放电等离子烧结制备钛酸锶钡基陶瓷的储能性能及其数值模拟

发布时间：2018-07-03 19:12

本文选题：钛酸锶钡陶瓷 + 放电等离子烧结　；参考：《浙江大学》2017年博士论文

【摘要】：随着脉冲功率系统小型化和轻量化的发展,开发具有更高储能密度的电介质材料成为当前研究的热点。本文选取钛酸锶钡(Ba1-xSrxTiO3)基陶瓷作为研究对象,系统地研究了制备工艺、微观结构和相组成对材料储能性能的影响。同时,结合数值模拟,预测了钛酸锶钡基陶瓷的介电击穿过程和储能密度。得到的主要结论如下:陶瓷的微观结构会直接影响其击穿场强,而微观结构又和制备工艺密切相关。传统固相烧结(CM)制备的Ba0.4Sr0.6TiO3样品致密度较低且微观结构不均匀。放电等离子烧结(SPS)制备的样品相对致密度均在99%以上,陶瓷晶粒细小且粒径分布均一。因此,相比于CM样品,微结构的改善使得SPS样品的击穿场强从180 kV/cm提高到260 kV/cm,最大储能密度从0.61 J/cm3提高到1.20 J/cm3,储能效率从72.6%提高到91.6%。为研究晶粒尺寸效应对材料击穿场强和储能密度的影响,本文采用溶胶凝胶法结合放电等离子烧结制备了具有不同晶粒大小的Ba0.4Sr0.6TiO3致密陶瓷,结果表明,平均晶粒尺寸约为200 nm的样品的储能性能最佳,其击穿场强高达240 kV/cm,最大储能密度为1.23J/cm3,储能效率为94.52%。在Ba0.4Sr0.6TiO3陶瓷中添加高绝缘性的MgO颗粒能有效地提高其击穿场强。由于SPS烧结温度低且烧结时间短,Ba0.4Sr0.6TiO3基体和MgO之间的扩散和化学反应被有效地抑制。结果显示,性能最佳的复相陶瓷组分为95 wt%Ba0.4Sr0.6TiO3+5 wt%MgO,其击穿场强达到300 kV/cm,最大储能密度为1.50 J/cm3,储能效率为88.5%。制备核壳结构的复相陶瓷也是提高材料储能性能的重要手段。本文采用液相法制备了具有不同摩尔分数的Ba0.4Sr0.6TiO3@SiO2核壳结构粉末,并结合放电等离子烧结获得了致密的Ba0.4Sr0.6TiO3@SiO2复相陶瓷。结果表明,核壳结构的界面处在750℃左右开始发生化学反应,原本均匀包覆在Ba0.4Sr0.6TiO3颗粒表面的无定型SiO2壳层结构逐渐消失,取而代之的是反应生成的Sr2TiSi2O8相。当SiO2包覆量较少时,生成的Sr2TiSi2O8纳米颗粒均匀包覆在Ba0.4Sr0.6TiO3基体表面并显著地提高复相陶瓷的击穿场强;随着SiO2含量的增多,Sr2TiSi2O8纳米颗粒聚集长大,在Ba0.4Sr0.6TiO3晶界处形成微米颗粒,使得其击穿场强有所下降。性能最佳的复相陶瓷组分为92 mol%Ba0.4Sr0.6TiO3 + 8 mol%Si02,其击穿场强高达400kV/cm,最大储能密度为1.60J/ccm3,储能效率为90.9%。在Ba0.4Sr0.6TiO3/MgO复相陶瓷中,Ba0.4Sr0.6TiO3基体的介电常数约为950,而MgO的介电常数仅为10。根据静电平衡方程,这种介电常数的巨大差异必然会导致局域电场的不均匀分布,从而影响介电击穿过程。本文基于随机模型,模拟了钛酸锶钡基陶瓷和氧化镁基陶瓷的击穿路径。结果表明,在Ba0.4Sr0.6TiO3基材料中,无论添加的MgO第二相是球状还是棒状,放电通道都会尝试“绕过”MgO晶粒;而在MgO基材料中,放电通道总是倾向于“穿过”Ba0.4Sr0.6TiO3晶粒。最后,基于Landau-Devonshire唯象理论和Ginzburg-Landau方程,本文利用相场模型模拟了Ba1-xSrxTiO3单晶和多晶的铁电性能,并通过模拟的电滞回线计算了其储能密度。结果表明,随着Sr含量的增加,其储能密度先增加后减小,当x=0.6时材料具有最佳的储能性能。
[Abstract]:With the development of miniaturization and light weight of pulse power system, the development of dielectric materials with higher energy storage density has become a hot spot of current research. This paper selected barium strontium titanate (Ba1-xSrxTiO3) based ceramics as the research object, and systematically studied the preparation process, the effect of microstructure and phase composition on the energy storage performance of the material. The dielectric breakdown process and the energy storage density of barium strontium titanate ceramics are predicted by value simulation. The main conclusions are as follows: the microstructure of the ceramics will directly affect the breakdown field, and the microstructure is closely related to the preparation process. The Ba0.4Sr0.6TiO3 sample prepared by the traditional solid phase sintering (CM) has a low density and the microstructure is not uniform. The relative density of the samples prepared by electric plasma sintering (SPS) is above 99%, and the ceramic grain is fine and the particle size distribution is uniform. Therefore, compared to the CM sample, the breakdown strength of the SPS samples increases from 180 kV/cm to 260 kV/cm, the maximum energy storage density is increased from 0.61 J/ cm3 to 1.20 J/cm3, and the energy storage efficiency is increased from 72.6% to 91.6%.. In order to study the effect of grain size effect on material breakdown field strength and energy storage density, the Ba0.4Sr0.6TiO3 compact ceramics with different grain sizes were prepared by sol-gel method and discharge plasma sintering. The results showed that the energy storage performance of the sample with an average size of 200 nm was the best, and the breakdown field strength was