Optical And Electrical Properties Of Potassium Sodium Bi_0.5Na_0.5TiO₃-BiFeO₃ Based Ceramics

Behind the development history of human modern civilization is the process of energy development and utilization.At different stages of development,human beings are largely depenedent on energy.It is the continuous use and exploration of energy that has promoted the progress of human society.After entering the new era,there are various types of energy.Thereis no doubt that using environmentally friendly and clean renewable energy is the ultimate goal of human society.In order to realize that,efficient electric energy storage devices are crucial.Dielectric energy storage-ceramics have attracted much attention because of their high energy storage density.Unfortunately,most of the dielectric ceramics on the market are lead-based materials,and lead is self-evident harmful to human body and the environment.Therefore,in view of this phenomenon,this paper is committd to the research of lead-free dielectric ceramics,and has developed a series of ceramic materials based on 0.7Bi0.5Na0.5TiO30.3BiF3O3(0.37NBT-0.3BFO),and has studied its microscopic morphology,phase structure,energy storage and other electrical properties.The research results of this paper may be helpful to the development of lead-free dielectrie energy storage materials.The specific research contents are as follows:(1)Considering that Bi0.5Na0.5TiO3(NBT)and BiF3O3(BFO)have great polarization potential,and the two can be infinite solid solution,in order to combine the polarization ability of them,we first obtained a preliminary relaxor binary matrix 0.7NBT-0.3BFO.Firstly,the antiferroelectric NaTaO3(Eg=4.0eV)with large band gap was introduced to modify it.Increase the breakdown field strength of the material,promote the transition of the material to the ergodic relaxation state(ER),refine the ferroelectric hystercsis loop,and reduce the residual polarization intensity of the system;Improve the energy storage performance from two aspects When the x=0.2,its energy storage density(Wrec)value is 2.43 J/cm3,and its energy storage efficiency(η)is 74.5%,and its breakdown field strength is significantly improved,reaching 220 kV/cm at x=0.3.(2)The energy storage performance is significantly improved after adding NT,but the energy storage efficiency can still be further enhanced.At the same time,it is found that the grain size is slightly increased after adding NT,and the maximum polarization strength(Pmax)of the material decreases rapidly after x>0.2.Therefore,Sr=Sr0.85Bi0.1TiO3(SBT),which is conducive to maintaining high polarization strength,and is easy to destroy the long-range order of the ferroelectric material dipole,and has the effect of grain refinement,is selected for solid solution into 0.7NBT-0.3BFO,So as to improve the energy storage property of the material.The experiment shows that SBT can induce more "ER" states and polar nano-regions(PNRs)at room temperature.Pmax of each component was maintained at 30 μC/cm2,and the best energy storage performance is obtained when the SBT content is 0.30(Wrec=2.32 J/cm3,η=82.5%),compared with NT doping,SBT doping has further improved the energy storage efficiency while maintaining a high energy storage density.(3)In view of previous research on NBT-BFO-SBT and NBT-BFO-NT ternary system,their energy storage performance is excellent,but there is still room for improvement.Although NBTBFO-SBT system has high energy storage efficiency,its breakdown field strength is generally lower than 200 kV/cm,which reduces its practical application value.Although NBT-BFO-NT system has high breakdown field strength,its energy storage efficiency is not high,and it is not conducive to its practical application.However,considering the advantages of the two systems,if they are combined,a ceramic system with better energy storage performance will be obtained.We studied the energy storage properties of(1-x)(0.7(0.7Bi0.5Na0.5TiO3-0.3BiFeO3)0.3Bi0.1Sr0.85TiO3)-xNaTaO3(NBT-BFO-SBT-xNT)relaxor ferroelectric ceramics.Compared with NBT-BFO-SBT system,NBT-BFO-SBT-xNT system can further improve the energy storage density while maintaining high energy storage efficiency after adding appropriate amount of NaTaO3.In NBT-BFO-SBT-0.09NT ceramics,Wrec=3.44 J/cm3 and η=86.7%,and its breakdown field strength reached 210 kV/cm.Then we measured the ferroelectric hysteresis loop of NBTBFO-SBT-0.09NT ceramics at different frequencies and temperatures.The results show that the material has good frequency stability and temperature stability,and the energy storage performance of the system is more excellent,and its application field will be broader.