An order-disorder ferroelectric host-guest inclusion compound

Area of Science:

• Materials Science
• Crystallography
• Physical Chemistry

Background:

• Host-guest complexes offer tunable properties for advanced materials.
• Phase transitions in molecular materials are crucial for applications in electronics and sensors.
• Understanding ferroelectric mechanisms is key to developing new functional materials.

Purpose of the Study:

• To synthesize and characterize a new host-guest complex, [(DIPA)([18]crown-6)](ClO4).
• To investigate the phase transitions and determine the nature of the transition at T2.
• To elucidate the mechanism driving the observed ferroelectric behavior.

Main Methods:

• Differential scanning calorimetry (DSC) and heat capacity measurements.
• Temperature-dependent dielectric constant and P-E hysteresis loop analysis.
• X-ray powder diffraction and second-harmonic generation (SHG) studies.

Main Results:

• The complex [(DIPA)([18]crown-6)](ClO4) undergoes two phase transitions at T1=278 K (Ibam-Pbcn) and T2=132 K (Pbcn-Pna21).
• The transition at T2 is identified as a centrosymmetric-to-polar, paraelectric-to-ferroelectric transition.
• Symmetry breaking was confirmed by X-ray diffraction and SHG measurements.

Conclusions:

• The ferroelectric behavior arises from the cooperative ordering of [18]crown-6 molecules and anions, coupled with the dynamic motion of perchlorate counterions.
• This study presents a new ferroelectric material with potential applications in switchable devices.
• The findings contribute to the understanding of structure-property relationships in molecular ferroelectrics.