Varistor characteristics of vanadium oxide-doped zinc oxide ceramics modified with bismuth oxide

The effect of Bi₂O₃ on microstructure, electrical properties, dielectric characteristics, and aging behavior vanadium oxide-doped zinc oxide varistor ceramics was systematically investigated. Analysis of the phase indicated that the ceramics modified with Bi₂O₃ consisted of ZnO grain as a main phase and a few secondary phases such as Zn₃(VO₄)₂, ZnV₂O₄, BiVO₄, V₂O₅, and Mn-rich phase. The average grain size increased from 5.6 to 7.2 μm and the sintered density decreased in the range of 5.51–5.37 g/cm³ up to 0.05 mol%, whereas a further addition increased it to 5.40 g/cm³ at 0.25 mol%. The breakdown field decreased from 4,874 to 2,205 V/cm with an increase in the amount of Bi₂O₃. The ceramics added with 0.025 mol% Bi₂O₃ were characterized by a surprisingly high nonlinear coefficient (60) and very low leakage current density (20 μA/cm²). Bi atoms in the bulk acted as a donor to increase the electron concentration with an increase in the amount of Bi₂O₃.