Switchable Polarization in an A-Site Deficient Perovskite through Vacancy and Cation Engineering

Area of Science:

• Materials Science
• Solid-State Physics
• Crystallography

Background:

• Crystal defects are often detrimental but can be engineered for functionality.
• Perovskites with ordered vacancies can exhibit complex structural instabilities.

Purpose of the Study:

• To demonstrate room-temperature ferroelectricity in an A-site-deficient perovskite Y1/3TaO3.
• To investigate the role of ordered vacancies and octahedral rotations in inducing ferroelectric polarization.
• To explore strategies for enhancing polarization in defect-ordered materials.

Main Methods:

• Compositional selection to favor specific structural instabilities.
• Superspace analysis of modulated crystal structures.
• Lattice-dynamics calculations to predict material properties.

Main Results:

• Y1/3TaO3 exhibits switching-like polarization at room temperature in the P b 2 1 m phase.
• Ordered vacancies and TaO6 octahedral rotations enable ferroelectric response.
• A phase transition to a paraelectric incommensurate phase occurs at ~750 K.
• Epitaxial strain is predicted to further enhance room-temperature polarization.

Conclusions:

• Defect ordering in perovskites can circumvent centrosymmetric states and induce ferroelectricity.
• The Y1/3TaO3 system demonstrates a viable strategy for achieving enhanced polarization.
• This defect-engineering approach is generalizable to other improper ferroelectrics and multiferroics.