烧结条件对Co_2O_3掺杂ZnO基陶瓷压敏电阻电性能的影响

Electrical properties of sintering condition on Co_2O_3-doped ZnO Varistors

利用固相反应法制备Co2O3掺杂ZnO—Bi2O3-TiO2-MnO2系低压压敏陶瓷，系统研究掺杂量、烧结温度和时间对压敏陶瓷结构、压敏电压梯度、漏电流密度和非线性系数的影响．结果表明：Co2O3掺杂量摩尔分数为1．0％，烧结温度为1200℃，烧结时间为5h时过压保护综合性能最好，其压敏电压梯度为17．1V／mm，非线性系数为15．7，漏电流密度为0．34μA／mm2；ZnO压敏陶瓷电阻由晶粒界面电阻和晶粒内禀电阻组成，当外加电压低于临界电压时，陶瓷样品表现为大电阻，且电压对电阻影响不明显，约为7×104^Ω，主要由界面电阻贡献；当外加电压高于压敏临界电压时，界面被击穿，陶瓷样品电阻突然减小至～10Ω，表现为晶粒内禀电阻特性．

Co2O3-doped ZnO-Bi2O3-TiO2-MnO2 varistors were prepared by solid-state reaction method. Influences of doping content, sintering temperature and holding time on the structure, breakdown voltage gradient, leakage current density and nonlinear coefficient of ZnO systems were discussed.As a result, when the Co2O3 doping content was 1 tool% with the sintering temperature of 1 200 ℃ and holding time of 5 h, the electrical properties were the best. And the breakdown voltage gradient, the nonlinear coefficient and the leakage current density were 17.1 V/mm, 15.7 and 0.34 μA/mm2 respectively.Besides, the resistances of ZnO systems were found to be formed by grain boundaries and grain bulk.As the applied voltage was lower than the threshold voltage, the varistors showed high resistances of -7 × 104^Ω which was independent of the loading voltage and thought to be related with grain boundaries.Otherwise, when the applied voltage was higher enough to break the grain boundaries, the resistance of ZnO ceramics would reduce to -10 Ω which was originated with the grain bulk.