Murata Manufacturing Co., Ltd.

Yasuhiro Nabika

Toshiharu Hirota

Tetsukazu Okamoto

Yoshitaka Nagao

Noriyuki Yamamoto

Hayato Katsu

Yoshiaki Abe

Norimitsu Kito

Takeo Haga

Yoichi Kawase

Yuichi Hirata

Yumin Saigo

Ryoichi Urahara

Satoshi Kakihara

Wataru Aoto

Takahiko Kawahara

Syunsuke Okuda

A laminated PTC thermistor element that includes a ceramic substrate including a plurality of ceramic layers, a plurality of internal electrodes within the ceramic substrate, and external electrodes on the surface of the ceramic substrate that provide electrical conduction to the internal electrodes. The ceramic substrate is 0.3 [&#x3bc;m] or more and 1.2 [&#x3bc;m] or less in average porcelain grain size. Furthermore, the relative density of the ceramic substrate has a lower limit of 70 [%], and an upper limit of &#x2212;6.43d+97.83 [%] when the average porcelain grain size is denoted by d.

Laminated PTC thermistor element

A barium titanate-based semiconductor ceramic composition which can be used for PTC thermistors for temperature sensors and which has characteristics, including a linear characteristic, advantageous for such PTC thermistors and a barium titanate-based semiconductor ceramic device. The barium titanate-based semiconductor ceramic composition is represented by the formula (BaMeSr)TiO+ySiO, wherein Me is at least one of Er, Sm, Ce, and La, 0.001&#x2266;v&#x2266;0.005, 0.42&#x2266;w&#x2266;0.49, 0.99&#x2266;x&#x2266;1.03, and 0.002&#x2266;y&#x2266;0.030.

Barium titanate-based semiconductor ceramic composition and barium titanate-based semiconductor ceramic device

A semiconductor ceramic contains erbium as a semiconducting agent in primary components of barium titanate, strontium titanate, lead titanate and calcium titanate, with the average grain diameter of the semiconductor ceramic exceeding about 5 &mgr;m but not exceeding about 14 &mgr;m. Further, the semiconductor ceramic contains as additives a compound containing Er with the Er being more than about 0.10 mol but no more than about 0.33 mol, a compound containing Mn with the Mn being about 0.01 mol or more but no more than about 0.03 mol, and a compound containing Si with the Si being about 1.0 mol or more but no more than about 5.0 mol, per 100 mol of the primary component. Thus, a semiconductor ceramic and positive-temperature-coefficient thermistor can be provided with high-flash-breakdown capability, excellent results in ON-OFF application tests and few irregularities in resistance values.

Semiconductor ceramic and positive-temperature-coefficient thermistor

Provided is a semiconductor ceramic and a semiconductor ceramic element each having a room temperature specific resistance of 3 &OHgr;&middot;cm or lower and a resistance temperature characteristic of 9%/&deg; C. or more. The semiconductor ceramic is characterized in that the ratio R /(R &plus;R ), in which R is the transgranular resistance value of the crystal particles and R is the intergranular resistance value of the crystal particles and R &plus;R is the overall resistance value representing the sum of R and R , is about 0.35 to 0.85.

Semiconductor ceramic, semiconductor ceramic element and circuit protection element

A semiconductor ceramic device comprises a body composed of a semiconductor ceramic having a positive resistance-temperature coefficient primarily composed of barium titanate and electrodes provided on the body, in which the resistance-temperature coefficient is 9%/&deg; C. or more, resistivity is 3.5 &cap;&middot;cm or less, and withstand voltage is 50 V/mm or more. As the semiconductor ceramic forming the body provided in a thermistor having positive resistance-temperature characteristics, a semiconductor ceramic having a positive resistance-temperature coefficient is used, in which the semiconductor ceramic has an average particle diameter of about 7 to 12 &mgr;m and comprises barium titanate as a major component and sodium in an amount of about 70 ppm or less on a weight basis.

