Influence of Ag doping on the microstructure and electrical properties of ZnO-Bi₂O₃-based varistor ceramics

Long-Biao Zhu1),Da-yang Chen2,3),Xin-xin Wu3),Qing-dong Zhong2),Yu-fa Qi3),and Li-yi Shi3) 1) Mechanical Engineering College,Nantong University,Nantong 226007,China 2) Key Laboratory of Modern Metallurgy and Material Processing,Shanghai 200072,China 3) Research Center of Nano Science and Technology,Shanghai 200444,China

摘 要：Silver in the form of AgNO3 was added to ZnO-based varistor ceramics prepared by the solid-state reaction method.The effects of AgNO3 on both the microstructure and electrical properties of the varistors were studied in detail.The optimum addition amount of AgNO3 in ZnO-based varistors was also determined.The mechanism for grain growth inhibition by silver doping was also proposed.The results indicate that the varistor threshold voltage increases substantially along with the AgNO3 content increasing from 0 to 1.5mol%.Also,the introduction of AgNO3 can depress the mean grain size of ZnO,which is mainly responsible for the threshold voltage.Furthermore,the addition of AgNO3 results in a slight decrease of donor density and a more severe fall in the density of interface states,which cause a decline in barrier height and an increase in the depletion layer.

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