Space-charge relaxation and electrical conduction in K0.5Na0.5NbO3 at high temperatures

Sodium potassium niobate K0.5Na0.5NbO3(KNN) ceramic was synthesized by a solid-state technique. The X-ray diffraction of the sample at room temperature showed a monoclinic phase. The real part (epsilon') and imaginary part (epsilon aEuro(3)) of dielectric permittivity of the sample were measured in a frequency range from 40 Hz to 1 MHz and in a temperature range from 350 to 850 K. The epsilon' deviated from Curie-Weiss law above 702 K, due to additional dielectric contributions resulting from universal dielectric response and thermally activated space charges at high temperatures. This anomaly arose from a Debye dielectric dispersion that slowed down following an Arrhenius law. We have established a link between the dielectric relaxation and the conductivity.