Anomalous structure transition in undercooled melt regulates polymorphic selection in barium titanate crystallization

Area of Science:

• Materials Science
• Crystallography
• Solid State Chemistry

Background:

• Titanate crystallization is crucial for optical and electrical applications.
• The complex polymorphism of barium titanate (BaTiO3) remains incompletely understood.
• Controlling polymorphic selection is vital for material property tuning.

Purpose of the Study:

• To elucidate the mechanisms of polymorphic selection during barium titanate crystallization.
• To investigate the role of melt structure and cooling conditions in phase formation.
• To link melt structural transitions to nucleation behavior.

Main Methods:

• In situ high-energy synchrotron X-ray diffraction.
• Ab initio molecular dynamic simulations.
• Controlled cooling experiments to manipulate undercooling.

Main Results:

• An anomalous structural transition in molten BaTiO3 was observed during cooling.
• Polymorphic selection (cubic vs. hexagonal) is controllable via undercooling.
• Large undercooling favors cubic phase, while small undercooling promotes hexagonal phase.
• Melt polymerization of Ti-O polyhedra governs nucleation selection.

Conclusions:

• The study establishes a link between non-isomorphic melt transitions and polymorphic crystallization.
• Undercooling and melt structure are critical parameters for controlling BaTiO3 phase formation.
• Findings offer a new perspective for designing titanate-based crystals and glasses.