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 st eps 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 ep silon") 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 var iations 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 mat ching 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].