems under investigation combine mixed anions (oxychlorides) having ordered and disordered anion lattices with single anion lattices (oxides). These model systems provide an opportunity to evaluate the impact of anion ordering on magnetic exchange interactions in extended solids. Crystallographic phase transitions are investigated by diffraction and differential thermal analysis methods. The research program has a large synthetic component combined with the investigation of physical properties. Bulk physical properties and structural details will be correlated in an attempt to identify structure - property relations.