THE USE OF IMAGING PLATES IN LABORATORY HIGH PRESSURE X-RAY POWDER DIFFRACTION EXPERIMENTS. J. Haines, J.M. LÇger C.N.R.S., Laboratoire de Physico-Chimie des MatÇriaux, 1, Place Aristide Briand, 92190 Meudon, France

The application of imaging plate (IP) detectors to high pressure diffraction experiments in the laboratory has led to significant increases in sensitivity, resolution, and intensity accuracy as compared to older techniques using film or energy- dispersive diffraction. The integration of two- dimensional IP data results in improved powder averaging and a much higher signal to noise ratio. The data now obtained from both sealed sources and rotating anodes allow for crystal structure refinement using the Rietveld method. A simple, low-cost laboratory IP system will be described along with the data treatment necessary to obtain refinable profiles. Examples of structure refinement of some high pressure metal dioxide phases will be presented. In particular, data obtained for the cubic, high pressure phases of the rutile-type dioxides permitted the oxygen positions to be refined, thereby demonstrating that these phases are not fluorite structured, but rather have a modified fluorite structure. Potential improvements to the technique and future prospects will also be discussed.