FERROELECTRIC ACTIVITY ON ORGANIC-CRYSTAL TRICHLOROACETAMIDE

Dielectric constants and D-E hysteresis loops have been measured on trichloroacetamide (TCAA) single crystals. Only along the crystallographic b-axis are remarkable dielectric anomalies found at T(C) = 354.6 K and T(I) = 356.9 K upon heating. The Curie-Weiss relation holds in the high-temperature phase with a very small Curie constant of about 5.6 K. Typical ferroelectric D-E hysteresis loops are observed only in a limited temperature range of a few degrees just below T(C); the spontaneous polarization P(s) and the coercive field E(c) are estimated to be about 0.2-mu-C/cm2 and 4 kV/cm, respectively, at 350 K. Since the E(c) steeply increases with decreasing temperature, it is difficult to reverse the P(s) at room temperature. Some discussions are presented for the causes of the weak ferroelectricity on TCAA.