Broadband and thin microwave absorber of nickel-zinc ferrite/carbonyl iron composite

Ni0.5Zn0.5Fe2O4/carbonyl iron composites for broadband and thin microwave absorbers were prepared from the starting materials of Ni0.5Zn0.5Fe2O4 and raw commercial carbonyl iron by a simple ball-milling technique. Flake-shaped particles are obtained after 2 h ball-milling, and the sample shows the highest permeability among all samples. Permeability and permittivity decrease gradually with increasing ball-milling time. Good microwave absorption properties can be obtained in the samples with ball-milling time 6 and 8 h. Their reflection loss values less than -20 dB in the ranges of 5.4-14.8 and 5.0-13.3 GHz over absorber thicknesses of 1.6-3.3 and 1.7-3.6 mm, respectively. The results can be qualitatively explained by a proper electromagnetic impedance match that is mainly due to the decrease of permittivity with increasing ball-milling time. (C) 2009 Elsevier B.V. All rights reserved.