In-situ construction of porous carbon/chromium-doped nickel-zinc ferrite composites for enhanced microwave absorption

To improve the inherently poor impedance matching of spinel ferrites, a synergistic strategy combining Cr 3+ doping, in-situ reduction to metallic Ni, and amorphous carbon modification via a ternary carbon source is proposed. A porous Cr 3+ -doped Ni-Zn ferrite composite co-modified with in-situ-generated metallic Ni and amorphous carbon was fabricated by pyrolysis of sucrose/citric acid/polyethylene glycol under N 2 atmosphere. The composites feature a hierarchical porous structure, with Ni nanoparticles and carbon uniformly decorating the ferrite surface. Saturation magnetization increases progressively with carbon content owing to the formation of ferromagnetic Ni 0 , while coercivity rises to 20 Oe. The complex permittivity is substantially enhanced: the real part ( ε ′) increases from 3.8 to 11.0 and the imaginary part ( ε ″) from 0.1 to 3.8 (at 10 GHz). At a thickness of 2.6 mm, the composite with 10 wt % carbon source achieves an effective absorption bandwidth of 5.44 GHz, while the 20 wt % sample delivers a minimum reflection loss of − 44.1 dB at a thickness of only 2.4 mm. This strategy offers an effective pathway for designing broadband, low-thickness ferrite-based microwave absorbers.