Preparation Of BaTiO₃ Based PTC Ceramics And The Propertied Of Themistors

BaTiO₃ based positive temperature coefficient resistance?PTC?ceramics have become the main thermal resistance materials in the world due to its advantages of safety,stable performance and low cost.With the development of science and technology,people on the room temperature resistivity of the lower and higher resistance jump requirements also more and more urgent,and,so far,for BaTiO₃ based PTC ceramic PTC effect mechanism is not fully clear.Therefore,this article BaTiO₃ as matrix,using solid phase sintering method for material preparation,and through A La,Ag double admixture B A base element Cu doped in combination with the electric field heat treatment process to achieve to improve the performance of PTC.On this basis,by Raman spectroscopy,XRD,SEM,Uv-vis absorption spectroscopy,resistance-temperature curve interface temperature and interface frequency spectrum characterizing the structure and properties of materials,to reveal the evolution of the ceramic PTC effect rule and mechanism.Phase structure analysis shows that perovskite structure ceramics without mixed phase can be obtained by proper preparation and treatment of doped ceramics.The introduction of La and Ag can reduce the room temperature resistivity of ceramics,and when doping 0.2%of La and 0.3%of Ag,the room temperature resistivity of ceramics is the lowest,reaching 10³ orders of magnitude.According to the study of Uv-vis absorption spectrum,the doping of La and Ag can reduce the bandgap width of materials and change the electrical transport properties of ceramics,thus causing the change of room temperature resistivity.On the basis of double admixture of A and B,the resistance jump of ceramics was significantly increased by adding appropriate amount of Cu.When the content of Cu was 0.05%,the resistance jump of ceramics was the highest,reaching 10² orders of magnitude.At the same time,it is found that the dielectric constant of the doped ceramics can reach more than 10⁴ with high dielectric loss,which can be attributed to the existence of mixed valence state and the structure of interfacial potential barrier layer.Using complex impedance spectroscopy analysis of ceramic grain and grain boundary character study found that with increasing temperature,ceramic grain resistance is very small and basic don't change,and the grain boundary resistance being very high,and with the temperature resistance has increased dramatically,consistent with ceramic resistance temperature curve change trend,the PTC effect and the internal connection of grain boundary properties.