Ngk Insulators, Inc.

Kunio Ohira

Osamu Imai

Ritsu Sato

A ZnO.sub.2 voltage non-linear resistor excellent in all characteristics of life under electrical stress, current impulse withstandability, discharge voltage ratio, change rate of discharge voltage after application of current impulse and moisture absorbency contains, as additive ingredients: 0.4-1.5 mol. % bismuth oxides as Bi.sub.2 O.sub.3, 0.3-1.5 mol. % cobalt oxides as Co.sub.2 O.sub.3, 0.2-1.0 mol. % manganese oxides as MnO.sub.2, 0.5-1.5 mol. % antimony oxides as Sb.sub.2 O.sub.3, 0.1-1.5 mol. % chromium oxides as Cr.sub.2 O.sub.3, 0.4-3.0 mol. % silicon oxides as SiO.sub.2, 0.5-2.5 mol. % nickel oxides as NiO, 0.001-0.05 mol. % aluminum oxides as Al.sub.2 O.sub.3, 0.0001-0.05 mol. % boron oxides as B.sub.2 O.sub.3, 0.0001-0.05 mol. % silver oxides as Ag.sub.2 O, and 0.0005-0.1 mol. % zirconium oxides as ZrO.sub.2, which bismuth oxides contain 30 wt. % of a .gamma.-type crystalline phase. A small-sizable ZnO.sub.2 voltage non-linear resistor having a higher varistor voltage in addition to the above characteristics contains, as additive ingredients: 0.3-1.5 mol. % bismuth oxides as Bi.sub.2 O.sub.3, 0.3-1.5 mol. % cobalt oxides as Co.sub.2 O.sub.3, 0.2-1.5 mol. % manganese oxides as MnO.sub.2, 0.5-1.5 mol. % antimony oxides as Sb.sub.2 O.sub.3, 0.1-1.5 mol. % chromium oxides as Cr.sub.2 O.sub.3, 4.0-10.0 mol. % silicon oxides as SiO.sub.2, 0.5-2.5 mol. % nickel oxides as NiO, 0.001-0.05 mol. % aluminum oxides as Al.sub.2 O.sub.3, 0.0001-0.05 mol. % boron oxides as B.sub.2 O.sub.3, 0.0001-0.05 mol. % silver oxides as Ag.sub.2 O, and 0.0005-0.1 mol % zirconium oxides as ZrO.sub.2, which bismuth oxides contain 30 wt. % of a crystalline .gamma.-type phase.

Voltage non-linear resistor

An excellent voltage non-linear resistor for use in a gapped lightning arrestor having a composition containing 1 0.5-1.2 mole % of bismuth oxide calculated as Bi.sub.2 O.sub.3, 2 0.3-1.5 mole % of cobalt oxide calculated as Co.sub.2 O.sub.3, 3 0.2-0.8 mole % of manganese oxide calculated as MnO.sub.2, 4 0.5-1.5 mole % of antimony oxide calculated as Sb.sub.2 O.sub.3, 5 0.1-1.5 mole % of chromium oxide calculated as Cr.sub.2 O.sub.3, 6 0.6-2.0 mole % of silicon oxide calculated as SiO.sub.2, 7 0.8-2.5 mole % of nickel oxide calculated as NiO, 8 0.004-0.04 mole % of aluminum oxide calculated as Al.sub.2 O.sub.3, 0.0001-0.05 mole % of boron oxide calculated as B.sub.2 O.sub.3 , 10.circle.  0.001-0.05 mole % of silver oxide calculated as Ag.sub.2 O, and 11.circle.  the rest of zinc oxide, 12.circle.  a limited current of 250-350 V/mm at a current density of 0.1 A/cm.sup.2 calculated per unit thickness of the sintered resistor, 13.circle.  a limited current ratio of V.sub.0.1A /V.sub.0.1mA of 1.2-1.7 at current densities of 0.1 A/cm.sup.2 and 0.1 mA/cm.sup.2, and 14.circle.  a deterioration rate of limited current of not more than 3% at a current density of 0.1 A/cm.sup.2 before and after applying twice a lightning surge current (4/10 .mu.s wave form) of 5 KA/cm.sup.2 per unit surface area.

Growing community of inventors

Ama, Japan

Kunio Ohira