Abstract: The miorostructure of varistor ceramics based on ZnO-Bi₂O₃-Sb₂O₃BaO systems has been investigated by XRD and EPMA techniques. A new grain boundary phase in which trace Zn tobe, dissolved is found besides the known ZnO,Bizoa and Zn_2.33Sb_0.67O₄ crystal phases, it is the BaSb₂O₆ crystal phase. This phase in grain forms mixes with the dispersed Bi₂O₃ grain boundary phase. With the increase in the amount of barium additive, it increases in amount and grows in grain size, while Zn_2.33Sb_0.67O₄ decreases in amount. It is also found that the long life stability of the varistor ceramics under a loaded voltage is improved due to the change of the composition and the microstructure in the intergranular layer.

Key words: BaSb₂O₆ phase, microanalysis, ZnO varistor ceramics