A Lithium Complex Ferroelectric with High Curie Temperature: [Li(1,10-Phenanthroline)₂]I

Area of Science:

• Materials Science
• Solid State Physics
• Chemistry

Background:

• Ferroelectric phase transitions are typically order-disorder or displacive.
• Symmetry-breaking transitions driven by coordination geometry distortion are uncommon in molecular ferroelectrics.

Purpose of the Study:

• To investigate a novel lithium complex molecular ferroelectric, [Li(1,10-phenanthroline)2]I.
• To characterize its symmetry-breaking ferroelectric phase transition mechanism.

Main Methods:

• Crystallographic analysis to identify geometric distortion.
• Polarization measurements to confirm ferroelectric behavior.
• Nonlinear optical measurements for property comparison.

Main Results:

• [Li(1,10-phenanthroline)2]I undergoes an Aizu mmmFmm2 type symmetry-breaking ferroelectric phase transition at 371 K.
• Ferroelectricity is linked to lithium coordination geometry distortion and iodide ion movement.
• Obtained ferroelectric loops at room temperature with nonlinear optical signals comparable to KDP.

Conclusions:

• This study presents the first lithium-based organic complex ferroelectric with a coordination geometry-triggered symmetry-breaking phase transition.
• The findings offer inspiration for designing new molecular ferroelectrics.
• The material exhibits promising ferroelectric and nonlinear optical properties.