The Influence of ZnF_2 Doping on the Electrical Properties and Microstructure in Bi_2O_3-ZnO-Based Varistors

摘要

ZnO varistors with different amounts of ZnF_2 from 0.00 to 0.80 mol% were prepared using a solid-state reaction technique, to explore the potential application of ZnO. The F-doping effects on the microstructure and electrical properties of ZnO-based varistors were investigated. The average grain size of ZnO increased from 4.93 to 6.48 μm as the ZnF_2 content increased. Experimental results showed that as the ZnF_2 content increased, the breakdown voltage decreased from 617 to 367 V/mm, and the nonlinear coefficient did not change much. However, a slight increase was observed in the leakage current. Besides, when the ZnF_2 content increased, the donor concentration increased from 0.669 × 10~(18) to 8.720 × 10~(18) cm~(-3). The study indicated that ZnF_2 played a similar role as sintering aids to promote grain growth and the substitutional F atoms in the bulk served as a donor to increase the donor concentration.