Semiconductor ceramic and semiconductor ceramic device

A semiconductor ceramic composed of barium titanate, lead titanate, strontium titanate, and calcium titanate as primary components, includes samarium oxide as a semiconductor-forming agent in the primary components, and the average diameter of crystalline particles of the semiconductor ceramic is about 7 to 12 &mgr;m. The semiconductor ceramic has a resistivity at room temperature not greater than 3.5 &OHgr;cm, a withstand voltage not less than 50 V/mm, a resistance-temperature coefficient &agr; not less than 9%/&deg;C. and also has less variability of resistance.

Semiconductor ceramic and device using the same

A ceramic for the PTC thermistor having a resistivity at room temperature of 5 &OHgr;&middot;cm or less, static withstanding voltage of 60 V/mm or more and temperature resistance coefficient of 9.0 %/&deg; C., having small dispersion of the resistance, is composed of principal components of about 30 to 97 mol % of BaTiO , about 1 to 50 mol % of PbTiO , about 1 to 30 mol % of SrTiO and about 1 to 25 mol % of CaTiO (the total content of them being 100 mol %), as well as about 0.1 to 0.3 mole of Sm, about 0.01 to 0.03 mole of Mn and 0 to about 2.0 mole of Si relative to 100 moles of the principal components, the composite material being preferably heat-treated in an oxidative atmosphere after being fired in a reducing or neutral atmosphere for obtaining the ceramic.

Composite material for positive temperature coefficient thermistor, ceramic for positive temperature coefficient thermistor and method for manufacturing ceramics for positive temperature coefficient thermistor

A barium titanate-based semiconductive ceramic composition for facilitating miniaturization of thermistor devices by improving rush current resistance characteristics is provided. In the barium titanate-based semiconductive ceramic composition, a fraction of the Ba in BaTiO,as the major component is replaced with 1 to 25 mole percent of Ca, 1 to 30 mole percent of Sr, and 1 to 50 mole percent of Pb; and wherein to 100 mole percent of the major component, the semiconductivity-imparting agent is added in an amount of 0.2 to 1.0 mole percent as a converted element content, and the additive comprises manganese oxide in an amount of 0.01 to 0.10 mole percent as a converted Mn content, silica in an amount of 0.5 to 5 mole percent as a converted SiO,content, and magnesium oxide in an amount of 0.028 to 0.093 mole percent as a converted Mg content.

Barium titanate-based semiconductive ceramic composition

A PTC thermistor has a disk-shaped main body with electrodes on its main surfaces which are facing mutually away from each other such that, during an initial period after a potential difference is applied between these electrodes, the side surface of the main body has an asymmetric temperature distribution between the electrodes in the direction normal to its main surfaces. The heat emission does not have a peak half-way between the electrodes in the direction of the thickness such that the thermistor has an improved resistance against flash pressure. This may be done by forming the electrodes in different sizes or by providing a non-uniform distribution in specific resistance to the main body such that the heat-emission peak is displaced from the center region between the two main surfaces of the main body.

PTC thermistor with improved flash pressure resistance

A thermistor element with positive temperature characteristic (PTC) has a planar ceramic member with a positive temperature characteristic of which the thickness is greater at its peripheral part than at the center part, decreasing either gradually or in a stepwise manner. Protrusions may be formed along its periphery. A PTC thermistor is formed with electrodes formed on both main surfaces of such a PTC thermistor, each electrode having a lower-layer electrode all over a main surface and an upper-layer electrode on the lower-layer electrode. The upper-layer electrode has a smaller surface area than the lower-layer electrode such that a portion of the lower-surface electrode is exposed at the periphery. The upper-layer electrodes may be formed at the center parts of the main surfaces, exclusive of the peripheral parts or where the protrusions are formed. The lower-layer electrodes may be mostly of Ni and the upper-layer electrodes mainly of Ag.

Positive temperature characteristic thermistor and thermistor element

A semiconducting ceramic whose rush breakdown voltage is high and which hardly cracks during lamination is provided. In the semiconducting ceramic having a positive resistance-temperature characteristic, the ratio of intra-granular resistance of the crystal grains and inter-granular resistance between crystal grains which together determine the value of resistance of the semiconducting ceramic is set so that the intra-granular resistance is less than about 20% of the value of resistance of the semiconducting ceramic (not including 0%).

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Omihachiman, Japan

Yasuhiro Nabika