Radiation-induced disorder in compressed lanthanide zirconates

Area of Science:

• Materials Science
• Nuclear Engineering
• Solid State Physics

Background:

• Lanthanide zirconate compounds (Ln2Zr2O7) exhibit unique structural properties under extreme conditions.
• Understanding material behavior under irradiation and high pressure is crucial for applications like nuclear waste management.

Purpose of the Study:

• To investigate the combined effects of swift heavy ion irradiation and high pressure on lanthanide zirconates.
• To elucidate how irradiation-induced disorder influences high-pressure phase transitions.

Main Methods:

• Swift heavy ion irradiation (2.2 GeV 197Au ions) of Sm2Zr2O7, Er2Zr2O7, and Nd2Zr2O7.
• High-pressure experiments (>25 GPa) using diamond anvil cells.
• Structural analysis before and after irradiation and compression.

Main Results:

• Irradiation transforms pyrochlores (Sm, Nd) to defect-fluorite structures and disorders Er2Zr2O7.
• Unirradiated compounds form a cotunnite-like phase (>29 GPa), then amorphize.
• Irradiated compounds bypass the cotunnite phase, directly forming amorphous structures (>25 GPa).

Conclusions:

• Irradiation-induced defects raise energy barriers, inhibiting cotunnite phase formation.
• Coupled irradiation and compression expand the amorphous phase stability to lower pressures.
• Lanthanide composition critically influences defect energetics and response to extreme conditions.