Research On Energy Storage Properties Of Barium Titanate-based Ferroelectric Thin Film

As a kind of energy storage device,solid dielectric capacitor has the advantages of extremely high charge and discharge efficiency,good stability and fatigue characteristics,and has application prospects in many fields.However,compared with other types of energy storage devices,the energy storage density of dielectric capacitors is relatively low,which greatly limits its application in the field of energy storage.Therefore,it is urgent to improve the energy storage density of dielectric capacitors.Among them,barium titanate（Ba Ti O₃,BTO）,as a traditional ferroelectric,has good potential for energy storage applications due to its excellent polarization properties.In this paper,the BTO-based energy storage thin film was prepared by the sol-gel method,and the energy storage performance of BTO was improved by A、B site doping and thin film compounding,these phenomena have been studied and analyzed in detail,and the specific results are as follows:1.The best conditions for the preparation of BTO thin films by the sol-gel method were explored,the solvent was determined to be glacial acetic acid,the substrate was determined to be Pt（111）/Ti/Si O₂/Si,and the annealing temperature was determined to be 650°C.The BTO film prepared under this condition has an energy storage density of 9.9 J/cm³ and an energy storage efficiency of 79.9%.Based on this condition,Ba_0.88Sr_0.12Ti O₃（BST）film and Bi_0.5Na_0.5Ti O₃（BNT）film were prepared.The polarization value and breakdown field strength of BST film decreased which is caused by the weak metallicity of Sr.The polarization value of the BNT film is significantly improved,but the breakdown field strength is also decreased correspondingly,which is caused by the volatilization of Bi and Na elements.2.12%Zr were doped into BTO to construct Ba Zr_0.12Ti_0.88O₃（BZT）film,the doping of Zr leads to a decrease in the crystallinity of the film,thereby reducing the polarization of the film,however,the amorphous film shows a high breakdown field strength,which improves the energy storage performance to 12.6 J/cm³ and 92.6%.Based on this research,Ba Mg_xTi_1-xO₃（BM_xT）films were constructed by doping different concentrations of Mg,and the highest polarization and breakdown strength are achieved simultaneously while x=0.18（67.7 J/cm³ and 94.9%）.This is because the doping of Mg can greatly improve the breakdown of BTO,so that the film can be polarized under a higher electric field.3.Aluminum oxide（AO）and BTO are used to construct a composite film with a sandwich structure.This structure makes the applied electric field preferentially concentrate on the amorphous AO in the middle,which enhances the breakdown performance of the film and increases the energy storage density to 14.3 J/cm³.Based on this structure,BNT with higher polarization value but lower breakdown performance was selected instead of BTO to construct AO/BNT and BNT/AO/BNT structures.The breakdown strength of both films were significantly improved,the energy storage density has also increased,especially the BNT/AO/BNT film,which has increased from8.7 J/cm³ to 19.9 J/cm³.This work provides an effective solution for improving the energy storage performance of ferroelectric thin films.