Preparation And Properties Of Y And Mn Doped Core-Shell Ba_0.85Ca_0.15Zr_0.1Ti_0.9O₃/PVDF Flexible Dielectrics

At present,emerging electronic devices are increasingly developing towards the direction of small size and multi-functionality,so that flexible micro energy storage devices are growing.Among them,as the functional dielectric material,the research about organic-inorganic composite materials is a major focus of attention for the flexible energy storage devices,and the main problem is low energy storage density.In order to improve the energy storage density,in this thesis,the BCZT/PVDF composite was prepared.Ba_0.85Ca_0.15Zr_0.1Ti_0.9O₃（BCZT）is the inorganic filler and polyvinylidene fluoride（PVDF）is the organic matrix.The effects of the BCZT filling amount,the donor（acceptor）doped BCZT fillers with wrapping acceptor（donor）doped BCZT,the Zr O₂ coating and the polydopamine（PDA）coating of fillers on the properties of BCZT/PVDF composites were studied.Finally,the effective storage density of the composites was significantly improved.Thus the research provides a new idea for the development of high-performance flexible capacitors.The main work is as follows.Firstly,the influence of different technologies on the phase structure and morphology of BCZT were studied.The optimized results are as follows:the spherical BCZT particles of～75.31 nm can be prepared by a sol-gel-hydrothermal method with the Na OH concentration of 8 mol/L.On this basis,BCZT/PVDF composite films with different contents of BCZT were prepared.The results show that the amount of fillers has a positive correlation with the dielectric constant and loss.At 1 k Hz,the dielectric constant of the BCZT/PVDF composite film with 10 wt.%BCZT is 9.60 and the dielectric loss is 0.089.The energy storage density of the composite film is 4.197 J/cm³ at 640 k V/cm.Secondly,the electrical properties of composite films with donor-doped@acceptor-doped BCZT fillers（Y@Mx@PDA/PVDF）were investigated with different Mn concentrations（1-4 mol%）.It confirmed that with the increase of Mn content,the dielectric constant first increased and then decreased,and the dielectric loss kept falling.The donor-doped@acceptor-doped core-shell structure can improve the energy storage density.At 1k Hz,the dielectric constant and the dielectric loss of the Y@M3@PDA/PVDF composite film are 14.2 and 0.136,respectively.The energy storage density of the composite film is5.031 J/cm³ at 640 k V/cm.Then,the effect of Zr O₂ coating on the properties of composite films was studied.The results show that the coated Zr O₂ layer can decrease the dielectric loss and increase the energy storage density.At 1 k Hz,the dielectric constant and the dielectric loss of the Y@M3@Z@PDA/PVDF composite film are 15.5 and 0.049,respectively.At 640 k V/cm,the energy storage density of the composite film is 5.956 J/cm³.Finally,the electrical properties of acceptor-doped@donor-doped composite films（Mx@Y@PDA/PVDF）with Mn doping concentration of 1-4 mol%were discussed.The results show that with the increase of Mn content,the dielectric constant of the composite film first increased and then decreased,while the dielectric loss decreased first and then increased.The acceptor-doped@donor-doped core-shell structure can achieve better energy storage performance than the above core-shell filler type.At 1 k Hz,the dielectric constant and loss of the M3@Y@PDA/PVDF composite film are 11.9 and 0.078,respectively.Besides,the ideal energy storage density is exhibited（5.557 J/cm³ at 640 k V/cm）.Furthermore,the effect of Zr O₂ coating on the properties of composite films was studied.The results indicated that coated Zr O₂ layer can decrease the composite dilectric loss and effectively improve the composite energy storage density.At 1 k Hz,the M3@Y@Z@PDA/PVDF composite film exhibits the biggest dielectric constant（22.8）with a small dielectric loss（0.053）.The energy storage density of the composite film is 6.972J/cm³ at 640 k V/cm.