Molecular Ferroelectric Pyridin-4-ylmethanaminium Perchlorate Undergoes Paraelectric-Ferroelectric and Ferroelectric-Ferroelectric Phase Transitions

Molecule-based ferroelectrics are a class of highly desirable intelligent materials for their rich switchable physical properties, easy and environmentally friendly processing, especial lightweight and mechanical flexibility. In the current work, a new molecule-based ferroelectrics pyridin-4-ylmethanaminium perchlorate was discovered undergoing paraelectric-ferroelectric phase transition at T-c = 258.40(8) K and ferroelectric-ferroelectric phase transition at T-1 = 255.93(2) K. It crystallizes in monoclinic crystal system with a centrosymmetric space group of C2/c at 293 K and also crystallizes in monoclinic crystal system but with a polar space group of Cc at 223 K. The spontaneous polarization can reach 1.25 mu C/cm(2) and the coercive field is about 2.6 kV/cm below 254 K. The paraelectric-ferroelectric phase transition belongs to displacive phase transition and the nearby ferroelectric-ferroelectric phase transition contains order-disorder features, which consistent with the dynamic process including deformations of each pyridin-4-ylmethanaminium cation and the resulting difference for -NH2 to be protonated. Because of the high pyroelectric coefficient values and small-amplitude anomalies of the epsilon' values in the vicinity of T-1 temperature, pyridin-4-ylmethanaminium perchlorate shows two ultrahigh pyroelectric figures of merit (FOMs) with M-1 approximate to 0.16 cm(2)/mu C and M-2 approximate to 0.21 cm(3/2).J(-1/2). The ultrahigh FOMs could make pyridin-4-ylmethanaminium perchlorate a potential element of the sensitive small-area pyroelectric detectors or pyroelectric vidicons.