Effect of Cr substitution on microwave absorption of BaFe 12O 19

Abstract

The chromium substituted barium hexaferrites were prepared by self-propagating combustion method. The crystalline structure, complex permittivity, complex permeability, and hyperfine parameters of BaFe 12− x Cr x O 19 ( x varies from 0.2 to 1.0 in a step of 0.2) were measured with X-ray diffraction, vector network analyzer and Mössbauer spectroscopy. At 850 °C, only a part of Cr 3+ ions are permitted to enter the lattice of barium ferrite. With further calcination at 1000 °C, all Cr 3+ ions enter the lattice. After substitution, the complex permittivity is increased. The Cr 3+ ions substitute for the Fe 3+ ions on the 2 a site, and simultaneously lead to a quadrupole splitting on the 4 f 1 site. These changes decrease the anisotropy field, which are accordant with the spectra of μ″. In the crystalline cells of the substituted barium ferrites, some Fe 2+ ions are formed. It results in a bigger dielectric loss.