High-Temperature Molecular Ferroelectric Tris(2-hydroxyethyl) Ammonium Bromide with Dielectric Relaxation

We
obtained one new molecular ferroelectric material tris­(2-hydroxyethyl)
ammonium bromide (TAB) that crystallizes in aqueous solution
at room temperature with a space group of R3m which belongs to ten polar space groups. There is a paraelectric-to-ferroelectric
phase transition at 424 K (from hexagonal R3̅m to hexagonal R3m phase).
Such a high transition temperature is close to that of diisopropylamine
bromide (426 K) and higher than that of many other molecular ferroelectrics,
such as triethylmethylammonium tetrabromoferrate­(III) (360 K); some
of the organic–inorganic perovskite ferroelectrics, such as
(cyclohexylammonium)2PbBr4 (363 K); and some
inorganic ferroelectrics, including BaTiO3 (393 K). The
saturated polarization and the coercive field of TAB measured
from the ferroelectric hysteresis loop are about 0.54 μC·cm–2 and 0.62 kV/cm, respectively. Given its superior
performance, including high phase transition temperature, room-temperature
ferroelectricity, small coercive electric field, and adjustable ladder-shaped
dielectric constant, TAB will have many potential applications.