SYNCHROTRON STUDIES OF PHASE TRANSFORMATIONS

Abstract

Material properties are dependent upon atomic arrangement. The structure provides a basis for calculation and for the interpretation of experiment. In the Earth context, mineral structure is composition, pressure and temperature sensitive, and changes in the phases present cause profound changes in properties. Examples include the relationship between sound velocities (elasticity) and structure as a function of depth in the Earth (Chen et al. 1999, Li et al. 1998, Liebermann and Li 1998, Parise et al. 1998). The selective sorption of ions and isotopes on mineral surfaces, and on particular faces on one growing surface, are excellent examples of how sorption is controlled by atomic arrangement (Reeder 1991, 1996). It is desirable therefore that material properties and structure be studied together, and if possible under the conditions of operation for that material. For the geosciences, this means studies of crystal structure and physical properties at elevated temperatures and pressures. For the solid state physics, chemistry and planetary science communities, it might also include high pressure/low temperature investigations of magnetic structures. Access to synchrotron radiation has made these types of studies routine. To address topical concepts and issues, beamlines have become more versatile and more easily reconfigured. This has decreased the cycle time between blue-sky concept and reality, and it will radically alter the mineral chemistry and mineral physics cultures, as national facilities are now firmly established at the cutting edge of solid state research (Hemley 1999). The science enabled by these facilities is impossible to reproduce in the home laboratory, as is the culture of interdisciplinary activity, interdependence between groups of collaborators, and speedy application of basic X-ray and neutron physics to applied problems. This mode of science is strange to many. The change however, is inevitable and will continue to gather momentum. The advent of …