Dielectric Properties and Defect Chemistry of WO3-Doped K0.5Na0.5NbO3 Ceramics

The dielectric properties and conductivity behavior of WO3-doped K0.5Na0.5 NbO3 ceramics were investigated as a function of temperature (25A degrees C to 600A degrees C) and frequency (40 Hz to 10(6) Hz). The dielectric loss and direct-current (DC) conductivity of the ceramics depend strongly on the tungsten content. A high-temperature dielectric relaxation near temperature of 500A degrees C was observed and analyzed using the semiempirical complex Cole-Cole equation. The activation energy of the dielectric relaxation was estimated to be similar to 2 eV and increased with increasing WO3. The frequency-dependent conductivity can be well described by the universal dielectric response law. The activation energy obtained from the DC conductivity changes from 0.93 eV to 1.49 eV. A possible mechanism for the high-temperature dielectric relaxation and conductivity is proposed based on the activation energy value and defect compensation.