Matsushita Electric Industrial Co., Ltd.

Atsushi Iga

Hideyuki Okinaka

Masahiro Ito

Masahiro Itoh

Mitsuaki Oshima

Seiichi Nakatani

Masakazu Tanahashi

Ryoichi Wada

Masatugu Yamaguchi

Yutaka Neichi

Masatake Ayusawa

Toshiaki Yagami

Zinc oxide ceramics and a method for producing the same are provided wherein zinc oxide varistors for low and high voltages having excellent electric characteristics and high reliability upon DC loading and surge can be obtained in high yield by low-temperature sintering. 0.2 to 20 parts by weight of a mixed powder of bismuth oxide, titanium oxide and antimony oxide is treated in advance at a temperature of 850.degree. C. or less. The synthetic powder thus obtained is added to 100 parts by weight of ZnO material powder to produce ceramics. By using the ceramics for a zinc oxide varistor, a zinc oxide varistor for a low or high voltage can be produced in high yield, which can be sintered at a low temperature and is excellent in electric characteristics and reliability upon DC loading and surge. Aluminum is sprayed on both sides of a sintered body so that an aluminum layer is formed. Copper is sprayed on the aluminum layer so that an electrode is formed. A lead wire is bonded to the electrode. Then, portions of the molded bodies other than the lead wire are coated and insulated so that the zinc oxide varistor can be obtained.

Zinc oxide ceramics and method for producing the same

By performing a debinder process before or at the time of firing, and by enhancing a programming rate in the temperature range of 650.degree..about.950.degree. C., the size of particles shows less distribution. Also, when the temperature comprising the particle growth range of 1025.degree..about.1200.degree. C. is maintained for many hours, a zinc oxide varistor having relatively large and uniformly formed particles can be provided. When a zinc oxide varistor compound is fired, a solid solution of zinc oxide spinel is fired at the programming rate of 175.degree. to 500.degree. C./hr in the temperature range comprising the primary phase of from 650.degree. to 950.degree. C., and at the programming rate of 30.degree. to 500.degree. C./hr in the range of from 1250.degree. to 1300.degree. C. Accordingly, a zinc oxide varistor having comparatively large and uniformed formed particles can be obtained. Sintered products obtained in this way show less distribution in operating voltage.

Method of manufacturing zinc oxide sintered compact body

A zinc oxide ceramic and a method for producing the zinc oxide ceramics are provided wherein a zinc oxide varistor for a high voltage which has excellent electric characteristics and great reliability for DC loading and surge can be produced in high yield by performing sintering at a temperature of 750.degree. to 1050.degree. C. At least one of B.sub.2 O.sub.3, Cr.sub.2 O.sub.3, GeO.sub.2, LaO.sub.3, MgO, Nb.sub.2 O.sub.5, Nd.sub.2 O.sub.3, PbO, PrO, Sb.sub.2 O.sub.3, SiO.sub.2, SnO.sub.2, Ta.sub.2 O.sub.5, WO.sub.3 and Y.sub.2 O.sub.3 powders and a Bi.sub.2 O.sub.3 powder are mixed. A mixture thus obtained is heat treated at a temperature of 400.degree. to 700.degree. C. and ground to prepare a synthetic powder. 0.5 to 20 parts by weight of the synthetic powder and 0.1 to 5.0 parts by weight of at least one of CoO, MnO.sub.2 and NiO powders are added and ground for 100 parts by weight of a zinc oxide powder. A binder is added to the ground powder to form a sheet. A silver paste is applied to the surface of the sheet to laminate four sheets. A lamination is integrally sintered at a temperature of 840.degree. C. A zinc oxide varistor of a lamination type comprises an internal silver electrode, an internal silver counter electrode, an effective layer, a noneffective layer, and an external silver electrode.

Zinc oxide ceramics and method for producing the same and zinc oxide

Method for manufacturing a ceramic capacitor having varistor

A magnetic recording and reproducing system having a magnetic switching device of the thin film type which is disposed in a magnetic head and composed of a layer which is made of a magnetic material having a low coercive force and a layer which is made of a magnetic material having a high coercive force both layers are premagnetized by a magnetizing means; the magnetic switching is effected in the magnetic switching device in response to a magnetic recorded signal located on a facing magnetic recording media so that the magnetic switching is detected as a pulse voltage by means of a detecting coil which is wound around the magnetic switching device, so as to thereby generate a reproduced output corresponding to the recorded signal.

Magnetic recording and reproducing system

This invention provides a reducing gas sensor which has a gas sensitive element composed of, as a main constituent, .gamma.-ferric oxide (.gamma.-Fe.sub.2 O.sub.3) and, as an additive, at least one compound in the group of WO.sub.3, MoO.sub.3, SiO.sub.2, GeO.sub.2, Li.sub.2 O, Na.sub.2 O, K.sub.2 O, CaO, SrO, BaO, Eu.sub.2 O.sub.3, La.sub.2 O.sub.3, CeO.sub.2, Al.sub.2 O.sub.3, Ga.sub.2 O.sub.3, In.sub.2 O.sub.3, SnO.sub.2, TiO.sub.2, MgO, NiO, ZnO, Mn.sub.2 O.sub.3 and Cr.sub.2 O.sub.3, a pair of electrodes and a heater element. The .gamma.-ferric oxide is in the form of a thin film, a plate or a thin surface layer on a sintered plate of .gamma.-ferric oxide. The gas sensor of the invention is much improved in the stability during use and also it has a high sensitivity.

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Osaka, Japan

Atsushi Iga