Study On Ferrelectric Behavior Regulation And Energy Storage Characteristics Of BiFeO₃-BaTiO₃-based Relaxor

The energy storage ceramics is a kind of important functional material that can realize electricity storage.They are widely used in the manufacture of pulse power capacitors,power pulse weapons,high-speed rail starters and so on.With the increasing attention of human society to sustainable green development,the harm of lead-based energy storage ceramic materials has been widely concerned.In this context,the study of lead-free energy storage ceramic materials has very important practical significance.Bismuth barium titanate(BiFeO₃-BaTiO₃)based lead-free energy storage ceramics have great potential in energy storage due to their high saturation polarization.However,due to its strong ferroelectricity,the remnant polarization are relatively large.Moreover,Bi₂O₃ volatilization during high temperature sintering will lead to impurity formation,and Fe³⁺will be oxidized to Fe²⁺,which will lead to the increase of leakage current and reduce the breakdown strength of ceramics.Combined with the above factors,the energy storage performance at a low level.Therefore,in this paper,three different ways are used to regulate its ferroelectricity,enhance its relaxation characteristics,and characterize the effects of ceramic ferroelectricity regulation on its microstructure,dielectric,ferroelectricity and charge-discharge properties.(1)The Bi position is doped with Sm to form 0.67 Bi_1-xSm_xFeO₃-0.33Ba TiO₃ solid solution.The results show that the ferroelectricity of BF-BT based ceramics decreases obviously with the increase of Sm³⁺content,and the relaxation of ceramics increases obviously.Thus,reduce the intensity of remanent polarization and improve the breakdown strength.So,at 200 k V/cm of electric field,x=0.1 component exhibits a comprehensive energy storage performance with recoverable energy storage density of 2.8 J/cm³ and energy storage efficiency of 55.8%respectively.To further improve energy storage efficiency,based on 0.67Bi0.9Sm_0.1FeO₃-0.33Ba TiO₃,the scheme of replacing partial Fe³⁺with high valence cation Nb⁵⁺is designed.And in theory,this design not only can reduce the Fe³⁺oxidation but also can improve the relaxation of ceramics,Thus,the breakdown strength and energy storage efficiency of ceramics are improved.Experimental results show that when y=0.2 components,A comprehensive energy storage performance of 3.40J/cm³ and 73.4%energy storage efficiency is obtained.(2)The incorporation of high relaxation medium as the third element is an effective way to reduce the ferroelectricity of ceramics.Sr_0.7Bi_0.2TiO₃ is a high relaxation medium.which is introduced into BF-BT ceramic materials as the third element.The effect of different Sr,Bi proportion of the third element on the relaxation of BF-BT based ceramics was first explored.Then,the optimal Sr_0.7Bi_0.2TiO₃ of relaxation was selected to be mixed into the BF-BT with different contents,where the 0.3(Sr_0.7Bi_0.2TiO₃)component is at 180 k V/cm electric field,recoverable energy storage density of 2.4 J/cm³ and energy storage density of 90.4%were obtained.(3)Through literature investigation,it is found that Bi(M₁M₂)O₃ medium can effectively improve the relaxation of BT-base,BNT-base and NN-base lead-free energy storage ceramics.In this paper,the Bi(M₁M₂)O₃ M₁=Mg,M₂=Ti,Zr,Sn,Hf medium selected to dropping into the BF-BT as a third element,Explore the different forbidden band widths Ti,Zr,Sn,Hf composition of the third element in energy storage differences.Experimental results show that Bi(Mg_0.5Ti_0.5)O₃ the doping of can maintain high saturation polarization intensity.The breakdown strength of ceramics was increased from 110k V/cm to 360k V/cm,Bi(Mg_0.5Sn_0.5)O₃ incorporation can greatly reduce the ferroelectricity of ceramics,but the saturation polarization intensity also decreases greatly.