Effect of Cr substitution on microwave absorption of BaFe_(12)O_(19)

摘要

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_xO_(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 Mossbauer spectroscopy. At 850 deg C, only a part of Cr~(3+) ions are permitted to enter the lattice of barium ferrite. With further calcination at 1000 deg C, all Cr~(3+) ions enter the lattice. After substitution, the complex permittivity is increased. The Cr ions substitute for the Fe~(3+) ions on the 2a site, and simultaneously lead to a quadrupole splitting on the 4/} site. These changes decrease the anisotropy field, which are accordant with the spectra of mu''. In the crystalline cells of the substituted barium ferrites, some Fe~(2+) ions are formed. It results in a bigger dielectric loss.