Manipulation of ferroelectric response of PVDF-TRFE free-standing flexible films due to incorporation of BaTiO₃ nanoparticle fillers

The main objective of the present work is to get insight into the polarization switching and dielectric response of PVDF-TrFE with incorporation of BaTiO₃ (BTO) nanoparticles. For this purpose, cost-effective solvent casting technique was used, to prepare PVDF-TrFE/BaTiO₃ composite free-standing films. It is necessary to prepare films in which BTO nanoparticles are distributed homogenously without agglomeration. Surface functionalization technique is reported to be useful in homogenous distribution of the nanofiller in polymer matrix. However, addition of surface modifier causes reduction in the permittivity of the polymer nanocomposite and deteriorates the desired properties. Therefore, the main aim of the present work is to obtain homogenous free-standing PVDF-TrFE/BaTiO₃ composite films in which filler is dispersed without any use of surface modifier. Hence ferroelectric particles are dispersed in the ferroelectric polymer matrix. It has been observed that nanocomposite is much more complex compared to the simple models based on spheres dispersed in a medium. Complexities arise due to the strain and interfacial effects of the BTO nanoparticles on the ferroelectric matrix which exhibits marked effect on structural and electrical response of the system. Consequently, specific concentration of filler has been identified at which optimum ferroelectric and dielectric properties of PVDF-TrFE/BaTiO₃ composite have been achieved. Incorporation of more than a desired concentration of filler affects the chain alignment and causes reduction in the β-phase content. Correlation between structural and electrical response has been discussed in detail to explain the non-monotonic trend of polarization as a function of BTO content.