Network-forming units, energy landscapes and conductivity activation energies in alkali borophosphate glasses: analytical approaches

TL;DR

This paper develops analytical methods to understand how compositional changes in alkali borophosphate glasses affect their ionic transport properties by linking structural units to energy landscapes and activation energies.

Contribution

It introduces extended theoretical approaches to relate glass composition, structural units, and ionic activation energies, validated against experimental data.

Findings

Good agreement with experimental conductivity activation energies

Structural unit concentrations influence energy landscape modifications

Analytical models predict compositional effects on ionic transport

Abstract

A major challenge in the modeling of ionically conducting glasses is to understand how the large variety of possible chemical compositions and specific structural properties influence ionic transport quantities. Here we revisit and extend a theoretical approach for alkali borophosphate glasses, where changes of conductivity activation energies with the borate to phosphate mixing ratio are related to modifications of the ionic site energy landscape. The landscape modifications are caused by varying amounts of different units forming the glassy network, which lead to spatial redistributions of the counter-charges of the mobile alkali ions. Theoretical approaches are presented to calculate variations of both network former unit concentrations and activation energies with the glass composition. Applications to several alkali borophosphate glasses show good agreement with experimental data.