Impedance and dielectric spectra in zirconia-polypyrrole hybrid nanocomposites

Zirconia (ZrO2) nanoparticles have been synthesized by a novel two-reverse emulsion technique and combined with polypyrrole (PPY) to form ZrO2-PPY nanocomposites. The complex impedance and dielectric permittivity of ZrO2-PPY nanocomposite have been investigated as a function of frequency and temperature for different compositions. The optical band gap of zirconia decreases with increase in polymer concentration. Two electrical responses in the impedance spectra corresponding to the grain and grain boundary effects are analysed by an equivalent circuit. Activation energies are very small (35-70 meV). The samples exhibit a large dielectric constant and at room temperature it becomes about 12 000 at 0.7 KHz for the highest content of zirconia. The high dielectric response is mainly originated by Maxwell-Wagner polarization.