Low frequency vibrational dynamics and polyamorphism in Y₂O₃-Al₂O₃ glasses

Area of Science:

• Materials Science
• Ceramics
• Glass Science

Background:

• Polyamorphism in ceramics like Y2O3-Al2O3 is crucial for understanding their properties.
• Investigating amorphous phases requires advanced experimental and theoretical approaches.

Purpose of the Study:

• To explore glass formation and polyamorphism in Y2O3-Al2O3.
• To characterize the distinct amorphous phases formed.
• To compare experimental findings with molecular dynamics simulations.

Main Methods:

• Drop quenching for rapid cooling of liquid samples.
• Reflected light microscopy for identifying amorphous regions.
• Raman spectroscopy for analyzing vibrational densities of states.
• Electron microprobe analysis for compositional confirmation.
• Polarizable-ion molecular dynamics simulations.

Main Results:

• Identification of distinct high-density amorphous (HDA) and low-density amorphous (LDA) regions.
• Raman spectra revealed differences in vibrational densities of states between LDA and HDA phases.
• Low-temperature heat capacities were determined from experimental and simulated spectra.
• Anomalous excess of vibrational states (boson peaks) were observed and differed between LDA and HDA glasses.
• Thermodynamic modeling showed quench rate influences vitrification.

Conclusions:

• Y2O3-Al2O3 exhibits polyamorphism, forming distinct LDA and HDA glasses.
• Vibrational properties and heat capacities vary between the amorphous phases.
• The study validates the use of molecular dynamics simulations in characterizing amorphous ceramic structures.
• Quench rate is a critical factor controlling the glass formation pathway in Y2O3-Al2O3.