Preparation And Properties Of Modified Barium Titanate/Polyimide Composite Material

Nowadays,dielectric capacitors have considerable applications in the electronics,motor,and active control system,such as embedded capacitors,high-charge storage capacitors,and memory devices,due to that they have well energy storage capacity and uniform electric fields.Among them,ferroelectric ceramic/polymer composites are considered to be one of the most promising materials because they can combine the advantages of ceramic dielectric and polymer dielectric,namely the high dielectric constant of ceramic materials,as well as the good mechanical strength and excellent processability of polymer materials.BaTiO₃ has been widely used as a ceramic filler because of its high dielectric permittivity.In addition,polyimide has high thermal stability and chemical stability,excellent processability,high mechanical strength and high electrical breakdown strength,which is widely used in electrical insulation,aerospace and microelectronics fields.In this study,a series of composite films loaded with various concentrations of fillers were successfully synthesized by solution casting method(modified barium titanate(Ba_0.87Sr_0.04Ca_0.09)(Ti_0.86Zr_0.08Sn_0.06)O₃ as filler and polyimide as polymer matrix).The effects of different modified barium titanate fillers,mass fractions?%?of fillers,shell-core structure fillers on dielectric properties,breakdown strength,energy storage properties and thermal properties of composite films were investigated.The specific research contents are as follows:?1?A series of modified barium titanate were synthesized by solgel method.The structure and component of modified barium titanate were measured by XPS and XRD et al.A series of polyimide?PI?composite films were prepared by solution casting method,and it has been found that after the surface of modified barium titanate was modified by APS,the com-patibility between filler and matrix can be improved.What's more,for all composite films,as the content of filler increases,the dielectric constant of the composite films also increases steadily,meanwhile,the breakdown strength gradually decreases.As a result,the composite films containing 46 wt%0.4 mol%Nb-BSCTZS fillers exhibit an excellent dielectric con-stant of 8.0 at 1 kHz.Meanwhile,the composite films containing 12 wt%0.4 mol%Nb-BSCTZS fillers exhibit an excellent energy density of 1.80 J/cm³ at 298 kV/mm,which is26.8%larger than pristine PI?1.42 J/cm³ at 313 kV/mm?.And all composite films nearly have no weight loss when the temperature is lower than 500°C,showing excellent thermal stability.?2?Using aluminum sulfate octahydrate as aluminum source and formic acid and ammonium formate as buffer solution,the surface of 0.4 mol%Nb-BSCTZS particles was successfully coated with an alumina shell by chemical coating method,and the shell-nuclear structure,composition and morphology were systematic characterized.It is found that the surface of 0.4 mol%Nb-BSCTZS particles can be coated uniformly with an Al₂O₃ shell layer with the thickness of about 6 nm.?3?Al₂O₃@0.4 mol%Nb-BSCTZS/PI composite films were prepared by solution casting method.It is found that using 0.4 mol%Nb-BSCTZS particles coated Al₂O₃ shell as fillers,the dielectric constant of composite films containing 46 wt%fillers is about 8.8.The break-down strength of composite films containing 12 wt%fillers is 298 kV/mm,about 6.8%over the composites with 12 wt%0.4 mol%Nb-BSCTZS fillers?279 kV/mm?.What's more,the energy density of 12 wt%Al₂O₃@0.4 mol%Nb-BSCTZS/PI composite films is 2.11 J/cm³under the field of 298 kV/mm,and it is about 48.6%larger than pristine PI?1.42 J/cm³,313kV/mm?,exceeding 12 wt%0.4 mol%Nb-BSCTZS/PI composite films 17.2%.