Ac-conductivity and dielectric response of new zinc-phosphate glass/metal composites

• Composites of ZnO-P2O5/metal were investigated by impedance spectroscopy.
• Original ac-conductivity behavior was discovered in ZnO-P2O5/metal composites.
• High dielectric constant is measured in ZnO-P2O5/metal composites.
• Dielectric constant as filler function is well interpreted with percolation theory.
• Observed relaxation processes are well described using electric modulus formalism.

The ac-conductivity and dielectric response of new composites based on zinc-phosphate glass with composition 45 mol%ZnO–55 mol%P2O5, filled with metallic powder of nickel (ZP/Ni) were investigated by impedance spectroscopy in the frequency range from 100 Hz to 1 MHz at room temperature. A high percolating jump of seven times has been observed in the conductivity behavior from low volume fraction of filler to the higher fractions, indicating an insulator – semiconductor phase transition. The measured conductivity at higher filler volume fraction is about 10−1 S/cm and is frequency independent, while, the obtained conductivity for low filler volume fraction is around 10−8 S/cm and is frequency dependent. Moreover, the elaborated composites are characterized by high dielectric constants in the range of 105 for conductive composites at low frequencies (100 Hz). In addition, the distribution of the relaxation processes was also evaluated. The Debye, Cole-Cole, Davidson–Cole and Havriliak–Negami models in electric modulus formalism were used to model the observed relaxation phenomena in ZP/Ni composites. The observed relaxation phenomena are fairly simulated by Davidson–Cole model, and an account of the interpretation of results is given.

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