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AssigneeMatsushita Electric Industrial Co., Ltd.
InventorsMasaaki Katsumata, Osamu Kanaya, Nobuharu Katsuki, Akihiro Takami
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The present invention relates to a zinc oxide varistor as a characteristic element of an arrestor for protecting a transmission and distribution line and peripheral devices thereof from surge voltage created by lightning, and more particularly a highly reliable zinc oxide varistor excellent in the non-linearity with respect to voltage, the discharge withstand current rating properties, and the life characteristics under voltage, a method of preparing the same, and PbO type crystallized glass for coating oxide ceramics employed for a zinc oxide varistor, etc. A zinc oxide varistor of the present invention includes a sintered body (1) and a high resistive side layer (3) consisting of crystallized glass with high crystallinity containing the prescribed amount of SiO.sub.2, MoO.sub.3, WO.sub.3, TiO.sub.2, NiO, etc., formed on the sides of the sintered body (1) to enhance the strength and the insulating property thereof, thereby improving the non-linearity with respect to voltage, the discharge withstand current rating properties and the life characteristics under voltage. The crystallized glass composition for coating of the present invention includes PbO as a main component and additives such as ZnO, B.sub.2 O.sub.3 , SiO.sub.2, MoO.sub.3, WO.sub.3, TiO.sub.2, and NiO to enhance the crystallinity and the insulating property thereof.
A zinc oxide varistor comprising a sintered body containing zinc oxide as a main component and having varistor characteristics, and a high resistive side layer formed on the sides of the sintered body, the side layer consisting of crystallized glass consisting of 50.0 to 75.0 percent by weight of PbO, 10.0 to 10.0 percent by weight of ZnO, 5.0 to 10.0 percent by weight of B.sub.2 O.sub.3, and 6.0 to 15.0 percent by weight of SiO.sub.2.
A zinc oxide varistor comprising a sintered body containing zinc oxide as a main component and having varistor characteristics, and a high resistive side layer formed on the sides of the sintered body, the side layer consisting of crystallized glass comprising PbO as a main component which contains at least 0.1 to 10.0 percent by weight of molybdenum oxide calculated in terms of MoO.sub.3.
A zinc oxide varistor comprising a sintered body containing zinc oxide as a main component and having varistor characteristics, and a high resistive side layer formed on the sides of the sintered body, the side layer consisting of crystallized glass comprising PbO as a main component which contains at least 0.5 to 10.0 percent by weight of WO.sub.3.
A zinc oxide varistor comprising a sintered body containing zinc oxide as a main component and having varistor characteristics, and a high resistive side layer formed on the sides of the sintered body, the side layer consisting of crystallized glass comprising PbO as a main component which contains at least 0.5 to 10.0 percent by weight of titanium oxide calculated in terms of TiO.sub.2.
A zinc oxide varistor comprising a sintered body containing zinc oxide as a main component and having varistor characteristics, and a high resistive side layer formed on the sides of the sintered body, the side layer consisting of crystallized glass comprising PbO as a main component which contains at least 0.5 to 5.0 percent by weight of nickel oxide calculated in terms of NiO.
Dependencies are inferred from the claim text.