Effect of Cr substitution on microwave absorption of BaFe12O19

The chromium substituted barium hexaferrites were prepared by self-propagating combustion method. The crystalline structure, complex permittivity, complex permeability, and hyperfine parameters of BaFe12−xCrxO19 (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 Cr3+ ions are permitted to enter the lattice of barium ferrite. With further calcination at 1000 °C, all Cr3+ ions enter the lattice. After substitution, the complex permittivity is increased. The Cr3+ ions substitute for the Fe3+ ions on the 2a site, and simultaneously lead to a quadrupole splitting on the 4f1 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 Fe2+ ions are formed. It results in a bigger dielectric loss.