Preparation And Properties Of High Dielectric Constant Polymer Thin Film

Due to the increasing scarcity of resources, human has higher demand forimproving resource utilization and storage efficiency. Related fields of study havedrawn increasing attention recently. The high energy density capacitor is one of themost important storage components in the electronic industry, and the high dielectricthin film layer is a critical factor affecting the high energy storage capacitor. In thispaper, solution casting method is employed to prepare PVDF thin films andPVDF/BaTiO₃composite films. Surface morphology, crystalline, thermal stability anddielectric properties of the films were evaluated.The dielectric properties test results of PVDF films showed that the maximumvalue of the dielectric constant reaches9.37at the concentration of6wt%, theminimum value of loss tangent reaches0.02, and the maximum value of thebreakdown strength reaches53V/μm at the concentration of8wt%. Aftercomprehensive analyze these results,8wt%is selected as the optimal concentration ofPVDF film. Evaluated the surface morphology, crystalline and thermal stability of8wt%PVDF thin films, it is found that both crystalline region and amorphous regionexist in the film, and the major crystalline phase is α, the thermal decompositiontemperature is440℃. Dielectric constant, loss tangent and breakdown strength alldecrease with the increase of film thickness. When the film thickness hits10μm, thesethree indicators are10.04,0.024,76V/μm respectively. After analyzing correspondingproperties of uniaxial stretched8wt%PVDF thin films, it is found that the dielectricconstant （10.12） improved by9.88%comparing to the unstretched PVDF film,meanwhile the loss tangent of stretched films reaches0.018, a slight decline comparingto the unstretched PVDF film. Similarly there is a decline in breakdown strength, from53V/μm to44V/μm.PVDF/BaTiO₃composite films were prepared via solution casting method. Thedielectric constant and the loss tangent of the composite films increase with theincrease of nano BaTiO₃mass fraction in the films. When BaTiO₃accounted for30 wt%, dielectric constant reached32.41improved by250%, also loss tangent increasedto0.082. When BaTiO₃accounted for10wt%, breakdown strength reaches amaximum value78V/μm, increased by more than40%comparing to the pure PVDFthin films. When doping nano BaTiO₃particles, a negative impact on the film-qualityof the composite film was found through SEM analysis. In addition, doping nanoBaTiO₃particles resulted in noticeable impact on the crystalline of the composite filmsthrough XRD analysis, thermal stability could also be improved by doping BaTiO₃particles verified by TG analysis.