抄録
Antiferroelectric properties of Cu(HCOO)24H2O and Cu(HCOO)24D2O were investigated experimentally. Dielectric constant as a function of temperature shows a behavior of the first order transition with a large discontinuity at the transition. The transition point is shifted from −37.7°C for hydrogenous crystal to −27.7°C by deuterium substitution. The Curie-Weiss constant for dielectric constant above the transition is 3.1×104°C in both crystals. Typical double hysteresis loop was observed in the antiferroelectric phase under a pulsive sinusoidal electric field. From the double loops at various temperatures, critical field to induce a forced transition and spontaneous polarization of sublattice as function of temperature were obtained. The critical field shows a linear dependence on temperature and it stays finite at the transition point. The spontaneous polarization is almost constant of 6 μ coul/cm2 and shows discontinuous vanishing at the transition point. This value agrees well to the calculated value from the transition entropy.
