Investigations On Ceramic/Glass Sandwich Structure Dielectric Pulse Power Capacitor

With the development of new fields such as active armor,high-energy electron guns,aerospace vehicle power systems,cardiac defibrillators and advanced electric aircraft,the requirements of pulse power systems are increasingly high,and even the output voltage?or current?of pulse needs to reach the order of 100 k V?or 100 k A?.The key component of pulse power system is the pulse power capacitor which used for energy storage.In order to achieve such a high pulse power outputting,the pulse power capacitor requires both high energy density and high power density,and also requires fast charge and discharge rate.At the same time,it is necessary to take into account the high reliability within the operating temperature and frequency range.The ceramic capacitors meet the requirements mentioned above.But their main limitations is that its low energy density??3 J/cm³?.In this paper,pulse power capacitors with high energy density and fast discharge performance were prepared by designed and tailored composite structure,interface modification and performance control towards the materials.The matrix of the capacitor was designed as a sandwich structure,glass-ceramic-glass.The ceramic dielectric was sintered by Nano-scale Ba_0.4Sr_0.6Ti O₃@Si O₂?BST@Si O₂?core-shell structure powders.High-resistance glass matrix materials were at the both side of the ceramic dielectric layer.The microstructure,dielectric constants,breakdown strength and energy density of the materials were analyzed and tested by using high-resolution transmission electron microscopy,scanning electron microscope,X-ray diffraction,and dielectric tester.The impact of multi-scale structure on the energy storage performance of dielectric capacitors are studied by the crystal structure theory,defect chemistry,interfacial chemistry and other theorys.The relationship between grain size,phase composition,shell thickness,glass base and other parameters and energy storage performance was established.Firstly,the molten salt method was used to prepare BST nanopowders successfully with controlled size,uniform dispersion and good crystallinity,and to match the requirements of the core-shell structure powders.The effects of barium-strontium ratio,molten salt ratio and temperature on powder properties were studied.The results show that when the synthesis temperature was 1200?and the molten salt ratio was 10,the cubic phase BST particles with good crystallinity and dispersibility,uniform solid solubility of Ba/Sr ratio can be prepared.Dielectric ceramics were obtained by sintering BST@Si O₂ core-shell powder.The effect of Si O₂ layer on the microstructure evolution and dielectric properties of BST@Si O₂ ceramic samples was studied.It was found that the incorporation of Si O₂ effectively improved the uniform of BST ceramics microstructure,but it also introducing a second phase.On the one hand,the good core-shell structure of BST@Si O₂ ceramics can significantly improve the breakdown strength of the material,on the other hand,it can also lead to a significant decrease in its dielectric constant.When the Si O₂ content was 8 wt.%,the breakdown strength reached730 k V/cm and the energy storage density reached a maximum of 1.46 J/cm³.Finally,glass-ceramic-glass sandwich structure composite was prepared by combining high-resistance glass material on the ceramic substrate successfully.The study showed that when the Si O₂ content was 6 wt.%,the breakdown strength of the sandwich-structured ceramic capacitor increased to 930 k V/cm,and the energy density reached 1.40 J/cm³.