Electrical conduction and dielectric studies of ZnO pellets

A series of Zinc Oxide pellets sintered at different temperatures was studied by means of dielectric spectroscopy in the wide frequency range of 1-10(6) Hz and temperature interval from 100 degrees C to 30 degrees C. Electrical conductivity was analysed using Jonsher's universal power law, and the values of s were found to decrease with the increase in temperature, which agrees well with the correlation barrier hopping (CBH) model. As the temperature increased, energy activation E-dc became less than 0.39 eV and dc conductivity (sigma(dc)) values in the range of 1.9 x 10(-14)-9.7 x 10(-10) Omega m(-1) were observed. The dielectric modulus showed ionic polarisation at the intermediate and high frequencies related to oxygen interstitial O-i, oxygen vacancy V-o and Zinc interstitial Zn-i. At low frequency, it revealed a Maxwell-Wagner-Sillars relaxation with barrier heights of grain boundaries between 0.74 and 0.88 eV for all the studied pellets. (C) 2012 Elsevier B.V. All rights reserved.