Doping Effect of Alkali Ions on the Microstructural and Electrical Properties of ZnO-Pr6O11-Based Varistor Ceramics

Abstract

The microstructural and electrical properties of ZnO-Pr6O11-based ceramics fabricated with 97.5mol% ZnO + 0.5mol% Pr6O11 + 1.0mol% Co3O4 + 0.5mol% Cr2O3 + 0.5mol% MNO3 (M=Li, Na, K, or Rb) were investigated. Scanning electron microscopy analysis revealed that the doping of alkali ions would inhibit the growth of ZnO grains in the as-prepared ZnO-Pr6O11-based ceramics, in which the addition of K+ ion showed the strongest effect. Through the analysis of electric field vs current density characteristics, it was found that the doping of Li+ ion into ZnO-Pr6O11-based ceramics would change the varistor into ohmic resistor, but the addition of Na+, K+ or Rb+ ion could improve the nonlinearity of the varistors, in which the addition of K+ ion resulted in the strongest improving effect.