Relaxor like colossal dielectric constant in CoWO sub(4) and CoWO sub(4) /PbWO sub(4) nanocomposites

Abstract

Dielectric constant epsilon' and dielectric loss epsilon" were measured in the frequency range of 500 Hz-3 MHz from room temperature (RT) to 350 degrees C for CoWO sub(4) and CoWO sub(4)/PbWO sub(4) nanocomposites sintered at 600 degrees C. Dielectric constant was found to be higher for nanocomposite samples as compared to CoWO sub(4) sample and was maximum for Pb/Co ratio optimal value of 0.028. Relaxor like anomaly and colossal dielectric constants were observed above RT due to Maxwell-Wagner effect without structural and phase transition of the materials. Relaxor like properties for these materials were confirmed by Vogel-Fulcher and modified Curie-Weiss laws. However the samples sintered at 1000 degrees C do not show relaxor like behaviour and exhibit low dielectric constant epsilon' at RT as compared to those sintered at 600 degrees C. P-E curve depicts the weak ferroelectric nature of the samples.