Microwave absorption studies of Ca-NiTi hexaferrite composites in X-band

The effect of Ni(2+)Ti(4+) substitution On complex permeability, permittivity and microwave absorption has been studied for [Ca(NiTi)(x)Fe(12-2x)O(19)](96.0)[La(2)O(3)](4.0) ferrite-polymer composites, wherein x varies from 0.0 to 1.0 in steps of 0.2, in frequency range from 8.0 to 12.4 GHz. The ferrite-composites with x > 0.0 exhibit significant dispersion in complex permittivity (epsilon'-j epsilon ") with maximum value of epsilon " observed for x = 0.6. The dispersion in complex permeability (mu'-j mu ") is not significant and is attributed to the shielding effect of polymer matrix over the ferrite crystallites. The variation of reflection loss has been studied as a function of frequency (f), Ni(2+)Ti(4+) content (x) and thickness of the absorber. A minimum reflection loss of - 30.0 dB is obtained for composite with x = 0.4 and an absorber thickness of 4.15 mm. The experimental values of the matching frequency and the matching thickness agree well with the theoretical values obtained by solving the equations numerically. (C) 2000 Elsevier Science S.A. All rights reserved.