Title of the project: Diffusion in ionic glasses studied with coherent X-rays
Name of the VDSP student: Christoph Tietz
Project supervised by: Bogdan Sepiol

I research atomic diffusion in bulk glassy materials using coherent X-ray scattering. While our offices and a lab are located at the main building of the faculty in Boltzmanngasse, the actual labs are the coherent beamlines P10 at the DESY in Hamburg or ID10 at the ESRF in Grenoble.

In our recent work we were able to show the existence of fixed cationic sites in a rubidium borate fast-ion conducting glass. On this arrangement of sites the positive ions can move rather freely, giving rise to the large ionic conductivities measured in this materials. Ions perform up to 10^9 jumps on these sites before structural changes occur, giving rise to the concept of fixed sites and vacancies previously known only for crystalline materials. The images in the top depicts a vacancy performing three successive jumps on the arrangement of ionic sites, and the sites continue to exists even when unoccupied, which is in accordance with the concept of a vacancy. And the two images in the bottom show the experimental setup at the beamline P10.

Sepiol group