Structural Properties and Dielectric Hysteresis of Molecular Organic Ferroelectric Grown from Different Solvents

Abstract

A comparative analysis of crystal structure, Raman spectra, and dielectric hysteresis loops was carried out for organic ferroelectric crystals of 2-methylbenzimidazole (MBI) grown from ethanol (MBIet), acetone (MBIac), deuterated acetone (MBId-ac), or prepared by sublimation from gas phase (MBIgas). Raman spectroscopy shows identical frequencies of molecular vibrations in all studied crystals, proving the same molecular structure. At the same time, a detailed analysis of the asymmetry of the powder XRD reflection profiles indicates the presence of nano-scaled regions with the same MBI symmetry and crystal structure but slightly different sizes and unit cell parameters. The formation of the MBI modifications is associated with possible penetration of solvent molecules into the voids of the MBI crystal structure. Dielectric hysteresis loops in MBIet and MBId-ac crystals at room temperature demonstrate significantly different values of coercive fields Ec. Analysis of hysteresis loops within the framework of the Kolmogorov-Avrami-Ishibashi (KAI) model shows that the polarization switching in MBId-ac occurs much faster than in MBIet crystals, which in the KAI model is associated with different values of the characteristic frequency ω0 and the activation field Ea of the domains wall motion.

Synthesis and Study of Organic Nanostructures Fabricated by Inclusion of 2-Methylbenzimidazole Molecules in Nanotubes of Chrysotile Asbestos, Mesoporous Silica, and Nanopores of Borate Glasses

“…Organic nanostructures used in this work were synthesized by introducing MBI molecules into porous borate glasses, chrysotile asbestos, and mesoporous silica. MBI crystals used for nanostructure preparation were grown by evaporation, as well as by slow cooling from saturated solutions in ethanol or acetone (or deuterated acetone (d-acetone)) [ 61 ] of MBI powder obtained by chemical methods. The solution was purified with activated carbon.…”

“…In TOPAS, the crystallite size D TOPAS is designated as Lvol-FWHM . To compare with the microstrain values ε s WHP and ε s SSP obtained, respectively, in WHP and SSP calculations done by program SizeCr, the microstrain parameter e 0 obtained by TOPAS was recalculated to (see [ 61 ] for explanation).…”

Croconic Acid Doped Triglycine Sulfate: Crystal Structure, UV-Vis, FTIR, Raman, Photoluminescence Spectroscopy, and Dielectric Properties

“…The drawings of the structure were made using the Vesta program [59]. Further details of the XRD experiment, WHP XRD line analysis and Rietveld refinement are the same as published elsewhere [60,61]. Raman spectra of the TGS:CA single crystals were studied using a T64000 spectrometer (Horiba Jobin-Yvon, Paris, France) equipped with a confocal microscope and a silicon charge-coupled device (CCD) cooled by liquid nitrogen.…”