Network structure of 0.7SiO(2)-0.3Na(2)O glass from neutron and x-ray diffraction and RMC modelling

Area of Science:

• Materials Science
• Solid-State Chemistry
• Glass Science

Background:

• Understanding the atomic-level structure of amorphous materials like sodium silicate glass is crucial for predicting their properties.
• Previous studies on sodium silicate glasses have provided limited detailed structural information, particularly regarding the arrangement of sodium ions.

Purpose of the Study:

• To elucidate the detailed atomic structure of 0.7SiO(2)-0.3Na(2)O glass.
• To determine nearest-neighbor distances, coordination numbers, and bond angle distributions.
• To investigate the local environment and interactions of sodium ions within the silicate network.

Main Methods:

• Neutron diffraction and high-energy X-ray diffraction experiments were performed.
• Data from both diffraction techniques were modeled simultaneously using the reverse Monte Carlo (RMC) simulation technique.
• Partial pair correlation functions were separated using RMC with reasonable constraints.

Main Results:

• The structure of 0.7SiO(2)-0.3Na(2)O glass was resolved, revealing detailed structural parameters.
• 63% of oxygen atoms were found to be in bridging positions within the silicate network.
• The sodium-oxygen (Na-O) distance was determined to be 2.29 Å with a coordination number of 2.5.
• A significantly smaller nearest-neighbor sodium-sodium (Na-Na) distance of 2.6 Å was observed, suggesting proximity of sodium ions.
• The average silicon-oxygen (Si-O) ring size was found to be 7.6.

Conclusions:

• The study provides unprecedented detail on the atomic arrangement in sodium silicate glass.
• The short Na-Na distance indicates a tendency for neighboring sodium ions to associate, possibly around the same oxygen atoms.
• These findings offer critical insights into the structure-property relationships of sodium silicate glasses, relevant for materials science applications.