Silver structure environments in ion-exchanged silicate glasses studied by X-ray absorption fine structure.

Area of Science:

• Materials Science
• Solid State Chemistry
• Spectroscopy

Background:

• Ion-exchange is a key method for introducing metal ions into glass matrices.
• Understanding the local structure of introduced ions is crucial for tailoring glass properties.
• X-ray absorption fine structure (XAFS) provides detailed information on atomic coordination and bonding.

Purpose of the Study:

• To investigate the structural geometry of silver (Ag+) ions in soda-lime silicate and soda aluminosilicate glasses after ion-exchange.
• To determine the influence of ion-exchange ratio on Ag+ coordination number, Ag-O distance, and local disorder.
• To compare the structural behavior of Ag+ in different glass compositions and after thermal treatment.

Main Methods:

• X-ray absorption fine structure (XAFS) spectroscopy was employed.
• Ion-exchange method was used to introduce Ag+ ions into glass samples.
• Analysis focused on coordination number, interatomic distances, and Debye-Waller factor (DWF).

Main Results:

• In soda aluminosilicate glass, Ag+ coordination number is 1.6 with Ag-O distances of 2.20 Å (x < 0.47) and 2.28 Å (x > 0.47).
• Ag+ ions initially occupy non-bridge oxygen (NBO) sites, followed by bridging oxygen (AlO4) sites.
• Local disorder of Ag-O coordination increases with ion-exchange ratio, especially beyond x=0.47.
• In soda-lime silicate glass, Ag+ coordination is 1.6, reducing to 1.3 after thermal treatment, with a consistent Ag-O distance of 2.14 Å.
• Debye-Waller factor (DWF) for Ag-O in soda aluminosilicate glass is higher than in soda-lime silicate glass.
• Small Ag clusters exhibit reduced interatomic distances and larger DWF, with Ag nanoparticles under tensile stress.

Conclusions:

• The local structure and coordination of Ag+ ions are highly dependent on the glass matrix composition and ion-exchange process.
• Ion-exchange dynamics dictate the stabilization sites and structural evolution of Ag+ in aluminosilicate glasses.
• XAFS is effective in characterizing the subtle structural changes and stress states of metal nanoparticles within glass systems.