Sintering time dependence of varistor properties and aging behavior in Co/Cr/La/Y co-doped ZnO-PrO_(1.83)-based ceramics

摘要

The microstructure, varistor properties, and aging behavior of the Co/Cr/La/Y co-doped ZnO-PrO_(1.83)-based ceramics have been investigated with different sintering times (1 h, 2 h, and 3 h). With increasing sintering time, the densities of sintered pellets increased in the order of 4.97. 5.26, and 5.51 g/cm~3 and the average grain size increased in the order of 4.1, 5.0, and 6.1 μm. The breakdown field decreased from 8953 to 6363 V/cm with the increase of sintering time. The nonlinear coefficient showed a maximum value (68.1) at sintering time of 2 h. Furthermore, the varistor ceramics sintered for 2 h exhibited an excellent stability, in which the variation rates of breakdown field and nonlinear coefficient for aging stress state (0.95E_(1 mA)/150 °C/24 h) are -0.5% and 1.3%, respectively.