Effect of Fe2O3 Dopant on Electronic Densities and Electrical Properties of ZnO-Based Varistors

The effect of the Fe2O3 dopant on the electronic densities and the electrical properties has been studied in a ZnO-Bi2O3-SnO2-Co2O3-MnO2-TiO2-Ni2O3-Fe2O3 system by the measurements of positron lifetime spectra, coincidence Doppler broadening spectra and current-voltage characteristics. The results show that the 3d electron signal in the spectrum of the varistor increases with the Fe2O3 content. The addition of small amount of Fe2O3 into the ZnO-based varistor leads to an increase in the donor concentration in the bulk and the defects in the varistor. As the Fe2O3 content increased, the threshold voltage (VT) and the nonlinear coefficient (α) of the varistor decreased monotonously.