Ultra-broadband electromagnetic wave absorption of ceramic composite coating by atmospheric plasma spraying

Dy doped ceramic material of Ba₄Fe_2.6Dy_1.4Nb₈O₃₀ with the tetragonal black bronze structure was synthesized by solid-state reaction at 1300°C. The composite powders of Ba₄Fe_2.6Dy_1.4Nb₈O₃₀/FeSiAl with good flowing were prepared by spray drying using the powders slurry. The obtained composite powders were then plasma sprayed to fabricate coating. The microstructure and absorption characteristics of electromagnetic wave (EMW) of the coating materials are investigated. Results show that the composite powders significantly remain the phase stability during atmospheric plasma spraying and adsorbing heredity of EMW for the coating. The coating powders have excellent EMW absorption with the minimum reflection loss of ?48.20 dB at the thickness of 3.5 mm. Also, the coating powders display the maximum effective absorption bandwidth of 6.24 GHz at the thickness of 1.5 mm, which covers the X-band. Moreover, the coating was found to have a certain EMW absorption performance at high temperature of 700°C. The Ba₄Fe_2.6Dy_1.4Nb₈O₃₀ ceramic material with low thermal conductivity ensured the electromagnetic absorption capacity of the coating at high temperature. The Ba₄Fe_2.6Dy_1.4Nb₈O₃₀/FeSiAl ceramic composite materials could have the potential applications as the high temperature EMW absorber.