NEW PHASE-TRANSITION IN FERROELECTRIC (CH3NHCH2COOH)3CACL2 AT LOW-TEMPERATURES

The specific heat of ferroelectric (CH3NHCH2COOH)3CaCl2 has been measu red precisely with an AC calorimeter. Two anomalies of specific heat a re observed: one is associated with a ferroelectric phase transition a t T1 = 130 K and the other is associated with a new phase transition a t T2 = 65 K. This shows the existence of a new low-temperature phase, which probably corresponds to a high-pressure antiferroelectric phase reported previously. Transition entropies are estimated as 2.51 and 1. 16 [J . mol-1 K-1] for phase transitions at T1 and T2, respectively.