| Ceramic dielectric capacitors are expected to be used in pulsed power systems due to their advantages such as ultra-high power density and good thermal stability.Recently,dielectric materials with high energy density(W)and energy storage efficiency(η)has attracted great attention.Doping with multiple ions in(K,Na)NbO3(KNN)-based ceramics can destroy the long-range ferroelectric domains and induce the formation of polar nano-regions(PNRs),which can reduce energy loss and ameliorate the energy storage performance of KNN-based ceramics.In this paper,the preparation,microstructure and energy storage characteristics of BiMeO3-doped KNN-based ceramics with multiple Me ions were studied.Firstly,the effects of Bi(Mg1/3Zn1/3Ta1/3)O3 doping on dielectric energy storage properties of KNN-based ceramics were studied.It is found that when the doping amount is below 10mol%,KNN-based ceramics show obvious relaxation characteristics and doping of Bi(Mg1/3Zn1/3Ta1/3)O3 can significantly reduce the grain size of KNN-based ceramics.Two-step sintering can improve densification and dielectric properties of Bi(Mg1/3Zn1/3Ta1/3)O3 doped KNN-based ceramics,and the recoverable energy density(Wrec)can be increased to 1.144J/cm3.Secondly,the effects of Bi(Mg1/4Zn1/4Yb1/4Ta1/4)O3 doping on dielectric energy storage properties of KNN-based ceramics were studied.It is found that with the increase of Bi(Mg1/4Zn1/4Yb1/4Ta1/4)O3 doping content,the temperature(Tm)corresponding to the maximum value of the dielectric constant gradually decreases.Compared with one-step sintering,the two-step sintered 095KNN-0.05 Bi(Mg1/4Zn1/4Yb1/4Ta1/4)O3 and 0.90KNN-0.10 Bi(Mg1/4Zn1/4Yb1/4Ta1/4)O3 ceramics sintered by two-step method are more dense.Energy-storage density(W)of 2.430J/cm3 and 2.083J/cm3,recoverable energy density(Wrec)of 1.898J/cm3 and 1.897J/cm3,energy storage efficiency(η)of 78.1%and 91.1%,were simultaneously achieved in the 0.95KNN-0.05Bi(Mg1/4Zn1/4Yb1/4Ta1/4)O3 and 0.90KNN-0.10Bi(Mg1/4Zn1/4Yb1/4Ta1/4)O3 ceramics,respectively.Finally,the effects of Bi(Mg1/5Zn1/5Ni1/5Hf1/5Ta1/5)O3 doping on dielectric energy storage properties of KNN-based ceramics were studied.It was found that all samples are single-phase perovskite oxide.This dopant can effectively inhibit the grain growth of KNN ceramics.When the doping content is 5mol%,the W and Wrec of the KNN-based ceramics sintered by the two-step method are 1.587J/cm3 and 1.222J/cm3,respectively,and the efficiency remains at 77.0%.Controlling the cooling rate from high temperature(1140℃)to synthesis temperature.of Bi(Mg1/5Zn1/5Ni1/5Hf1/5Ta1/5)O3-doped KNN powder(850℃)is beneficial for maximum polarization(Pm)of KNN-based ceramics.0.95KNN-0.05 Bi(Mg1/5Zn1/5Ni1/5Hf1/5Ta1/5)O3 ceramic sample heat-treated with a cooling rate of about 100℃/h shows a Pm of 35.88μC/cm2,W of 3.0 J/cm3,Wrec of 1.514J/cm3,η of 50.5%,when electric field of 172kV/cm is applied. |
