Ferroelectricity and Phase Transitions in Disodium Hydrogen Orthophosphate

Abstract

The variation of dielectric constant versus temperature of disodium hydrogen orthophosphate has been studied from room temperature upto near melting point. It has been found that there are three transition temperatures in the heating cycle at the temperatures 46, 55 and 74 °C. The first two transition temperatures possess a small change in their high dielectric constant values, where as at 74 °C, the dielectric constant attains a tremendous value of 50,900. The cooling cycle shows a broad transition temperature, nearby 56 °C. The results have been explained on the basis of activated polarization process and structural imbalance due to the elimination of water molecules at low temperature (nearly 46 to 55 °C). The occurrence of broad peak in cooling cycle is explained on the basis of relaxor systems which are generally due to heterovalent disorder.