| Barium strontium titanate (BaxSr1-xTiO3, BST) was an infinite solid solution of SrTiO3 and BaTiO3 with ABO3 perovskite structure. With the x value increased from 0 to 1, BST ceramics transformed from cubic paraelectric phase of SrTiO3 to tetragonal ferroelectric phase of BaTiO3. The Curie temperature can be adjusted between near absolute zero and 120℃, meeting different application requirements with different dielectric properties. When 0≤x≤0.4, the BST ceramics was cubic paraelectric phase with its Curie temperature far below room temperature, which can be treated as linear dielectrics for solid state energy storage material candidates..In this work, BaxS1-xTiO3 (BST, x≤0.4) ceramics was firstly selected to study the influence of x values on the phase structure, microstructure, dielectric properties and storage characteristics. Especially, the relationship between energy density and energy efficiency was optimized under high electric field conditions. The results showed that the BST ceramics was pure cubic perovskite structure at room temperature, and the grain size was several to ten micrometers with dense microstructure. With the increasing of x values, the Curie temperature of BST ceramics was gradually moved to higher temperatures, but was far below room temperature. At a given electric field, the energy density of BST ceramics gradually increases, but the energy efficiency decreases with the increase of x values. At room temperature, the Bao.3Sro.7TiO3 ceramics has high dielectric constant (εr=650@1kHz) and a very low dielectric loss (tan8=7.6×10-4@1kHz). The Ba0.3Sr0.7TiO3 ceramics has and optimized energy density (y=0.23J/cm3) and energy efficiency (η=95.7%) with the applied electric field of 90kV/cm, which should be more suitable for solid pulse power energy storage applications.Secondly, the BaxSr1-xTiO3 (x=0.3,0.4) ceramics was selected as base material, and BBS frit was used to lower its sintering temperature. The effect of BBS frit doping amount on the phase structure, microstructure, dielectric properties, and storage characteristics of the ceramics was investigated. The results showed that the BBS frit can reduce the sintering temperature of the ceramics from 1350℃ to 1150 ℃. Meanwhile, impure phases 2CaO-SiO2 and 3CaO·SiO2 can be detected after BBS frit addition. The grain size was refined with the improvement of density and the breakdown strength of the ceramics. The energy density of Bao.3Sro.7Ti03 ceramics was 0.4724J/cm3 with an applied electric field of 135kV/cm, being 1.17 times that of pure Ba0.3Sr0.7TiO3 ceramics. The energy density of Bao.4Sro.6Ti03 ceramics was 0.3977J/cm3 with an applied electric field of 110kV/cm, being 1.26 times that of pure Ba0.4Sr0.6TiO3 ceramics. In particular, the addition of BBS frit can significantly reduce the dielectric loss at high temperature conditions. With the BBS frit doping amount of 4wt%, the dielectric loss of Ba0.3Sr0.7TiO3 ceramics at 220℃, as well as Ba0.4Sr0.6TiO3 ceramics at 250℃, was still less than 0.05, indicating BBS frit doping expanded the high temperature applications of BST energy storage ceramics.Finally, the BaxSr1-xTiO3 (x=0.3,0.4) ceramics was still selected as base material. However, the composition of the BBS frit was improved to BBSZ one with the addition of Al2O3 and ZrO2 network intermediates. The effect of BBSZ frit doping amount on the phase structure, microstructure, dielectric properties, and storage characteristics of the ceramics was investigated. The results showed that the BBSZ frit can also reduce the sintering temperature of the ceramics to 1150℃, and impurity phase of 3CaO·SiO2 can be detected. The microstructure characteristics with large and small grains closely interlaced can be observed. BBSZ frit doping improved the breakdown strength of the ceramics more effectively than BBS frit doping, which should be due to the addition of network intermediate in BBSZ frit. The energy density of Ba0.3Sr0.7TiO3 ceramics was 0.6337J/cm3 with an applied electric field of 160kV/cm, being 1.57 times that of pure Ba0.3Sr0.7TiO3 ceramics. The energy density of Ba0.4Sr0.6TiO3 ceramics was 0.5044J/cm3 with an applied electric field of 130kV/cm, being 1.59 times that of pure Ba0.4Sr0.6TiO3 ceramics. The addition of BBSZ frit can also significantly reduce the dielectric loss at high temperature conditions. With the BBSZ frit doping amount of 4wt%, the temperature with the dielectric loss lower than 0.05 of Ba0.4Sr0.6TiO3 and Ba0.3Sr0.7TiO3ceramics was reached to 260℃ and 300℃ respectively, showing great potential for high-temperature energy storage applications. |
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