Study Of Low Resistivity, High Properties BaTiO₃-based PTC Ceramic Materials

With the rapid development of the electronics industry, the BaTiO3-based PTC ceramics has become a kind of useful electrical function ceramics, which have broad application prospects and important research value. Especically, in recent years, the doped-BaTiO3 ceramics become the focus of research due to its lower resistivity at room temperature and resistance to high pressure performance.In this paper, using BaTiO3 and TiO2 as starting materials, BaTiO3-based PTC thermistors have been prepared by solid-state reaction method. The microstructure and morphology of BaTiO3-based PTC ceramics with different formulations and process have been characterized by the X-ray diffraction and scanning electron microscopy. The effects of donor doping, acceptors doping, Ca doping, additives and process on the properties of BaTiO3-based PTC ceramics have been discussed. The approaches of reducing room-temperature resistivity, improving PTC and voltage resistance properties were analyzed.The results show that the room-temperature resistivity appeared a U-curve with the increase of donor content. Room-temperature resistivity of PTC ceramics with double donor doping was lower than that of ceramics with single donor doping. Voltage resistance properties first increased then decreased with the increasing of Ca amount. Extending holding time or increasing the content of acceptor can improve the PTC effect of the material, but the room temperature resistivity gradually increased. The PTC effect could be sharply rised by increasing the content of Zr.Through repeated experimentation and comparison, a kind of low room-temperature resistivity, high properties PTC ceramic materials were invented. A minimum R25 of 3.32Ω associated with ρmax/ρmin=6.4×104 and 80 V of withstand voltage was achieved for 97.96Ba0.9935Ca0.005La0.0015Ti0.9995Nb0.0005O3-2AS2TZ-0.04Mn samples sintered at 1350℃ for 1.5 h and incubating at 1200℃ for 6 h.