Microwave absorption characteristics of cobalt doped zinc spinel ferrites in Ku-band (12.4–18 GHz)

Abstract

This research study targets to fabricate microwave absorbers with narrow sample thickness, strong absorption power and broad bandwidth simultaneously. The zinc-cobalt spinel ferrites with compositional formula Zn1-xCoxFe2O4 (x = 0.00, 0.25, 0.50, 0.75 and 1.00) are successfully synthesized via sol–gel citrate route by sintering at 1000 °C. Vector network analyzer is employed to determine dielectric permittivity εr=ε′-jε" and magnetic permeability μr=μ′-jμ" in Ku-band. Enhancement in dielectric losses from 0.3051 to 0.4066 and magnetic losses from 0.0087 to 0.5911 with increasing cobalt concentration from x = 0.00 to x = 1.00 at 12.4 GHz frequency helps in achieving good absorption. Normalized wave impedance and quarter wavelength model are used to maximize absorption or minimize reflection. Significant absorption is achieved by tuning thickness of the sample from 1.8 mm to 3 mm. The composition x = 0.75 exhibits superior absorbing properties by showing reflection loss as low as −31.45 dB along with −10 dB bandwidth of 5.6 GHz at a matching thickness of 2.2 mm. The fabricated ferrite samples are proved to be promising applicants for absorption of electromagnetic interference (EMI) in radar and stealth technology.