Dresden 2020 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 21: Transport - Ions and Electrons

MM 21.1: Talk

Tuesday, March 17, 2020, 10:15–10:30, IFW B

Site energy distribution of sodium ions in a sodium rubidium borate glass — •Martin Schäfer, David Budina, and Karl-Michael Weitzel — Universität Marburg, Fachbereich Chemie

A charge attachment induced transport experiment [1] has been conducted on a Na⁺ and Rb⁺ containing glass employing an external Rb⁺ ion beam. Native Na⁺ ions are replaced by external Rb⁺ ions giving rise to a pronounced concentration depth profile as measured by time-of-flight secondary ion mass spectrometry. From the theoretical analysis of this concentration profile a unique site energy distribution (SED) of mobile Na⁺ ions in the glass is derived [2]. The full width at half maximum of the populated part of this SED is 0.32 eV. The mechanism involves Na⁺ sites being vacated top-down and being filled by Rb⁺ also top down. Therefore, the Fermi energy of Na⁺ ions decreases with ongoing experiment, while that of the Rb⁺ ions stays constant. Agreement between experiment and the Nernst-Planck-Poisson theory for describing the transport is reached by assuming that both the migration and the chemical diffusion driven contribution to the total flux depend on the local concentration. [1] M. Schäfer, K.-M. Weitzel, Materials Today Physics, 5, 12-19, (2018). [2] M. Schäfer, D. Budina, K.-M. Weitzel, Phys. Chem. Chem. Phys, in press (2019).