Enhanced Microwave Absorption in Ba₀.₆Sr₀.₄Fe₁₂₋ₓZnₓO₁₉ Hexaferrites via Impedance Matching Optimization for X-Band Radar Applications

Achieving optimal microwave absorption performance in ferrite-based materials requires a delicate balance between magnetic loss, dielectric loss, and impedance matching rather than maximizing magnetic properties alone. In this work, Zn²⁺-substituted Ba₀.₆Sr₀.₄Fe₁₂₋ₓZnₓO₁₉ (x = 0.25, 0.50, and 0.75) M-type hexaferrites were synthesized via a conventional solid-state reaction method, and their structural, magnetic, and electromagnetic absorption properties were systematically investigated. X-ray diffraction analysis confirmed hexagonal M-type phase formation, while scanning electron microscopy revealed composition-dependent grain growth from 200–300 nm (x = 0.25) to 3.1–4.3 µm (x = 0.75). Magnetic measurements showed that saturation magnetization decreased from 57.95 emu/g (x = 0.25) to 37.29 emu/g (x = 0.50) due to weakened superexchange interactions. Despite this reduction in magnetic strength, the x = 0.50 composition exhibited superior microwave absorption performance, achieving a minimum reflection loss of − 24.94 dB at 10.78 GHz, corresponding to 99.7% absorption efficiency. Effective absorption (RL < − 10 dB) was maintained across the C–X band (4–12 GHz), with the strongest attenuation occurring in the X-band region (8–12 GHz). Electromagnetic analysis revealed that the enhanced absorption originates from optimized impedance matching (Z _i ₙ/Z₀ ≈ 1) and synergistic magnetic–dielectric loss mechanisms, including natural ferromagnetic resonance and interfacial polarization. These findings demonstrate that impedance matching optimization, rather than high saturation magnetization, governs the microwave absorption efficiency in Zn-substituted Ba–Sr hexaferrites, providing practical design guidelines for X-band radar absorbing materials.