Enhanced Dielectric and Ferroelectric Properties of Core-Shell Structure of SrTiO3/PVDF Composite Films Cross-Linked with Silane Coupling Agent

Gore-shell structure of SrTiO3/PVDF composite films cross-linked with silane coupling agent 3-aminopropyltriethoxysilane (3-APTS) were prepared by solution casting method and characterized by XRD, FTIR, TG, DSC, SEM, dielectric and ferroelectric test. SrTiO3 (ST) can be homogeneously distributed into PVDF matrix without obvious agglomeration in the presence of silane coupling agent, which may be related to the formation of core-shell structure in which 3-APTS acts as a cross-linker between polymer and inorganic material. The introduction of ST is helpful to improve the crystallinity, but will lead to a slight decrease in the electroactive beta-phase content of composite films. The dielectric constant of composite film will increase up to 2.5 times larger than that of neat PVDF when the mass content of ST is up to 30%, and without leading to obvious increase of dielectric losses. Meanwhile, the P-s value of this film is increased up to about two times larger than that of pure PVDF. Our study suggests that the incorporation of surface modified ST into PVDF matrix is a useful way to obtain well dispersed film and improve its dielectric and ferroelectric property.