EFFECT OF DC AND AC BIAS FIELDS ON THE DIELECTRIC AND FERROELECTRIC PROPERTIES OF A KTN CERAMIC

Dielectric measurements have been performed on a KTN ceramic with comp osition KTa0.6Nb0.4O3 under various de bias electric fields E. The tem perature and field dependences of epsilon'(r) and tan delta are relate d to the presence of polarization fluctuations. Around T-C, epsilon'(r ) exhibits a nonlinearity following the relationship: epsilon'(r) = C/ (T - T-C) - AE/(T - T-C)(v). The temperature dependence of the polariz ation-electric field hysteresis loops allowed us to determine the temp erature variation of the remanent polarization.