Microstructure and electrical properties of ZnO–Pr6O11–Bi2O3-based varistor ceramics with sintering changes

The effect of sintering temperature on microstructure, electrical properties, and dielectric characteristics of the ZnO–Pr 6 O 11 –Bi 2 O 3 -based varistor ceramics was systematically investigated. When the sintering temperature increased, the average grain sizes increased from 1.7 to 4.9 μm, and the densities of the sintered pellets increased from 5.45 to 5.83 g/cm 3 until the sintering temperature is 1200 °C. When the sintering temperature increased from 1100 to 1150 °C, the breakdown field decreased sharply from 24.6 to 5.1 kV/cm, and the non–ohmic coefficient decreased sharply from 75.0 to 8.6. When the sintering temperature exceeded 1150 °C, the breakdown field decreased to 3.1 kV/cm at 1250 °C, and the non-ohmic coefficient was roughly 10, and then almost not affected by the sintering temperature. The dielectric constant increased from 115.7 to 896.9 with the increase of sintering temperature.