Enhanced Dielectric Tunability at Ultra-Low Bias in PVDF Realized by Ferroelectric–CNT Core-Shell Structure

Polymer composites have emerged as promising tunable dielectric material in microwave devices owing to their low density, flexibility, and ease of processing compared to rigid ceramic counterparts. Nevertheless, their progress is constrained by limited tunability ( T u ) and the requirement of high bias fields. Herein, we integrate ferroelectric Barium Strontium Titanate (BST) with electrically nonlinear Carbon Nanotubes (CNTs) in core-shell configuration to achieve high T u under ultra-low bias. The resulting nanocomposite exhibited high T u of 38.92% at an exceptionally low DC bias field of 0.23 V cm -1 , representing a 1.72-fold improvement over conventional systems. Importantly, dielectric loss (tan δ ) is well-suppressed from 273.76 to 2.27 (at 100 kHz) due to effective charge trapping at the core-shell interface, which prevents direct electron hopping between conductive pathways. Furthermore, the dielectric breakdown strength ( E b ) reaches 253.9 kV cm -1 at 1 vol% loading, nearly double of the uncoated conductive filler system (129.03 kV cm -1 ). These results highlight a new paradigm for combining nonlinear and ferroelectric materials within a core-shell architecture to realize low-bias, high-performance dielectric nanocomposites, offering significant potential for flexible electronics and next-generation microwave systems.