(Bi_0.5Na_0.5)TiO₃ Doped PTCR Ceramics Of Low Cuire Temperature

BaTiO₃-based low Curie point PTC thermo-sensitive ceramics are favored by science and industry with its unique step resistance temperature characteristics,mainly used for temperature sensing,temperature compensation and electronic circuit overload protection,etc.,widely used in the communications,automatic control,automotive,power electronics and other industries.Traditional low-point PTC material is doped SrTiO₃ as Curie point mobile agent,and the drawback is the larger grain size,poor resistance to high voltage and poor temperature coefficient,PTC effect not ideal.Low-temperature PTC material prepared with Sr/Pb as a Curie point bi-directional mobile agent enhance the performance of the material to a certain extent.But Pb in the material will cause pollution to the environment,not meeting the development trend of electronic devices green.With the advancement of electronic science and technology,the low temperature PTC materials prepared by the above two methods have been unable to meet the high demand of electronic components industry,and it is urgent to develop new material system.In this paper,the most widely used,Curie temperature of about 100℃low temperature PTC material with Bi_0.5Na_0.5TiO₃（BNT）and Sr element as a Curie point mobile agent is prepared.Lift resistance ratio greater than 7,the temperature coefficient greater than 40%,grain size small uniform high performance lead-free low temperature PTC thermosensitive ceramic material has been got.The main contents are as follows:（1）BNT was prepared by polymer network method to study the effect of BNT doping on the lattice structure,microstructure and electrical properties of BaTiO₃-based ceramics.（2）BNT doped low temperature PTC ceramics are prepared and its semi-conductive is studied,to explore the donor Y doping and acceptor Mn doping on the electrical properties and microstructure of the impact.（3）The modification of BNT doped low temperature PTC ceramics was studied.The effects of Sr/BNT,Ca element,liquid SiO₂ and TiO₂ on the electrical properties and microstructure of the composites are studied systematically.（4）The influence of donor Y doping on the microcosmic electrical properties of grain conductance and grain boundary conductance was studied by impedance spectroscopy.The grain boundary barrier properties of BNT doped low temperature PTC ceramic materials were calculated and analyzed based on the classical PTC model,and the high PTC effect of the materials was explained.