Effects of sintering temperature on structural, magnetic and microwave absorption properties of Ni0.5Zn0.5Fe2O4 ferrites

Abstract

Ni0.5Zn0.5Fe2O4 ferrites were prepared by the sol–gel auto-combustion method and sintered at 1150 °C, 1250 °C, 1350 °C and 1450 °C. Structural, magnetic, and microwave absorption properties were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectra, Vibrating sample magnetometer and vector network analyzer, respectively. Sintering temperature has a remarkable effect on the concentration of both Fe2+ and oxygen vacancies and further influence the permittivity and permeability. The excellent microwave absorption properties are obtained at the sintering temperature of 1350 °C, and its effective absorption bandwidth reaches 9.55 GHz from 3.67 to 13.22 GHz at a thin thickness of 2.5 mm. It is notable that the two reflection loss peaks of Ni0.5Zn0.5Fe2O4 ferrites appeared at both low and high frequency regions. The peak at low frequency is associated with the great magnetic loss tangent (greater than1) and the peak at high frequency satisfies the quarter-wavelength matching model. The microwave absorption performance of Ni0.5Zn0.5Fe2O4 ferrites was attributed to both dielectric and magnetic mechanisms while the magnetic part dominates.