Room-temperature ferroelectricity in diisopropylammonium bromide

A room-temperature ferroelectric, diisopropylammonium bromide (DPB), with dielectric constant ε ≈ 12 000 and a clear hysteresis loop at Tc = 425 K is reported. At 417 K DPB undergoes the irreversible phase transition from nonpolar orthorhombic P212121 to the ferroelectric monoclinic phase (P21) and subsequently, at 425 K, to the paraelectric prototype phase (P21/m). The molecular mechanism of the paraelectric–ferroelectric transition is ascribed to the ‘order–disorder’ behaviour of the diisopropylammonium cations.