Tailored Synthesis of Nb5+/Mn2+ Cosubstituted BaFe12O19 for Broadband Microwave Absorption: A Magnetic-Dielectric Synergy Strategy

Abstract With the rapid advancement and widespread adoption of millimeter-wave technology, developing high-performance microwave-absorbing materials has become critical for addressing electromagnetic interference and radiation pollution. To meet electromagnetic compatibility requirements in the 18−40 GHz frequency range, this study proposes a Nb5+-Mn2+ cosubstitution strategy and fabricates Ba(NbMn)xFe12-2xO19 absorbers via a sol-gel method. The results show that increasing the substitution ratio (X) modifies ion occupation, shifting the absorbers’ natural resonance frequency to the 21 GHz and 35 GHz atmospheric windows while broadening the microwave absorption bandwidth. Specifically, when X = 0.3, the absorber achieves an absorption peak of −43.37 dB in the K-band with an effective absorption bandwidth (EAB) of 6.46 GHz. When X = 0.2, it exhibits a superior absorption peak of −54.51 dB in the Ka-band, accompanied by an ultrabroad EAB of 12.87 GHz. The mechanism analysis reveals that Nb5+-Mn2+ cosubstitution constructs a synergistic magnetoelectric loss system: it enhances magnetic loss, triggers multidielectric polarization, and optimizes impedance matching which collectively enables excellent broadband microwave absorption through magnetoelectric synergy. This work provides a viable strategy for designing high-frequency microwave absorbers and highlights the significant potential of Nb5+-Mn2+ cosubstituted M-type barium ferrites in electromagnetic wave absorption applications.