Dresden 2009 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 26: Poster II

DY 26.5: Poster

Thursday, March 26, 2009, 16:00–18:00, P1A

Models for the mixed glass former effect in ion-conducting glasses — •Michael Schuch, Christian Mueller, and Philipp Maass — Institut für Physik, Technische Universität Ilmenau, Germany

A widely applied empirical method to increase ionic conductivities in ionic conducting glasses is to make use of the mixed network former effect (MNFE), which manifests itself in a minimum of the conductivity activation energy upon mixing of two network formers. We will present two theoretical models for the MNFE: In the first “mixed barrier model” [1] the resident sites of the mobile ions are considered to have comparable binding energy, while the energy barriers between the sites become lowered in heterogeneous environments containing both types of network formers. This model should apply to network formers with the same geometry of the network forming units (e.g. tetrahedral units in silicate-germanate systems). In the second “network unit trapping model” the barriers are considered to be weakly fluctuating, while the site energies associated with the network forming units differ significantly. This model should apply to network formers with different geometry of the units (e.g. trigonal und tetrahedral units in boro-phosphate systems). For both models we calculate the behavior of the dc- and ac- conductivities, as well as of the conductivity activation energy upon mixing and compare the theoretical results to the experimental findings.

[1] M. Schuch, C. Müller, P. Maass, and S. W. Martin preprint.