Optimization Of Energy Storage Performance And Low-temperature Firing Of BaTiO₃-based Ferroelectric Ceramics

The over-exploitation and misuse of fossil energy has caused a serious energy crisis and environmental pollution in the past decades,making it urgent to develop low energy loss and environmentally friendly energy storage materials.Barium titanate（BT）-based lead-free dielectric energy storage capacitors are widely used in various fields of military,medical and electronic equipments,due to their good dielectric and ferroelectric properties.However,BT-based ceramics with the low energy density and high sintering temperatureare unable to meet the requirements of miniaturization and integration of devices.In this paper,the energy storage performance of BT-based ceramics is improved through the composition modificationand the fabrication processe.The effects of sintering aids on the sintering temperature and energy storage performance of BT-based ceramicsare also investigated.Bismuth niobium-lithiumate(Bi Li_0.5Nb_0.5O₃,BLN)and bismuth titanomagnesite(Bi Mg_0.5Ti_0.5O₃,BMT)component were introduced into BT ceramic matrix and a series of（1-x）BT-x Bi Me O₃（Me=Li,Nb or Mg,Ti）ceramics were prepared by solid state method.The results indicated that the introduction of the complex ions of Bi³⁺and Me³⁺interrupted the ferroelectric long-range order in BT ceramics and reduced the residual polarization of BT ceramics.It can be seen that composition optimization helps BT-0.375BMT（BT-BMT）ceramics to obtain the large difference between the maximum polarization and the residual polarization resulting in excellent energy storage properties.BT-BLN ceramics was prepared ultizing viscous polymer processing（VPP）to further improve the energy storage properties.The relative density of BT-BLN ceramics was increased from 96.62%to 99.31%due to the VPP techmology,thereby improving the breakdown field strength from 230 k V/cm to 470 k V/cm.Finally,a high effective energy storage density of 5.34 J/cm³ and a high energy storage efficiency of 87.11%were achieved.The effects of lithium carbonate（Li₂CO₃）,Li F and 65Bi₂O₃-20B₂O₃-15Si O₂（BBS）on the sintering temperature and the energy storage properties of the BT-BMT ceramics were studied systematically.The sinering temperature of BT-BMT ceramics was reduced to 1030℃by doping Li₂CO₃ with a low melting point（720°C）.The breakdown field strength of the BT-BMT ceramic with the Li₂CO₃ doping amount of 1 wt%was 150k V/cm,while an effective energy storage density of 0.78 J/cm³ and an energy storage efficiency of 73.86%were achieved.However,the introduction of too much Li₂CO₃ leads to a reduction in the density and breakdown field strength of the BT-BMT ceramics.The sintering temperature of the BT-BMT ceramics was reduced to 1060℃by doping Li F.The breakdown field strength of the BT-BMT ceramics achieved 320 k V/cm for a concentration of 1.5 wt%Li F.The effective energy storage density of 2.97 J/cm³ and the energy storage efficiency of 87.00%were obtained with the introduction of 1.5 wt%Li F The 65Bi₂O₃-20B₂O₃-15Si O₂（BBS）addition could lower the BT-BMT ceramic sintering temperature to 1080℃,which contribute to the refined grains and high breakdown field strength.The maximum polarization of BT-BMT-1 wt%BBS was 31.05μC/cm² at the dielectric breakdown strength of 250 k V/cm.An enhanced energy storage density of 3.46J/cm³ and an energy storage efficiency of 79.48%were achieved.In addition,BT-BMT ceramics doped with above sintering aids showed excellent energy storage performance in terms of temperature stability.