Enhanced electroactive phase, dielectric properties and tuning of bandgap in Ho3+ modified PVDF-HFP composite films

Free-standing self-polarised films of Ho3+ modified Polyvinylidene fluoride co-hexafluoropropylene (PVDF-HFP) have been prepared using a simple and cost-effective solvent casting method. A study was initiated to bring out the impact of rare earth hydrated salt on the electroactive nucleation of PVDF-HFP. Holmium hydrated salt acts as an excellent filler to induce electroactive gamma and beta phases of PVDF-HFP. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy were used to authenticate the enhancement in the electroactive phases of PVDF-HFP. Furthermore, differential scanning calorimetric (DSC) measurements reveal an increase in the melting temperature, which indicates an enhancement in the polar beta phase. An excellent enhancement in the dielectric constant value has been observed for Ho3+ incorporated composite films. The value reached 24 similar to (at 1 kHz), which is similar to 3 times greater than the pure polymer for the highest salt-loaded film. The effect of rare earth hydrated salt on the optical properties of the PVDF-HFP composite films has also been examined by analysing the direct and indirect band gaps of hybrid films. In addition, the ferroelectric properties of the prepared composites were also analysed by P-E measurements, and the composite films show remarkable improvement in polarisation. These multi-functionalities, such as the enhanced electroactive nature, flexibility lightweight, high value of dielectric constant, and the possibility for bandgap tuning make the prepared PVDF-HFP/Ho3+ cast films useful in piezo, photonic device applications.

Automated summary

Free-standing self-polarised films of Ho3+ modified Polyvinylidene fluoride co-hexafluoropropylene (PVDF-HFP) have been prepared using a simple and cost-effective solvent casting method. The impact of rare earth hydrated salt on the electroactive nucleation of PVDF-HFP has been investigated, and Ho3+ acts as an excellent filler to induce electroactive gamma and beta phases of PVDF-HFP. The composite films show remarkable improvement in dielectric constant and polarisation, making them useful in piezo, photonic device applications.