Temperature dependence of electric and dielectric behaviors of Ni/polyvinylidene fluoride composites

Composites of polyvinylidene fluoride (PVDF) filled with metallic particles of nickel (Ni) were prepared via a blending and hot-molding technique. Rescaled temperature dependence of electric and dielectric behaviors of Ni/PVDF composites were studied at wide content ranges. Results show that there is significant positive temperature coefficient effect and giant dielectric constant as the concentration of Ni is near the percolation threshold. The nonuniform distribution of filler particles in PVDF host is observed from the scanning electron microscope micrograph since they are aggregated in amorphous regions of PVDF and form a network of conducting chains. Two relaxation peak regions of dielectric constant are observed from -10 to 40 degrees C and from 100 to 150 degrees C, which can be attributed to the contribution of polar effect of PVDF. The percolation theory, the thermal expansion model, and the simple concept of polarization in the capacitors are employed to explain these experimental results.