Dielectric properties of Li_0.4K_0.6NbO₃ crystal

Abstract

Dielectric constants and spontaneous polarization of Li_0.4K_0.6NbO₃-LKN are measured, including the ferroelectric phase transition temperature. The shape of the dielectric spectra looks more like a second order but it shows a thermal hysteresis in the heating and cooling cycles. The Curie range of LKN is wider than that of the relaxors PMN and SBN. Dielectric constants do not obey Devonshire's law. Complex impedance and dielectric constants have been studied in the frequency domain at several temperatures. A strong low frequency dielectric dispersion below 1kHz is revealed in the high temperature range. The normalized behavior of the complex dielectric constants satisfies the universal dynamic response with its power exponent of n=0.04. In the high frequency region, the complex impedance is described by a modified Cole-Cole arc.