Murata Manufacturing Co., Ltd.

Ryouichi Urahara

Yukio Sakabe

Akinori Nakayama

Hideaki Niimi

Mitsutoshi Kawamoto

Kazutaka Nakamura

Iwao Fukutani

Kenjiro Hadano

Terunobu Ishikawa

Tsuyoshi Kawada

Satoshi Ueno

Hideaki Nimi

Kuzuhiro Kaneko

The present invention provides barium titanate semiconductive ceramic having low specific resistance at room temperature and high withstand voltage, which fully satisfies the demand for enhancing withstand voltage. The average ceramic grain size of the barium titanate semiconductive ceramic is controlled to about 0.9 &mgr;m or less. By this control, the ceramic possesses low specific resistance at room temperature and high withstand voltage fully satisfying a recent demand for enhancing withstand voltage and may suitably used for applications such as controlling temperature and limiting current, or in exothermic devices for constant temperature. Accordingly, the barium titanate semiconductive ceramic enables an apparatus using the same to have enhanced performance and reduced size.

Barium titanate semiconductive ceramic

The present invention provides a barium titanate-based semiconducting ceramic which exhibits excellent PTC characteristic and which can be fired at a temperature lower than 1000.degree. C. The present invention also provides an electronic element fabricated from the ceramic. The semiconducting ceramic contains, in a semiconducting sintered barium titanate; boron oxide; an oxide of at least one of barium, strontium, calcium, lead, yttrium and a rare earth element; and an optional oxide of at least one of titanium, tin, zirconium, niobium, tungsten and antimony in which the atomic boron is

Semiconductor ceramic and electronic element fabricated from the same

A laminated-type varistor includes a laminated structure and a pair of external electrodes disposed on a surface of the laminated structure. The laminated structure includes effective sintered body layers and internal electrodes. The internal electrodes are connected to the external electrodes and are disposed apart from each other in the direction perpendicular to lamination surfaces. Each of the internal electrodes has a multilayer electrode structure in which a plurality of electrode layers are arranged in layers while an ineffective sintered body layer is disposed therebetween. The laminated-type varistor has increased maximum peak current and maximum energy and reduction in clamping voltage.

Laminated-type varistor

The present invention provides a varistor which has low variation in electric characteristics and enhanced withstand electrostatic voltage and which can be fired at low temperature; as well as a method for producing the same. The laminated varistor comprises a sintered laminate formed by laminating alternating layers of semiconducting ceramic which comprises ZnO as a primary component and at least Bi oxide as a secondary component, and internal electrodes which predominantly comprise Pt and Pd as an inevitable impurity; and external electrodes maintaining electrical contact with the internal electrodes, wherein the Pd content is controlled to be about 0.1 wt. % or less based on the content of Pt, which is a primary component of the internal electrodes.

Material and paste for producing internal electrode of varistor,

A semiconductive ceramic composition having negative resistance-temperature characteristics, wherein the composition comprises lanthanum cobalt oxide as the primary component, and, as secondary components, at least one oxide of an element selected from B, Fe and Al and at least one oxide of an element selected from Si, Zr, Hf, Ta, Sn, Sb, W, Mo, Te, Ce, Nb, Mn, Th and P. A semiconductive ceramic composition having a resistivity of approximately 10 .OMEGA..multidot.cm to 100 .OMEGA..multidot.cm at room temperature is obtained by controlling the amount of additives. Since the resistivity at room temperature can be enhanced to several times or more that of the conventional compositions while characteristics of the conventional compositions are maintained, the composition may be widely applied to control heavy current.

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Yokaichi, Japan

Ryouichi Urahara