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DF: Dielektrische Festkörper
DF 4: Gl
äser II (gemeinsam FV DF/DY)
DF 4.10: Talk
Tuesday, March 9, 2004, 17:00–17:15, H23
From binary Na-silicate to ternary Na-alumino-silicate melts: the evolution of Na dynamics and intermediate range order — •Florian Kargl1, Andreas Meyer1, and Helmut Schober2 — 1Physikdepartment E13, TU München, 85748 Garching — 2Institut Laue-Langevin, 38042 Grenoble, France
Neutron scattering investigations of binary alkali silicate melts revealed correlations on intermediate lengthscales of 6-8 Å. Within MD-simulations on Na-silicates evidence was found that these correlations arise from Na-rich channels percolating in the remaining SiO-network. Fast Na-diffusion takes place via these channels [1]. Substituting the network forming component SiO2 by GeO2 leads to a change in structure and in the microscopic transport mechanism, respectively, as verified by inelastic neutron scattering. We present our recent investigations on sodium alumino-silicate melts containing besides SiO2 a second network former, Al2O3. Our main aim was to study the interplay between microscopic dynamics and structure and its influence on macroscopic properties. From quasielastic neutron scattering experiments we conclude that the channel structure is disrupted by adding Al2O3 to the Na-silicates resulting in an increase of viscosity as well as a decrease of Na-relaxation times [2].
[1] A. Meyer, J. Horbach, W. Kob, F. Kargl, H. Schober (submitted)
[2] F. Kargl, A. Meyer, Chem. Geol. (submitted)