Enhanced dielectric polarization from disorder-engineered Fe3O4@black TiO2-x heterostructure for broadband microwave absorption

Core-shell structure has been attracting considerable interest to enhance microwave absorption due to its distinct designable interface. To broaden absorption bandwidth, it is necessary to integrate semiconductor with magnetic material. However, it still remains a huge challenge to construct such core-shell heterostructure. Herein, a novel core-shell Fe3O4@black TiO2-x (Fe3O4@b-TiO2-x) heterostructure was successfully fabricated via a surface treatment strategy in vacuum. The unique multi-interfacial structure was constructed by a disordered TiO2-x layer tightly wrapping Fe3O4@TiO2 nanostructure, which exhibited a broadband microwave absorption. Typically, the effective absorption bandwidth (RL <-10 dB) of Fe3O4@b-TiO2-x, heterostructure spanned as wide as 13.0 GHz, while the maximum reflection loss can reach up to -47.6 dB. The enhanced microwave attenuation capability can be attributed to the introduction of outer disordered TiO2-x thin layer. The multiple interfaces constructed by Fe3O4-TiO2 and TiO2-TiO2-x as well as defect dipoles encapsulated within black TiO2-x layer, contributed to the boosted polarization dissipation. Moreover, the well-designed TiO2-TiO2-x shell is beneficial to the penetration of the magnetic field line radiated out from Fe3O4 core, which endowed the Fe3O4@b-TiO2-x with superior magnetic-dielectric synergetic dissipation effect. The novel finding might pave a way to design broadband microwave absorber based on core-shell functional structure.