Evidence for Weak-Ferroelectricity of (NH₄)₂ZnCl₄ in the Phase between Ferro- and Antiferro-Electric Phases

Abstract

The dielectric properties of (NH 4 ) 2 ZnCl 4 near the ferroelectric transition temperature were studied. The dielectric constant along the a axis shows a step-wise anomaly at -4.5°C and kinks at 3°C and 46°C. It was found that (NH 4 ) 2 ZnCl 4 in a narrow temperature range from -4.5°C to 3°C, that is, between ferroelectric and antiferroelectric phases is weak-ferroelectric. Spontaneous polarization is 0.005 µC/cm 2 at about -3°C in comparison with 0.36 µC/cm 2 at about -120°C in the ferroelectric phase.