Ferroelectricity and phase transitions in pyridinium periodate single crystal

Single crystals of pyridinium periodate were grown, and their physical prop erties were studied. Anomalies of the electric permittivity and birefringen ce were observed at T-c1 = 321 K and T-c2 = 211 K. These observations gave evidences for the existence of three phases denoted as I, II, and III. Hyst eresis loops were observed both in phase II and III. Pyroelectric measureme nts showed two anomalies at T-c1 and T-c2 The anomaly at T-c1 is related to the transition between a para- and ferroelectric phase, and the anomaly at T-c2 to the transition between two ferroelectric phases.