Sintering effect on ageing behavior of rare earths (Pr6O11-Er2O3-Y2O3)-doped ZnO varistor ceramics

The electrical properties and ageing behavior of the rare earths (Pr6O11-Er2O3-Y2O3)-doped ZnO varistor ceramics were systematically investigated at sintering temperature range of 1335–1350 °C. With an increase in the sintering temperature, the sintered density increased from 5.41 to 5.64 g/cm3 and the average grain size increased from 5.8 to 7.9 μm. The varistor properties and ageing behavior were significantly affected by small sintering temperature range of 1335–1350 °C. The breakdown field noticeably decreased from 5767 to 3628 V/cm with an increase in the sintering temperature. The varistor ceramics exhibited the highest nonlinear coefficient (43.2) at the sintering temperature of 1340 °C. The varistor ceramics sintered at 1350 °C exhibited a surprisingly excellent stability by exhibiting 0.3% in the variation rate of the breakdown field and 0.3% in the variation rate of the nonlinear coefficient for ageing stress of 0.95 E1mA/150 °C/24 h.