Effect of Bismuth Content in In-Situ Repair Medium on the Repair Effect of Varistor Based on Simulation

The root cause of the limited energy absorption capability (EAC) of ZnO varistors is the presence of edge open pores, which can be addressed by filling them with an in-situ repair medium (ISRM). Research findings indicate that as the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{Bi}\left(\text{NO}_{3}\right)_{3}$</tex> doping concentration in the ISRM increases, the nonlinearity coefficient, leakage current density, and EAC of varistors after re-sintering initially rise and then decline. When the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{Bi}\left(\text{NO}_{3}\right)_{3}$</tex> doping concentration is less than <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$20 \text{mol} \%$</tex>, the regrain boundary barrier is the primary factor influencing varistor performance. At a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{Bi}\left(\text{NO}_{3}\right)_{3}$</tex> doping concentration of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{2 5 m o l \%}$</tex>, the weakened bonding between the repair layer and the varistor body becomes the dominant factor influencing varistor performance. Doping the ISRM with <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$20 \text{mol} \% \text{Bi}\left(\text{NO}_{3}\right)_{3}$</tex> enables the varistor to absorb up to 19.1 kJ of energy during pressurization, optimizing its EAC. This research offers a novel direction for the advancement of higher-performing varistors.