Impact of calcination on low-temperature sintered Bi 2 O 3 varistors: Varistor properties and surge current absorption

This study investigated the effects of calcination on the densification, microstructure, varistor properties, and surge current absorption capability of low-temperature sintered ZnO-Bi 2 O 3 -Sb 2 O 3 -Co 3 O 4 -Mn 3 O 4 -Nb 2 O 5 varistors. The ZnO, Co 3 O 4 , and Mn 3 O 4 were premixed and calcined at various temperatures to reduce grain resistance and improve surge absorption capacity. Calcination at 600 degrees C and 800 degrees C, compared to 1000 degrees C and no calcination, enhanced the surge absorption capacity, attributed to reduced grain resistivity. The introduction of trivalent Co and Mn in place of Zn 2+ ions, notably in the 600 degrees C-calcined samples, increased donor concentration and reduced grain resistivity. Conversely, the 1000 degrees C-calcined samples exhibited higher Schottky barriers and lower leakage currents due to increased adsorbed oxygen interacting with Co 2+ and Mn 2+ ions.