Murata Manufacturing Co., Ltd.

Kunitaro Nishimura

Masami Yamaguchi

Haruhumi Mandai

Harufumi Mandai

Yoshiaki Kohno

A boundary layer type semiconducting ceramic capacitor with high capacitance is disclosed. The capacitor comprises a semiconducting ceramic body in which grain boundaries on crystal grains of the semiconducting ceramic body are insulated, characterized in that said semiconducting ceramic body has a composition consisting essentially of 98.1 to 99.88 mole % of a main component (Sr.sub.1-x Ba.sub.x)Tio.sub.3 or (Sr.sub.1-x Ba.sub.x)TiO.sub.3 modified with a titanete and/or a zirconate, wherein x is a mole fraction of Ba and takes a value ranging from 0.30 to 0.50, and 0.1 to 1.0 mole % of at least one semiconductorizing agent selected from the group consisting of rare earth elements, Nb, Ta and W, and that said grain boundaries of the crystal grains are insulated by at least one insulating agent selected from the group consisting of Mn, Bi, Cu, Pb, B and Si, and that the maximum crystal grain present in the semiconducting ceramic body has a grain size ranging from 100 to 250.mu.. The composition contains 0.02 to 0.2 mole % of Mn as a mineralizing agent or insulating agent. The composition may further contain at least one of 0.05 to 0.5 mole % of SiO.sub.2 and 0.02 to 0.2 mole % of Al.sub.2 O.sub.3.

Boundary layer type semiconducting ceramic capacitors with high

A method for producing boundary layer semiconductor ceramic capacitors comprises firing shaped bodies of a semiconductor ceramic material in a neutral or reducing atmosphere, heat-treating the resultant semiconductor ceramic bodies to insulatorize crystal grain boundaries of the semiconductor ceramics, and providing opposite electrodes on surfaces of the heat-treated semiconductor ceramic bodies and is characterized in that said heat-treating is carried out by heating the semiconductor ceramic bodies together with power of an insulatorizing agent with stirring in a neutral or oxidizing atmosphere at a temperature ranging from 950.degree. to 1300.degree. C. As a semiconductor ceramic material, there may be used semiconductor ceramics of a barium titanate system, or of a strontium titanate system, or a complex semiconductor ceramic mainly comprising barium titanate or calcium titanate and strontium titanate. This method enables one to produce boundary layer semiconductor ceramics as good quality with small standard deviation and high yield.

Method for producing boundary layer semiconductor ceramic capacitors

A semiconductor ceramic composition for boundary layer capacitors which consists essentially of 99.6 to 99.995 wt. % of a semiconductor ceramic component consisting of strontium titanate or modified strontium titanate solid solution and at least one semiconductorizing agent, and 0.005 to 0.1 wt. % of phosphorus together with or without 0.015 to 0.3 wt. % of copper is disclosed. The composition makes it possible to produce boundary layer capacitors having high permittivity and high breakdown voltage at high percent non-defective.

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Youkaichi, Japan

Kunitaro Nishimura