Microwave behavior of substituted lithium ferrite composites in X-band

Abstract

Dense and crack-free substituted lithium ferrite–polymer composite films of thickness ∼80 μm were fabricated. The substituted lithium ferrite powders with general composition Li 0.5− x /2Co x Mn 0.1Fe 2.4− x /2O 4, where x = 0.0 , 0.2, 0.4 and 0.6, were prepared by citrate-route. Epoxy resin EPG-280 was used as a polymer. The composite films required lower processing temperature ∼100 °C. Cavity-perturbation technique was employed to measure the complex permittivity ( ∈ ′ – j ∈ ″ ), and the complex permeability ( μ′−j μ″), of the composite films at X-band microwave frequencies (8–12 GHz). The dispersion in the complex permittivity of ferrite composite films was found to be significant. The maximum value of ∈ ″ was observed for the film with x = 0.6 and 75% volume loading of ferrite component. The permeability μ ′ of films was found to decrease with an increase in frequency as well as with the volume loading of ferrite component in composite films. The single-phase spinel structure of the substituted lithium ferrite powders for compositions x = 0.0 , 0.2, 0.4 and 0.6 was confirmed by X-ray diffraction pattern. The microstructure of composite films was observed by scanning electron microscopy.