Materials science and materials engineering involve the investigation of structure property relationships and the use of these findings to produce materials with predetermined properties. Studies of this type play a major role at the ESRF and span a wide range of applications. All aspects of materials science studies cannot be covered by this brief exposé. The trend in materials science research at the ESRF is that micro focussing; time-resolved studies in situ and the application of combinations of techniques are on the rise. Also, focussing down to the nanometre range and applications of extreme magnetic fields are emerging areas. In order to illustrate these trends we have chosen a few examples from the categories: extreme conditions; use of pair distributions; general applications of X-ray diffraction to problems in materials science; and new developments.

Enormous advantages in examining materials under non-ambient conditions such as high pressure or high temperature have been made due to developments in diamond anvil cells, large volume presses and laser heating in combination with the third generation X-ray source at the ESRF. The use of pressure at ID09B shows for the first time a pressure-induced isomorphic volume collapse of the itinerant YCo5 magnet. High pressure at low temperature studies of magnetite prove that there is a clear correspondence between electronic and structural transitions (drop in conductance and cubic to cubic distortions) disproving the Verwey-Mott concept. High pressure studies of Fe above 2 Mbars at ID27 suggest that the Earth’s inner core is lighter than a mixture of Fe and Ni at the same conditions implying a larger content of light elements.

High-resolution powder diffraction has proven to be a very useful tool in many materials science applications. Thanks to automatisation, hundreds of diffraction patterns can now be collected in a short time. A systematic investigation of the phase diagram of LiNH2:LiBH4 at ID31 has revealed a new solid phase Li4BN3H10 with promising applications as hydrogen storage for fuel cells. ID31 has also been used to obtain detailed atomic models for icosahedral Mg-Zn-rare-earth quasicrystals from high-resolution powder diffraction via real space pair distribution functions indicating a procedure to obtain structural information from aperiodic crystals. Wide-angle X-ray scattering studies of the behaviour of nanolayered clay particles suspended in oil under a polarising electric field at BM01A suggest new ways to obtain self-assembled nanostructures. The high-energy beamline ID15 has been used to resolve the debated phase behaviour of the alloy Au-Ni by means of high-energy X rays (60 and 90 keV) by mapping the diffuse scattering of the system. It was concluded that this system exhibits a competition of ordering and phase separation. Measuring of static structure factors of a new form of CO2 in combination with Raman measurements at ID27 proved that the new form a-CO2 (carbonia) is a new single-bonded glass analogue to the known SiO2/GeO2 polymorphs. The new amorphous material was synthesised above 40 GPa at temperatures as high 680 K in a diamond anvil cell.

New developments in the materials science sector include a detailed mapping of the photo-dissociation of HgI2 by pump (laser)-probe (single X-ray pulses) methods at ID09B. Probing the excited liquid with a time resolution of 100 ps showed a two-body dissociation channel (HgI2 to HgI+I) to be the dominant channel. The sub-micrometre range is particularly interesting in materials science as it is the critical length scale for many intergranular interactions such as cracks and dislocations; these interactions give rise to the bulk properties of materials. To meet these challenges ID11 has been extended to a long beamline giving a transverse resolution of below 100 nm by using state-of-the art modular focussing optics. Pioneering work has also been performed employing high magnetic fields at beamline BM26B. Pulsed magnetic fields up to 30 Tesla were used to study the Jahn-Teller distortion of TbVO4. It was shown that the high magnetic field modified the distortion and that these changes can be detected by X-ray powder diffraction.

A. Kvick