up to 240 kV/cm. The large energy storage density is 1.23J/cm3, and the energy storage efficiency of 94.52%. in Ba0.4Sr0.6TiO3 ceramics with high insulating MgO particles can effectively improve the breakdown field strength. The diffusion and chemical reaction between the Ba0.4Sr0.6TiO3 matrix and MgO is effectively suppressed because of the low sintering temperature and the short sintering time of SPS. The results show that the best complex phase ceramics have the best performance. The composition is 95 wt%Ba0.4Sr0.6TiO3+5 wt%MgO, the breakdown field strength is 300 kV/cm, the maximum energy storage density is 1.50 J/cm3, the energy storage efficiency is 88.5%. to prepare the shell structure complex phase ceramics is also an important means to improve the material storage performance. In this paper, the liquid phase method was used to prepare the Ba0.4Sr0.6TiO3@SiO2 nuclear shell powder with different mole fraction. The compact Ba0.4Sr0.6TiO3@SiO2 composite ceramics were obtained by spark plasma sintering. The results showed that the chemical reaction of the core shell structure began to occur at about 750 degrees C. The amorphous SiO2 shell structure which was originally coated on the surface of Ba0.4Sr0.6TiO3 particles gradually disappeared, and replaced by the reaction generated Sr2TiSi2O8 phase. When SiO2 When the coating amount is less, the Sr2TiSi2O8 nanoparticles are evenly coated on the surface of the Ba0.4Sr0.6TiO3 matrix and significantly improve the breakdown field strength of the composite ceramics. As the content of SiO2 increases, the Sr2TiSi2O8 nanoparticles gather and grow, and the micron particles are formed at the Ba0.4Sr0.6TiO3 grain boundary, which makes the breakdown field strength decrease. The ceramic component is 92 mol%Ba0.4Sr0.6TiO3 + 8 mol%Si02, the breakdown field strength is as high as 400kV/cm, the maximum energy storage density is 1.60J/ccm3, the energy storage efficiency is 90.9%. in the Ba0.4Sr0.6TiO3/MgO complex ceramics, the dielectric constant of the Ba0.4Sr0.6TiO3 matrix is about 950, and the dielectric constant of MgO is only 10. based on the electrostatic equilibrium equation, and the dielectric constant is huge. The difference inevitably leads to the inhomogeneous distribution of the local electric field, thus affecting the dielectric breakdown process. Based on the random model, the breakdown path of barium strontium titanate based ceramics and Magnesium Oxide based ceramics is simulated. The results show that in the Ba0.4Sr0.6TiO3 based materials, no matter the second phase of the addition of MgO is a ball or a rod, the discharge channel will try to "go around" In the MgO based material, the discharge channel is always inclined to "pass through" the Ba0.4Sr0.6TiO3 grain. Finally, based on the Landau-Devonshire phenomenological theory and the Ginzburg-Landau equation, the ferroelectric properties of the Ba1-xSrxTiO3 single crystal and the polycrystalline are simulated by the phase field model, and the energy storage density of the Ba0.4Sr0.6TiO3 is calculated by the simulated hysteresis loop. The results showed that with the increase of Sr content, the energy storage density first increased and then decreased. When x=0.6, the material had the best energy storage performance.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TQ174.1

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