Matsushita Electric Industrial Co., Ltd.

Michio Matsuoka

Kazuo Eda

Mikio Matsuura

Seiichi Nakatani

Osamu Makino

Masayuki Sakai

Yoshihiko Nakatani

Nobuji Nishi

Takeshi Masuyama

Yasuharu Kikuchi

Akihiro Takami

Takayuki Kuroda

Masanobu Tanaka

Masanori Inada

Harumasa Kajita

Masatsugu Yamaguchi

Makino Osamu

Eda Kazuo

Kikuchi Yasuharu

Katsuo Nagano

Mikio Ishida

The present invention provides a voltage-dependent resistor of the bulk-type in which zinc oxide (ZnO) powder and additives are admixed to form a sintered body composition having as the main constituent, zinc oxide, and in which the mixture is formed into a resistor body, the body is sintered, and electrodes are applied to the opposite surfaces of the sintered body, the improvement comprising the step of, prior to sintering and admixture with said zinc oxide, admixing all amount of boron oxide (B.sub.2 O.sub.3) with other additives in the form of a borosilicate glass, which is composed of 5 to 30 weight percent of boron oxide (B.sub.2 O.sub.3) and 70 to 95 weight percent of silicon oxide (SiO.sub.2). A process for the production of said resistor is also provided.

Voltage-dependent resistor and method of making the same

A voltage-dependent resistor having at least one zinc oxide (ZnO) layer adjacent to at least one metal oxide layer of bismuth oxide (Bi.sub.2 O.sub.3) and at least one of the members selected from the group consisting of cobalt oxide (Co.sub.2 O.sub.3) manganese oxide (MnO.sub.2) antimony oxide (Sb.sub.2 O.sub.3) and zinc oxide (ZnO).

Voltage-dependent resistor

A voltage-dependent resistor of the layered structure type is provided by employing the nonohmic property of the hetero-junction between a zinc oxide layer and a metal oxide layer consisting essentially of at least one member selected from the group consisting of cobalt oxide, manganese oxide, barium oxide, strontium oxide, lead oxide and rare earth oxides.

A combustible gas detecting element, the sensitive element of which has at least one material selected from the group consisting of gamma-type ferric oxide (.gamma.-Fe.sub.2 O.sub.3) and alpha-type ferric oxide (.alpha.-Fe.sub.2 O.sub.3) and has a microstructure with an average grain size smaller than 0.5 micrometers and a porosity of from 35 to 85%. The sensitivity is increased by adding at least one material selected from a group consisting of tin (Sn) and zinc (Zn) in a ratio from 0.5 to 70 mol %, based on stannic oxide (SnO) and zinc oxide (ZnO) relative to the ferric oxide component. The element is manufactured from fine particles obtained by coprecipitating metallic ions from a solution containing Fe ions and at least one member selected from the group consisting of Sn ions and Zn ions, and the fine particles are pressed and then sintered or are formed into a paste, printed on a substrate and then sintered.

Combustible gas sensor

There is provided a novel combustible gas detecting element and method for production thereof. The element comprises a gas sensing body comprising a sintered body or film of an amorphous semiconductor comprising a metal oxide, a sulfate and halide.

Combustible gas detecting element

Combustible gas detecting element for detecting the concentration of a combustible gas such as isobutane, ethane, propane and hydrogen. It comprises .gamma.-Fe.sub.2 O.sub.3, .gamma.-Al.sub.2 O.sub.3 and at least one of La, Ce, Pr and Nd in terms of La.sub.2 O.sub.3, Ce.sub.2 O.sub.3, Pr.sub.2 O.sub.3 and Nd.sub.2 O.sub.3, respectively. This gas detecting element is an improvement over .gamma.-Fe.sub.2 O.sub.3, and is advantageous for its highly stable load life even under severe conditions of a high temperature and a high humidity and for its high sensitivity to a combustible gas.

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.

This invention provides a humidity sensor having a negative coefficient of resistivity for relative humidity, which comprises 99.99 to 10 mole percent of iron oxide (Fe.sub.2 O.sub.3) and 0.01 to 90 mole percent of at least one member selected from alkali metal oxides, which are lithium oxide (Li.sub.2 O), sodium oxide (Na.sub.2 O), potassium oxide (K.sub.2 O) and cesium oxide (Cs.sub.2 O). The amount of the alkali metal oxide in the sensor is preferably 0.01 to 25 mole percent. This sensor is advantageous because it can accurately detect the changes in humidity and it has a long, stable life.

Humidity sensor

A voltage-dependent resistor comprising a sintered body consisting essentially of ZnO, as a main constituent, and, as additives, bismuth oxide (Bi.sub.2 O.sub.3), titanium oxide (TiO.sub.2) and one or two members selected from the group consisting of aluminum fluoride (AlF.sub.3), chromium fluoride (CrF.sub.3), nickel fluoride (NiF.sub.2) and strontium oxide (SrO) with electrodes applied to the opposite surfaces of the sintered body. This voltage-dependent resistor has a low C-value, a high n-value and a high power dissipation for surge energy and high stability to a high D.C. load. Other additives such as cobalt oxide (CoO), manganese oxide (MnO), barium oxide (BaO), boron oxide (B.sub.2 O.sub.3), chromium oxide (Cr.sub.2 O.sub.3), nickel oxide (NiO) and germanium oxide (GeO.sub.2) improve the voltage nonlinear property of the sintered body.

This invention provides a surge absorber for absorbing surges of electric current. The absorber has a metal oxide varistor hermetically sealed in a hollow insulator by a top and a lower electrical terminal and also has a conductive rod extending substantially downwardly and electrically connected to ground and to the lower electrical terminal by solder and also thermally connected to the metal oxide varistor whereby when the varistor is heated by a surge of an electric current therethrough to a temperature to heat the solder above the melting point of the solder, said conductive rod gets separated from the lower electrical terminal to fall downwardly, thereby stopping the electric current through the metal oxide varistor to ground. The lower electrical terminal is preferably so constructed that a hole is produced therein upon the separation of the conductive rod from the lower electrical terminal for equalizing the atmospheric pressure in the hollow and the pressure of the outside atmosphere, thereby preventing the absorber from exploding.

Surge absorber

A process for making a bulk-type voltage-dependent resistor and more particularly to a varistor comprising a zinc oxide sintered body using heat-treated zinc oxide powder. By heat-treating zinc oxide powder before the sintering step, a bulk-type voltage-dependent resistor is obtainable which is characterized by a high n-value in a region of current higher than 10A/cm.sup.2 and high power dissipation as well as a lower C-value.

Process for making a voltage dependent resistor

A voltage-dependent resistor comprising a sintered body comprising ZnO as a major part and Bi.sub.2 O.sub.3 and GeO.sub.2 as additives with electrodes applied to the opposite surfaces of the sintered body. This voltage-dependent resistor has a low C-value and a high n-value in I=(V/C).sup.n along with high power dissipation for surge energy and high stability to a high D.C. load. Further, other additives such as NiO, Co.sub.2 O.sub.3, MnO, TiO.sub.2 and Cr.sub.2 O.sub.3 can advantageously be added to the sintered body.

Growing community of inventors

Ibaraki, Japan

Michio Matsuoka