High-pressure effect on PbTiO3: an investigation by Raman and x-ray scattering up to 63 GPa

Area of Science:

• Materials Science
• Condensed Matter Physics
• Crystallography

Background:

• Lead titanate (PbTiO3) is a well-known ferroelectric perovskite with applications in electronics.
• Understanding its structural behavior under extreme conditions is crucial for material design and fundamental physics.
• Previous studies suggested potential phase boundaries in PbTiO3 under pressure, but experimental data remained limited.

Purpose of the Study:

• To investigate the structural phase transitions of lead titanate (PbTiO3) under high pressure at room temperature.
• To determine the sequence of phases and the mechanisms governing structural changes up to 63 GPa.
• To examine the existence of a pressure-induced morphotropic phase boundary in PbTiO3.

Main Methods:

• High-pressure X-ray scattering experiments were conducted up to 63 GPa.
• Raman scattering spectroscopy was employed to probe vibrational modes and phase transitions.
• In-situ measurements were performed at room temperature.

Main Results:

• Three distinct continuous phase transitions were observed at approximately 13 GPa, 20 GPa, and 45 GPa.
• The transitions occurred between different tetragonal-like phases, indicating a complex structural evolution.
• No evidence for a pressure-induced morphotropic phase boundary was found in the studied pressure range.

Conclusions:

• PbTiO3 exhibits a rich phase diagram under high pressure, characterized by a sequence of tetragonal-like phases.
• Structural phase transitions are driven by mechanisms including oxygen octahedra tilting.
• Ferroelectricity reenters at high pressures, challenging previous assumptions about its pressure dependence.