Westfälische
Wilhelms-Universität Münster
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Institut für Materialphysik Wilhelm-Klemm-Str. 10 48149 Münster Geschäftsführender Direktor: Prof. Dr. Helmut Mehrer |
Tel. (0251) 83-33571
Fax: (0251) 83-38346 e-mail: mehrer@nwz.uni-muenster.de www: http://www.uni-muenster.de/Physik/MP/ |
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Forschungsschwerpunkte 2001 - 2002 Fachbereich 11 - Physik
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Tracer diffusion and ionic conduction in single and mixed alkali borate glases
Tracer diffusion
and ionic conductivity studies have been performed on single and mixed sodium-rubidium borate
glasses as functions of temperature, composition and in one case also as function of pressure. The
diffusivity of mobile ions deduced from the ionic conductivity via the Nernst-Einstein relation are
compared with tracer diffusivities. For 0.2 [XNa2O (1-X) Rb2O]
0.8B2O3 the conductivity shows
minimum near X = 0.4 and a maximum in the activation enthalpy indicating a conventional mixed
alkali effect. The Rb diffusivity decreases exponentially with decreasing Rb content. Respectively the
Na diffusivity decreases with decreasing Na content but remains nearly constant at the Rb rich side.
Both diffusivities intersect near X = 0.2. The Haven ratio is temperature independent on th Na side
and decreases with decreasing temperature on the Rb side.The temperature dependencies of Na and
Rb diffusion yield distinct trends for the activation enthalpies. The complementary measurements of
conductivity and tracer diffusion provide detailed insight in the dynamics of ionic transport in mixed
Na-Rb-borate glasses.
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