Structure-property relationships in critically connected (GeTe₄)_100-(As₂Se₃) glasses

Area of Science:

• Materials Science
• Solid State Chemistry
• Glass Science

Background:

• Chalcogenide glasses, specifically GeTe4-As2Se3 systems, are crucial for optical and electronic applications.
• Understanding the relationship between composition, structure, and properties is essential for material design.
• Average coordination number (Z_av) is a key parameter in predicting glass properties.

Purpose of the Study:

• To investigate the thermal, optical, mechanical, and structural properties of GeTe4-As2Se3 glasses across the entire composition range.
• To determine the influence of chemical composition versus network connectivity on glass properties.
• To identify potential applications for these glasses, particularly in infrared technology.

Main Methods:

• Melt quenching method was used to prepare glasses in the GeTe4-As2Se3 pseudo-binary system.
• Thermal analysis (glass transition temperature, thermal stability), mechanical testing (hardness), and structural analysis (Raman spectroscopy) were performed.
• Average coordination number (Z_av) was calculated to correlate with observed properties.

Main Results:

• Glass forming ability was maximum at Z_av = 2.4, but showed an initial decrease with As2Se3 addition, contrary to expectations.
• Glass transition temperature (Tg) exhibited three distinct regions based on composition, influenced by chemical effects rather than network connectivity.
• Raman studies revealed a shift in dominant structural units (GeTe4/2, AsSe3/2, AsTe3/2) across the composition range, correlating with property variations.

Conclusions:

• Chemical composition effects dominate over network connectivity in critically coordinated GeTe4-As2Se3 glasses.
• The observed trends in glass transition temperature and hardness suggest distinct structural regimes within the glass system.
• These glasses exhibit infrared transparency up to 18 μm, making them suitable for infrared optical applications.