Exceptional structural phase transition near room temperature in an organic–inorganic hybrid ferroelectric

An organic–inorganic hybrid ferroelectric, (C 6 H 5 CH 2 CH 2 NH 3 ) 2 [HgI 4 ], undergoes a structural phase transition near room temperature, triggered by a flip of half the organic cations and an order–disorder transition of the inorganic anions, and may be regarded as a displacive-type ferroelectric.