Microstructure and magnetic characteristics of low-temperature-fired modified Z-type hexaferrite with Bi2O 3 additive

We have investigated the effect of Bi₂O₃ additive on the densification, low-temperature firing, and magnetic characteristics of modified Z-type Ba₃Co₂(1-x-y)Zn _2xCu_2yFe_23.5O₄₁ hexaferrite. Our results show that Bi₂O₃ additive not only improves the densification and promote the firing of modified Z-type hexaferrite prepared by the dry gel self-propagating method below 900°C, but can also improve the magnetic properties. The average values of basic magnetic parameters of the hexaferrites with a small amount of Bi₂O₃ additive are stable: 50.0 emu/g saturation magnetization, 6.0 emu/g residual magnetization, 50 to 90 Oe coercive force, and 380 K Curie temperature. However, the main magnetic properties of low-fired hexaferrites are improved in that they attain an initial permeability of 4.0, a quality factor in excess of 50, a cutoff frequency greater than 1.0 GHz, and a dc resistivity of 3.30×10 ⁷ Ω·cm. We discuss the relative mechanisms and factors involved in generating these effects in this paper