Barium-titanate ceramic semiconductor and ptc thermistor using same

Provided are: a barium-titanate ceramic that has a low resistivity near room temperature, a high withstand voltage, and positive resistance-temperature characteristics; and a PTC thermistor using same. In this barium-titanate ceramic semiconductor, which is represented by the general formula BaTiO3 and has positive resistance-temperature characteristics, zirconium is substituted in for some of the titanium sites, with the zirconium content being in the 0.14-0.88 mol% range. Said barium-titanate ceramic semiconductor also contains at least one rare-earth element selected from the group consisting of yttrium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. This barium-titanate ceramic semiconductor is used as a thermistor body having positive resistance-temperature characteristics, forming a PTC thermistor.