Murata Manufacturing Co., Ltd.

Akinori Nakayama

Yukio Sakabe

Atsushi Kishimoto

Hayato Katsu

Masato Goto

Terunobu Ishikawa

Naoaki Abe

Satoshi Ueno

Yasunobu Yoneda

Kazutaka Nakamura

Hideaki Niimi

Ryouichi Urahara

Hiroshi Takagi

Tomoaki Ushiro

Yoichi Kawase

Satoshi Fujita

Mitsutoshi Kawamoto

Sakyo Hirose

Hiroaki Taira

Yasushi Ueno

Hideaki Nimi

Hiroyuki Kubota

Wataru Aoto

Tohru Higashi

Kousuke Shiratsuyu

Tohru Tominaga

Terunobi Ishikawa

A semiconductor ceramic and a positive-coefficient characteristic thermistor are provided which have a stable PTC characteristic, a high double point, and a wide operating temperature range. The semiconductor ceramic contains, as a main component, a barium titanate-based composition having a perovskite structure expressed by a general formula ABO. Out of 100 mol % of the Ti, an amount in a range of 0.05 mol % or more to 0.3 mol % or less of Ti is replaced with W as a semiconductor forming agent, the ratio m of A sites mainly to B sites is 0.99&#x2266;m&#x2266;1.002, and an actually-measured sintered density is 70% or more and 90% or less of the theoretical sintered density. In the positive-coefficient characteristic thermistor, a component body is formed of the semiconductor ceramic.

Semiconductor ceramic and positive-coefficient characteristic thermistor

A semiconductor ceramic includes a BaTiO-based composition, as a main component, having a perovskite structure represented by general formula ABO, wherein part of Ba constituting the A site is replaced with Na, Bi, Ca, and a rare-earth element having an ionic radius smaller than that of the Na; the content of the rare-earth element when the total number of moles of the elements constituting the A site is 1 mole is 0.0005 to 0.015 on a molar basis; and the content of the Ca when the total number of moles of the elements constituting the A site is 1 mole is 0.05 to 0.20 (preferably 0.125 or more and 0.175 or less) on a molar basis. A PTC thermistor includes a component bodyformed of the semiconductor ceramic. Accordingly, high reliability is achieved even if an alkali metal element is present.

Semiconductor ceramic and positive temperature coefficient thermistor

A semiconductor ceramic includes a BaTiO-based composition, as a main component, having a perovskite structure represented by general formula ABO. The molar ratio m between the A site and the B site satisfies 1.001&#x2266;m&#x2266;1.01. Part of Ba constituting the A site is replaced with Bi, Ca, a rare-earth element, and Na. The molar content of the Ca when the total number of moles of the elements constituting the A site is 1 mole is 0.05 to 0.20 (preferably 0.125 to 0.175). A PTC thermistor includes a component body formed of the semiconductor ceramic. Accordingly, there is provided a lead-free semiconductor ceramic that substantially does not contain lead and that has desired PTC characteristics and high reliability.

A semiconductor ceramic includes a BaTiO-based composition, as a main component, having a perovskite structure represented by general formula ABO. Part of Ba constituting an A site is replaced with at least an alkali metal element, Bi, and a rare-earth element, and the molar ratio m between the A site and a B site is 0.990&#x2266;m&#x2266;0.999 (preferably 0.990&#x2266;m&#x2266;0.995). Preferably, part of the Ba is replaced with Ca, and the content of the Ca when the total number of moles of the elements constituting the A site is 1 mole is 0.042 to 0.20 (preferably 0.125 to 0.175) on a molar basis. A PTC thermistor includes a component body formed of the semiconductor ceramic. Accordingly, there are provided satisfactory rise characteristics even if an alkali metal element is present.

