Organic–inorganic hybrid [H2mdap][BiCl5] showing an above-room-temperature ferroelectric transition with combined order–disorder and displacive origins

Abstract

Recently, molecule-based ferroelectric materials have drawn much attention due to their potential multifunctional optoelectronic device applications such as sensors, actuators, optical and memory devices. Therefore, the design of molecular ferroelectrics, explore their ferroelectrics origins and high performance are of significance. In this work, an organic–inorganic hybrid compound [H2mdap][BiCl5] (mdap=N-methyl-1,3-diaminopropane; 1) is found to exhibit brilliant ferroelectricity below 372K. Ferro-paraelectric transition origins the order–disorder of the organic cations and relative displacements of the cis-connected ions in the anionic chains in the crystal lattice via the structural analysis. Second harmonic generation and ferroelectric hysteresis loop measurements reveal typical polarization switching with a spontaneous polarization of 2.38μCcm−2 at 353K.