Microwave absorption properties of porous NiZn ferrite powders synthesized by solution combustion method: Effect of fuel contents

Abstract

Hierarchical porous Ni0.5Zn0.5Fe2O4 ferrite powders were prepared by using metal nitrates as oxidants and glycine as fuel. The fuel contents were used for tuning the microstructure, magnetic, permittivity, and permeability properties to obtain a high microwave absorption performance. The pure NiZn ferrite powders were directly crystallized at lower fuel contents, while about 2 wt% intermetallic FeNi3 phase appeared at fuel to total metal nitrates molar ratio of 2. The combusted powders with high specific surface areas of 51 m2/g showed porous and foamy microstructure. The saturation magnetization of the combusted powders increased from 36.5 to 78.5 emu/g by the formation of FeNi3 phase at the higher fuel contents. With the increase of glycine fuel to total metal nitrates molar ratio from 1 to 2, the real and imaginary parts of permittivity increased from 4.5 to 6 and from 0.8 to 1.1, respectively, while the values of real and imaginary permeability slightly increased. The high microwave absorption performance, including reflection loss of −48 dB with effective bandwidth of 2.9 GHz in Ku band at the matching thickness of 4.5 mm, was obtained at the fuel to total metal nitrates ratio of 2.