Atomic-scale diffusion in ordered intermetallics and glasses studied by X-ray photon correlation spectroscopy

Bogdan Sepiol, Markus Stana, Manuel Ross

Macroscopic tracer methods achieve extremely high sensitivity and are widely applicable in the diffusion studies. Sometimes, however, if we want to find out the diffusion mechanism it is an advantage to use methods measuring atomic movements directly in space and in time. Only a few scattering methods are sensitive enough to resolve jump vectors on the atomic scale but they are limited to a restricted number of suitable isotopes. Moreover, they are always restricted in the time/energy resolution and thus limited to very fast diffusion processes.
It was a particular challenge to find a new method overcoming these experimental barriers and enabling measurements of long or short-range ordered alloys as well as amorphous solids. The advent of modern synchrotron sources opened the way for a new experimental technique which is not a subject to many restrictions. We managed to develop the relatively new technique of X-ray photon correlation spectroscopy to work on the atomic scale (aXPCS). This technique operates in the time regime and measures fluctuations in atomic positions. The time resolution towards faster dynamics is only limited by the readout time of the detector and the intensity of the X-ray beam. Towards slower dynamics it is limited by the measurement time restrictions and the persistence of the experimenter.
The first successful aXPCS experiment was carried out only few years ago by our group [1]. This talk will give an overview of experiments starting from disordered Au-Cu [1] and Ni-Pt [2] alloys to well-ordered B2 intermetallics like Fe-Al and Ag-Mg, as well as new application as a direct observation of single atomic motion in lead silicate glass [3] and in fast ionic conductors like alkali borate glasses.
This work was financially supported by the Austrian Science Fund (FWF) project P-28232.

Dynamik Kondensierter Systeme
ÖFOS 2012
Experimentalphysik, Festkörperphysik, Kondensierte Materie
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