ASAXS - Helmholtz-Zentrum Berlin

Abstract
In the present work an evaluation method for anomalous small-angle X-ray scattering
(ASAXS) to analyze nanochemical compositions of all involved phases of a sample has been
developed and was applied to a glass ceramic. The nanochemical analysis differs from the
known methods of partial structure factors or functions (PSF) by the applicability to
virtually any system, because the new evaluation method does not require any limiting
assumptions regarding the anomalous corrections of the atomic scattering factors of the
individual elements. Unlike the PSF’s normally used, the relevant sample properties,
i.e. nanostructure and nanochemical compostion, will be determined directly from the
differential scattering cross sections as a function of the X-ray energy and the scattering
vector. Extensive ASAXS experiments at a selected oxyfluoride glass ceramic were done
and analyzed by the developed method. The investigated glass ceramic, which is co-doped
with selected lanthanides like erbium and ytterbium, shows the nonlinear optical property
of frequency upconversion.
It was shown that it is possible to determine quantitatively the average compositions
of all phases of a system using ASAXS. In contrast to EDX studies, ASAXS provides
average compositions, which represent the sample better from a statistical point of view.
The nanochemical composition analysis of the glass ceramic yielded the result that the
cadmium is not part of the nanoparticle phase, which has an average composition of
17% Pb 2% Er 17% Yb 64% F (at %).
TEM studies imply that the nanoparticles in the glass can be described by ellipsoids.
It was shown that the scattering curves of the ASAXS studies can be simulated by such
a structural model.
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