Energy Storage Behavior Modulation Of Antiferroelectric Ceramics Based On Sodium Niobate

Nowadays,dielectric ceramic capacitors with high power and energy densities satisfy the expanding demand for big energy storage devices,electric cars,and portable electronics.However,the actual use of dielectric ceramic capacitors is severely constrained by their comparatively poor mechanical qualities and the sharp drop in energy storage density and efficiency under high electric field and high temperature environments.When it comes to high energy storage density（>5.5 J/cm³）,ultra-high efficiency（>90%）,outstanding mechanical qualities,and exceptional temperature stability,currently reported lead-free dielectric ceramics,for instance,can rarely match these requirements.High charging and discharging efficiency in particular can make sure that less heat is produced throughout the charging and discharging process,which will ultimately make sure that the device will fail due to thermal runaway.Hence,a major issue and difficulty to advance the commercialization of devices has been how to develop and achieve lead-free dielectric energy storage ceramics with high energy storage density,efficiency,and great temperature stability.As a promising lead-free antiferroelectric material,Na Nb O₃（NN）ceramics can induce reversible transitions between the antiferroelectric and ferroelectric phases at high electric fields,leading to low antiferroelectric residual polarization values,high saturation polarization,and high energy storage.It has received a lot of attention recently in the dielectric energy storage field.However,when compared to the present lead-based antiferroelectric ceramics,its total energy storage performance—including energy storage density,efficiency,and stability—still has some room for improvement.Consequently,the goal of this work is to obtain effective and complete energy storage performance using NN-based antiferroelectric ceramics as the research object.To explore the internal relationship between structure and performance and to provide the most fundamental candidate materials for lead-free dielectric ceramics in high efficiency dielectric capacitors,three different approaches are taken to optimize the energy storage behavior of NN-based antiferroelectric ceramics.Synergistically stable antiferroelectric phase and domain engineering strategies:To lower tolerance factor of the system and increase the stability of the AFE phase,linear dielectric Ca Ti O₃（CT）is incorporated into NN.Moreover,the addition of non-equivalent ions can increase A/B positional disorder and create local random fields,which helps construct AFE domains and enhances the relaxation properties of NN ceramics.With excellent energy storage properties(W_rec=5.52 J/cm³,η≈83.3%and breakdown voltage of 560 k V/cm),good charge-discharge performance,and superior stability in a wide temperature/wide frequency/high fatigue range,it shows greater potential than most lead-free dielectric ceramics.This is due to the collaborative AFE R phase and stable domain engineering construct NN-0.3 CT lead-free relaxation AFE ceramics.Local nano-polarization configuration strategy:NN is added into linear dielectric CT ceramics.In order to achieve high saturation polarization intensity,extremely low residual polarization intensity,and very low hysteresis,the local nano-polarization configuration is built.On the other hand,the added NN significantly decreases the average grain size and leakage current density of the ceramics,ensuring excellent breakdown strength.In the end,the successful design of 0.6CT-0.4NN type linear lead-free relaxation ferroelectric ceramics won the outstanding energy storage performance(W_rec=7.01 J/cm³,η≈94.3%),as well as having excellent mechanical properties（vickers hardness H_v=8.22 GPa）at high electric fields of 680 k V/cm.Additionally,the proposed ceramics still have outstanding thermal stability of energy storage and excellent charge-discharge performance.The lead-free quasi-linear relaxation ferroelectric ceramics designed by this strategy have great potential of dielectric energy storage and promote the practical application of lead-free dielectric capacitors.Multi-scale cutting strategy:At the atomic level,a ternary system is created by adding BNT and CT to pure NN ceramics.A number of non-equivalent ions are then added to improve local random fields,which lowers the intensity of residual polarization and upholds high saturation polarization.From the perspective of grain size,the grain size of NN ceramics is greatly reduced by the design of ternary system to form more grain boundaries with high resistivity and improve the breakdown strength of the ceramics.From the mesoscopic scale,NN-based lead-free relaxation ferroelectric ceramics with the coexistence of polymorphic nanodomains are created after the introduction of BNT and CT breaks the long-range ordered antiferroelectric domains in NN ceramics at room temperature.Cutting based on multi-scale collaboration strategy has thus achieved high W_rec of 7.42 J/cm³,ultra-highηof 94.2%,high compressive strength of 620 k V/cm,good thermal stability,frequency stability,and charge and discharge performance to construct the ternary relaxation ferroelectric ceramics.This work provides a useful design idea for the development of high efficiency dielectric energy storage lead-free ceramic materials and promotes the development of lead-free dielectric ceramic materials in capacitors.