Energy Storage Properties In Filled Tungsten Bronze Tantalate Ceramics

Because of climate change,energy deficiency in the whole world,human put forward higher requirements on energy storage technology.Although the battery possesses a higher energy density,but their power density is too low to meet application condition of high-power pulsed systems.Dielectric capacitors possess very high power density,in this thesis,our aim is to improve the energy density of dielectric capacitors.Tungsten bronze ceramics compose one of the most important dielectric families which are only secondary to perovskites.With a moderate dielectric constant and very low dielectric loss,Tungsten bronze ceramics are considering as promised candidates for energy storage applications.Ba5LaTi3Ta7O30 a typical linear dielectric material.Optimal dielectric constant of 15,dielectric strength of 639 kV/cm and energy storage density of 2.9 J/cm3 were obtained for ceramics sintered at 1550 ℃ by conventional solid sintering method(CS).At the same time,Ba5LaTi3Ta7O30 ceramics have very low dielectric loss(~10-3)and high energy storage efficiency of 82%.Maximum energy storage efficiency(~94%)was obtained in BasLaTi3Ta7O30 sintered at 1525 ℃ with a corresponding dielectric strength of 585 kV/cm and energy storage density of 2.3 J/cm3.The dielectric breakdown mechanism was also investigated based on the morphology of the fracture surface and mainly belonged to thermal breakdown.In order to further improve energy storage density,BasLaTi3Ta7O30 ceramics with higher density(~98%),relatively smaller grain size and lower porosity were obtained by sintering at 1040℃ by spark plasma sintering(SPS).Optimal,dielectric strength of 1061.3 kV/cm and energy storage density of 12.4 J/cm3 were obtained.Although Ba5LaTi3Ta7O30 ceramics have good energy storage properties,however the optimal sintering condition is quite strict.Therefore,Sr-based tungsten bronze ceramics with easier sintering conditions were prepared by conventional solid sintering method(CS)and the energy storage performances were investigated systematically.Optimal energy storage properties were obtained in SrsLaTi3Ta7O30 ceramics sintered at 13750C with a maximum dielectric strength of 742.6 kV/cm and energy storage density of 4.18 J/cm3.