D.C. electrical conductivity and dielectric constant measurements on crystalline K2CO3·1.5 H2O

Abstract

The d.c. electrical conductivity and dielectric constant at 100 kHz of a K2CO3·1.5 H2O crystal grown at 40±1°C have been measured in the temperature range 30–620°C. It has been observed that the conductivity shows two peaks at 190 and 230°C. It also shows changes in slope at 430 and 600°C, during heating. During cooling, the conductivity shows changes in slope at 590, 420 and 260°C. The dielectric constant measurement shows two peaks at 190 and 215°C and some changes at 420 and 600°C. The peaks in electrical conductivity and dielectric constant correspond to the dehydration process. Changes of slopes at ∼ 430 and ∼ 600°C correspond to phase transition and extrinsic to intrinsic transition respectively. During cooling, the presence of an intermediate structure between 420 and 260°C is indicated. The peaks observed in the conductivity and dielectric constant measurements at dehydration temperatures have been explained on the basis of the release of water molecules during dehydration and subsequent dissociation of a fraction of these released water molecules into H+ and OH− ions. Availability of these charged particles increases the conductivity whereas the formation of space charge increases the dielectric constant.