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

Crystals

Alexey Redkov¹  Elena Balashova²  Boris Krichevtsov²  Alexander Fokin²  Aleksandr A. Levin² 

[1] Institute of Problems of Mechanical Engineering, 61 Bolshoy pr. V.O., 199004 St. Petersburg, Russia;Ioffe Institute, 26 Politekhnicheskaya, 194021 St. Petersburg, Russia;

关键词: organic ferroelectrics;    powder XRD;    crystal structure;    Raman spectroscopy;    dielectric hysteresis loops;    polarization switching;   

DOI  :  10.3390/cryst11111278

来源: DOAJ

【 摘 要 】

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 (MBI_et), acetone (MBI_ac), deuterated acetone (MBI_d-ac), or prepared by sublimation from gas phase (MBI_gas). 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 MBI_et and MBI_d-ac crystals at room temperature demonstrate significantly different values of coercive fields E_c. Analysis of hysteresis loops within the framework of the Kolmogorov-Avrami-Ishibashi (KAI) model shows that the polarization switching in MBI_d-ac occurs much faster than in MBI_et crystals, which in the KAI model is associated with different values of the characteristic frequency ω₀ and the activation field E_a of the domains wall motion.

【 授权许可】

Unknown