Structural Characterisation of Silver Ion Exchange in Alumino-Silicate Glasses

Abstract

Ion exchange, which is commonly used to alter the optical and mechanical properties of glasses usually involves a one-for-one substitution of an alkali cation (Na+1) from the glass by a monovalent dopant cation (Ag+1). The structural chemistry of this process, however, is far from understood. In this study we have used XAFS spectroscopy to determine the environments of sodium in a tetrasilicate and aluminosilicate glass and also ion exchange the sodium for silver. We find that the coordination number of sodium falls in the presence of aluminium, but that this is also accompanied by an increase in site disorder. By contrast, the environment of ion exchanged silver is less disordered, the nearest neighbour coordination resembling that of Ag2O. The presence of aluminium in the glass is clearly effective in removing some of the steric constraints of mobile cations, defining preferred routes for ion exchange.

Atomic-Scale Structural Characterization of Silver-Doped Phosphate-Based Glasses Prepared by Coacervation

“…The first peak is attributed to the Ag ⇔ O scattering path and has been fitted using Ag 3 PO 4 as a model calculated via FEFF . In all glasses, Ag–O distances are around 2.35/2.36 Å, in agreement with Ag–O distances previously found in MQ silver-doped glasses. , …”

“…56 In all glasses, Ag−O distances are around 2.35/ 2.36 Å, in agreement with Ag−O distances previously found in MQ silver-doped glasses. 57,58 The second, lower-amplitude, peak at ca. 3.51 Å has been attributed to a combination of two scattering paths for Ag ⇔ P (Ag ⇔ P 1 and Ag ⇔ P 2 ).…”