Berlin 2008 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 20: Glasses III (joint session DF/DY)

DY 20.5: Vortrag

Mittwoch, 27. Februar 2008, 15:30–15:45, EB 407

Barium diffusion in mixed cation glasses — •Michael Grofmeier, Frank Natrup, and Hartmut Bracht — Institute of Materials Physics, University of Münster, Germany

Diffusion of barium in mixed cation glasses of the composition xNa_2O*(3*x)BaO*4SiO_2 with x = 0.0, 0.1, 0.3 and 1.0 and 0.4K_2O*2.6BaO*4SiO_2 was investigated by means of the radiotracer diffusion technique below the respective glass transition temperatures. In accord with our previous results of calcium diffusion in soda-lime silicate glasses, the mobility of alkaline-earth ions increases with the alkali content in all analyzed glass systems with no decrease in the diffusion activation enthalpy, but a raise in the pre-exponential factor. A distinct dependency of the activation enthalpy of alkaline-earth ions on the type and content of the alkali ions in the glass is observed. The results provide evidence for elastic and electrostatic contributions to cation diffusion in glasses and support the formation of dissimilar cation pairs, that were derived from nuclear magnetic resonance investigations of soda-lime silicate glasses and glasses containing sodium and barium. Finally, a striking correlation between the pre-exponential factor of alkaline-earth ion diffusion in soda-lime and potassium barium glasses is found whose origin remains unsolved.