Preparation,Properties And Mechanism Of NaNbO₃-based Energy Storage Ceramics

Dielectric capacitors have the advantages of high power density,excellent temperature stability and ultra-fast charge-discharge rate,etc.However,in the field of high-speed development of electronics technology,the existing dielectric energy storage materials can not meet the needs of electronic components to the direction of integration,miniaturization and lightweight development,the need to develop a higher energy storage performance of dielectric materials.In this paper,sodium niobate（NaNbO₃,NN）was used as the research object,and the NN ceramics were modified by the conventional solid-phase reaction method for the doping of（1-x）NaNbO₃-x Bi(Mg_0.5Sn_0.5)O₃（（1-x）NN-x BMS）,(Na_1-xBi_x)(Nb_1-xSn_0.75x)O₃(N_1-xB_xN_1-xS_0.75x),（1-x）NaNbO₃-x Bi(Sb_0.33Ti_0.5)O₃（（1-x）NN-x BST）,（1-x）NaNbO₃-x Bi(Ni_0.67Ta_0.33)O₃（（1-x）NN-x BNT）series of dielectric energy storage materials,the phase structure and electrical properties of the above systems are discussed in detail and in depth.（2）Using NaNbO₃ as matrix,introducing hetervalent ions,constructing local random field and reducing grain size,a kind of NN-based relaxor ferroelectric materials with pure perovskite structure（（1-x）NN-x BMS）was synthesized.It was found that the0.91NN-0.09BMS ceramic has good densities and excellent dielectric properties.It achieving large W_rec=4.93 J/cm³and highη=81.5%under a high electric field of 550k V/cm.The energy storage performance also has excellent temperature（20℃～180℃）and frequency（2 Hz～100 Hz）stability,and has the feasibility of operating at high temperature environment.In addition,the 0.91NN-0.09BMS ceramic has a very large current density（971.93 A/cm²）and an ultra-high power density（87.47 MW/cm³）as well as an ultra-fast discharge time（25 ns）.（2）The effects of the introduced ions on the electrical properties of the materials were investigated by introducing(Bi³⁺,Sn⁴⁺)and(Bi³⁺,Sb³⁺,Ti⁴⁺)ions into the NN matrix.N_0.86B_0.14N_0.86S_0.105 ceramics have a pure perovskite structure,high E_b（550k V/cm）,large W_rec（3.47 J/cm³）and Good charge-discharge characteristics(C_D=542.58A/cm²,P_D=37.98 MW/cm³ and t_0.9=14.8 ns).0.89NN-0.11BST ceramics have a pure perovskite structure with the best energy storage performance(W_rec=2.97 J/cm³,η=79.5%)at E_b（410 k V/cm）and excellent energy storage stability（1 Hz～100 Hz,20℃～140℃）,and exhibits good charge-discharge characteristics(C_D=726.6 A/cm²,P_D=43.6 MW/cm³,t_0.9=23 ns).（3）By introducing Bi(Ni_0.67Ta_0.33)O₃ into NN ceramics,disordering of A and B site ions is formed to generate PNRs and enhance the relaxation properties.The fast response of PNRs under the applied electric field effectively improves the energy storage performance of NN-based relaxation ferroelectric ceramics.0.85NN-0.15BNT ceramics exhibits extremely high W_rec（5.53 J/cm³）andη（82.0%）at 575 k V/cm and shows good thermal and frequency stability.0.85NN-0.15BNT ceramics also obtain ultra-fast discharge time(t_0.9=27.5 ns),high current density（C_D=506.42 A/cm²）and higher power density（P_D=35.45 m W/cm³）.These factors indicate that 0.85NN-0.15BNT ceramics have promising applications in lead-free dielectric ceramic capacitors.