Transactions of Nonferrous Metals Society of China The Chinese Journal of Nonferrous Metals

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Transactions of Nonferrous Metals Society of China

Vol. 28    No. 7    July 2018

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Dielectric characteristics and nonlinear properties of ZnO-polypyrrole composites
Fariba TABRIZI1, Mojtaba PARHIZKAR1, Hassan BIDADI1, Mohammad GHAFOURI2,3

1. Faculty of Physics, University of Tabriz, Tabriz, Iran;
2. Department of Basic Science, Shabestar Branch, Islamic Azad University, Shabestar, Iran;
3. Faculty of Physics, Islamic Azad University of Shabestar, Shabestar, Iran

Abstract:The nonlinear properties and frequency characteristics of ZnO-polypyrrole composites were investigated at 200 Hz- 5 MHz frequency interval with different zinc oxide contents. Samples were prepared using hot press method at 130 °C. Results show an optimum point for breakdown voltage at ZnO content of 70%. Breakdown voltage decreases from 590 to 380 V and after that tends to increase from 450 to 740 V due to the absence of polypyrrole at grain boundaries. No matter how breakdown voltage behaves, nonlinear coefficient increases from 4.2 to 9 by increasing ZnO content because of the increase in acceptor-like states at grain boundaries by increasing ZnO content. The electrical parameters such as dielectric constant, dielectric loss and series resistance of samples show a strong dependence on frequency especially below 1 kHz. These parameters fall off by increasing frequency up to 1 kHz, which is related to charge transportation through the Schottky barrier at grain boundaries. The high dielectric constant of samples below 1kHz is related to the Maxwell-Wagner polarization at grain boundaries. The presence of different anomalies at different frequency intervals is related to interfacial polarization because of different structures of grains and intergranular layer with a huge difference in conductivity.


Key words: dielectric characteristics; electrophysical properties; composite varistor; frequency dependence

ISSN 1004-0609
CN 43-1238/TG

ISSN 1003-6326
CN 43-1239/TG

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