Dense yttria phase eclipsing the A-type sesquioxide structure: high-pressure experiments and ab initio calculations

Area of Science:

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

Background:

• Yttrium sesquioxides exhibit complex structural behavior under varying conditions.
• Understanding phase transitions is crucial for materials applications.

Purpose of the Study:

• To investigate the high-pressure phase transition properties of yttrium sesquioxides.
• To compare high-temperature and room-temperature compression behaviors.

Main Methods:

• In situ X-ray diffraction experiments were performed.
• Ab initio calculations and structural optimizations were utilized.

Main Results:

• The high-pressure phase sequence differs between high-temperature and room-temperature compression.
• A reconstructive transformation to the Gd2S3 structure occurs around 8 GPa at high temperatures.
• A metastable displacive transformation from B- to A-type structures occurs at room temperature.
• The Gd2S3 structure formation significantly decreases the band gap.
• The Gd2S3 phase shows partial recovery at ambient pressure.

Conclusions:

• High-pressure and high-temperature conditions induce different structural pathways in yttrium sesquioxides.
• The Gd2S3 phase exhibits unique electronic properties due to band gap reduction.
• The quenchability of the Gd2S3 structure depends on enthalpy differences.