Matsushita Electric Industrial Co., Ltd.

Akihiro Takami

Yasuo Wakahata

Iwao Ueno

Kimio Kobayashi

Masaaki Katsumata

Nobuharu Katsuki

Osamu Kanaya

Keiichi Noi

Kaori Okamoto

Kaori Shiraishi

Kazuhide Ebine

Kimiko Kumazawa

Michio Matsuoka

Takayuki Kuroda

Youichi Ogoshi

Katsuo Nagano

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 comprises 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 comprises 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.

Crystallized glass compositions for coating oxide-based ceramics

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 comprises 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 comprises 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.

Zinc oxide varistor, a method of preparing the same, and a crystallized

A method for manufacturing semiconductor-type laminated ceramic capacitors with a grain boundary-insulated structure including the steps of calcinating starting material of mixed powder in air or in nitrogen atmosphere after grinding, mixing and drying the mixed powder; forming raw sheets; printing a pattern of inner electrode paste on the surface of the raw sheets; calcinating the laminated body in air; sintering the laminated raw sheets in reducing atmosphere or in nitrogen atmosphere after calcination; re-oxidizing in air after sintering; and covering the edges of sintered ceramic sheets with outer electrode paste and baking after re-oxidation, terminals of inner electrodes being exposed to the edges, wherein: the starting material of mixed powder comprises a material of the composition Sr.sub.(1-x) Ba.sub.x TiO.sub.3 containing excess Ti to make a final molecular ratio of Ti to Sr.sub.(1-x) Ba.sub.x in the range of 0.95.ltoreq. Sr.sub.(1-x)Ba.sub.x /Ti&lt; 1.00 (where x is in the range of 0&lt; x.ltoreq. 0.3); a first component of at least one or more kinds of the compounds selected from Nb.sub.2 O.sub.5, Ta.sub.2 O.sub.5, V.sub.2 O.sub.5, W.sub.2 O.sub.5, Dy.sub.2 O.sub.5, Nd.sub.2 O.sub.3, Y.sub.2 O.sub.3, La.sub.2 O.sub.3, or CeO.sub.2 ; a second component of Mn and Si converted into MnO.sub.2 and SiO.sub.2 respectively; and an optional third component of at least one or more kinds of the compounds selected from Na.sub.2 SiO.sub.3, NaAlO.sub.2, Li.sub.2 SiO.sub. 3, LiAlO.sub.2, and Al.sub.2 O.sub.3.

Ceramic capacitor with a grain boundary-insulated structure

A laminated semiconductor ceramic capacitor with a grain boundary-insulated structure comprises a semiconductor ceramic block with a grain boundary-insulated structure, a plurality of Ni inner electrodes and outer electrodes, wherein the Ni inner electrodes are obtained from a paste containing a powder prepared by solubilizing at least one compound containing an atom selected from the group consisting of Li, Na and K into Ni or an Ni containing compound; the Ni inner electrodes are placed in a substantially parallel manner within the ceramic block to reach to the corresponding opposite edges of the ceramic block alternatively one by one; and the outer electrodes are electrically connected to the corresponding edges of the inner electrodes, respectively.

Laminated semiconductor ceramic capacitor with a grain

Semiconductor-type laminated ceramic capacitor with a grain

It is a voltage-dependent non-linear resistance ceramic composition comprising SrTiO.sub.3 as host material, Dy.sub.2 O.sub.3 or Dy.sub.2 O.sub.3 and Nb.sub.2 O.sub.5 or Ta.sub.2 O.sub.5 or Ta.sub.2 O.sub.5 and Nb.sub.2 O.sub.5 as accelerating agent for semiconductorization, thereby changing crystal to a low resistance, and changing crystal boundary to a high resistance. In case Dy.sub.2 O.sub.3 or Dy.sub.2 O.sub.3 and Nb.sub.2 O.sub.5 are used as the accelerating agent for semiconductorization, one kind or more selected from the group consisting of Na, K, Ca, Cd, In, Ba, Pb, Ag, Ce, La, Sc, Y, Cs, Au, Mg, Zr, Sn, Sb, W, Bi, Ni, Fe, Ga, Pt, Tl, Al, Si, Be, Li, Eu, Gd, Tb, Tm, Lu, Th, Ir, Os, Hf and Ru. Alternatively, in case Ta.sub.2 O.sub.5 or Ta.sub.2 O.sub.5 and Nb.sub.2 O.sub.5 are used as the accelerating agent for semiconductorization, one kind or more selected from the group consisting of Na, K, Ca, Cd, In, Ba, Pb, Mg, Zr, Sn, Sb, W, Bi, Eu, Gd, Tb, Tm, Lu, Th, Ir, Os, Hf, Ru, Ga, Pt, Tl, La, Sc, Y, Cs, and Au. As a result, baristor characteristic is obtainable by means of the high resistance at crystal boundaries and capacitor between crystal granules--crystal boundary--crystal granule. From this matter, an element having both functions of the baristor characteristics and the capacitor characteristics are obtainable, and performs effect in surge absorption and noise elimination.

Voltage-dependent non-linear resistance ceramic composition

This is a voltage-dependent non-linear resistance ceramic composition wherein resistance of crystal is decreased by containing SrTiO.sub.3 as host material, and Nb.sub.2 O.sub.5 and Ta.sub.2 O.sub.5 as semiconductorization accelerating agent, and further by adding as additive one kind or more oxide of element selected from the group consisting of MnO.sub.2, Ga, Pt, Tl, Si, Ti, Li, La, Cu, Y, Cs, Au, Mo, S, Be, Al, Na, K, Ca, Cd, In, Ba, Pb, Eu, Gd, Tb, Tm, Lu, Th, Ir, Os, Hf, Ru, Mg, Zr, Sn, Sb and W, these additive is segregated at crystal granule boundaries, thereby making the crystal granule boundaries to high resistance. Accordingly, by the high resistance layer at the crystal boundaries the varistor characteristic is obtainable, and a capacitance characteristic is obtainable between the crystal granule-crystal granule boundary-crystal granule. From this, an element having both functions of the varistor characteristics and the capacitor characteristics are obtainable, and performs effect in surge absorption and noise elemination.

There is provided a voltage-dependent resistor comprising a bulk consisting essentially of zinc oxide as the major part and as additives 0.01 to 10 mol % of Bi.sub.2 O.sub.3, CoO, MnO, TiO and NiO and electrodes on the bulk, said electrodes having been formed by baking a silver paste comprising silver powder and a glass frit on the bulk, said glass frit containing as its principal content 80 to 95% by weight of Bi.sub.2 O.sub.3 and correspondingly 20 to 5% by weight of SiO.sub.2, said glass frit also containing 1 to 5 parts by weight of B.sub.2 O.sub.3 for 100 parts of said principal content. The electrodes can also contain minor amounts of CoO, Sb.sub.2 O.sub.3, a mixture of Sb.sub.2 O.sub.3 with Ag.sub.2 O or MgO, or a mixture of CoO with MgO or Ag.sub.2 O.

Growing community of inventors

Katano, Japan

Akihiro Takami