Study On The Relationship Between Microstructure And Properties Of High Curie Point PTC Material

BaTiO₃ based PTCR?positive temperature coefficient of resistance?ceramics with high Curie point are widely used in communication,network equipment,automatic control,household appliances,electric vehicles and other fields because of their resistance-temperature characteristics when resistance jumps near Curie point and static volt-ampere characteristics of constant temperature heating near Curie point.With the development of energy saving and emission reduction,white household appliances and electric vehicles will be greatly developed.These industries increasingly require PTC thermal ceramic materials as key components to have lower room temperature resistivity,higher Curie temperature and stronger voltage resistance.Currently,the Curie point movers are Pb and Ba_1?2Na_1?2TiO₃.When Ba_1?2Na_1?2TiO₃ is used to increase the Curie temperature of PTC,the Curie temperature increases less,only 160?,and the Curie temperature is low,which can not meet the demand of high Curie point in practical application environment.In this paper,Pb oxide Pb₃O₄ is used as curie point mobile agent to study the effect of Pb on the microstructure and properties of PTC materials.The resistance-temperature characteristics of PTC materials with different Curie points under high voltage are tested,and the relationship between the microstructure and properties of PTC materials with high Curie points is explored.The main contents of this paper are as follows:?1?BaTiO₃ based ceramics with different concentration of Pb doping were prepared by two-step sintering using Pb as Curie point mover.The effects of Pb doping on the microstructure,density and electrical properties of ceramics were studied.?2?The voltage effect of materials with different Pb doping concentration at high voltage was studied,and the influence of Pb on PTC effect was analyzed.?3?PTC materials with uniform grain size and good electrical properties were doped at 230?.The effects of donor Y and acceptor Mn on the electrical properties of the materials were investigated,and the effects of material density on the electrical properties of the materials were analyzed when Y was doped.The effects of Ca and liquid SiO₂ on the microstructures and electrical properties of the materials were studied.