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Final report

Combined efforts of different spectroscopic methods of materials reveal important information on their structure and the dynamics. We have established a joint team for a combined investigation of the vibrational properties of disordered and nanstructured materials using inelastic neutron and Raman spectroscopy. We are using the neutron source ''Heinz Maier-Leibnitz'', Garching as well as the Raman equipment of both labs (UCF and TUM). Further members of our team are Prof. Sudipat Seal (Nanoscience Technology Center, UCF), Prof. Tobias Unruh, Univ. Erlangen-Nürnberg (Formely FRM II, Garching) and Bernhard Schmid, Univ. Mainz.

For our research projects, which are still going on, we are interested in the following material classes: (i) Phosphate glasses for optical amplifications [1], (ii) Cerium oxide nanocomposites for applications in fuel cells, gas sensors, ultraviolet absorbents and high-temperature coatings [2].
From the combined spectroscopic measurements we reveal the vibrational and structural properties of these materials using a recent theory [3] which relates the Raman spectrum to that accessible by neutrons. The combined efforts enable us to taylor the materials for meeting the optimal applicational goals. Based on recent measurements and further theoretical efforts we have written publications [4,5] on the vibrational properties of the material class (i). A further publication is in preparation.

The cerium oxide nanoparticles (class ii) are synthesized by Prof. Seal and his group in Orlando and are characterized by high resolution electron microscopy and x-ray crystallography. We have performed measurements on this material class in the summer at Garching using the TOF-TOF neutron spectrometer as well as the E13 Raman equipment [6]. The financial aid of BaCaTec was used for the stay of Prof. Schulte in Garching (during which the measurements on class (ii) were made) and for a visit of Prof. Schirmacher to the University of Central Florida in Orland in order to prepare the theoretical evaluation of the measurements and the publications. This visit was also valuable for discussions with Prof. Seal on the unique properties of cerium oxide nanoparticles and on future joint investigations.

[1] A. Schulte, Y. Guo, W. Schirmacher, T. Unruh, T. Cardinal, Vibrational Spectroscopy, 48, 12 (2008)
[2] S. Patil, S. Seal, Y. Guo, A. Schulte, J. Norwood, Appl. Phys. Lett. 88, 243110 (2006)
[3] W. Schirmacher, B. Schmid, Phys. Rev. Lett. 100, 137402(2008)
[4] T. Unruh, A. Schulte, Y. Guo, B. Schmid, W. Schirmacher, J. Noncryst. Sol. in press (see attachment).
[5} A. Schulte, Y. Guo, W. Schirmacher, B. Schmid, T. Cardinal, T. Unruh. Proc. XXIIth Intl. Conf. on Raman Spectroscopy, Eds. P. M Champion, L. D. Ziegler, AIP Conf. Proc., vol 1267, 257-258 (2010) (see attachment).
[6] A. Schulte, W. Schirmacher, T. Cardinal, S. Seal, T. Unruh, User Meeting 2010, Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM