Influence of crystalline phase evolution of shells on microwave absorption performance of core-shell Fe₃O₄@TiO₂ nanochains

Core-shell electromagnetic nanostructures with dielectric-magnetic dual-loss mechanisms are promising candidates for highly efficient microwave absorption attenuation. Herein, chain-like Fe₃O₄@TiO₂ nanomaterials have been first prepared, and the crystalline phase composition of TiO₂ shells has been regulated through controlling the sintering temperatures as 450 °C, 550 °C, and 650 °C. According to XRD patterns, the components of Fe₃O₄, TiO₂, and FeTiO₃ are ascertained, and the proportion of amorphous, anatase, and rutile phases is approximately determined. XPS results confirm the existence of Ti⁴⁺ and absence of oxygen vacancy in three samples. Investigation of microwave absorption properties indicates that S650 can possess the minimum reflection loss value of −21.29 dB (5.58 GHz) and the maximum effective absorption bandwidth of 5.09 GHz (11.83–16.92 GHz), superior than two other samples. Analyses of electromagnetic parameters reveal that dielectric loss plays a major role in the microwave absorption, heterogeneous interfaces are more conducive to strengthening dielectric loss than heterophase interfaces in the TiO₂ shells, and increasing crystal phases is beneficial for improving impedance matching. This work first reports the influence of crystalline phase evolution on dielectric loss and impedance matching, which delivers a new approach to optimize the microwave absorption performance.