ZINC OXIDE-BASED SINTERED COMPACT AND ZINC OXIDE VARISTOR

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PROBLEM TO BE SOLVED : To obtain zinc oxide varistor which is free from antimony oxide and nevertheless exhibits excellent electric characteristics although the addition of antimony oxide, a toxic material, has been heretofore essential to give excellent surge absorption characteristics to bismuth oxide-containing type zinc oxide varistor. SOLUTION : Chromium oxide combined synthetic powder is prepared by adding an oxide of at least one kind of elements selected from the group of Bi, B, Si and rare earth elements into chromium oxide. The zinc oxide-based sintered compact is obtained at least by adding at least 0.05 to 5.0 pts.wt. chromium oxide combined synthetic powder, 0.1 to 10.0 pts.wt. oxide of at least one kind of element selected from a group comprising Ti, Sn, zircon, Nb, Ta, V, Mo, W, Si and rare earth metals and 0.5 to 7.0 pts.wt. compound of at least one kind of element selected from a group comprising an oxide of Bi, Co, Mn, Ni and B, boric acid and an Al salt into 100 pts.wt. zinc oxide, mixing the resultant blend and forming the resultant mixture and then firing the mixture at 700 to 980 °C and cooling the fired mixture.