Molecular ferroelectric pyridin-2-ylmethanaminium perchlorate with phase transition induced by disorder of perchlorate

Molecular ferroelectrics are a kind of functional materials that have large application prospects. Comparing with the traditional inorganic ferroelectrics, they have some advantages, such as easy design, environmentfriendliness, nontoxicity, and flexibility. In this study, a new molecular ferroelectric pyridin-2ylmethanaminium perchlorate was discovered, which undergoes a ferroelectric phase transition at around 264.8 K. The spontaneous polarization reaches 0.22 mC cm(-2), and the coercive fields are as small as 1.1 kV cm(-1) at 202 K. The single- crystal X-ray diffraction analysis reveals that the space group transforms from a polar space group of P21 at 173 K to a centrosymmetric space group of P2(1)/c at 293 K. By analyzing the crystal structure changes below and above the phase transition temperature, it can be concluded that the phase transition is induced by the disorder of perchlorate. Its ferroelectricity was confirmed by the measurements of differential scanning calorimetry, dielectric and hysteresis loop.