Study On Phase Structure,electrical Properties And Temperature Characteristics Of SrTiO₃ Based Pulse Energy Storage Dielectric Ceramics

In recent years,energy storage materials have attracted much attention.The energy storage components of electric energy mainly include batteries,supercapacitors and dielectric capacitors.Compared with the three materials,dielectric capacitors have been widely studied for their high temperature stability and fast charge-discharge speed.However,the energy storage density of these devices is relatively low.Therefore,improving energy storage density has become a hot spot in the research area.As a linear dielectric,Sr Ti O₃ has high breakdown strength and low dielectric loss,which can be used as the matrix of energy storage ceramic materials.In this paper,0.8Sr_0.8Pb_0.2Ti O₃-0.2Bi(Mg_0.5Zr_0.5)O₃-x(K_0.5Na_0.5)Nb O₃（0.8SPT-0.2BMZ-x KNN）dielectric ceramics were prepared by traditional solid state reaction method.The phase structure,electrical properties,energy storage performance and temperature stability of dielectric ceramics were studied with the variation of KNN amount.The experimental results show that 0.8SPT-0.2BMZ-x KNN ceramic samples transform from pseudocube structure to tetragonal phase gradually and the cell volume decreases gradually with the increase of KNN introduction.When x=0.03,the 0.8SPT-0.2BMZ-0.03KNN ceramic sample has good temperature stability in the temperature range of-55 ^oC to 125 ^oC,and meets the X7R standard of pulse power capacitor.The I-E curve is two flat current peaks,which increase slowly with the increase of temperature and electric field.No other discharge peaks appear,which conforms to the characteristics of relaxation phase energy storage.At 240 k V/cm,the recoverable energy storage density and efficiency are 1.27 J/cm~3 and 90%,respectively.At300 k V/cm,0.8SPT-0.2BMZ-0.03KNN dielectric ceramics have a high discharge energy density of 2.05 J/cm~3 and a high power density of 143 MW/cm~3.As the temperature increases from 30 ^oC to 150 ^oC,the variation of energy storage density is less than 15%,and the variation of discharge power density is less than 5%.In this paper,（1-x）Sr_0.7Pb_0.2Ca_0.1Ti O₃-x Bi(Mg_0.5Zr_0.5)O₃（（1-x）SPCT-x BMZ）dielectric ceramics were prepared by traditional solid state reaction method.The influence of introduction of BMZ on phase structure,electrical properties,energy storage performance and temperature stability were studied.The results show that BMZ can form perovskite solid solution with SPCT and has a single phase structure.With the increase of BMZ introduction,Curie temperature of dielectric ceramics gradually shifted to high temperature direction.When introduction is x=0.20,0.8SPCT-0.2BMZ meets X7R standard.The I-E curve exhibits two wide current peaks as the field intensity changes,and is characterized by relaxation ferroelectric phase.The calculated results of P-E loops show that the recoverable energy storage density of ceramic samples reaches 1.82 J/cm~3 and the efficiency is more than 91%at220 k V/cm.At 380 k V/cm,the discharge energy density and power density of the ceramic samples are 2.89 J/cm~3 and 276 MW/cm~3,respectively.As the temperature increases from 30^oC to 150 ^oC,the variation of energy storage density and discharge energy density are less than10%,and the variation of power density is less than 5%.The dielectric properties of Sr Ti O₃ based ceramic materials were improved by introducing other substances.These two materials are potential candidates for Multi-layer Ceramic Capacitors（MLCC）.