Sintering effect on varistor properties and degradation behavior of ZVMB varistor ceramics

摘要

ZnO-V_2O_5-Mn_3O_4-Bi_2O_3 (ZVMB) varistor ceramics were sintered at a low temperature range of 800-875 ℃, and the microstructure, electrical properties, dielectric characteristics, and DC-accelerated aging behavior were systematically investigated. Analysis of the microstructure indicated that the average grain size increased from 3.8 to 6.4 μm with the increase of sintering temperature, and the density of the sintered pellets increased from 5.48 to 5.53 g/cm~3 when the sintering temperature was increased from 800 to 850 ℃, and then decreased when the sintering temperature was further increased. The breakdown field noticeably decreased from 13,412 to 706 V/cm with the increase of sintering temperature. The nonlinear coefficient exhibited a maximum value (43.0) at 825 ℃ and a minimum value (19.8) at 875 ℃. The varistors sintered at 850 ℃ exhibited the highest stability; variation rates for the breakdown field and the nonlinear coefficient were —10.3 and -50.2%, respectively, after application of a stress of 0.85 E_(1mA)/85 ℃/24 h.