High-pressure transformations of NbO2F

Area of Science:

• Materials Science
• Solid-State Chemistry
• Crystallography

Background:

• Niobium dioxyfluoride (NbO2F) exhibits a ReO3-type structure at ambient conditions.
• Understanding material behavior under extreme conditions is crucial for developing new technologies.

Purpose of the Study:

• To investigate the structural evolution of NbO2F under high pressure.
• To determine the phase transition pressures and structural changes in NbO2F.

Main Methods:

• High-pressure powder diffraction using diamond anvil cells.
• Synchrotron X-ray radiation for diffraction measurements.
• Rietveld refinement for structural analysis.

Main Results:

• A phase transition from cubic (Pm3m) to rhombohedral (R3c) structure occurred at 0.47 GPa.
• The rhombohedral phase involves tilting of Nb(O/F)6 octahedra and anion arrangement approaching hexagonal close packing.
• NbO2F becomes X-ray amorphous above 17-18 GPa.

Conclusions:

• NbO2F undergoes significant structural transformations under high pressure.
• The observed phase transitions are driven by octahedral tilting and anion packing rearrangements.
• The amorphous phase indicates a loss of long-range order at extreme pressures.