XAFS Studies of Silver Environments in Ion-Exchanged Glasses

The X-ray absorption fine structure (XAFS) technique was used to analyze the structural geometry of Ag atoms introduced into soda-lime silicate glass and soda aluminosilicate glass by ion-exchange methods. The results show that Ag ions in aluminosilicate glass are coordinated by about two oxygens and the nearest-neighbor Ag-O distance increases when the Ag-for-Na ion-exchange ratio is larger than 0.47. When the exchange ratio is low, the introduced Ag ions are stabilized at the non-bridge oxygen (NBO) site with a Ag-O distance of 2.20 Å, and the Na ions in the AlØ4 site are exchanged by Ag + ions after full replacement of the NBO sites with a Ag-O distance of 2.28 Å. The disorder of Ag-O coordination increases with increasing ion-exchange ratio in aluminosilicate glass where Ag ions are coordinated by NBO and bridge oxygen (BO).