摘要
As functional materials, PTC thermistor ceramics characterized by a drastic increase in resistivity at its transition temperature have been widely used in high-technology areas such as temperature measurement and indication, temperature control, protective switches and so on. At present, the PTC thermistors are fabricated by means of doping BaTiO<sub>3</sub> and their PTC effects result from the existence of acceptor state or electronic trap on grain boundary. But the fabrication process
