Effects of surface modification on electrical properties of KNN nanorod-incorporated PVDF composites

The demand of self-powered electronic devices has stimulated a great interest in daily life. To fulfill this, thrust researchers are engaged to develop different piezoelectric self-powered-based devices. The piezoelectricity is broadly dependent on the electroactive phase of the polymer structure. Herein, lead-free potassium sodium niobate (KNN) nanorods-incorporated PVDF polymer-based nanocomposite films have been developed wherein KNN nanorods have been surface-modified by three diverse surface modifiers such as 3-aminopropyltrimethoxysilane (APS), polyaniline (PANI) and polyvinylpyrrolidone (PVP) for resolving the agglomeration problem of the nanorods and to look into their effect on the microstructural growth including nucleation of polar crystals. The nanocomposite films have been developed simply by solution cast method. The growth of electroactive phases (β and γ) of the PVDF polymer has been observed to be improved significantly by incorporation of surface-modified KNN nanorods. The calculated beta fraction (F(β)) and gamma fraction (F(γ)) as calculated by the FTIR spectrum (98% and 99%) are maximum for the silane- and PVP-modified KNN nanorods-incorporated PVDF polymer, because of the higher molecular weight and homogeneous distribution of the nanorods throughout the PVDF matrix. The total crystallinity evaluated by XRD patterns, specifically β crystal part for the surface-modified KNN nanorods-based film, has been improved (17% for pure PVDF, 45% for untreated KNN-based film and more than 50% for the surface-modified KNN-based films). The remnant polarization values are also remarkably higher (0.49 μC/cm² for silane, 0.022 μC/cm² for PVP and 0.015 μC/cm² for PANI-modified KNN nanorods-based composites, respectively) for surface-modified KNN nanorods-based composite with contrast to pure PVDF (0.001 μC/cm²) and untreated KNN-based film (0.002 μC/cm²). The dielectric constant values for modified KNN nanorods-incorporated PVDF polymer composites have also been demonstrated as substantial enhancement which are 68, 71 and 70, respectively, for silane-, PANI- and PVP-modified samples, whereas the values are 2 and 38 for pure PVDF and untreated KNN-based films. This study clearly defines that the selection of a suitable surface modifier (interface) can play a noteworthy role in exploitation of excelling electroactive phases of PVDF to the maximum extent to enhance its dielectric, ferroelectric as well as piezoelectric response with low level of loading.