Changing the polarization and mechanical response of flexible PVDF-nickel ferrite films with nickel ferrite additives

Abstract

Polymer-based flexible nanocomposite films, of nickel ferrite nanoparticles in a polyvinylidene fluoride (PVDF) polymer matrix, were fabricated using a blade coating technique. A two-step process is used to prepare nanocomposite films. The first process involves the synthesis of nickel ferrite (NiFe2O4) nanoparticles using sonochemical method, and then incorporation of various weight percentage (5, 10, 20, and 30%) of nickel ferrite nanoparticles into the PVDF to form polymer nanocomposites. Nickel ferrite nanoparticles demonstrated a magnetization of 37.3 emu/g at magnetic field of 5 kOe while 30% Nickel-ferrite-PVDF nanocomposite shows 23.8 emu/g. Finally, the ferroelectric and local polarization switching properties of pure PVDF and nanocomposite films were investigated via piezoresponse force microscopy (PFM) measurements. The pure PVDF film demonstrates a negative piezoelectric coefficient from the PFM hysteresis loop measurement whereas the nanocomposite film shows a positive piezoelectric coefficient with an opposite PFM signal.