Complex permittivity, permeability, and X-band microwave absorption of CaCoTi ferrite composites

The effect of Co2+Ti4+ substitution on complex permeability, permittivity, and microwave absorption has been studied for [Ca(CoTi)(x)Fe12-2xO19](96.0)[La2O3](4.0) ferrite-epoxy composites, wherein x varies from 0 to 1.0 in steps of 0.2, in the frequency range from 8.0 to 12.4 GHz. The ferrites with x > 0 exhibit significant dispersion in complex permittivity (epsilon'-j epsilon") with the maximum value of epsilon' observed for x equal to 0.2. The dispersion in complex permeability (mu'-j mu') is not significant. The variations of reflection loss and percentage absorption have been studied as a function of frequency, Co2+Ti4+ content, and thickness of the absorber. A maximum reflection loss of 31.0 dB is obtained for composites with x equal to 0.2 and absorber thickness of 2.5 mm. The experimental values of the matching frequency and the matching thickness agree well with the theoretical values obtained from an impedance-matching solution map. (C) 2000 American Institute of Physics. [S0021-8979(00)04008-1].