| In recent years,with the rapid development of electronic information technology,higher requirements have been put forward for energy storage electronic components,making the development of energy storage devices with smaller volume,higher energy density and lower energy loss particularly important.Among them,dielectric capacitors are widely used in pulse power electronic equipment such as hybrid electric vehicles and automatic external shock absorbers due to their high power density,excellent mechanical stability and fast charging and discharging speed.However,due to the low energy storage density and small total energy storage,it is difficult to commercialize.Therefore,the improvement of the energy storage density of dielectric materials is the key to the study of pulsed power capacitors.Sr Ti O3 belongs to a typical anisotropic dielectric with a cubic perovskite structure at room temperature,a moderate dielectric constant(about 300),and a very low dielectric loss(< 0.01).Breakdown field strength of pure Sr Ti O3 ceramics can reach 100 k V/cm and as repored the doping can increase the energy storage density of Sr Ti O3-based ceramics.In this case,the composition optimization is carried out by defect doping to modify Sr0.7Bix Ti O3(x=0.1~0.4)ceramics by A-site Bi doping.Sr0.7Bix Ti O3(x=0.1,0.2,0.3,0.4)ceramics were prepared by the traditional solid-state reaction method.Among them,changing the content of Bi3 + at the A site mainly has the following three effects:(1)Due to the low melting point of Bi3 +,a liquid phase will be formed during the sintering process,which promotes mass transfer of the material phase,reduces the sintering temperature,and refines the grains,resulting in higher activation energy and increased breakdown field strength of the grains;(2)Since the hybridization between the 6p orbital of Bi and the 2p orbital of O can enhance polarization,appropriate Bi3 + doping at the A site is beneficial to the improvement of system polarization;(3)Due to the difference in radius and the difference in electricity price,the change in the content of Bi3 + at the A-site will introduce A-site defects,resulting in lattice distortion,relaxation characteristics,widening and depressing the dielectric peaks,which can reduce the residual polarization while improving the material Temperature stability.The synergistic effect of these three factors is beneficial to improve the energy storage performance of ceramics.Among them,when x=0.2,Sr0.7Bi0.2Ti O3 ceramics can obtain a charging energy storage density of 1.68 J/cm3 under an electric field of 230 k V/cm,a discharge energy storage density of 1.10 J/cm3,and an energy storage efficiency of65.48%.At the same time,the ceramic also has good temperature stability and fatigue strength,as well as fast charging and discharging speed.In order to further optimize the energy storage performances of Sr0.7Bi0.2Ti O3,Ba Ti O3 was selected to form a solid solution with it.Sr0.7-y Bay Bi0.2Ti O3(y = 0,0.02,0.04,0.06,0.08,0.10)ceramics were prepared by traditional solid state method.The introduction of Ba Ti O3 can lead to the following effects:(1)Ba Ti O3 has high polarization characteristics,which is beneficial to the improvement of the polarization performance of the system;(2)When Ba2 + replaces Sr2 +,relaxor will occur due to the difference of ionic radius to improve temperature stability.When y=0.04,Sr0.66Ba0.04Bi0.2Ti O3 ceramics can achieve a charging energy storage density of 1.97J/cm3,a discharge energy storage density of 1.71 J/cm3,and an energy storage efficiency of 86.80% at 290 k V/cm.At the same time,the ceramic also has good temperature stability and fatigue strength,as well as fast charging and discharging speed.Mn CO3 was selected to optimize energy storage performance by B-site doping of Sr0.66 Ba 0.04 Bi 0.2Ti O3+z Mn(z=0.0%,0.2%,0.4%,0.6%,0.8%)ceramics by traditional solid-state method.With increasing Mn content,the maximum polarization and breakdown field strength gradually decrease,and the residual polarization decreases and then increases,and the corresponding energy storage efficiency first increases and then decreases with further Mn doping.When z=0.4%,Sr0.66 Ba 0.04 Bi 0.2Ti O3+0.4% Mn obtained a charging energy storage density of 1.44 J/cm3,a discharge energy storage density of 1.35 J/cm3,and an energy storage efficiency of 93.75% at 260 k V/cm.Simulateneously,the ceramic also has good temperature stability and fatigue behavior,as well as fast charging and discharging speed. |
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