The Effect of Fluorine Doping on Structural and Dielectric Properties of Molecular Ferroelectric Diisopropylammonium Bromide

Abstract

An interest in organic molecular ferroelectrics is increasing due to their numerous advantages such as eco-friendly, lightweight, cost-effective, scalable and low processing temperatures. In the present work, the organic molecular ferroelectric diisopropylammonium bromide (DIPAB) and 50% fluorine-doped diisopropylammonium bromide (DIPABF) are synthesized in the form of polycrystalline powder using solution growth technique. The X-ray diffraction measurements done on as prepared DIPAB and DIPABF samples confirmed the room temperature orthorhombic phase (P2₁2₁2₁). The temperature-dependent dielectric studies are carried out on DIPAB confirmed its phase transitions nearly at 416 K and 429 K. But, DIPABF has shown a frequency-dependent transition near 429 K and the transition at 416 K is suppressed. It is also observed from the temperature-dependent dielectric constant and dielectric loss curves that the ferroelectric to paraelectric transition at 429 K is broad in DIPABF and it is frequency dependent. This confirms the presence of dielectric relaxation in DIPABF. The origin of such dielectric relaxation is explained with respect to temperature-dependent dipole rotation and electronegativity. Overall, DIPAB and DIPABF organic polycrystalline ferroelectric materials have been successfully synthesized and demonstrated its temperature-dependent dielectric relaxation in DIPABF.