FERROELECTRIC PHASE TRANSITION IN SODIUM DIHYDROGEN ORTHOPHOSPHATE

Ferroelectric transition and variation of dielectric constant with temperature in a compound is very important for the better application of the materials. In the present work we have studied the variation of dielectric constant with temperature of Sodium Dihydrogen Orthophosphate. During our investigation it is found that the temperature variation of the dielectric constant in heating cycle shows a very sharp jump in the dielectric constant, where the compound attains value from its value of 5600 to 42000 at 0the temperature of 42C (Fig. 1 & 2) which again falls in temperature range of 46 C to 51C. The cooling curve has nearly same nature, but has moderately low value of dielectric constant and also the peaks are less sharp. Sharp rise in the dielectric constant have been explained on the basis of activated polarization process and ferroelectric 0 0transition at 46 C while the initial fluctuations in dielectric constant between 27 C to 46 0C is due to the structural imbalance occurred by the elimination of water molecule from the compound. The occurrence of broad peak in is explained on the basis of relaxor systems which are generally due to heterovalent disorder. In the cooling cycle slight deviation in result have been explained on the basis of hysteresis and prolonged heating (annealing) of the specimen, as the annealing also shifts the transition temperature.