Dielectric study of KNbO3 ceramics over a large range of frequency (102-109Hz) and temperature (300-800 K)

Abstract

KNbO3 ceramics were sintered at 1263K thanks to a LiF additive. The ferroelectric-paraelectric transition is of first order and occurs at T c∼670K. A dielectric study in a large frequency range (102-109Hz) shows: – a strong frequency dispersion of the permittivities at low frequency for T > 500 K which comes mainly from conductivity phenomena – a dispersion at high frequency in both ferroelectric and paraelectric regions which comes from a network relaxation of correlation chains of Nb5 + cations. The latter effect was revealed thanks to a new high frequency-high temperature device usable up to 109Hz and 800 K simultaneously.