Improved dielectric properties of triphasic (NiFe2O4–2LaFeO3)–Ni–PVDF cermet–polymer composite films via magnetic field-assisted solidification

Abstract

In the quest for advanced composite materials with exceptional dielectric properties, in this work we investigated the preparation and performance of triphasic (NiFe₂O₄–2LaFeO₃)–Ni–poly(vinylidene fluoride) (PVDF) cermet–polymer percolative composites. Utilizing a solution-casting technique for composite film formation, the research focuses on enhancing dielectric performance through the incorporation of electroceramic (NiFe₂O₄–2LaFeO₃:NFO–2LFO), metallic nickel (Ni) fillers and magnetic field-assisted solidification. These composite films comprising a triphasic blend of magnetic electroceramic and metallic filler within a PVDF polymer matrix exhibited an intricate interplay between magnetic domains, crystalline phases, and polymer matrices. Applying a weak magnetic field during solidification facilitates the alignment of magnetic domains, leading to a 33% improvement in dielectric performance. Morphological analysis revealed homogeneous microstructures and well-defined interfaces. Through experimental measurements and percolation theory approximations, it is demonstrated that when the Ni content is close to the percolation threshold (f_c), the dielectric constant due to space charge polarization of the composite with a 0.35 volume fraction of NFO–2LFO and a 0.18 volume fraction of Ni reached up to 595 with a low dielectric loss. These results highlight the critical role of interfacial polarization and magnetic field-induced alignment in enhancing the dielectric properties. The high magnetic responsiveness allows the fillers to magnetically aligned orientations within the PVDF polymer leading to significant gain in the performance.