Preparation Process And Properties Of BaTiO₃/PVDF Composites

In this study, BaTiO3/PVDF dielectric composites were prepared by solution casting method and spin-coating method. Preparation process was optimized by selecting substrate, controlling forming temperature. Dopamine was used to improve the breakdown strength of composites, and the improve mechanism was discussed. On the basis of dopamine modification, multi-layer PVDF-Dopa@BT/PVDF-PVDF composites were synthesised to enhance the dielectric constant of composites futher.(1) The best condition of solution casting method to prepare BaTiO3/PVDF were as follows:using metal substrate to form film at80℃, and forming time was about4-5h, BaTiO3particles dispersed well in PVDF matrix;(2) Dopa@BT/PVDF composites, in which dopamine was used as surface modifier, were prepared via casting solution method. Experimental results showed that-OH and-NH2of dopamine can bond with-OH of BaTiO3and-F of PVDF respectively and so the breakdown strength was increased. When Dopa@BT volume fraction varied from3vol%to15vol%, the breakdown strength of nanocomposites changed from210kV/mm to 163kV/mm. Dielectric constants stay around10to14. When BaTiO3volume fraction in the composites was10vol%, energy density of the composites was2.02J/cm3.(3) PVDF-BaTiO3/PVDF-PVDF composites can be well prepared by dry-film spin coating method and dielectric constants were increased through interface polarization. When BaTiO3volume fraction varied from3vol%to15vol%, dielectric constants enhanced from1.5times to2.6times. Because of the distortion of electric field in part of composites, the breakdown strength was decreased. When BaTiO3volume fraction was3vol%, breakdown strength of multi-layer composites was only72kV/mm.(4) Dielectric constants of PVDF-BaTiO3/PVDF-PVDF composites prepared by wet-film spin coating method increased less than multi-layer composites prepared by dry-film spin coating method. When BaTiO3volume fraction varied from3vol%to15vol%, dielectric constants enhanced from1.4times to1.8times. When BaTiO3volume fraction was3vol%, breakdown strength was104kV/mm higher than dry-film composites.(5) Breakdown strength of PVDF-Dopa@BT/PVDF-PVDF composites was lower than single layer Dopa@BT/PVDF composites but dielectric constant was sharply increased. When BaTiO3volume fraction in the composites was15vol%, breakdown strength, dielectric constant and energy density of the composites were191kV/mm,25.7and2.84J/cm3respectively.