A semiconductor ceramic includes a BaTiO-based composition, as a main component, having a perovskite structure represented by general formula ABO. Part of the A site Ba is replaced with an alkali metal element, Bi, Ca, Sr, and a rare-earth element. When the molar amounts of Ca and Sr are x and y, respectively, and the total number of moles of the elements constituting the A site is 1 mole, 0.05&#x2266;x&#x2266;0.20, 0.02&#x2266;y&#x2266;0.12, and 2x+5y&#x2266;0.7. A PTC thermistor includes a component body formed of the semiconductor ceramic. Even when an alkali metal element and Bi are present, there is provided a lead-free semiconductor ceramic with high reliability in which the surface discoloration is not caused and the degradation of resistance over time can be suppressed even after the application of an electric current for a long time.

A varistor is provided which can be driven at a low voltage, has a small leak current, and can realize a high ESD resistance and a high surge resistance. The varistor is formed using a ceramic composition for a varistor which contains zinc oxide as a primary component and sub-components including praseodymium at a content of 0.05 to 3.0 atomic percent of the total, cobalt at a content of 0.5 to 10 atom percent of the total, at least one of potassium, sodium, and lithium at a total content of 0.005 to 0.5 atom percent of the total, at least one of aluminum, gallium, and indium at a total content of 2&#xd7;10to 0.5 atom percent of the total, and zirconium at a content of 0.005 to 5.0 atom percent of the total.

Porcelain composition for varistor and varistor

A semiconductor ceramic having a negative temperature coefficient of resistance, the element comprising about 0.1 to 20 mol % of AMnO (A represents at least one of Ca, Sr, Ba, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy and Ho) and to a spinel composite oxide made of a solid solution of Mn and at least one element in Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Mg and Al. As a perovskite Mn composite oxide, one or more of CaMnO , SrMnO , BaMnO , LaMnO , PrMnO , NdMnO , SmMnO , EuMnO , GdMnO , TbMnO , DyMnO and HoMnO may be used.

Semiconductor ceramic having a negative temperature coefficient of resistance and negative temperature coefficient thermistor

A semiconductor ceramic device includes a semiconductor ceramic sintered body and external electrodes. The semiconductor ceramic sintered body contains a lanthanum cobalt type oxide major component, about 0.1 to 10 mol % on an element conversion basis of an oxide of Cr as a sub-component, and about 0.001 to 0.5 mol % on an element conversion basis of at least one of the oxides of Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba, Ni, Cu and Zn.

Lanthanum cobalt oxide semiconductor ceramic and related devices

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

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 semiconducting ceramic contains a lanthanum cobalt oxide as a major component represented by La.sub.x CoO.sub.3 wherein 0.600.ltoreq.x.ltoreq.0.999. The average crystal grain size of cobalt oxide present in the major component is not more than about 20 .mu.m. A change in resistivity between the semiconducting ceramic products can be suppressed.

Semiconducting ceramic, semiconducting ceramic element, and method for

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.

Semiconductive ceramic composition and semiconductive ceramic element

A semiconductive ceramic in which the B constant is maintained at about 4000 K or more at elevated temperature to thereby decrease power consumption, and the B constant is lowered less than 4000 K at low temperature so as to avoid unnecessary increase of resistance; as well as a semiconductive ceramic element using the same. The semiconductive ceramic is formed of a lanthanum cobalt oxide, which serves as the primary component, and, as a secondary component, at least one oxide of Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba, Ni, Cu and Zn. The semiconductive ceramic element is fabricated through use of the semiconductive ceramic and an electrode formed thereon.

Semiconductive ceramic and semiconductive ceramic element using the same

A semiconducting ceramic having negative resistance-temperature characteristics and a critical temperature consisting essentially of a rare-earth transition element oxide which is an oxide of a combination of samarium and nickel, wherein the samarium is partially replaced with Ln which is at least one other element selected from the group consisting of bismuth and rare-earth elements excluding lanthanum and cerium.

Semiconducting ceramic compounds having negative resistance-temperature

Provided is a semiconductive ceramic composition comprising a lanthanum cobalt oxide and having a negative resistance-temperature characteristic, which contains, as the side component, a chromium oxide in an amount of from about 0.005 to 30 mol % in terms of chromium, and also a semiconductive ceramic device comprising the composition. The device is usable for rush current inhibition, for motor start-up retardation and for halogen lamp protection, and is also usable in temperature-compensated crystal oscillators.

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Nagaokakyo, Japan

Akinori Nakayama