POWDER DIFFRACTION AT SYNCHROTRONS

D. E. Cox

Physics Department, Brookhaven National Laboratory, Upton, NY 11973, USA

Keywords: Synchrotron radiation, powder diffraction

In the past decade, synchrotron x-ray powder diffraction has emerged as a very important technique for structural characterization in condensed matter sciences. Dedicated powder diffraction beam lines have been commissioned or are being constructed at almost all second and third generation synchrotron sources, and there has been a correspondingly rapid growth in the user community. Among the many applications of synchrotron radiation are (i) the ab-initio solution and refinement of unknown crystal structures from very high-resolution powder data, a rapidly evolving field which has seen many exciting advances, especially for framework structures such as zeolites, fullerene derivatives and other molecular compounds, and small organic molecules of pharmaceutical significance (ii) in-situ studies of phase transformations and equilibria as a function of temperature or pressure, particularly for materials with unusual electronic and magnetic properties and for mineralogical systems under conditions similar to those in the earth's mantle (iii) in-situ studies of reaction kinetics and chemical synthesis (iv) the determination of cation distribution in mixed systems such as high T_c oxides, and oxidation states in mixed-valence compounds by the use of resonant scattering techniques (v) the determination of residual strain. A brief review of instrumentation, experimental techniques and methods of data analysis will be given, and a few examples of recent investigations in some of the above areas will be described.

Work supported by the U.S. Department of Energy, Division of Materials Sciences, under Contract No. DE-AC02-98CH10886.