PTC thermistor and method for manufacturing PTC thermistor

Abstract

Provided is a PTC thermistor which uses a barium titanate semiconductor ceramic that has low Curie point and can be operated at low temperatures near room temperature, said barium titanate semiconductor ceramic also having low room-temperature resistivity and high resistance-temperature characteristics. As a semiconductor ceramic that constitutes a PTC thermistor, a semiconductor ceramic which contains Mn, an agent for making materials semiconductive and a perovskite compound containing Ba, Ti, Sr and Ca is used. When the total parts by mole of Ba, Sr and Ca and the agent for making materials semiconductive contained in the semiconductor ceramic is taken as 100, the parts by mole (a) of Sr contained therein and the parts by mole (b) of Ca contained therein satisfy the following relations: when 20.0<=a<=22.5, 12.5<=b<=17.5; and when 22.5<=a<=25.0, 12.5<=b<=15.0. When the total parts by mole of Ti and Mn contained in the semiconductor ceramic is taken as 100, the parts by mole (c) of Mn contained therein satisfies 0.030<=c<=0.045.

Description

technical field [0001] The present invention relates to a PTC (Positive Temperature Coefficient, positive temperature coefficient) thermistor using a barium titanate-based semiconductor ceramic having positive resistance temperature characteristics. Background technique [0002] As a barium titanate-based semiconductor ceramic composition having a positive resistance-temperature characteristic, for example, a semiconductor ceramic composition disclosed in Patent Document 1 is known. [0003] The semiconductor ceramic composition of this Patent Document 1 is a composition having a positive resistance-temperature characteristic mainly composed of barium titanate, and contains 20 to 30 mol of strontium titanate, 0.05-0.20 mol of calcium titanate, 0.05-0.15 mol of manganese oxide, 2.5-3.5 mol of silicon oxide, and 0.25-0.30 mol of oxides of rare earth elements. [0004] The semiconductor ceramic composition of this patent document 1 can be used suitably for the PTC thermistor o...

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Problems solved by technology

[0005] However, in the semiconductor ceramic composition of Patent Document 1, although the characteristics of low resistance and high withstand voltage can be obtained, in order to realize high-precision temperature detection, the PTC characteristics (relative to the change in resistance vs. The characteristics of the size of the temperature change, and the greater the resistance change relative to the temperature change, the better), there is a problem that it is not necessarily possible to achieve sufficient characteristics

[0006] Therefore, in the case of using the semiconductor ceramic composition of Patent Document 1, it is actually impossible to obtain a PTC thermistor for overheat detection with desired characteristics.

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