Influence of Dysprosia Addition on Microstructure and Electrical Properties of Praseodymia-based Zinc Oxide Varistors

The microstructure and electrical properties of varistor ceramics, which are composed of Zn-Pr-Co-Cr-Dy-oxide system, were investigated at various dysprosia (Dy2O3) addition contents. The Dy2O3 microstructurally played the role of inhibition for the densification and grain rowth. As the Dy2O3 content increased, the density decreased in the range of 5.51-4.90 g/cm(3), reaching maximum at 0.5 mol% and the average ZnO grain size decreased in the range of 17.7-6.0 mu m. The incorporation of Dy2O3 significantly improved the nonlinear properties of varistors, above 30 in nonlinear exponent, compared with that without Dy2O3. The varistors with the best performance of nonlinear properties was obtained Dy2O3 content of 1.0 mol%, 49 in nonlinear exponent and 0.5 mu A in leakage current.