Advantages and limitations of active phase silanization in PVDF composites: Focus on electrical properties and energy harvesting potential

Abstract

In order to further improve the performance of 0.94[(Bi0.5Na0.5)TiO3]-0.06BaTiO3/polyvinylidene fluoride (NBT-BT/PVDF) flexible composite films prepared by the hot-pressing method, the effect of surface modification of the NBT-BT particles on the structure and properties of the films was investigated. Two coupling agents, namely, (3-aminopropyl)triethoxysilane (APTES) and dodecyl triethoxysilane (DDTES) were added to enhance dispersion and interfacial adhesion of the active phase powder with the polymer matrix. The highest amount of the electroactive PVDF β-phase was formed in APTES-modified samples while in DDTES samples mainly γ-phase was formed as shown by Fourier-transform infrared spectroscopy analysis. Differential scanning calorimetry measurements indicated that the addition of filler particles reduced the total crystallinity degree of the PVDF. Dielectric permittivity values as well as dielectric losses decreased for silanized samples due to reduced tension at the interface between particles and polymer. Strong intermolecular interaction between the PVDF chains and the APTES-modified particles led to enhanced breakdown strength of these samples. The highest level of agglomeration in the DDTES-modified samples induced the deterioration of ferroelectric properties. The highest voltage output of ~15 V and 225 μW of power was obtained for the APTES-modified harvester, evidencing their potential for energy harvesting applications. Highlights: Surface of NBT-BT particles was successfully modified by the silanization method. NBT-BT-PVDF flexible lead-free composite films were prepared by hot pressing. APTES coupling agent enabled the transformation of PVDF α-phase into electro-active β. APTES-modified samples showed the highest breakdown strength. Notable properties for energy harvesting application found, up to 225 μW of generated power.