Study On PTC Effect And Impedance Spectroscopy Analysis In BaTiO₃-based Ceramics

PTCR ceramic chips integrate mechanical, electrical, heat properties, and are widely applied in all sorts of temperature controlled heaters, degaussing devices, automobile, communications, etc. In recent years, with the development of organic PTCR materials and integrated circuit in micro-electronic fields, the PTCR ceramic materials are facing more and more intensive competition. It's urgent to further improve the capability of BaTiO₃-based PTCR ceramic materials.For BaTiO₃ ceramic materials, the study includes two aspects of semiconducting and PTC effect. On the previous basis of donor doping for the purpose of semiconducting, the paper focused on the study of PTC effect from aspects of acceptor doping, sintering process and domain process.The study of acceptor doping contained the doping mechanisms of the different acceptor dopants such as Mn,Co,Cr, the modes of acceptor doping, double doping and multi-acceptor doping with limited doping amount. By controlling the cooling process and comparing the final PTC effect of the materials, the sintering process was studied. The domain switching process in BaTiO₃ ferroelectric materials is an important factor influencing macro-electric characteristic. The laws of domain transformation and how to control the domain structure still need to be further studied. In addition, Impedance Spectroscopy was used to analyze the micro-electric characteristic.Results indicate that different acceptor dopants play different roles due to different doping mechanisms. Materials with different dopants are corresponding to different sintering process. The grain boundary resistivity shows PTC effect while the grain resistivity shows NTC effect. The macro-resistivity of BaTiO₃-based materials is decided by grain boundary resistivity and shows PTC effect.