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

The effect of Ni2+Ti4+ substitution on complex permeability, permittivity and microwave absorption has been studied for [Ca(NiTi)xFe12-2xO19]96.0[La2O3]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 (ε′-jε′′) with maximum value of ε′′ observed for x=0.6. The dispersion in complex permeability (μ′-jμ′′) 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), Ni2+Ti4+ 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.