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• Fabrication of flexible magnetoelectric PVDF/NiFe 2 O 4 nanofiber composite films. • Addition of NiFe 2 O 4 in PVDF plays an important role in transforming α to β phase. • PVDF/NiFe 2 O 4 films exhibit enhanced ferroelectric and magnetic properties. • DC EFM and MFM studies prove the multiferroic nature of the composite films. • PVDF/NiFe 2 O 4 nanogenerator and MME generators, generate a voltage of 10 V and 4.8 V. Flexible nanocomposite films of poly(vinylidene fluoride)(PVDF)/nickel ferrite (NiFe 2 O 4) fiber were made using solvent casting method. The NiFe 2 O 4 fibers with a diameter of 400 nm were synthesized initially by means of electrospinnig technique. Studies of XRD and FTIR confirmed the formation of both α and β phases in the composite films. The presence of α-phase was diminished with the incorporation of NiFe 2 O 4 and a maximum β-phase percentage (68%) was obtained. SEM and AFM analyses also demonstrated the transformation of the microstructures from α to β phase. The ferroelectric properties were tested with respect to NiFe 2 O 4 loading and the composite film with 10 wt% NiFe 2 O 4 exhibited a high P max value of 1.46 μC/cm2. VSM studies revealed the ferrimagnetic behaviour of the films and exhibited a maximum saturation magnetization value of 4.2 emu/cm3. Local ferroelectric properties were investigated through their domain switching behavior using dynamic contact electrostatic force microscopy (DC-EFM), and magnetic force microscopy (MFM) was used to analyze the magnetic properties. The magnetoelectric cross-coupling between ferroelectric and ferrimagnetic orderings is verified through the variations in ferroelectric parameters under different magnetic fields. Then a nanogenerator was fabricated using the composite films and generated an open circuit voltage of 10 V (peak-peak). Additionally, these films were made into magneto-mechano-electric (MME) generator, which could generate a 4.8 V (peak-peak) output voltage under a weak AC magnetic field of 10 Oe at 50 Hz. [ABSTRACT FROM AUTHOR]

A two-step synthesis method was used to prepare a flexible PVDF/ZnFe 2 O 4 multiferroic nanocomposite film. ZnFe 2 O 4 nanofibers synthesized using electrospinning technique were incorporated into a PVDF matrix to form PVDF/ZnFe 2 O 4 composite films through the solution-casting process. XRD patterns confirmed the formation of the polar β-phase in films, which is responsible for ferroelectricity. The percentage of the β-phase, calculated by FTIR analysis, reached 88% with the incorporation of ZnFe 2 O 4 in PVDF. The transformation of α to β-phase microstructure were examined using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The dielectric constant and tangent loss of the composites with respect to ZnFe 2 O 4 loading were measured. The dielectric constant increase with the increasing concentration of ZnFe 2 O 4 , and a maximum value of 30 was obtained for a ZnFe 2 O 4 concentration of 15 wt%. Ferroelectric properties were analyzed by taking into consideration the domain switching behavior, which was investigated by dynamic contact electrostatic force microscopy (DC-EFM), whereas the magnetic properties were analyzed using magnetic force microscopy (MFM). The as-synthesized composite films were further used to fabricate a nanogenerator, which was capable of generating up to 7 V (peak–peak) as a maximum open circuit voltage for a 15 wt% ZnFe 2 O 4 -loaded film at 1.5 N of applied force. In addition, the nanogenerator delivered an output power of 4 μW at a load resistance of 500 kΩ, and the results were compared with previous results. • Fabrication of flexible multiferroic PVDF/ZnFe 2 O 4 nanofiber composite films. • Addition of ZnFe 2 O 4 in PVDF plays an important role in transforming α to β phase. • PVDF/ZnFe 2 O 4 films exhibit enhanced dielectric and ferroelectric properties. • DC EFM and MFM studies prove the multiferroic nature of the composite films. • PVDF/ZnFe 2 O 4 nanogenerator generates a voltage of 7 V and power of 4 μW. [ABSTRACT FROM AUTHOR]