SEMICONDUCTOR CERAMIC AND POSITIVE TEMPERATURE COEFFICIENT THERMISTOR

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Disclosed is a semiconductor ceramic which is mainly composed of a BamTiO3 composition having a perovskite structure represented by the following general formula : AmBO3, wherein the constituent elements are blended so that the molar ratio (m) of the site A to the site B is within the range of 1.001 ≤ m ≤ 1.01, a part of Ba constituting the site A is substituted by either Li and/or Na, as well as Bi, Ca and a rare earth element, and when the total mole number of the elements constituting the site A is taken as 1 mole, the Ca content is within the range of 0.05-0.20 (preferably 0.125-0.175) in terms of molar ratio.  Also disclosed is a PTC thermistor wherein a component element (1) is formed from the semiconductor ceramic.  Consequently, the semiconductor ceramic can secure desired PTC characteristics and achieve good reliability, while being a lead-free semiconductor ceramic which does not substantially contain lead.