Pressure-induced anomalies and structural instability in compressed β-Sb₂O₃

Area of Science:

• Materials Science
• Solid State Physics
• High-Pressure Physics

Background:

• Antimony trioxide (Sb2O3) exists in various polymorphs, with the orthorhombic β-Sb2O3 (valentinite) being metastable.
• Understanding the behavior of metal oxides under high pressure is crucial for materials science and geophysics.

Purpose of the Study:

• To investigate the high-pressure structural behavior of orthorhombic β-Sb2O3 (valentinite).
• To elucidate the mechanisms and origins of pressure-induced phase transitions in β-Sb2O3.

Main Methods:

• Synchrotron in situ X-ray diffraction (XRD) was employed to analyze structural changes.
• First-principles theoretical calculations, including density functional theory (DFT), were used to complement experimental findings.
• Phonon velocities, density of states, and dispersion curves were calculated to understand structural instability.

Main Results:

• β-Sb2O3 undergoes an isostructural phase transition to a distorted β phase between 7-15 GPa, marked by symmetry breaking and elasticity softening.
• A new high-pressure monoclinic phase of Sb2O3 was discovered above 15 GPa.
• At approximately 33 GPa, the monoclinic phase began to lose long-range order, forming an amorphous component alongside the crystalline phase.

Conclusions:

• High pressure induces significant structural transformations in β-Sb2O3, including phase transitions and amorphization.
• The study provides insights into the pressure-induced structural instability and phase transition mechanisms in sesquioxides.
• The findings contribute to understanding the local structures and relationships among sesquioxides under extreme conditions.