Frequency and temperature dependent dielectric and conductivity behavior of KNbO3 ceramics

Abstract

Dielectric and conductivity measurements were carried out on the potassium niobate ceramics both as a function of temperature (50 to 550 °C) and frequency (102 to 106 Hz). A low-frequency dielectric relaxation in the temperature range of 100 to 200 °C is observed and analyzed with the Cole–Cole function. The activation energy of dielectric relaxation is estimated to be 0.84 eV. Frequency dependent conductivity data are analyzed with an augmented Jonscher relation. Potassium niobate exhibits universal conductivity behavior. Activation energies obtained for the dc conductivity and the hopping frequency are 1.01 and 0.94 eV, respectively. A possible mechanism for both the low-frequency dielectric relaxation and the frequency dependent conductivity is proposed based on activation energies and off stoichiometry of KNbO3, which is resulted due to potassium oxide evaporation during preparation processes.