La-substituted W-type Barium Nickel Ferrites for Tunable and High-performance Electromagnetic Wave Absorption

W-type barium nickel ferrite (BaNi2Fe16O27) is highly promising for electromagnetic wave (EMW) absorption due to the magnetic loss capability to EMWs, low cost, large-scale production capabilities, high temperature resistance, and excellent chemical stability. However, the poor dielectric loss hampers the utilization of magnetic ferrites, resulting in the difficulty in improving the EMW absorption performance. Developing more efficient strategies to improve the EMW absorption of ferrite is highly desired yet remains challenging. Here, an efficient substitution strategy of using rare earth La3+ to substitute Ba2+ in W-type ferrite was achieved, leading to the preparation of novel La-substituted ferrites (Ba1-xLaxNi2Fe15.4O27). The influences of La3+ substitution on ferrites' EMW absorption and the dissipative mechanism toward EMWs were systematically explored and discussed. Particularly, the introduction of La3+ efficiently induced lattice defects, enhanced defect-induced polarization ability, and reduced the material's bandgap, thereby leading to the enhanced dielectric properties of ferrites. The presence of La3+ also enhanced the ferromagnetic resonance loss to strengthen the magnetic properties. This contributed to the significantly improved EMW absorption of Ba1-xLaxNi2Fe15.4O27 in comparison to the pure W-type ferrites, e.g., when x = 0.2, the best EMW absorption performance was obtained with a minimum reflection loss of −55.6 dB and an effective absorption bandwidth of 3.44 GHz.