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Structural evolution and microwave absorption properties of MnFe2O4/BaTiO3 nanoparticle systems and their composites
(Springer, 2026) Atalay, Selcuk; Durmaz, Ergun; Seker, Omer Faruk
In this study, MnFe2O4/BaTiO3 nanoparticle systems were systematically investigated as microwave absorbers in the X-band (8-12.4 GHz). Nanoparticles were physically mixed at different weight ratios and examined both before and after annealing at 1100 C for 3 h. The microstructural and magnetic properties were evaluated using SEM, TEM, XRD, XPS, FTIR and M-H hysteresis measurements, respectively. Structural analyses revealed that the as-mixed samples consist of coexisting MnFe2O4 and BaTiO3 phases, while annealing induces an in-situ transformation into an Mn/Ti-substituted M-type barium hexaferrite phase. This phase evolution leads to a significant increase in saturation magnetization and coercivity, indicating a transition toward harder magnetic behavior. Microwave absorption performance was evaluated using reflection loss measurements. The non-annealed 50 MnFe2O4-50 BaTiO3 composite exhibits the best absorption performance, with a minimum reflection loss (RL) of approximately - 23 dB at 10.8-11.0 GHz. In contrast, annealed samples show reduced absorption efficiency, with minimum reflection loss values in the range of - 10 to - 16 dB. These results demonstrate that enhanced magnetic hardness does not necessarily improve microwave absorption in MnFe2O4/BaTiO3-based absorbers.