Broadband microwave absorption via Cr3⁺-induced lattice strain and magnetic optimization in cobalt ferrite
摘要
The escalating issue of electromagnetic pollution drives the demand for high-performance microwave absorbers featuring broad bandwidth and strong absorption. Cobalt ferrite (CoFe2O4) is a promising candidate but often suffers from narrow absorption bandwidth and imperfect impedance matching. In this study, a series of Cr3⁺-doped cobalt ferrites (CoCryFe2₋yO4, y = 0–1.0) were synthesized via a facile hydrothermal method to systematically investigate the effects of Cr3⁺ substitution on their structural, morphological, and electromagnetic wave absorption properties. X-ray diffraction and Fourier-transform infrared spectroscopy confirmed the formation of a pure spinel phase, while scanning electron microscopy revealed that Cr3⁺ doping effectively refined particle size from 1.56 μm (y = 0) to 0.40 μm (y = 1.0), enhancing dispersion uniformity. The incorporation of Cr3⁺ ions effectively optimized the electromagnetic parameters, resulting in significantly improved microwave absorption performance. The sample with y = 1.0 exhibited an optimal reflection loss of − 21.29 dB at 8.06 GHz, along with a broad effective absorption bandwidth (RL < − 15 dB) spanning 3.28–16.82 GHz. Detailed analysis of the complex permittivity and permeability revealed that the enhanced absorption originated from synergistic magnetic loss mechanisms, including eddy current and natural resonance effects. In contrast, dielectric losses played a minor role. These findings demonstrate that strategic Cr3⁺ doping in cobalt ferrites offers a promising approach to design lightweight, high-efficiency microwave absorbers for practical applications in the 2–18 GHz frequency range.