Study on the Effect of NiO Addition on the Current Carrying Performance of ZnO varistors

In this paper, the effects of different NiO content doping on the comprehensive electrical properties of ZnO varistors, especially the current carrying capability, were investigated. The results show that the comprehensive electrical properties are better when the NiO content is 0.96 mol%, with a voltage gradient of 260.18 V/mm, a leakage current of
$k$
, a nonlinear coefficient of 64.42, a residual voltage ratio of 1.63, a 42 mm sample in diameter can pass an 450 A 2 ms square impulse for 18 times, a current carrying capacity of 32.5 A/cm
²
, and an energy The energy absorption capacity of 276.9 J/cm
³
. The relationship between the microstructure and macroscopic electrical properties of ZnO varistor under different NiO doping was investigated and analyzed by measuring the phase composition, microstructure, grain boundary parameters and impedance spectrum of ZnO varistor samples. It is indicated that appropriate NiO doping improves the nonlinearity and residual voltage ratio. Because NiO enters the ZnO grains to form substitution defects, releases the compressive stress generated by interstitial A13+ ions, and allows more A13+ ions to enter the ZnO grains, lowering the grain resistance and the donor concentration of the grain boundary, and raising the grain boundary barrier. Macroscopically, it improves the current carrying capability of the ZnO varistor.