Magnetic Field Effects on the Structure, Dielectric and Energy Storage Properties of High-Entropy Spinel Ferrite Fe[sub.2]O[sub.4]/PVDF Nanocomposites

Energy depletion is one of the significant threats to global development. To increase the usability of clean energy, the energy storage performance of dielectric materials must be urgently enhanced. Semicrystalline ferroelectric polymer (PVDF) is the most promising candidate for the next generation of flexible dielectric materials thanks to its relatively high energy storage density. In this work, high-entropy spinel ferrite (La[sub.0.14]Ce[sub.0.14]Mn[sub.0.14]Zr[sub.0.14]Cu[sub.0.14]Ca[sub.0.14]Ni[sub.0.14]Fe[sub.2]O[sub.4]) nanofibers (abbreviated 7FO NFs) were prepared by the sol-gel and electrostatic spinning methods, then blended with PVDF to prepare composite films using the coating method. A magnetic field was used to control the orientation distribution of the high-entropy spinel nanofibers in the PVDF matrix. We investigated the effects of the applied magnetic field and the content of high-entropy spinel ferrite on the structure, dielectric, and energy storage properties of the PVDF substrate films. The 3 vol% 7FO/PVDF film treated in a 0.8 T magnetic field for 3 min exhibited a good overall performance. The maximum discharge energy density was 6.23 J/cm[sup.3] at 275 kV/mm and the efficiency was 58% with 51% β-phase content. In addition, the dielectric constant and dielectric loss were 13.3 and 0.035, respectively, at a frequency of 1 kHz.