An Above-Room-Temperature Molecular Ferroelectric: [Cyclopentylammonium]₂CdBr₄

Area of Science:

• Materials Science
• Solid State Physics
• Crystallography

Background:

• Molecular ferroelectrics offer tunable structures as alternatives to inorganic ferroelectrics.
• Achieving high Curie temperatures (Tc) above room temperature in molecular ferroelectrics remains a significant challenge for practical applications.

Purpose of the Study:

• To synthesize and characterize a novel organic-inorganic hybrid molecular ferroelectric with an enhanced Curie temperature.
• To investigate the mechanism of ferroelectric phase transition and confirm ferroelectric properties in thin films.

Main Methods:

• Single crystal X-ray diffraction to determine crystal structure and phase transition.
• Polarization-temperature and dielectric-temperature measurements to identify Curie temperature.
• Piezoresponse force microscopy (PFM) to observe domain structures and polarization switching.

Main Results:

• A new organic-inorganic hybrid molecular ferroelectric, [cyclopentylammonium]2CdBr4 (1), was successfully synthesized.
• Compound 1 exhibits a ferroelectric phase transition at 340.3 K (Tc), demonstrating above-room-temperature ferroelectricity.
• The ferroelectric mechanism involves an order-disorder transition of organic cations and inorganic anions, yielding a spontaneous polarization of 0.57 μC/cm².
• PFM confirmed antiparallel 180° stripe domains and polarization switching in thin films.

Conclusions:

• The synthesized [cyclopentylammonium]2CdBr4 is a promising molecular ferroelectric with a moderate above-room-temperature Curie temperature.
• The observed ferroelectric properties and polarization switching in thin films open avenues for applications in flexible electronics, soft robotics, and biomedical devices.