Microstructure and varistor properties of Y2O3-doped ZnO–Pr6O11–CoO–Cr2O3–La2O3 ceramics

The microstructure, electrical properties, and aging behavior of Y2O3–doped ZnO–Pr6O11–CoO–Cr2O3–La2O3 varistor ceramics have been systematically investigated for different amounts of Y2O3. As the amount of Y2O3 increased, the sintered density increased from 4.97. 5.18, and 5.20 g/cm3 and the average grain size decreased from 4.1, 3.9, and 3.7 μm. The breakdown field increased from 8953 to 9731 V/cm with an increase in the amount of Y2O3. The varistor ceramics doped with 0.5 mol% in the amount of Y2O3 exhibited the highest nonlinear coefficient of 60.9. The varistor ceramics doped with 1.0 mol% in the amount of Y2O3 exhibited a surprisingly excellent stability by exhibiting –0.5% in the variation rate of the breakdown field and 2.5% in the variation rate of the nonlinear coefficient for aging stress of 0.95 EB/150 °C/24 h.