Preparation Of Fine-grained SrTiO₃-based Ceramics By Precipitation Coating Mothed And Its Energy Storage Properties

With the rapid development of the electronics industry,electronic devices develop toward the miniaturization direction.As energy storage dielectrics in pulse power technology,the energy storage density of ceramic capacitors limits the miniaturization application of pulse power technology.Currently how to further improve the energy storage density of ceramics in pulse power systems is one of the problems urgent need to be solved.In this paper,the sol-coprecipitation method was applied to fabricate the B₂O₃-Al₂O₃-SiO₂-coated SrTiO₃（BAS-coated ST）nanopowders,2MgO-2Al₂O₃-5SiO₂-coated SrTiO₃（MAS-coated ST）nanopowders and B₂O₃-Al₂O₃-SiO₂-coated Ba_0.4S_0.6TiO₃（BAS-coated BST）nanopowders in order to obtain the fine-grained ST-based ceramics with high breakdown strength（BDS）,high energy storage density and high energy storage efficiency.The ST-based ceramics were fabricated by conventional solid-phase sintering method,and the effect of BAS and MAS concentration on the sintering behavior,microstructure,dielectric properties and energy storage properties of ST-based ceramics was investigated.The sol-coprecipitation method was applied to fabricate the BAS-coated ST nanopowders,and the ST-xwt%BAS（x=0;1;2;3;4;6;8;10）ceramics were fabricated by conventional solid-phase sintering method.It could be found that the addition of BAS can decrease the sintering temperature evidently,inhibit the grain growth and improve the BDS of ceramics.When the value of x was 2,compared with pure ST ceramics,the sintering temperature of the sample was reduced by 120℃,and the average grain size of the sample was only about 340 nm.Due to the reduction of the grain size of samples and the increase of the BAS content,the ST-2wt%BAS ceramics showed the optimal energy storage performance with the energy storage density of 1.47 J/cm³ at 350 kV/cm which were both higher than that of pure ST ceramics（0.52 J/cm³,180 kV/cm）.The oxalate co-precipitation mothed was applied to prepare the uniform BST nanopowders,and the BAS was uniformly coated on the surface of BST particles to fabricate the BAS-coated ST nanopowders.The BST-xwt%BAS ceramics（x=0;1;2;3;4;5）were fabricated by conventional solid-phase sintering method.The addition of BAS could decrease the sintering temperature of BST ceramics evidently and hinder the diffusion reaction between BST at high temperature,so the average grain size of ceramics reduced significantly.The average grain size of BST-3wt%BAS ceramics was 150 nm,almost like the size of pristine BST nanopowder（100 nm）.But,when the BAS content further increased,some grains of ceramics grow abnormally and result in the pore.When the value of x was 3,due to the fine grain and compact structure,the BST-3wt%BAS ceramics exhibited the weak interfacial polarization and excellent energy storage properties with high BDS（410 kV/cm）,high energy storage density（1.8 J/cm³）and high energy storage efficiency（81.8%）,which were all higher than that of pure BST ceramics（0.74 J/cm³,76.3%,210 kV/cm）.The MAS-coated ST particles were prepared by sol-coprecipitation method,and the ST-xwt%MAS（x=0;1;2;3;4;5）ceramics were obtained after calcining at1320℃.With the addition of MAS,the average grain size of ST-xwt%MAS ceramics decreased obviously.The BDS and energy storage density of ceramics significantly improved due to the addition of MAS.When the value of x was 2,the the average grain size of ceramics dropped from 15μm for pure ST ceramics to 290nm for ST-2 wt%MAS ceramics.And the ST-2 wt%MAS ceramics showed the optimal energy storage performance with the energy storage density of 1.12 J/cm³and the energy storage efficiency of 81.8% at 340 kV/cm,the BDS and energy storage density were both higher than that of pure ST ceramics（0.52 J/cm³,180 kV/cm）.At the same time,compared with the ST-2 wt%MAS ceramics prepared by chemical coating method,the microstructure of the ST-2 wt%MAS ceramics prepared by high energy ball milling mothed was damaged and result in the pore,so the BDS and the energy storage density of the ST-2 wt%MAS ceramics prepared by chemical coating method were both much higher than that of the ST-2 wt%MAS ceramics prepared by high energy ball milling mothed.