Combustion synthesis of porous Fe3-xZnxO4 powders for high-performance microwave absorbers

Fe3-xZnxO4 (x = 0.1, 0.2, and 0.3) powders were synthesized by facile combustion method using metal nitrates as oxidants and glycine as fuel. The structural, microstructural, magnetic, and microwave absorption properties are characterized as a function of Zn2+ substitution. With the increase of Zn2+ contents, some hematite (alpha-Fe2O3) phases appeared together with the magnetite (Fe3O4) phase. The transmission and scanning electron microscopy observations showed that the particle size was decreased from 120 to 70 nm, while the amount and size of pores increased with adding Zn2+ cations. The as-synthesized Fe2.9Zn0.1O4 powders had the highest saturation magnetization of 92 emu/g, which decreased to 72 emu/g for the Fe(2.7)Zn0.3O(4) sample. The Fe2.8Zn0.2O4 sample exhibited an intense reflection loss of-53 dB in the Ku band at the matching thickness of 2 mm. Despite the reduction of reflection loss, the effective bandwidth increased up to 5.5 GHz with the Zn content, which is attributed to the better impedance matching and higher contribution of magnetic and dielectric loss mechanisms.

Automated summary

Fe3-xZnxO4 powders with different Zn2+ substitution were synthesized via a combustion method. The increase of Zn2+ content led to decreased particle size, increased pore amount, and different variations in saturation magnetization and reflection loss.