Optimization Of Energy Storage Properties And Mechanism For NaNbO₃ Lead-Free Dielectric Ceramics With Adding Bi-Based Chalcogenide

Dielectric materials have become the cornerstone of passive electronic components in the world today due to their numerous excellent performances.Filters and resonators designed using the inductor’s pass direct current,block alternating current characteristics.Various pulse discharge systems based on high power density and ultra-fast charge and discharge rates have led to the rapid development of dielectric materials.NaNbO₃（NN）itself has a series of characteristics such as low price,light weight,good dielectric strength,high polarization strength and antiferroelectric phase at room temperature.In this paper,NaNbO₃ ceramics are chose as the research object.Firstly,the dielectric materials with better energy storage performances are designed and prepared.Furthermore,the microstructure,energy storage properties,dielectric properties and charge/discharge capacity of the ceramic materials are systematically investigated.The main areas of research include the following three aspects:（1）(Bi_0.5Na_0.5)_0.7Sr_0.3TiO₃（BNST）is added to NaNbO₃-Bi(Ni_1/2Sb_2/3)O₃ ceramics.The original long-range ordered structure is enhanced by the inequivalent substitution strategy at the A and B sites to break the relaxation of the system.Besides,Bi₂O₃ can reduce the overall sintering temperature and refine the grains of ceramics,which enhances the dielectric strength of ceramics.Especially,the 0.8（NN-BNS）-0.2BNST ceramic sample obtained a high energy storage performance(U_rec)=4.1 J/cm³ and energy storage efficiency（?）=75.4%.However,the?and the temperature stability were not excellent due to the influence of the heterogeneous phases in the system.（2）In order to eliminate the undesirable effect of the second phase and increase the insulation of the samples,Zr O₂ with a higher forbidden band width was chosen to replace Sb₂O₃,and NaNbO₃-Bi(Ni_1/2Zr_1/2)O₃（NN-BNZ）-BNST ceamics were perpared.0.8（NN-BNZ）-0.2BNST ceramic with a high Urec（8.6 J/cm³）,excellentη（83.5%）,high power density（P_D=107.7 MW/cm³）and a very fast charge/discharge rate(t_0.9=45 ns)are obtained under the synergistic effects of the engineering strategy of high polarizability ion substitution at the A-site,enhanced relaxation and grain refinement by lowering the sintering temperature.（3）After doping with BNST,both ceramics have good energy storage performance,but the?of ceramics is relative low（75.4%and 83.5%）.For the application of the energy storage ceramic materials,higher energy storage efficiency can reduce energy consumption,which exhibites more environmentally friendly.Therefore,Ca TiO₃ was chosen to further dope the NN-BNZ substrate to obtain a better energy storage efficiency.The final energy storage efficiency of 91%was achieved at 0.15 CT,but 0.1CT showed the best performance(U_rec=5.1 J/cm3,η=83%),applied with a P_D of 74.5MW/cm³ and an ultra-fast charge/discharge rate(t_0.9=36 ns).The above three ceramics were doped to enhance the relaxation,enhance the dielectric strength and regulate the polarization strength,and finally obtain more excellent energy storage characteristics.In summary,0.8（NN-BNZ）-0.2BNST ceramics exhibited the best energy storage characteristics,the best stability and the best charge-discharge performance.