Unary and binary doping effect of M2+ (M = Mn, Co, Ni, Zn) substituted hollow Fe3O4 approach for enhancing microwave attenuation

Unary and binary M2+ (M = Mn, Co, Ni, Zn) substituted hollow Fe3O4 were prepared by one-step solvothermal method. The crystallographic structure, morphology, element components and microwave absorbing properties of as -prepared products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), Energy-dispersive X-ray (EDX) and vector network analyzer (VNA). The unary and binary Co2+ substitution of hollow Fe3O4 could result in a significant improvement of microwave absorption performance, including the expanding of effective absorption bandwidth, the thinner thickness and the increment of absorbing intensity. The sample of CoFe2O4 could reach an optimal reflection loss of -28.78 dB at 15.52 GHz under the thickness of 1.5 mm, moreover, the efficient absorption bandwidth (less than 10 dB) is expanded to 5.56 GHz which is most outstanding among these samples. The minimum reflection loss of Co0.75Zn0.25Fe2O4 could reach -49.60 dB at 9.88 GHz under the thickness of 2 mm. The as-prepared products could be used as microwave absorber with the advantages of strong absorption, broad bandwidth and thin thickness. The favorable performance could be attributed to the strong magnetic loss, dielectric loss and good impedance matching properties.