Dielectric Behaviour of KDP and Rochelle Salt Powders

Abstract

The dielectric constant of compressed powders of KDP and Rochelle salt has been measured st 1 MHz as a function of particle sizes ranging from 20µ to 600µ over a wide temperature range to cover ferro and paraelectric phases. Dielectric anomalies indicating the ferroelectric behaviour in both KDP and Rochelle salt powders are observed upto 20µ particle size. The existence of ferroelectricity was further confirmed by observing ferroelectric hysteresis loops. The measured values of the dielectric constant in Rochelle salt were independent of particle size while in KDP they decreased with decreasing particle size. The experimental values are compared with the values calculated by modified Bruggeman's formula. It is found that the agreement in theoretical and experimental values in Rochelle salt was with in 25%. In KDP the agreement between experimental and theoretical values was poor and the measured values were less than 1/4th of the calculated values.