Specific Heat Anomaly of Ferroelectric Cadmium Niobate at the Curie Temperature

The anomalous specific heat of ferroelectric ${\mathrm{Cd}}_2$ ${\mathrm{Nb}}_2$ ${\mathrm{O}}_7$ has been measured in the region of its Curie temperature, $T_c=193\mathrm{}°$K, using a vacuum adiabatic calorimeter. The values of the transition energy and the transition entropy change are 18±2 cal/mole and 0.09±0.01 cal/°K-mole, respectively. A comparison between the experimental values of the transition entropy change, the spontaneous polarization, and the Curie constant is made.