Enhancement of 𝜷-phase in PVDF films embedded with ferromagnetic Gd5Si4 nanoparticles for piezoelectric energy harvesting

摘要

Self-polarized Gd₅Si₄-polyvinylidene fluoride (PVDF) nanocomposite films have been synthesized via a facile phase-inversion technique. For the 5 wt% Gd₅Si₄-PVDF films, the enhancement of the piezoelectric β-phase and crystallinity are confirmed using Fourier transform infrared (FTIR) spectroscopy (phase fraction, F β _, of 81% as compared to 49% for pristine PVDF) and differential scanning calorimetry (crystallinity, Δ X c , of 58% as compared to 46% for pristine PVDF), respectively. The Gd₅Si₄ magnetic nanoparticles, prepared using high-energy ball milling were characterized using Dynamic Light Scattering and Vibrating Sample Magnetometry (VSM) to reveal a particle size of ～470 nm with a high magnetization of 11 emu/g. The VSM analysis of free-standing Gd₅Si₄-PVDF films revealed that while the pristine PVDF membrane shows weak diamagnetic behavior, the Gd₅Si₄-PVDF films loaded at 2.5 wt% and 5 wt% Gd₅Si₄ show enhanced ferromagnetic behavior with paramagnetic contribution from Gd₅Si₃ phase. The interfacial interactions between Gd₅Si₄ and PVDF results in the preferential crystallization of the β-phase as confirmed via the shift in the CH₂ asymmetric and symmetric stretching vibrations in the FTIR. These results confirm the magnetic Gd₅Si₄ nanoparticles embedded in the PVDF membrane lead to an increased β-phase fraction, which paves the way for future efficient energy harvesting applications using a combination of magnetic and piezoelectric effects.