Effect of Y2O3 and CeO2 co-doping on microstructure and electrical properties of ZnO-Bi2O3-based varistors

ZnO-Bi 2 O 3 -based varistors co-doped with Y 2 O 3 and CeO 2 were prepared by the solid-phase sintering method. The phase composition, microstructure, and elemental distribution of ZnO varistors were characterized by XRD , FE-SEM, and EDS. The relationship between microstructure and electrical properties of ZnO varistors is analyzed. The experimental results show that Y 2 O 3 and CeO 2 improve the voltage gradient and nonlinear coefficient through synergistic interaction. At the doped ratios of 0.20 mol% Y 2 O 3 and 0.08 mol% CeO 2 , the best comprehensive electrical properties of ZnO varistors can be obtained with voltage gradient E 1 mA = 319 V/mm, leakage current density J L = 0.67 μA·cm −2 , nonlinear coefficient α = 36, residual voltage ratio K = 1.79, and aging coefficient K ct = 0.860. • High gradient ZnO varistors with excellent comprehensive properties were prepared by doping rare earth elements Y and Ce. • Rare earth element Y is mainly distributed in the grain boundary layer of ZnO varistors to inhibit the growth of ZnO grains, and the voltage gradient is increased. • CeO 2 doping can effectively improve the barrier height, donor concentration, and interface state density of the ZnO varistor, resulting in nonlinear coefficient enhancement. • The best comprehensive properties of ZnO varistors prepared by the co-doping of 0.20 mol% Y 2 O 3 and 0.08 mol% CeO 2 are obtained.