Effect of the concentration of precursors on the microwave absorbent properties of Zn/Fe oxide nanopowders

Zn/Fe oxide compound powders were obtained by the hydrothermalmethod using ferric nitrate Fe(NO3)(3).9H(2)O and zinc nitrate Zn(NO3)(2).6H(2)O at 200 degrees C and different precursor molar ratios x = Fe3+/Zn2+ equal to 2.8/0.2, 2.5/0.5, 1.8/1.2 and 1.5/1.5. The samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy/energy dispersive X-ray analysis (SEM-EDAX). Room temperaturemeasurements of the frequency dependence of the complex magnetic permeability and complex dielectric permittivity, over the frequency range from0.1 to 6 GHz, were performed. For precursor molar ratios x = 2.8/0.2, x = 1.8/1.2 and x = 1.5/1.5 the obtained samples showed a ferromagnetic-like resonance behaviour. This behaviour was assigned to the prevalent compounds in the obtained samples, Fe2O3 (for x = 2.8/0.2) and ZnFe2O4 (for x = 1.8/1.2 and x = 1.5/1.5). Based on the magnetic and dielectric measurements, the microwave absorbent properties of the four samples were analysed, and the sample containingmostly of ZnFe2O4 (for x = 1.8/1.2) was found to be the best electromagnetic absorber in the frequency range 1.36-6 GHz.