Study On The Energy Storage Performance Of Silver Niobate-Based Antiferroelectric Ceramics

Decline of the earth’s environment and the continuous improvement of human awareness of environmental protection has significantly turned the concept of using fossil energy to the use of renewable clean energy.Advancements in science and technology has also promoted the emergence of more renewable clean energy sources.Renewable clean energy sources such as wind solar,and geothermal energy can only be obtained under specific conditions,and these energies are widely used for electricity generation.Nowadays electric energy is an indispensable resource in human life,which considerably affects the development and progress of human society.In addition to the large storage batteries in power stations,power buses,subways,smart phones,charging treasure,and mini wireless headphones provide convenience to people,but also require reliable and stable energy storage systems to be able for sustainable use.A reliable energy storage system is urgently needed to utilize and store electric energy.At present,the dielectric materials used for energy storage capacitors mainly include linear dielectric（LD）,ferroelectric（FE）,antiferroelectric（AFE）and relaxor ferroelectric（RFE）materials.Among them,linear dielectrics have high breakdown field strength and low energy loss,but they cannot meet high energy storage applications due to their small dielectric constant.Antiferroelectric materials and relaxor ferroelectric materials have large saturation polarization values and good energy storage performance,which are more suitable for use in the field of energy storage.In recent years,many lead-free AFEs ceramics,such as NaNbO₃ and AgNbO₃,have been designed and applied to energy storage devices.Among these,AgNbO₃ has more typical double P-E loop characteristics and larger Pmax,and is considered to be the most promising candidate for preparing high-performance dielectric capacitors.However,AgNbO₃ is mainly produced by solid-phase methods at present.The AgNbO₃ prepared by this method has poor energy storage performance.At room temperature,the AgNbO₃ has small recoverable energy density,low energy storage efficiency and breakdown field strength is low,and poor charge-discharge performance and temperature stability.Considering the current scenario,this paper will primarily focus on accomplishing the following three tasks:1.In this chapter,we studied the effect of A-site lanthanum content on the energy storage performance of B-site low tantalum substituted(Ag_1-xLa_x)(Nb_0.96Ta_0.04)O₃ antiferroelectric ceramics.The introduction of La³⁺and Ta⁵⁺reduces the tolerance factor and polarizability of B-site cations,increases the local structural heterogeneity of AgNbO₃,thereby improving the stability of AFE phase and refining the polarization-electric field（P-E）loop.In addition,the incorporation of La³⁺and Ta⁵⁺decreases the grain size of AgNbO₃ ceramics and increases the band gap,thus increasing E_b.The results show that the(Ag_0.88La_0.04)(Nb_0.96Ta_0.04)O₃ ceramics have a higher recoverable energy density of 6.79 J/cm³ and a higher efficiency of 82.1%,which exceeds many newly reported AgNbO₃-based ceramics in overall energy storage performance.In addition,the discharge time of the ceramic is 16 ns and the power density is 145.03MW/cm³,which is better than many lead-free dielectric ceramics.2 In this chapter,we designed Ce⁴⁺and Ta⁵⁺co-modified(Ag_0.96Ce_0.01)(Nb_1-xTa_x)O₃ relaxation antiferroelectric（AFE）ceramics.The introduction of Ce⁴⁺and Ta⁵⁺reduces the M1-M2 phase transition temperature to near room temperature,enhances the cation disorder at A and B sites,thereby inhibiting the FIE characteristics,improving the stability of AFE and increasing the relaxation degree.As a result,an ultrahigh recoverable energy density of 7.37 J/cm³ was simultaneously obtained in(Ag_0.96Ce_0.01)(Nb_0.7Ta_0.3)O₃ ceramics,which is much higher than that of the latest AgNbO₃-based ceramics,and a high efficiency of 75.66%was obtained.In addition,the ceramic has excellent actual discharge capacity with ultrafast discharge time of 23ns and ultra-high power density of 294.28 MW/cm³,which exceeds than a number of recently reported lead-free dielectric ceramics,and the discharge performance is quite stable in a wide temperature range of 20-180℃.This provides a reference for the design and development of high-performance lead-free dielectric capacitors for harsh environments.3 we designed Sm³⁺and Ta⁵⁺co-modified(Ag_0.94Sm_0.02)(Nb_1-xTa_x)O₃ silver niobate antiferroelectric ceramics.The results show that the introduction of Sm³⁺and Ta⁵⁺reduces the M1-M2 phase transition temperature below room temperature,reduces the ionic radius of A-site ions and the electronic polarizability of B-site ions,and volume of oxygen octahedron.The cation shift and[Nb/Ta O₆]octahedron tilt angle decrease,resulting in a significant increase in antiferroelectricity and energy storage density.With Ta=25 mol%,the best energy storage performance was obtained in(Ag_0.94Sm_0.02)(Nb_0.75Ta_0.25)O₃ ceramics with an exceptional energy storage density of W_rec=8.03 J/cm³.At the same time,its energy storage efficiency isη=74.49%,which was significantly improved as compared to pure silver niobate.In addition,the ceramic exhibits excellent temperature stability（η≤4.32%in the range of 20～180℃）,frequency stability（η≤1.86%in the range of 50～500 Hz）and cycle stability（η≤1.07%）.More interestingly,the ceramic also shows good charge-discharge characteristics with a discharge time of t0.9=23 ns,P_d=336.6 MW/cm³,which provides a new idea to develop high-performance lead-free dielectric capacitors.