Effect of B_2O_3 doping on the Microstructure and Electrical Properties of ZnO-based Varistors

摘要

B_2O_3 doped ZnO-Bi_2O_3-Sb_2O_3-based varistors were fabricated by conventional solid state reaction method. The structure and electrical properties were investigated by XRD, SEM and electrical measurements. The grain size obviously increases with increasing B_2O_3 content, while the content of Zn_7Sb_2O_(12) spinel on the grain boundaries gradually decreases, which implies that B_2O_3 doping inhibits the growth of Zn_7Sb_2O_(12) spinel. The density (ρ) of ZnO varistors increases with increasing B_2O_3 content (x) and reaches the maximum at x = 0.4 mol%. The sample with x≈ 0.6 mol% sintered at 1150 °C exhibits the best performance, with nonlinear coefficient of 48 and leakage current of 4 μA.