Sandwich-like Fe₃O₄/Fe₃S₄ composites for electromagnetic wave absorption

The outstanding electromagnetic wave (EMW) absorbers are highly needed in view of the extensive utilization of electromagnetic devices. Herein, for the first time, a series of hexagonal microflake-like Fe₃O₄/FeS₂/Fe₇S₈ composites (sample S1) and sandwich-like Fe₃O₄/Fe₃S₄ composites (sample S3) were effectively prepared through a facile and highly tunable strategy. By the means of tailoring addition of thiourea and D-glucose in the hydrothermal process, the different morphologies, crystal structures and EMW absorption performances of composites could be attained. Among these absorbers, owing to the effective combination of matched impedance and excellent dielectric/magnetic loss, the sandwich-like Fe₃O₄/Fe₃S₄ composites (sample S3) possessed excellent EWM absorption performance. That is, the minimum reflection loss (RL_min) of −45.33 dB at the matched thickness of 3.30 mm as well as the EAB of 5.03 GHz at 2.00 mm were achieved for sample S3 with 60 wt% loading. Noteworthy, as for the composites with 70 wt% loading, it exhibited broad EAB of 5.18 GHz at only 1.71 mm. Impressively, the EAB still reached 4.39 GHz even at the ultra-thin thickness of 1.46 mm. Therefore, it can be predictable that the sandwich-like Fe₃O₄/Fe₃S₄ composites will be a powerful attractive EMW absorber. Besides, it should be emphasized that the reports on the EMW absorption performance of iron sulfur compounds (e.g., Fe₃S₄, FeS₂ and Fe₇S₈) are extremely scanty so far, so our finding featured with a facile, green and greatly tunable strategy provides a unique horizon to design the high-performance EMW absorbers in the future.