Introduction by A. Fitch, ESRF

Innovative materials with improved or novel properties are emerging from research programs in pure and applied materials science, solid-state physics and chemistry. Fundamental to an understanding of any material's behaviour is detailed knowledge of the structure, encompassing the arrangement of the constituent atoms, their electronic structure, and an appreciation of their means of interaction. From such awareness, further developments can flow. Synchrotron radiation provides several complementary techniques such as diffraction, spectroscopy and imaging, to investigate the structures of materials from the atomic level through to the microstructure. The structure of a material is, however, no more than a snapshot under specific conditions. Dynamic properties are also of crucial importance as materials evolve under the influence of changing temperatures, pressures, or chemical environment. Synchrotron techniques, because of the rapidity with which measurements can be made, also provide the capacity to observe dynamic systems evolving or transforming in situ.

In the following articles, we highlight several applications of X-ray diffraction to probe the structure in different states of matter, such as single crystals, powders, deposited thin gold films and even a molten metal oxide at very high temperature. The fabrication of certain of the samples and the diffraction measurements themselves present their own challenges. The results provide fundamental insights into a range of phenomena, including magnetic and electronic properties, microstrain, texture and microstructure, phase separation, and unusual thermal-expansion behaviour, with applications ranging from potential systems of data storage, through to the characterisation of distinct forms of crystalline drug molecules.