Low-Temperature Phase Transitions of an Organic Ferroelectrics, Phenazine–Chloranilic Acid

The heat capacity of a ferroelectrics consisting of two organic components having a centrosymmetric molecular shape, phenazine–chloranilic acid, was precisely measured by adiabatic calorimetry below room temperature. The paraelectric–ferroelectric phase transition was detected at 248 K as a heat capacity anomaly. The excess entropy involved is consistent with the previously assumed displacive nature. In addition to the ferroelectric phase transition, two phase transitions were observed in heat capacity and dielectric constant at 136 and 146 K.