The 6th International Conference on Matter and Radiation at Extremes (ICMRE2023)

216 / 2023-04-15 20:54:25

Development of X-ray fluorescence holography under high pressure

x-ray fluorescence holography,high pressure,SrTiO3

High Pressure Physics and Materials Science > Transitions-poster

X-ray fluorescence holography (XFH) is an atomic structure determination technique that utilizes fluorescing atoms as a wave source or a monitor of the interference field within a crystal sample. ^[1] Because it provides three-dimensional atomic images around a specified element within a range of up to a few nm in real space, XFH is used for medium-range local structural analysis. However, XFH has not been measured under high pressure yet. In this work, we combined the XFH with the diamond anvil cell (DAC) to study the local structures around Sr atom in a single-crystalline SrTiO₃ at high pressure. The experiment of XFH was carried out at BL39XU of SPring-8 using the normal mode setup. A symmetry DAC with a wide window has been newly designed, and the window allowed us to collect the XFH patterns from the sample irradiated through a beryllium gasket. The most serious difficulty to be solved under high pressure is the scattered X-rays from the diamond anvils and gasket, which are superimposed on the XFH image from the sample. We have demonstrated that nano polycrystalline diamond is a good material for the anvil that does not generate the background scattering.^[2] As a result, Kossel lines of SrTiO₃ were successfully observed. Furthermore, the position of the Kossel line gradually moved as a pressure dependence of the XFH image. Bragg scattering from the beryllium gasket remained as background signal of our XFH images, however, methods to remove the Bragg scattering are discussed in the poster presentation.