Achieving impressive millimeter-wave absorption properties in Nb5+ doped barium ferrite by simply controlling the sintering atmosphere

To enhance the millimeter-wave absorption properties around atmospheric window of 35 GHz, Nb5+ doped barium ferrite precursors are sintered at 1400 degrees C for 3 h in air, Ar, N-2 respectively. The magnetic loss region covers 30 similar to 40 GHz in the sample sintered in air and extends to 26.5 similar to 40 GHz in the sample sintered in N-2. The epsilon' and epsilon '' vary from similar to 5 to similar to 0.4 by sintering in air to similar to 10 and similar to 0.3 by sintering in Ar, and to similar to 13 and similar to 2.0 in N-2. Ultimately, contributed by enhanced permittivity and extended magnetic-loss region, the sample sintered in N-2 exhibits impressive millimeter-wave absorption properties around 35 GHz with broad bandwidth more than 12 GHz and maximum reflectivity of -37 dB under thin thickness of 0.55 mm. (C) 2019 Elsevier B.V. All rights reserved.