Halobismuthates(III) and haloantimonates(III) with the
R3MX6chemical composition create a new and
broadly unexplored
class of ferroelectric compounds. In this paper, we report the haloantimonate(III)
ferroelectric comprising an aromatic (1,2,4-triazolium) cation, i.e.,
(C2N3H4)3[SbBr6] (TBA). Temperature-resolved structural and spectroscopic
studies indicate thatTBAundergoes two solid–solid
phase transitions between tetragonal [P42/m(I)] and monoclinic [P21/n(II) andP21(III)] phases.TBAexperiences a paraelectric–ferroelectric
phase transition at 271/268 K (II–III) driven by “order–disorder”
and “displacive” molecular mechanisms. The ferroelectric
properties of phase III have been confirmed by hysteresis loop measurement,
and additionally, the acentric order has been further supported by
second-harmonic generation measurements. Insight into the molecular
origins of the ferroelectric polarization was provided by periodicab initiocalculations using the Berry phase approach at
the density functional theory (DFT-D3) method level employed for calculations
of spontaneous polarization.