Study On Energy Storage Of Silver Niobate-based Lead-free Ceramics

Silver niobate（AgNbO₃）-based antiferroelectric ceramics have great potential for application in the field of dielectric energy storage because of their unique antiferroelectric properties and high Curie temperature,and because of their high energy density and good temperature stability.However,as far as effective energy storage density and efficiency are concerned,pure AgNbO₃ceramics can not meet the requirements of device application.It is of great scientific significance to explore the preparation methods and theories for improving the energy storage properties of such ceramics.In this paper,the rare-earth doping modification of silver-based niobate ceramics was carried out.The effects of rare-earth doping on the microstructures,phase structure,ferroelectric/antiferroelectric properties,dielectric properties and energy storage properties of AgNbO₃ceramics were systematically studied.The innovations and main conclusions of this paper are as follows:1.The long-range ordering of the original structure is destroyed by Sb doping,which leads to the local structure nonuniformity.The relaxation characteristics are introduced,which combine the advantages of antiferroelectric and relaxed ferroelectric.The modified Ag(Nb_1-xSb_x)O₃-based ceramics have both high polarization strength of antiferroelectric and high energy storage efficiency of relaxed ferroelectric.The diffusion factor of Ag(Nb_0.98Sb_0.02)O₃sample is 1.97,which is very close to the ideal relaxation ferroelectric.T_M1-M2moves significantly from 75 ^oC at x=0 to-65 ^oC at x=0.04 to lower temperature,which improves the room temperature stability of the antiferrous phase.The introduction of Sb⁵⁺increases the room temperature dielectric constant of AgNbO₃-based ceramics.For these reasons,Ag(Nb_0.98Sb_0.02)O₃(W_rec=1.74 J/cm³,η=40.97%)has better energy storage performance than pure AgNbO₃(W_rec=1.26 J/cm³,η=28.4%).2.Energy storage performance of AgNbO₃ceramics can be controlled by Co-doping of Eu and Ta in many ways.The incorporation of Eu³⁺with a smaller ion radius can effectively reduce the cell volume,shorten the cation displacement,reduce the tolerance factor T and improve the antiferroelectric stability.Ta⁵⁺doping can effectively reduce the average polarizability of the B-cation and increase the E_Fand E_Afield values.The incorporation of Eu and Ta resulted in the decrease of T_M1-M2and T_M2-M3and T_M1-M2below room temperature.The dielectric constant at room temperature can be significantly increased.The defects of Eu^??_Agand V’_Agresult in finer P-E curves in the induction ferroelectric region.The above characteristics effectively enhance W_recandηof Ag_0.94Eu_0.02Nb_0.9Ta_0.1O₃samples(W_rec=4.2 J/cm³,η=70.1%).Ag_0.97Eu_0.01Nb_0.9Ta_0.1O₃not only has high energy density but also has good temperature stability.The variation range of W_recandηis less than 3.2%in the temperature range of 20-120 ^oC.However,the temperature stability of Ag_0.94Eu_0.02Nb_0.9Ta_0.1O₃still needs to be improved.The core conclusions of this paper indicate that the relaxation characteristics are introduced by local structural heterogeneity due to the B-bit doping of Sb5+.A/B co-doping reduces the tolerance factor（t）,improves the antiferroelectric stability,and reduces the average polarization,which can effectively improve the energy storage performance of antiferroelectric ceramics.The method of this paper can provide theoretical reference and data support for the subsequent design of high performance energy storage materials.