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

•Guideline to prepare phase-separated porous as well as void-free transparent PVDF films.•Polarization switching behaviors of the flexible PVDF film can be reversed in sign with the nickel ferrite additives.•Incorporation of the nickel ferrite has an 600% enhancement in the thermal stability of PVDF film.•3-fold and 7-fold enhancement in the average hardness and reduced modulus of the PVDF film with the nickel ferrite additive.