Structural, nonlinear electrical characteristics, and stability against DC-accelerated aging stress behavior of Er-doped 20 nm ZnO-Bi₂ O₃ -Mn₂ O₃ -based varistors

In this research, ZnO-Bi₂ O₃ -Mn₂ O₃ varistors manufactured from 20 nm ZnO powder and doped with different amounts of Er₂ O₃ were fabricated via the conventional ceramic processing method. The effect of various Er₂ O₃ concentrations (0.5-2.0 mol%) on the sintered density, structural improvement, and nonlinear behavior of the 20 nm ZnO-Bi₂ O₃ -Mn₂ O₃ varistors was discussed. Different Er₂ O₃ concentrations exerted considerable influence on the varistors. The addition of large amounts of Er₂ O₃ led to the inhibition of grain growth by increasing the amount of the Er₂ O₃ -rich spinel phase. X-ray diffraction analysis showed that the addition of Er₂ O₃ to the varistor systems led to the development of Er₂ O₃ -rich phases during sintering. During sintering, the considerable surface area of the nanoparticle powder resulted in numerous interactions in the surfaces of the ceramics manufactured from 20 nm ZnO powder. The electrical behaviors of the varistors were substantially influenced by Er₂ O₃ . E_1 mA evidently increased from 2,144.7 to 5,482.2 V/mm with the increment in doping amount. The nonlinear coefficient also dramatically increased with the increase in Er₂ O₃ content. The ZnO nanoparticle-Bi₂ O₃ -Mn₂ O₃ varistors doped with 1.0-2.0 mol% Er₂ O₃ possessed high voltage and nonlinearity and were stable against DC-accelerated aging stress.