Boosted Interfacial Polarization from Multishell TiO₂ @Fe₃ O₄ @PPy Heterojunction for Enhanced Microwave Absorption

Core@shell structures have been attracting extensive attention to boost microwave absorption (MA) performance due to the unique interfacial polarization. However, it still remains a challenge to synthesize sophisticated 1D semiconductor-based materials with excellent MA competence. Herein, a hierarchical cable-like TiO₂ @Fe₃ O₄ @PPy is fabricated by a sequential process of solvothermal treatment and polymerization. The complex permittivity of ternary composites can be optimized by tunable PPy coating thickness to improve the loss ability. The maximum reflection loss can reach -61.8 dB with a thickness of 3.2 mm while the efficient absorption bandwidth can achieve over 6.0 GHz, which involves the X and Ku band at only a 2.2 mm thickness. Importantly, the heterojunction contacts constructed by PPy-Fe₃ O₄ and Fe₃ O₄ -TiO₂ contribute to the enhanced polarization loss. Besides, the configuration of magnetic Fe₃ O₄ sandwiched between dielectric TiO₂ and PPy facilitates the magnetic stray field to radiate into the TiO₂ core and out of the PPy shell, which significantly promotes magnetic-dielectric synergy. Electron holography validates the distinct charge distribution and magnetic coupling. The new findings might shed light on novel structures for functional core@shell composites and the design of semiconductor-based materials for microwave absorption.