Effect of Dy2O3 addition on microstructure, electrical properties, and aging behavior of ZnO–V2O5–MnO2–CoO varistor ceramics

The microstructure, electrical properties, and aging behavior of ZnO–V2O5–MnO2–CoO–Dy2O3 varistor ceramics were investigated for different contents of Dy2O3. The microstructure consisted of ZnO grain as a main phase and secondary phases such as Zn3(VO4)2, ZnV2O4, and DyVO4. The average grain size increased from 7.6 to 10.1 μm and the sintered density slightly increased from 5.53 to 5.57 g/cm3 with the increase of Dy2O3 content. The varistor ceramics added with 0.05 mol% Dy2O3 exhibited the most nonlinear properties, with nonlinear coefficient of 30, and the highest stability against DC-accelerated aging stress. The Dy2O3 acted as an acceptor due to the decrease of donor density in the range of 2.73 × 1018/cm3 to 1.28 × 1018/cm3.