A novel polarization mechanism induced by controlling the shell thickness of core‐shell structured fillers using TEOS in SiO₂@KNN/PVDF composites for enhanced dielectric properties

Abstract This study systematically investigated the impact of tetraethyl orthosilicate (TEOS) content on the composition and microstructure of SiO₂‐coated K_xNa_1‐xNbO₃ core‐shell structured fillers (KNN@SiO₂). Subsequently, these fillers were incorporated into Polyvinylidene fluoride (PVDF) to fabricate KNN@SiO₂/PVDF composites, and the impact of SiO₂ shell thickness on the dielectric properties was thoroughly explored, revealing the underlying mechanisms. It was found that variations in the SiO₂ shell thickness significantly affected the dielectric characteristics of the composites, with the dielectric constant showing a non‐monotonic dependence. The dielectric constant of the composites first went up and then went down with the rise in shell thickness, with a maximum value of approximately 27 for 6‐KNN@SiO₂/PVDF. The dielectric loss also exhibited a non‐monotonic trend, with the lowest loss observed for 6‐KNN@SiO₂/PVDF. This study proposed the Shell Exchange Affects Dielectric Cluster Region Mechanism (SE‐DCRM) to explain the abnormal changes in relaxation time and permittivity of the composites caused by the coating thickness of KNN@SiO₂ fillers. The results provide a deeper understanding of the polarization mechanisms and optimization strategies of core‐shell structured fillers within ceramic/polymer composites. Highlights Prepared KNN@SiO₂/PVDF composites with varying shell thicknesses. Observed non‐monotonic dependence of dielectric constant on shell thickness. Optimized polarization characteristics of composites by adjusting SiO₂ thickness. Proposed Shell Exchange Affects Dielectric Cluster Region Mechanism (SE‐DCRM). SE‐DCRM effectively explains abnormal dielectric property changes in composites.