High‐Performance X‐Band Electromagnetic Interference Shielding in Flexible Barium Hexaferrite/Cobalt‐Based Microwires/Silicone Rubber Ternary Composites via Magnetic–Conductive Synergy

ABSTRACT Modern electronic systems increasingly demand lightweight, flexible electromagnetic interference (EMI) shielding materials. We report, for the first time, a ternary composite of barium hexaferrite (BHF) particles and cobalt (Co)‐based microwires (Co–Microwires) embedded in a silicone rubber (SR) matrix, engineered to exploit magnetic and conductive synergy for enhanced EMI shielding. Composites were systematically investigated as a function of BHF loading (wt.%) and microwire count. XRD revealed that the optimized 40% BHF with 6 Co–Microwires in SR composite exhibits the highest crystallinity (71.56%) and smallest average crystallite size (30.66 ± 4.8 nm), indicating a refined microstructure. This composite achieved a maximum shielding effectiveness (SE) of 16.9 dB at 9.8 GHz, surpassing the 10 dB industrial benchmark. This performance is unattainable by either BHF or microwires in SR alone (<3 and ∼11.1 dB, respectively), confirming synergistic enhancement. The shielding mechanism is compositionally tunable: from 0 to 30 wt.% BHF, improved impedance matching drives a transition from reflection‐dominated to absorption‐dominated shielding; at 40 to 50 wt.%, increased dielectric heterogeneity and interfacial polarization restore reflection dominance, yielding a balanced attenuation regime. These findings establish these ternary composites as a new class of flexible, lightweight, and tunable EMI shielding materials for advanced wireless communication technologies.