Relaxor like colossal dielectric constant in CoWO₄ and CoWO₄/PbWO₄ nanocomposites

Dielectric constant ε′ and dielectric loss ε″ were measured in the frequency range of 500 Hz–3 MHz from room temperature (RT) to 350 °C for CoWO₄ and CoWO₄/PbWO₄ nanocomposites sintered at 600 °C. Dielectric constant was found to be higher for nanocomposite samples as compared to CoWO₄ 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 °C do not show relaxor like behaviour and exhibit low dielectric constant ε′ at RT as compared to those sintered at 600 °C. P–E curve depicts the weak ferroelectric nature of the samples.