SEMICONDUCTOR CERAMIC AND POSITIVE TEMPERATURE COEFFICIENT THERMISTOR

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Disclosed is a semiconductor ceramic which is mainly composed of a BaTiO3 composition having a perovskite structure represented by the following general formula : AmBO3, wherein a part of Ba constituting the site A is substituted by an alkali metal element, Bi, Ca, Sr and a rare earth element, and when the total mole number of the elements constituting the site A is taken as 1 mole, the contents of Ca and Sr satisfy the following relations : 0.05 ≤ x ≤ 0.20, 0.02 ≤ y ≤ 0.12 and 2x + 5y ≤ 0.7, wherein x represents the molar ratio of Ca and y represents the molar ratio of Sr. Also disclosed is a PTC thermistor wherein a component element (1) is formed from the semiconductor ceramic. Consequently, a highly reliable lead-free semiconductor ceramic is obtained, in which surface discoloration does not occur and long-term deterioration in the resistance can be suppressed when a current is applied thereto for a long time, even though an alkali metal element or Bi is contained therein.