Dielectric loss and microwave absorbing properties of the prepared MgCu₂Nb₂O₈ composite ceramics

MgCu₂Nb₂O₈ composite ceramics were synthesized by the solid reaction sintering technology. Influences of the sintering temperature on phase composition, microstructure, and microwave absorption properties of the ceramics were investigated. The composite ceramic material exhibited remarkable microwave absorption characteristics, with optimal reflection loss of − 24.7 dB at 17.4 GHz and effective bandwidth of 1.5 GHz. Introduction of different phases in the composite material led to multiple interfaces and defects, enhancing the interface polarization and dipole polarization. Density Functional Theory (DFT) calculations were utilized to explore the mechanisms of dielectric loss. The results demonstrated significant reduction in the density of states (DOS) of the p orbitals near the Fermi level, while DOS of the d orbitals increased, resulting from disruption of local microstructural symmetry and induction of additional electric dipoles at the interfaces. The simulation results are consistent with the experimental results. Consequently, the microwave absorption capacity of the MgCu₂Nb₂O₈ composite ceramics were significantly improved.